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1
Lancaster, Melanie L., Michael G. Gardner, Alison J. Fitch, Talat H. Ansari, and Anita K. Smyth. "A direct benefit of native saltbush revegetation for an endemic lizard (Tiliqua rugosa) in southern Australia." Australian Journal of Zoology 60, no. 3 (2012): 192. http://dx.doi.org/10.1071/zo12063.
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Land alteration for intensive agriculture has been a major cause of species decline and extinction globally. In marginal grazing regions of southern Australia, native perennial shrubs are increasingly being planted to supplement pasture feeding of stock. Such revegetation has the benefits of reducing erosion and salinity, and importantly, the potential provision of habitat for native fauna. We explored the use of revegetated native saltbush by the sleepy lizard (Tiliqua rugosa) an endemic Australian species common in the region. We repeatedly sampled revegetated saltbush throughout 2010 and 2011 for adults (n = 55) and juveniles (n = 26). Using genotypes from eight microsatellite loci, parents were assigned to half of all juveniles with high statistical confidence. Parents were sampled in the same patch of revegetated saltbush as their offspring, thus supporting the observation that juvenile sleepy lizards remain within the home range of their parents before dispersal. Most importantly, our findings indicate that revegetated saltbush provides important habitat for T. rugosa at significant life stages – before and during breeding for adults, and before dispersal for juveniles. We conclude that revegetation using simple, monoculture plantations provides beneficial habitat for T. rugosa and may also be beneficial habitat for other native species in human-altered agricultural landscapes.
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Görlach, Bruno Maximilian, Jon Niklas Henningsen, Jens Torsten Mackens, and Karl Hermann Mühling. "Evaluation of Maize Growth Following Early Season Foliar P Supply of Various Fertilizer Formulations and in Relation to Nutritional Status." Agronomy 11, no. 4 (April 9, 2021): 727. http://dx.doi.org/10.3390/agronomy11040727.
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The efficiency of phosphorus (P) use in agriculture needs to be improved, with farmers being increasingly forced by law to reduce P soil fertilization. Thus, P foliar application might become more important in agriculture. The effect of foliar P fertilization has not been widely studied in maize, despite it being a crop with high P demand during juvenile development. Our aim was to investigate the effect of P foliar application during juvenile development on maize crop growth and yield. We conducted outdoor pot experiments to investigate the effect on P uptake, translocation, and dry matter following three applications of foliar fertilizer of various P formulations and with additional P soil fertilization between the 4th and 6th leaf stage during two growing seasons. To determine direct and possible long-term effects, plants were harvested at various developmental stages. P foliar application resulted in a significant increase in P concentration in all plant parts ten days after the last application, regardless of P form, nutritional status, or year. P concentration remained high only in those parts of the plant that were present during foliar application. Biomass effects were sporadically visible until flowering, but not at maturity. We conclude that foliar P fertilization during juvenile development does not increase yield but might nevertheless be a useful remedy for short-term P deficits.
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Ping, Li, Bingyong Xu, Qian Zhou, Yawen Hong, Qingmei Sun, Jincheng Wang, and Difeng Zhu. "Comparative Pharmacokinetic Study of Forchlorfenuron in Adult and Juvenile Rats." Molecules 26, no. 14 (July 14, 2021): 4276. http://dx.doi.org/10.3390/molecules26144276.
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Forchlorfenuron (CPPU) is a plant growth regulator extensively used in agriculture. However, studies on CPPU pharmacokinetics are lacking. We established and validated a rapid, sensitive, and accurate liquid chromatography–mass spectrometry method for CPPU detection in rat plasma. CPPU pharmacokinetics was evaluated in adult and juvenile rats orally treated with 10, 30, and 90 mg/kg of the compound. The area under the plasma drug concentration–time curve from 0 to 24 h (AUC), at the final time point sampled (AUC0–t), and the maximum drug concentration of CPPU increased in a dose-dependent manner. The pharmacokinetic parameters AUC0–t and absolute bioavailability were higher in the juvenile rats than in adult rats. The mean residence time and AUC0–t of juvenile rats in the gavage groups, except for the 10 mg/kg dose, were significantly higher in comparison to those observed for adult rats (p < 0.001). The plasma clearance of CPPU in juvenile rats was slightly lower than that in the adult rats. Taken together, juvenile rats were more sensitive to CPPU than adult rats, which indicates potential safety risks of CPPU in minors.
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Buikstra, Jane E., Lyle W. Konigsberg, and Jill Bullington. "Fertility and the Development of Agriculture in the Prehistoric Midwest." American Antiquity 51, no. 3 (July 1986): 528–46. http://dx.doi.org/10.2307/281750.
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In this article we develop and apply a method for estimating fertility in paleodemographic study. The proportion D30+/D5+, generated from standard life table calculations, is used to estimate relative fertility rates for eight Woodland and Mississippian populations represented by skeletal series from west-central Illinois. The inferred pattern of fertility increase through time is then considered in the context of key variables that define diet, technology, and sedentism. We conclude that changes in diet or food preparation techniques are implicated in this demographic change. The absence of a significant increment in juvenile mortality in association with the elevated fertility rates suggests that these changes in fertility explain the regional population increase previously inferred from mortuary and habitation site densities.
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Pianezzola, E., S. Roth, and B. A. Hatteland. "Predation by carabid beetles on the invasive slug Arion vulgaris in an agricultural semi-field experiment." Bulletin of Entomological Research 103, no. 2 (November 13, 2012): 225–32. http://dx.doi.org/10.1017/s0007485312000569.
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AbstractArion vulgaris Moquin-Tandon 1855 is one of the most important invasive species in Europe, affecting both biodiversity and agriculture. The species is spreading in many parts of Europe, inflicting severe damage to horticultural plants and cultivated crops partly due to a lack of satisfactory and effective management solutions. Molluscicides have traditionally been used to manage slug densities, although the effects are variable and some have severe side-effects on other biota. Thus, there is a need to explore potential alternatives such as biological control. The nematode Phasmarhabditis hermaphrodita is the only biological agent that has been applied commercially so far. However, other biological control agents such as carabid beetles have also been found to be promising. In addition, some carabid species have been shown to feed on A. vulgaris in the field as well as in the laboratory. Two species in particular have been found to be important predators of A. vulgaris, and these species are also common in agricultural environments: Pterostichus melanarius and Carabus nemoralis. This study is the first to use semi-field experiments in a strawberry field, manipulating densities, to investigate how P. melanarius and C. nemoralis affect densities of A. vulgaris eggs and juveniles, respectively. Gut contents of C. nemoralis were analysed using multiplex PCR methods to detect DNA of juvenile slugs. Results show that both P. melanarius and C. nemoralis significantly affect densities of slug eggs and juvenile slugs under semi-field conditions and that C. nemoralis seems to prefer slugs smaller than one gram. Carabus nemoralis seems to be especially promising in reducing densities of A. vulgaris, and future studies should investigate the potential of using this species as a biological control agent.
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Triyanto, Triyanto, Tarsim Tarsim, and Deny Sapto Chondro Utomo. "INFLUENCES OF LAMP IRRADIATION EXPOSURE ON GROWTH AND SURVIVAL OF JUVENILE SNEAKHEAD FISH Channa striata (Bloch, 1793)." e-Jurnal Rekayasa dan Teknologi Budidaya Perairan 8, no. 2 (February 21, 2020): 1029. http://dx.doi.org/10.23960/jrtbp.v8i2.p1029-1038.
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The research has been conducted by February to March 2018 in the Laboratory of Aquaculture, Faculty of Agriculture, Lampung University. The research aim of this to acknowledge the influences of lamp irradiation exposure on growth and survival of juvenile sneakhead fish (Channa striata). This research used a completely randomized design with five treatments, A (12B;12D), B (9B;15D), C (6B;18D), D (3B;21D), and E (0B;24D) with three replications. The research showed that the effect of the length of light irradiation exposure has a significant effect on growth and survival of juvenile snakehead fish. The best treatment found in treatment D, that the resulted highest value of weight growth (5,46 g), daily weight growth (0,121 g/day), length growth (5,37 cm), daily length growth (0,119 cm/day), and survival rate of 97%.
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Alonso, Valentina, Shyon Nasrolahi, and Adler Dillman. "Host-Specific Activation of Entomopathogenic Nematode Infective Juveniles." Insects 9, no. 2 (June 2, 2018): 59. http://dx.doi.org/10.3390/insects9020059.
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Entomopathogenic nematodes (EPNs) are potent insect parasites and have been used for pest control in agriculture. Despite the complexity of the EPN infection process, hosts are typically killed within 5 days of initial infection. When free-living infective juveniles (IJs) infect a host, they release their bacterial symbiont, secrete toxic products, and undergo notable morphological changes. Collectively, this process is referred to as “activation” and represents the point in a nematode’s life cycle when it becomes actively parasitic. The effect of different host tissues and IJ age on activation, and how activation itself is related to virulence, are not well understood. Here, we employed a recently developed bioassay, which quantifies IJ activation, as a tool to address these matters. Appreciating that activation is a key part of the EPN infection process, we hypothesized that activation would positively correlate to virulence. Using the EPNs Steinernema carpocapsae and S. feltiae we found that EPN activation is host-specific and influenced by infective juvenile age. Additionally, our data suggest that activation has a context-dependent influence on virulence and could be predictive of virulence in some cases such as when IJ activation is especially low.
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Holmes, Eric J., Parsa Saffarinia, Andrew L. Rypel, Miranda N. Bell-Tilcock, Jacob V. Katz, and Carson A. Jeffres. "Reconciling fish and farms: Methods for managing California rice fields as salmon habitat." PLOS ONE 16, no. 2 (February 24, 2021): e0237686. http://dx.doi.org/10.1371/journal.pone.0237686.
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Rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as ecologically functioning floodplain rearing habitat for juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods to enhance habitat benefits for fall-run Chinook Salmon reared on winter-flooded rice fields in the Yolo Bypass, a modified floodplain managed for flood control, agriculture, and wildlife habitat in the Sacramento River Valley of California. Investigations included studying the effect of 1) post-harvest field substrate; 2) depth refugia; 3) duration of field drainage; and 4) duration of rearing occupancy on in-situ diet, growth and survival of juvenile salmon. Post-harvest substrate treatment had only a small effect on the lower trophic food web and an insignificant effect on growth rates or survival of rearing hatchery-origin, fall-run Chinook Salmon. Similarly, depth refugia, created by trenches dug to various depths, also had an insignificant effect on survival. Rapid field drainage yielded significantly higher survival compared to drainage methods drawn out over longer periods. A mortality of approximately one third was observed in the first week after fish were released in the floodplain. This initial mortality event was followed by high, stable survival rates for the remainder of the 6-week duration of floodplain rearing study. Across years, in-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant than those sampled concurrently in the adjacent Sacramento River channel. Correspondingly, observed somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater than concurrently and previously observed growth rates in the adjacent Sacramento River. The abundance of food resources and exceptionally high growth rates observed during these experiments illustrate the potential benefits of using existing agricultural infrastructure to approximate the floodplain wetland physical conditions and hydrologic patterns (shallow, long-duration inundation of cool floodplain habitats in mid-winter) under which Chinook Salmon evolved and to which they are adapted.
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Hafez, S. L., P. Sundararaj, Z. A. Handoo, A. M. Skantar, L. K. Carta, and D. J. Chitwood. "First Report of the Pale Cyst Nematode, Globodera pallida, in the United States." Plant Disease 91, no. 3 (March 2007): 325. http://dx.doi.org/10.1094/pdis-91-3-0325b.
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In 2006, a cyst nematode was discovered in tare dirt at a potato (Solanum tuberosum) processing facility in eastern Idaho. The nematode was found during a routine survey conducted jointly by the Idaho State Department of Agriculture and the USDA Animal and Plant Health Inspection Service through the Cooperative Agricultural Pest Survey program. Extensive additional sampling from two suspect fields led to the identification of the same nematode in a 45-acre (18.2-ha) field located in northern Bingham County. The morphology of cysts and second-stage juveniles and molecular analyses established the identity of the species as the pale cyst nematode Globodera pallida (Stone 1973) Behrens 1975. Morphological characters used for identification included cyst shape, characteristics of cyst terminal cone including nature of fenestration, cyst wall pattern, anal-vulval distance, number of cuticular ridges between anus and vulva, and Granek's ratio (1,4). The second-stage juvenile morphologies critical for identification were the following: body and stylet length, shape of stylet knobs, shape and length of tail and hyaline tail terminus, and number of refractive bodies in the hyaline part of tail (1,4). Diagnosis as G. pallida was clearly confirmed by two molecular tests. First, PCR-RFLP (restriction fragment length polymorphism) profiles of a ribosomal DNA fragment using restriction enzymes RsaI, TaqI, and AluI (2) were consistent with a G. pallida control and not G. rostochiensis. Second, the ribosomal DNA region that extends from the 3′ end of the 18S ribosomal subunit and includes all of ITS1, 5.8S, and ITS2 to the 5′ end of the 28S ribosomal subunit was used to generate sequence for the most accurate species determination. Sequences obtained from three individual juveniles were compared with those from several Globodera species (3), revealing unequivocal similarity to G. pallida. This detection represents a new country record for G. pallida in the United States. Collection of additional information regarding distribution of this nematode within the region is underway. References: (1) J. G. Baldwin and M. Mundo-Ocampo. Heteroderinae, Cyst- and Non-cyst-forming Nematodes. Pages 275-362 in: Manual of Agricultural Nematology. W. R. Nickle, ed. Marcel Dekker, New York, 1991. (2) V. C. Blok et al. J. Nematol. 30:262, 1998. (3) L. A. Pylypenko et al. Eur. J. Plant Pathol. 111:39, 2005. (4) A. R. Stone. Nematologica 18:591, 1973.
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Gibson, Neil, Colin Yates, Margaret Byrne, Margaret Langley, and Rujiporn Thavornkanlapachai. "The importance of recruitment patterns versus reproductive output in the persistence of a short-range endemic shrub in a highly fragmented landscape of south-western Australia." Australian Journal of Botany 60, no. 7 (2012): 643. http://dx.doi.org/10.1071/bt12194.
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Calothamnus quadrifidus subsp. teretifolius A.S.George & N.Gibson is a short-range endemic shrub whose habitat has been greatly reduced by clearing for agriculture. Reproductive output was high in all populations sampled, although there were large differences among populations in fruit set, the number of seeds per fruit and seed germination. These traits showed no relationship to population size, degree of isolation, or fragment size, which contrasts strongly with the patterns found in a widespread congener. Demographic studies in remnants with an intact understorey showed stable adult populations with continuous seedling recruitment. In contrast, there was consistent widespread failure of seedling and juvenile recruitment in degraded roadside remnants that also showed significant mortality of reproductive adults. In these degraded remnants, recruitment failure appears to be the primary cause of species decline.
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SILVA, LUNARA GRAZIELLY COSTA DA, JEFFERSON FRANCISCO LIMA MOREIRA, HERICLES BRUNO BEZERRA HOLANDA, EMANUEL LUCAS BEZERRA ROCHA, and POLIANA COQUEIRO DIAS. "EVALUATION OF CARNAUBA PROGENIES AND ESTIMATES OF GENETIC PARAMETERS IN THE JUVENILE PHASE." Revista Caatinga 31, no. 4 (December 2018): 917–25. http://dx.doi.org/10.1590/1983-21252018v31n414rc.
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ABSTRACT Carnauba (Copernicia prunifera) is a forest species with multiple uses, and is of great economic and social importance for several communities involved in extractive agriculture in northeastern Brazil. However, there are few studies on genetic variability in this species. Thus, this work aimed to produce information about the genetic characterization of C. prunifera seeds and seedlings, using provenance and progeny evaluations. A progeny test was performed in a plant nursery, using seeds of 36 matrices sampled in the municipalities of Mossoró and Apodi (Rio Grande do Norte State), and Russas and Icapuí (Ceará State). Three groups were derived according to the spatial distance between the collected matrices. Biometric analyses of the seeds were performed, adopting a completely randomized experimental design, with four replicates of 25 seeds in each analysis. A randomized block design (five replicates and five plants per plot) was used at the seedling production phase. The data evaluated included the emergence speed index, emergence percentage, leaf size, leaf base diameter, and survival (at 30, 60, and 90 days after sowing). The restricted maximum likelihood method was used in the statistical analysis, with the aid of SELEGEN software. In order to evaluate genetic variability in the C. prunifera population samples, it was verified that the juvenile characters presented a moderate genetic control. The three groups of spatially delimited matrices presented no significant genetic differences. This information may assist in the development of forestry practice for this species.
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Ranard, Katherine, Matthew Kuchan, and John Erdman. "Effect of Natural Vs. Synthetic α-tocopherol on Neurogenesis-Related Genes in Cerebella of Juvenile α-tocopherol Transfer Protein-Null Mice." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 1060. http://dx.doi.org/10.1093/cdn/nzaa054_132.
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Abstract Objectives Vitamin E (α-tocopherol, α-T) restriction during brain development alters the expression of neurogenesis-related genes in cerebella of juvenile α-tocopherol transfer protein-null (Ttpa−/−) mice. Synthetic α-T (SYN), compared to natural α-T (NAT), downregulates cerebellar myelin genes in adolescent Ttpa−/− mice. We studied how early-life exposure to SYN or NAT affects the expression of neurogenesis-related genes in juvenile Ttpa−/− mice. Methods Male and female Ttpa+/+ and Ttpa−/− mice were nursed by Ttpa+/−dams fed AIN-93G-based diets containing either SYN (∼816 mg α-T/kg diet) or NAT (∼600 mg α-T/kg diet). Homogenized brain tissues from 21 day old weanlings (n = 9/group) were used to measure total α-T concentrations via HPLC-PDA. The expression of genes critical for brain development (Rora, Shh), myelination (Plp1, Cntnap1, Mbp, Mobp, Nr1h3), and synaptic function (Cplx1, Necab1, Prkcg) were measured in the cerebellum via real-time qPCR. Results α-T concentrations were significantly lower in brains of Ttpa−/− mice (17.7 nmol/g) compared to Ttpa+/+ mice (37.5 nmol/g) (P < 0.001). Exposure to SYN vs. NAT resulted in similar total α-T brain levels within each genotype (Ttpa−/−: 19.8 vs. 15.6 nmol/g; Ttpa+/+: 42.5 vs. 32.6 nmol/g). Consistent with previous studies, Necab1 was significantly downregulated in Ttpa−/− mice (P < 0.05). The other selected neurogenesis-related genes were similarly expressed between all groups, regardless of genotype or dietary α-T source. Conclusions Brain α-T concentrations at weaning depended on the presence of Ttpa. α-T source did not modulate the selected neurogenesis genes, possibly because the natural and synthetic α-T diets each provided sufficient total α-T during development. Funding Sources Abbott Nutrition through the Center for Nutrition, Learning, and Memory (CNLM), Division of Nutritional Sciences Vision 20/20 Grant Program, and Division of Nutritional Sciences Margin of Excellence Research Program (all through the University of Illinois at Urbana-Champaign). KMR was supported by the AFRI NIFA Predoctoral Fellowships Grant Program (2019–67,011-29,514) from the U.S. Department of Agriculture, National Institute of Food and Agriculture.
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Daunt, F., V. Afanasyev, A. Adam, J. P. Croxall, and S. Wanless. "From cradle to early grave: juvenile mortality in European shags Phalacrocorax aristotelis results from inadequate development of foraging proficiency." Biology Letters 3, no. 4 (May 15, 2007): 371–74. http://dx.doi.org/10.1098/rsbl.2007.0157.
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In most long-lived animal species, juveniles survive less well than adults. A potential mechanism is inferior foraging skills but longitudinal studies that follow the development of juvenile foraging are needed to test this. We used miniaturized activity loggers to record daily foraging times of juvenile and adult European shags Phalacrocorax aristotelis from fledging to the following spring. Juveniles became independent from their parents 40 days post-fledging. They compensated for poor foraging proficiency by foraging for approximately 3 h d −1 longer than adults until constrained by day length in early November. Thereafter, juvenile foraging time tracked shortening day length up to the winter solstice, when foraging time of the two age classes converged and continued to track day length until early February. Few individuals died until midwinter and mortality peaked in January–February, with juvenile mortality (including some of the study birds) five times that of adults. In their last two weeks of life, juveniles showed a marked decline in foraging time consistent with individuals becoming moribund. Our results provide compelling evidence that juveniles compensate for poor foraging proficiency by increasing foraging time, a strategy that is limited by day length resulting in high winter mortality.
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SYMES, CRAIG T., and STEPHAN WOODBORNE. "Migratory connectivity and conservation of the Amur Falcon Falco amurensis: a stable isotope perspective." Bird Conservation International 20, no. 2 (March 30, 2010): 134–48. http://dx.doi.org/10.1017/s0959270910000237.
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SummaryStable isotopes (δD, δ13C, δ15N) were measured in adult and juvenile Amur Falcon Falco amurensis feathers to understand the migratory connectivity of this species. Using the OIPC (Online Isotopes in Precipitation Calculator) and a calibration curve for American Kestrels Falco sparverius we predicted the breeding range of South African Amur Falcons in the Palaearctic. δD values for juvenile feathers (mean ± SE = -58.1 ± 2.5‰, range -83.9 to -25.7‰) and predicted Palaearctic annual precipitation values indicated that juvenile Amur Falcons in South Africa originated from across their entire Palaearctic range. This rejects the leapfrog migration hypothesis and suggests the widespread movement of birds south, with a funnelling effect into the subregion where they become concentrated over a narrower distribution range. Adult δDf values were more depleted (-37.4 ± 1.8‰, range = -71.3 to -9.3‰) than predicted annual precipitation values for sites where feathers moulted in South Africa (-20.2 ± 0.9‰) but there was no correlation between δDp and δDf. This, together with significant variation of δ13C among sites and annual fluctuations in roost sizes, suggests that roost site fidelity is low in the overwintering range. Populations not confined to breeding sites in South Africa are able to move widely across the subregion, feeding on a broad range of arthropods that become seasonally abundant during the austral summer. Total population estimates for South Africa are significantly lower than global estimates so a significant proportion of the population may not overwinter in South Africa or global populations are significantly lower than estimated. In South Africa, roosts that number hundreds to thousands of individuals are often in large exotic trees, e.g. Eucalyptus sp. They are often tolerant of disturbance at roosts which may be of little concern for their conservation. Habitat changes in the overwintering range in South Africa though, particularly due to agriculture, afforestation and strip mining, may affect global population numbers. There is also concern over the persecution of birds along their migratory route.
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Taborsky, Barbara. "Mothers determine offspring size in response to own juvenile growth conditions." Biology Letters 2, no. 2 (January 5, 2006): 225–28. http://dx.doi.org/10.1098/rsbl.2005.0422.
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Through non-genetic maternal effects, mothers can tailor offspring phenotype to the environment in which young will grow up. If juvenile and adult ecologies differ, the conditions mothers experienced as juveniles may better predict their offspring's environment than the adult environment of mothers. In this case maternal decisions about investment in offspring quality should already be determined during the juvenile phase of mothers. I tested this hypothesis by manipulating juvenile and adult maternal environments independently in a cichlid fish. Females raised in a poor environment produced larger young than females raised without food limitations, irrespective of the feeding conditions experienced during adulthood. This maternal boost was due to a higher investment in eggs and to faster larval growth. Apparently, mothers prepare their offspring for similar environmental conditions to those they encountered as juveniles. This explanation is supported by the distribution of these fishes under natural conditions. Juveniles live in a different and much narrower range of habitats than adults. Therefore, the habitat mothers experienced as juveniles will allow them to predict their offspring's environment better than the conditions in the adult home range.
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Crane, Mason J., David B. Lindenmayer, and Ross B. Cunningham. "The use of den trees by the squirrel glider (Petaurus norfolcensis) in temperate Australian woodlands." Australian Journal of Zoology 58, no. 1 (2010): 39. http://dx.doi.org/10.1071/zo09070.
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Effective conservation relies on understanding the biology of particular species and how they use key resources. For many arboreal mammals, tree hollows are a key den site. We examined the use of tree hollows by the squirrel glider (Petaurus norfolcensis) in south-eastern Australia. Over a five-month study, individual squirrel gliders used multiple hollow trees (average = 7) as den sites. Den sites were often adjacent to areas where nocturnal activities took place. The average distance between den sites used by individual gliders on successive days was 218 m. Dens were often shared by an adult pair and a juvenile. Den trees were disproportionably used, with gliders showing preference for 1–2 primary den trees often located on steep slopes. Our findings have implications for the number and spatial arrangement of den trees needed to promote the conservation of populations of the squirrel glider, particularly where land is used for agriculture and livestock grazing.
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Donelson, Jennifer M., Philip L. Munday, and Mark I. McCormick. "Parental effects on offspring life histories: when are they important?" Biology Letters 5, no. 2 (January 6, 2009): 262–65. http://dx.doi.org/10.1098/rsbl.2008.0642.
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Both the parental legacy and current environmental conditions can affect offspring life histories; however, their relative importance and the potential relationship between these two influences have rarely been investigated. We tested for the interacting effects of parental and juvenile environments on the early life history of the marine fish Acanthochromis polyacanthus . Juveniles from parents in good condition were longer and heavier at hatching than juveniles from parents in poor condition. Parental effects on juvenile size were evident up to 29 days post-hatching, but disappeared by 50 days. Offspring from good condition parents had higher early survival than offspring from poor-condition parents when reared in a low-food environment. By contrast, parental condition did not affect juvenile survival in the high-food environment. These results suggest that parental effects on offspring performance are most important when poor environmental conditions are encountered by juveniles. Furthermore, parental effects observed at hatching may often be moderated by compensatory mechanisms when environmental conditions are good.
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Spaan, Robert S., Clinton W. Epps, Rachel Crowhurst, Donald Whittaker, Mike Cox, and Adam Duarte. "Impact of Mycoplasma ovipneumoniae on juvenile bighorn sheep (Ovis canadensis) survival in the northern Basin and Range ecosystem." PeerJ 9 (January 19, 2021): e10710. http://dx.doi.org/10.7717/peerj.10710.
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Determining the demographic impacts of wildlife disease is complex because extrinsic and intrinsic drivers of survival, reproduction, body condition, and other factors that may interact with disease vary widely. Mycoplasma ovipneumoniae infection has been linked to persistent mortality in juvenile bighorn sheep (Ovis canadensis), although mortality appears to vary widely across subspecies, populations, and outbreaks. Hypotheses for that variation range from interactions with nutrition, population density, genetic variation in the pathogen, genetic variation in the host, and other factors. We investigated factors related to survival of juvenile bighorn sheep in reestablished populations in the northern Basin and Range ecosystem, managed as the formerly-recognized California subspecies (hereafter, “California lineage”). We investigated whether survival probability of 4-month juveniles would vary by (1) presence of M. ovipneumoniae-infected or exposed individuals in populations, (2) population genetic diversity, and (3) an index of forage suitability. We monitored 121 juveniles across a 3-year period in 13 populations in southeastern Oregon and northern Nevada. We observed each juvenile and GPS-collared mother semi-monthly and established 4-month capture histories for the juvenile to estimate survival. All collared adult females were PCR-tested at least once for M. ovipneumoniae infection. The presence of M. ovipneumoniae-infected juveniles was determined by observing juvenile behavior and PCR-testing dead juveniles. We used a known-fate model with different time effects to determine if the probability of survival to 4 months varied temporally or was influenced by disease or other factors. We detected dead juveniles infected with M. ovipneumoniae in only two populations. Derived juvenile survival probability at four months in populations where infected juveniles were not detected was more than 20 times higher. Detection of infected adults or adults with antibody levels suggesting prior exposure was less predictive of juvenile survival. Survival varied temporally but was not strongly influenced by population genetic diversity or nutrition, although genetic diversity within most study area populations was very low. We conclude that the presence of M. ovipneumoniae can cause extremely low juvenile survival probability in translocated bighorn populations of the California lineage, but found little influence that genetic diversity or nutrition affect juvenile survival. Yet, after the PCR+ adult female in one population died, subsequent observations found 11 of 14 ( 79%) collared adult females had surviving juveniles at 4-months, suggesting that targeted removals of infected adults should be evaluated as a management strategy.
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Sarker, J., and MAR Faruk. "Experimental infection of Aeromonas hydrophila in pangasius." Progressive Agriculture 27, no. 3 (December 28, 2016): 392–99. http://dx.doi.org/10.3329/pa.v27i3.30836.
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Experimental infections of Aeromonas hydrophila in juvenile pangasius (Pangasianodon hypophthalmus) were studied. Five different challenge routes included intraperitoneal (IP) injection, intramuscular (IM) injection, oral administration, bath and agar implantation were used with different preparations of the bacteria to infect fish. The challenge experiments were continued for 15 days. A challenge dose of 4.6×106 colony forming unit (cfu) fish-1 was used for IP and IM injection and oral administration method. Generally, IP route was found more effective for infecting and reproducing clinical signs in fish that caused 100% mortality at the end of challenge. IM injection, oral and bath administration routes were also found effective for infecting and reproducing the clinical signs in fish to some extent. Agar implantation with fresh colonies of bacteria also caused 100% mortality of challenged fish very quickly with no visible clinical signs in fish. The major clinical signs of challenged fish included reddening around eyes and mouth, bilateral exophthalmia, hemorrhage and ulceration at fin bases and fin erosion.Progressive Agriculture 27 (3): 392-399, 2016
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Kroon, Frederieke J., and Dean H. Ansell. "A comparison of species assemblages between drainage systems with and without floodgates: implications for coastal floodplain management." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 11 (November 1, 2006): 2400–2417. http://dx.doi.org/10.1139/f06-134.
Full textAbstract:
Coastal floodplains provide essential nursery habitat for a large number of fish and prawn species, many of which are commercially and recreationally important. Human activities in coastal floodplains, such as those associated with agriculture and (or) development, can have detrimental impacts on this nursery function. We examined the potential role of flood mitigation structures, in particular tidal floodgates, in depleting estuarine and inshore fisheries stocks in eastern Australia. We compared species assemblages (abundance and biomass) in reference and gated drainage systems in the Clarence River floodplain (New South Wales, Australia) over a 1-year period. We subsequently determined which environmental variables were associated with the observed patterns in species assemblages. Our results show that abundance, biomass, and assemblages of juvenile fishes and invertebrates differed significantly and consistently between drainage systems with and without floodgates. The major environmental variables of concern in systems with floodgates were (i) presence of a floodgate, (ii) elevated concentrations of nutrients, and (iii) abundance of aquatic weeds. We discuss our findings in light of potential strategies to improve coastal floodplain management for fisheries production purposes.
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Devillers, James, and Hugo Devillers. "Lethal and Sublethal Effects of Pyriproxyfen on Apis and Non-Apis Bees." Toxics 8, no. 4 (November 17, 2020): 104. http://dx.doi.org/10.3390/toxics8040104.
Full textAbstract:
Pyriproxyfen is a juvenile hormone mimic used extensively worldwide to fight pests in agriculture and horticulture. It also has numerous applications as larvicide in vector control. The molecule disrupts metamorphosis and adult emergence in the target insects. The same types of adverse effects are expected on non-target insects. In this context, the objective of this study was to evaluate the existing information on the toxicity of pyriproxyfen on the honey bee (Apis mellifera) and non-Apis bees (bumble bees, solitary bees, and stingless bees). The goal was also to identify the gaps necessary to fill. Thus, whereas the acute and sublethal toxicity of pyriproxyfen against A. mellifera is well-documented, the information is almost lacking for the non-Apis bees. The direct and indirect routes of exposure of the non-Apis bees to pyriproxyfen also need to be identified and quantified. More generally, the impacts of pyriproxyfen on the reproductive success of the different bee species have to be evaluated as well as the potential adverse effects of its metabolites.
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Strauss, Eli D., Daizaburo Shizuka, and Kay E. Holekamp. "Juvenile rank acquisition is associated with fitness independent of adult rank." Proceedings of the Royal Society B: Biological Sciences 287, no. 1922 (March 4, 2020): 20192969. http://dx.doi.org/10.1098/rspb.2019.2969.
Full textAbstract:
Social rank is a significant determinant of fitness in a variety of species. The importance of social rank suggests that the process by which juveniles come to establish their position in the social hierarchy is a critical component of development. Here, we use the highly predictable process of rank acquisition in spotted hyenas to study the consequences of variation in rank acquisition in early life. In spotted hyenas, rank is ‘inherited’ through a learning process called ‘maternal rank inheritance.’ This pattern is very consistent: approximately 80% of juveniles acquire the exact rank expected under the rules of maternal rank inheritance. The predictable nature of rank acquisition in these societies allows the process of rank acquisition to be studied independently from the ultimate rank that each juvenile attains. In this study, we use Elo-deviance scores, a novel application of the Elo-rating method, to calculate each juvenile's deviation from the expected pattern of maternal rank inheritance during development. Despite variability in rank acquisition among juveniles, most of these juveniles come to attain the exact rank expected of them according to the rules of maternal rank inheritance. Nevertheless, we find that transient variation in rank acquisition in early life is associated with long-term fitness consequences for these individuals: juveniles ‘underperforming’ their expected ranks show reduced survival and lower lifetime reproductive success than better-performing peers, and this relationship is independent of both maternal rank and rank achieved in adulthood. We also find that multiple sources of early life adversity have cumulative, but not compounding, effects on fitness. Future work is needed to determine if variation in rank acquisition directly affects fitness, or if some other variable, such as maternal investment or juvenile condition, causes variation in both of these outcomes.
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Kerr, Tricia D., Stan Boutin, Jalene M. LaMontagne, Andrew G. McAdam, and Murray M. Humphries. "Persistent maternal effects on juvenile survival in North American red squirrels." Biology Letters 3, no. 3 (March 29, 2007): 289–91. http://dx.doi.org/10.1098/rsbl.2006.0615.
Full textAbstract:
Maternal effects can have lasting fitness consequences for offspring, but these effects are often difficult to disentangle from associated responses in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels ( Tamiasciurus hudsonicus ) by manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival persisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territory quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers, which may explain the persistent survival advantages their juveniles experienced.
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Wyss, Eric, Lucius Tamm, Joachim Siebenwirth, and Stephan Baumgartner. "Homeopathic Preparations to Control the Rosy Apple Aphid (Dysaphis plantagineaPass.)." Scientific World JOURNAL 10 (2010): 38–48. http://dx.doi.org/10.1100/tsw.2010.12.
Full textAbstract:
A laboratory model system with the rosy apple aphid (Dysaphis plantagineaPass.) on apple seedlings was developed to study the effects of homeopathic preparations on this apple pest. The assessment included the substanceLycopodium clavatumand a nosode of the rosy apple aphid. Each preparation was applied on the substrate surface as aqueous solution of granules (6c, 15c, or 30c). Controls were aqueous solutions of placebo granules or pure water. In eight independent, randomized, and blinded experiments under standardized conditions in growth chambers, the development of aphids on treated and untreated apple seedlings was observed over 17 days, each. Six experiments were determined to assess the effects of a strict therapeutic treatment; two experiments were designed to determine the effects of a combined preventative and therapeutic treatment. After application of the preparations, the number of juvenile offspring and the damage on apple seedlings were assessed after 7 and 17 days, respectively. In addition, after 17 days, the seedling weight was measured. In the final evaluation of the six strictly therapeutic trials after 17 days, the number of juvenile offspring was reduced after application ofL. clavatum15c (-17%,p= 0.002) and nosode 6c (-14%,p= 0.02) compared to the pure water control. No significant effects were observed for leaf damage or fresh weight for any application. In the two experiments with combined preventative and therapeutic treatment, no significant effects were observed in any measured parameter. Homeopathic remedies may be effective in plant-pest systems. The magnitude of observed effects seems to be larger than in models with healthy plants, which renders plant-pest systems promising candidates for homeopathic basic research. For successful application in agriculture, however, the effect is not yet sufficient. This calls for further optimization concerning homeopathic remedy selection, potency level, dosage, and application routes.
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Dembélé, Siaka, Robert B. Zougmoré, Adama Coulibaly, John P. A. Lamers, and Jonathan P. Tetteh. "Accelerating Seed Germination and Juvenile Growth of Sorghum (Sorghum bicolor L. Moench) to Manage Climate Variability through Hydro-Priming." Atmosphere 12, no. 4 (March 24, 2021): 419. http://dx.doi.org/10.3390/atmos12040419.
Full textAbstract:
Agriculture in Mali, a country in Sahelian West Africa, strongly depends on rainfall and concurrently has a low adaptive capacity, making it consequently one of the most vulnerable regions to climate change worldwide. Since early-season drought limits crop germination, and hence growth, ultimately yield during rain-fed depending on production is commonly experienced nowadays in Mali. Germination and establishment of key crops such as the staple sorghum could be improved by seed priming. The effects of hydro-priming with different water sources (e.g., distilled, tap, rain, river, well water) were evaluated respectively for three priming time durations in tepid e.g., at 25 °C (4, 8, and 12 h) and by hot water at 70 °C (in contrast to 10, 20, and 30 min.) in 2014 and 2015. Seed germination and seedling development of nine sorghum genotypes were monitored. Compared to non-primed seed treatments, hydro-priming significantly [p = 0.01] improved final germination percentage, germination rate index, total seedling length, root length, root vigor index, shoot length, and seedling dry weight. The priming with water from wells and rivers resulted in significant higher seed germination (85%) and seedling development, compared to the three other sources of water. Seed germination rate, uniformity, and speed were enhanced by hydro-priming also. It is argued that hydro-priming is a safe and simple method that effectively improve seed germination and seedling development of sorghum. If used in crop fields, the above most promising genotypes may contribute to managing early season drought and avoid failure of seed germination and crop failure in high climate variability contexts.
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Wilson, Shaun K., Martial Depczynski, Christopher J. Fulton, Thomas H. Holmes, Ben T. Radford, and Paul Tinkler. "Influence of nursery microhabitats on the future abundance of a coral reef fish." Proceedings of the Royal Society B: Biological Sciences 283, no. 1836 (August 17, 2016): 20160903. http://dx.doi.org/10.1098/rspb.2016.0903.
Full textAbstract:
Species habitat associations are often complex, making it difficult to assess their influence on populations. Among coral reef fishes, habitat requirements vary among species and with ontogeny, but the relative importance of nursery and adult-preferred habitats on future abundances remain unclear. Moreover, adult populations may be influenced by recruitment of juveniles and assessments of habitat importance should consider relative effects of juvenile abundance. We conducted surveys across 16 sites and 200 km of reef to identify the microhabitat preferences of juveniles, sub-adults and adults of the damselfish Pomacentrus moluccensis . Microhabitat preferences at different life-history stages were then combined with 6 years of juvenile abundance and microhabitat availability data to show that the availability of preferred juvenile microhabitat (corymbose corals) at the time of settlement was a strong predictor of future sub-adult and adult abundance. However, the influence of nursery microhabitats on future population size differed spatially and at some locations abundance of juveniles and adult microhabitat (branching corals) were better predictors of local populations. Our results demonstrate that while juvenile microhabitats are important nurseries, the abundance of coral-dependent fishes is not solely dependent on these microhabitats, especially when microhabitats are readily available or following large influxes of juveniles.
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Sievers, Katie T., Rene A. Abesamis, Abner A. Bucol, and Garry R. Russ. "Unravelling Seascape Patterns of Cryptic Life Stages: Non-Reef Habitat Use in Juvenile Parrotfishes." Diversity 12, no. 10 (September 30, 2020): 376. http://dx.doi.org/10.3390/d12100376.
Full textAbstract:
Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish <10-cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a diverse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish.
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Ripperger, Simon, Linus Günther, Hanna Wieser, Niklas Duda, Martin Hierold, Björn Cassens, Rüdiger Kapitza, Alexander Koelpin, and Frieder Mayer. "Proximity sensors on common noctule bats reveal evidence that mothers guide juveniles to roosts but not food." Biology Letters 15, no. 2 (February 2019): 20180884. http://dx.doi.org/10.1098/rsbl.2018.0884.
Full textAbstract:
Female bats of temperate zones often communally rear their young, which creates ideal conditions for naive juveniles to find or learn about resources via informed adults. However, studying social information transfer in elusive and small-bodied animals in the wild is difficult with traditional tracking techniques. We used a novel ‘next-generation’ proximity sensor system (BATS) to investigate if and how juvenile bats use social information in acquiring access to two crucial resources: suitable roosts and food patches. By tracking juvenile–adult associations during roost switching and foraging, we found evidence for mother-to-offspring information transfer while switching roosts but not during foraging. Spatial and temporal patterns of encounters suggested that mothers guided juveniles between the juvenile and the target roost. This roost-switching behaviour provides evidence for maternal guidance in bats, a form of maternal care that has long been assumed, but never documented. We did not find evidence that mothers guide the offspring to foraging sites. Foraging bats reported brief infrequent meetings with other tagged bats that were best explained by local enhancement. Our study illustrates how this recent advance in automated biologging provides researchers with new insights into longstanding questions in behavioural biology.
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S.H.S. Senarathne. "Feasibility of using Problematic Aquatic Weeds in Productive Manner by Generating Vermicompost in Coconut Triangle Area of Sri Lanka." CORD 33, no. 1 (April 1, 2017): 15. http://dx.doi.org/10.37833/cord.v33i1.52.
Full textAbstract:
Aquatic weeds cause severe productivity loss in agriculture. These plants invade lakes, ponds, rivers, canals and agricultural fields, becoming noxious weeds. The study was conducted at the vermicomposting unit of the Coconut Research Institute, Lunuwila, in the Low country Dry Zone of North Western province of Sri Lanka from August 2012 to May 2013 to find out the feasibility of producing vermicompost from three aquatic weeds; Salvinia molesta, Eichhornia crassipes and Lagenandra toxicaria. Vermicompost and compost were prepared separately from aquatic weeds and Gliricidia and Guinea grass combinations. During the vermicomposting process, growth parameters of earthworms; number of earthworms, was taken in every ten days interval further, physical, chemical and biological properties of compost and vermicompost were analyzed. Experiment was carried out in a Complete Randomized Design (CRD) with eight treatment and five replicates in each treatment. Eichhornia and Salvinia recorded the highest adult earthworm number and juvenile number with the lowest mortality rate. Electrical conductivity (6.75 dSm-1), organic carbon (13.21%), phosphorous (3.61%), potassium (5.03%) and calcium (6.12%) were significantly high in Lagenandra toxicaria, Gliricidia and Guinea grass treatment was significantly high in nitrogen content (3.93%) and low in C: N ratio (2.51), compared to aquatic weeds. Salvinia showed comparatively higher nitrogen content and lower C: N ratio among aquatic weeds. Both Eichhornia and Lagenandra showed significantly higher microbial activity. Vermicompost was superior in all the properties compared to compost in the same substrate. The study revealed that aquatic weeds such as Salvinia molesta, Eichhornia crassipes and Lagenandra toxicaria which are readily available in the coconut triangle can be successfully used to produce Vermicompost. It can be concluded that the Vermicompost produced from aquatic weeds locally could be a suitable organic fertilizer for organic coconut farming in Sri Lanka.
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González-Varo, Juan P., Sarah Díaz-García, Juan M. Arroyo, and Pedro Jordano. "Seed dispersal by dispersing juvenile animals: a source of functional connectivity in fragmented landscapes." Biology Letters 15, no. 7 (July 2019): 20190264. http://dx.doi.org/10.1098/rsbl.2019.0264.
Full textAbstract:
Juvenile animals generally disperse from their birthplace to their future breeding territories. In fragmented landscapes, habitat-specialist species must disperse through the anthropogenic matrix where remnant habitats are embedded. Here, we test the hypothesis that dispersing juvenile frugivores leave a footprint in the form of seed deposition through the matrix of fragmented landscapes. We focused on the Sardinian warbler ( Sylvia melanocephala ), a resident frugivorous passerine. We used data from field sampling of bird-dispersed seeds in the forest and matrix of a fragmented landscape, subsequent disperser identification through DNA-barcoding analysis, and data from a national bird-ringing programme. Seed dispersal by Sardinian warblers was confined to the forest most of the year, but warblers contributed a peak of seed-dispersal events in the matrix between July and October, mainly attributable to dispersing juveniles. Our study uniquely connects animal and plant dispersal, demonstrating that juveniles of habitat-specialist frugivores can provide mobile-link functions transiently, but in a seasonally predictable way.
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Maršálek, Petr, Ivana Mikuliková, Helena Modrá, and Zdeňka Svobodová. "Effect of prochloraz fungicide on neopterin and biopterin concentrations in blood plasma of common carp." Acta Veterinaria Brno 83, no. 2 (2014): 101–5. http://dx.doi.org/10.2754/avb201483020101.
Full textAbstract:
Neopterin and biopterin are often used as markers of cell mediated immunity. The aim of this study was to evaluate the effect of prochloraz on neopterin and biopterin concentrations in blood plasma of common carp as possible indicators for monitoring perturbations of the immune system caused by xenobiotics like pesticides. Prochloraz is a widely used imidazole fungicide in horticulture and agriculture. A total of 60 juvenile common carp were divided into four groups of 15 fish and exposed to prochloraz at concentrations of 0, 50, 150 and 380 µg·l-1, respectively. The total length of exposure was 28 days. Neopterin and biopterin concentrations were determined by reverse phase high performance liquid chromatography with fluorescence detection. Our results indicated that concentrations of neopterin (25 ± 7.6 nmol·l-1) and biopterin (190 ± 29 nmol·l-1) in plasma of untreated common carp were comparable with those in mammals. Neopterin concentrations significantly (P< 0.01) increased after exposure to prochloraz in comparison to non-exposed fish, while biopterin concentrations were not influenced by exposure to prochloraz. This study contains new data on neopterin and biopterin concentrations in fish plasma and investigates neopterin and biopterin in their non-traditional role as markers of cell mediated immunity of fish associated with pesticide exposure.
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Boseto, David, Clare Morrison, Patrick Pikacha, and Tikai Pitakia. "Biodiversity and conservation of freshwater fishes in selected rivers on Choiseul Island, Solomon Islands." South Pacific Journal of Natural and Applied Sciences 25, no. 1 (2007): 16. http://dx.doi.org/10.1071/sp07003.
Full textAbstract:
During a terrestrial biodiversity survey of Choiseul Island, we conducted freshwater fish surveys in seven sites between July 2005 and August 2006. We found 32 fish species from 15 families (38% of known Solomon Island freshwater fish). Most species were uncommon with the exception of Kuhlia marginata (6/7 sites), K. rupestris (5/7 sites) and Glossogobius sp. 1 (5/7 sites). No introduced species were found in any of the sites. Species richness ranged from 2-14 species per site and was highest in Lumutu River and Kolombangara River. This difference between sites is partially attributed to substrate type (higher richness in sites with gravel substrates than mud) and distance from the coast (higher richness near the coast than inland). The results of this survey in conjunction with a previous survey bring the total number of freshwater fish species on Choiseul Island to 41. This diversity is threatened by habitat degradation through sedimentation and over harvesting of some species. We recommend a number of activities to ameliorate these threats including seasonal banning of fish harvest during breeding periods and mass juvenile migrations, discouraging the practice of streamside agriculture, and education of locals on the negative impacts of logging on watershed health and productivity.
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Tulaby Dezfuly, Zahra, Amir Aramoon, Mojtaba Alishahi, Mostafa Halimi, and Roya Rahnama. "The Effects of Lead Toxicity on the Hematological Parameters Common Carp (Cyprinus carpio) at Varying Salinity Levels." Iranian Journal of Toxicology 14, no. 1 (January 10, 2020): 1–8. http://dx.doi.org/10.32598/ijt.14.1.1.
Full textAbstract:
Background: Lead (Pb) is an important metal used in industries, mining and agriculture. It is equally important to the aquatic ecosystems and has negative impact on the health of aquatic organisms. Methods: The LC50 of lead toxicity at varying salinities was first determined for 96 hours. Then juvenile fish were transferred to tanks individually and were exposed to 0, 15, 30, 60 and 120 mg/l of Pb at varying salt concentration of 0, 0.1, 0.2 or 0.4 g/l. The blood samples were taken after the 4th day and the hematological parameters were evaluated. Results: Red Blood Cells (RBC) and White Blood Cells (WBC) were decreased in almost all lead treated groups. The Hb levels decreased consistent with increasing lead concentrations (P<0.05). The mean corpuscular volume, hemoglobin and the concentration were not affected by the lead concentrations compared to those for the control group. The WBC and RBC counts showed an inverse correlation with the lead concentrations in the Pb-exposed fish. A direct correlation was also observed in the lead concentration and the heterophile rate (P<0.05). Conclusion: The results showed that salinity did not affect the hematological parameters, but the LC50 values decreased with increasing salinity.
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Khanna, Sharma, Ohri, Bhardwaj, Abd_Allah, Hashem, and Ahmad. "Impact of Plant Growth Promoting Rhizobacteria in the Orchestration of Lycopersicon esculentum Mill. Resistance to Plant Parasitic Nematodes: A Metabolomic Approach to Evaluate Defense Responses Under Field Conditions." Biomolecules 9, no. 11 (October 31, 2019): 676. http://dx.doi.org/10.3390/biom9110676.
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The present study deals with biological control of Meloidogyne incognita in 45-days old Lycopersicon esculentum, inoculated with Pseudomonas aeruginosa(M1) and Burkholderia gladioli (M2). The improved plant growth and biomass of nematode infested Plant growth promoting rhizobacteria (PGPR) inoculated plants was observed. Remarkable reduction in the numbers of second stage juvenile (J2s), root galls was recorded after treatment of microbes relative to experimental controls. Moreover, the lowered activities of oxidative stress markers (H2O2 (hydrogen peroxide), O2− (superoxide anion), malondialdehyde (MDA)) was estimated in plants after rhizobacterial supplementation. Higher activities of enzymatic (SOD (Superoxide dismutase), POD (Guaiacol peroxidase), CAT (Catalase), GPOX (Glutathione peroxidase), APOX (Ascorbate peroxidase), GST (Glutathione-S-transferase), GR (Glutathione reductase), DHAR (Dehydroascorbate reductase), PPO (Polyphenol oxidase)) and non-enzymatic (glutathione, ascorbic acid, tocopherol) antioxidants were further determined in nematode infected plants following the addition of bacterial strains. The upregulation of photosynthetic activities were depicted by evaluating plant pigments and gas exchange attributes. An increase in the levels of phenolic compounds (total phenols, flavonoids, anthocyanins), osmoprotectants (total osmolytes, carbohydrates, reducing sugars, trehalose, proline, glycine betaine, free amino acids) and organic acids (fumaric, succinic, citric, malic acid) were reflected in infected plants, showing further enhancement after application of biocontrol agents. The study revealed the understanding of plant metabolism, along with the initiative to commercially exploit the biocontrol agents as an alternative to chemical nematicides in infected fields for sustainable agriculture.
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Li, Peirong, Xinru Li, Wei Wang, Xiaoling Tan, Xiaoqi Wang, and Xueqing Yang. "Transcriptional identification of differentially expressed genes during the prepupal–pupal transition in the oriental armyworm, Mythimna separata (Walker) (Lepidoptera: Noctuidae)." Bulletin of Entomological Research 111, no. 4 (March 22, 2021): 485–98. http://dx.doi.org/10.1017/s0007485321000171.
Full textAbstract:
AbstractThe oriental armyworm, Mythimna separata (Walker) is a serious pest of agriculture that does particular damage to Gramineae crops in Asia, Europe, and Oceania. Metamorphosis is a key developmental stage in insects, although the genes underlying the metamorphic transition in M. separata remain largely unknown. Here, we sequenced the transcriptomes of five stages; mature larvae (ML), wandering (W), and pupation (1, 5, and 10 days after pupation, designated P1, P5, and P10) to identify transition-associated genes. Four libraries were generated, with 22,884, 23,534, 26,643, and 33,238 differentially expressed genes (DEGs) for the ML-vs-W, W-vs-P1, P1-vs-P5, and P5-vs-P10, respectively. Gene ontology enrichment analysis of DEGs showed that genes regulating the biosynthesis of the membrane and integral components of the membrane, which includes the cuticular protein (CP), 20-hydroxyecdysone (20E), and juvenile hormone (JH) biosynthesis, were enriched. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that DEGs were enriched in the metabolic pathways. Of these DEGs, thirty CP, seventeen 20E, and seven JH genes were differentially expressed across the developmental stages. For transcriptome validation, ten CP, 20E, and JH-related genes were selected and verified by real-time PCR quantitative. Collectively, our results provided a basis for further studies of the molecular mechanism of metamorphosis in M. separata.
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Sibly, Richard M., John M. Grady, Chris Venditti, and James H. Brown. "How body mass and lifestyle affect juvenile biomass production in placental mammals." Proceedings of the Royal Society B: Biological Sciences 281, no. 1777 (February 22, 2014): 20132818. http://dx.doi.org/10.1098/rspb.2013.2818.
Full textAbstract:
In mammals, the mass-specific rate of biomass production during gestation and lactation, here called maternal productivity, has been shown to vary with body size and lifestyle. Metabolic theory predicts that post-weaning growth of offspring, here termed juvenile productivity, should be higher than maternal productivity, and juveniles of smaller species should be more productive than those of larger species. Furthermore because juveniles generally have similar lifestyles to their mothers, across species juvenile and maternal productivities should be correlated. We evaluated these predictions with data from 270 species of placental mammals in 14 taxonomic/lifestyle groups. All three predictions were supported. Lagomorphs, perissodactyls and artiodactyls were very productive both as juveniles and as mothers as expected from the abundance and reliability of their foods. Primates and bats were unproductive as juveniles and as mothers, as expected as an indirect consequence of their low predation risk and consequent low mortality. Our results point the way to a mechanistic explanation for the suite of correlated life-history traits that has been called the slow–fast continuum.
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Louzao, Maite, Karine Delord, David García, Isabel Afán, José Manuel Arcos, and Henri Weimerskirch. "First days at sea: depicting migration patterns of juvenile seabirds in highly impacted seascapes." PeerJ 9 (May 11, 2021): e11054. http://dx.doi.org/10.7717/peerj.11054.
Full textAbstract:
Increasing human activities have detrimental consequences on marine ecosystems and their impact can have cumulative effects. Within marine ecosystems, seabirds respond to ecosystem variability and face multiple human pressures, especially threatened species. In long-lived species, juveniles and immatures could represent up to 50% of the total population, but their migratory movements remain largely unknown. Here, we depict the migratory patterns of juvenile Balearic shearwaters Puffinus mauretanicus, the most threatened European seabird, using miniaturised satellite transmitters. At the end of the 2012 breeding season, five tagged juveniles left the breeding colonies of Eivissa Island (western Mediterranean) the first week of July. They moved westwards to reach the Atlantic Ocean between 3 and 13 days afterwards. Juveniles showed a two-phase migratory pattern: they first travelled slower close to the breeding colonies, and then moved towards their wintering areas in the Atlantic Ocean by rapid directional movements. Environmental cues (e.g.,marine productivity, water mass distribution, frontal systems) might have a prominent role in driving the migratory patterns of juvenile Balearic shearwaters, moving from warm and poor marine areas in the Mediterranean Sea to cooler and rich non-breeding grounds in the Atlantic Ocean. Based on observational findings, we observed certain spatial overlap of juvenile Balearic shearwaters with areas of high human impact, but the relationship between flying travel speed and both fishing effort and cumulative human impacts were not statistically significant. These results suggest that more research is needed to assess whether the movement patterns of migrating juveniles are affected by human activities. Therefore, understanding the at-sea spatial ecology of juveniles should be a priority for research and conservation due to the importance of this population component in long-lived species, as well as assessing their vulnerability to multiple anthropogenic pressures.
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Marler, Thomas E., and Murukesan V. Krishnapillai. "Longitude, Forest Fragmentation, and Plant Size Influence Cycas micronesica Mortality Following Island Insect Invasions." Diversity 12, no. 5 (May 14, 2020): 194. http://dx.doi.org/10.3390/d12050194.
Full textAbstract:
Island invasions may cause severe changes in biodiversity, but the factors that influence these changes are not well understood. We established 120 plots in Cycas micronesica habitats throughout Guam in 2005 following the invasion of the armored scale Aulacaspis yasumatsui, then observed plant mortality through 2020. We used transects in Yap as benchmarks, as the Yap C. micronesica population is not threatened. The initial Guam plots contained about 1600 seedlings, 1160 juveniles, and 1240 mature plants per ha. Seedling mortality was 100% by 2006, juvenile mortality was 100% by 2014, and the 2020 census revealed 96% mortality of the plant population. Localities in western Guam and isolated forest fragments exhibited the greatest mortality, with 100% extirpation from two fragmented western localities. The juvenile and mature trees in Yap were unchanged from 2010 to 2018, but the seedling count was heterogeneous among the years. Constrained recruitment from seedlings to juveniles explained these dynamics. Yap transects contained about 6120 seedlings, 3400 juveniles, and 1250 mature plants per ha. Biological control of the invasive insects remains the acute conservation action needed for the Guam population. Lessons learned may be useful in other regions where invasions of non-native pests threaten biodiversity.
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Derégnaucourt, Sébastien, and Manfred Gahr. "Horizontal transmission of the father's song in the zebra finch ( Taeniopygia guttata )." Biology Letters 9, no. 4 (August 23, 2013): 20130247. http://dx.doi.org/10.1098/rsbl.2013.0247.
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As is the case for human speech, birdsong is transmitted across generations by imitative learning. Although transfer of song patterns from adults to juveniles typically occurs via vertical or oblique transmission, there is also evidence of horizontal transmission between juveniles of the same generation. Here, we show that a young male zebra finch ( Taeniopygia guttata ) that has been exposed to its father during the sensitive period for song learning can lead a brother, that has never heard the paternal song, to imitate some sounds of the father. Moreover, song similarity between the two brothers was higher than the similarity measured between the paternal song and the song of the brother that had a week-long exposure to the father. We speculate that the phenomenon of within-generation song learning among juveniles may be more widespread than previously thought and that when a juvenile evaluates potential models for imitative learning, a sibling may be as salient as an adult.
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Segura-Cobeña, Eduardo, Joanna Alfaro-Shigueto, Jeffrey Mangel, Angel Urzua, and Konrad Górski. "Stable isotope and fatty acid analyses reveal significant differences in trophic niches of smooth hammerhead Sphyrna zygaena (Carcharhiniformes) among three nursery areas in northern Humboldt Current System." PeerJ 9 (April 22, 2021): e11283. http://dx.doi.org/10.7717/peerj.11283.
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Fishery pressure on nursery areas of smooth hammerhead in northern Peruvian coast have become a serious threat to sustainability of this resource. Even though, some management actions focused on conservation of the smooth hammerhead populations were proposed in recent years, their scientific foundations are often limited, and biomass of smooth hammerhead in Peruvian waters continues to decrease. To inform management and conservation, this study aims to evaluate the trophic niche of smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast using stable isotope and fatty acid analyses. First, we compared the environmental characteristics of each nursery area (i.e., sea surface temperature and chlorophyll-a concentration) and concluded that nursery areas differed significantly and consistently in sea surface temperature. Subsequently, we evaluated isotopic composition of carbon and nitrogen and fatty acid profiles of muscle and liver tissues collected from juvenile smooth hammerhead from each nursery area. We found that juvenile smooth hammerhead captured in San José were enriched in heavier 13C and 15N isotopes compared to those captured in Máncora and Salaverry. Furthermore, the broadest isotopic niches were observed in juveniles from Máncora, whereas isotopic niches of juveniles from Salaverry and San José were narrower. This difference is primarily driven by the Humboldt Current System and associated upwelling of cold and nutrient rich water that drives increased primary production in San José and, to a less extent, in Salaverry. Compared to smooth hammerhead juveniles from Máncora, those from San José and Salaverry were characterised by higher essential fatty acid concentrations related to pelagic and migratory prey. We conclude that smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast differ significantly in their trophic niches. Thus, management and conservation efforts should consider each nursery area as a unique juvenile stock associated with a unique ecosystem and recognize the dependence of smooth hammerhead recruitment in San José and Salaverry on the productivity driven by the Humboldt Current System.
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Adekunle, O. K., and O. A. Akinsanmi. "Bioactivity of Fusarium oxysporum f. sp. glycines and Sclerotium rolfsii filtrates on egg hatching, survival and infectivity of juveniles of Meloidogyne incognita race 2." Australian Journal of Experimental Agriculture 45, no. 1 (2005): 99. http://dx.doi.org/10.1071/ea02129.
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The effects of culture filtrates of Fusarium oxysporum and Sclerotium rolfsii on egg hatching and juvenile survival of Meloidogyne incognita in vitro and impact of these filtrates on infectivity of M. incognita were investigated on soybean seedlings. Five- and 10-day-old filtrates of F. oxysporum caused 65 and 54% egg-hatching inhibition, while that of S. rolfsii caused 61 and 49% inhibition, respectively. Juveniles of M. incognita died within 6 days when incubated in 5-day-old filtrate of F. oxysporum, while the similar filtrate of S. rolfsii caused 100% juvenile mortality on the fifth day. Filtrates reduced root galling, egg population, number of adult females in soybean plants at harvest and also soil population. Culture filtrates could be used as source of biological nematicides.
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Jarrold, Michael D., and Philip L. Munday. "Diel CO 2 cycles and parental effects have similar benefits to growth of a coral reef fish under ocean acidification." Biology Letters 15, no. 2 (February 2019): 20180724. http://dx.doi.org/10.1098/rsbl.2018.0724.
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Parental effects have been shown to buffer the negative effects of within-generation exposure to ocean acidification (OA) conditions on the offspring of shallow water marine organisms. However, it remains unknown if parental effects will be impacted by the presence of diel CO 2 cycles that are prevalent in many shallow water marine habitats. Here, we examined the effects that parental exposure to stable elevated (1000 µatm) and diel-cycling elevated (1000 ± 300 µatm) CO 2 had on the survival and growth of juvenile coral reef anemonefish, Amphiprion melanopus . Juvenile survival was unaffected by within-generation exposure to either elevated CO 2 treatment but was significantly increased (8%) by parental exposure to diel-cycling elevated CO 2 . Within-generation exposure to stable elevated CO 2 caused a significant reduction in juvenile growth (10.7–18.5%); however, there was no effect of elevated CO 2 on growth when diel CO 2 cycles were present. Parental exposure to stable elevated CO 2 also ameliorated the negative effects of elevated CO 2 on juvenile growth, and parental exposure to diel CO 2 cycles did not alter the effects of diel CO 2 cycles on juveniles. Our results demonstrate that within-generation exposure to diel-cycling elevated CO 2 and parental exposure to stable elevated CO 2 had similar outcomes on juvenile condition. This study illustrates the importance of considering natural CO 2 cycles when predicting the long-term impacts of OA on marine ecosystems.
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Giroud, Sylvain, Sandrine Zahn, François Criscuolo, Isabelle Chery, Stéphane Blanc, Christopher Turbill, and Thomas Ruf. "Late-born intermittently fasted juvenile garden dormice use torpor to grow and fatten prior to hibernation: consequences for ageing processes." Proceedings of the Royal Society B: Biological Sciences 281, no. 1797 (December 22, 2014): 20141131. http://dx.doi.org/10.1098/rspb.2014.1131.
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Torpor is thought to slow age-related processes and to sustain growth and fattening of young individuals. Energy allocation into these processes represents a challenge for juveniles, especially for those born late in the season. We tested the hypothesis that late-born juvenile garden dormice ( Eliomys quercinus ) fed ad libitum (‘AL’, n = 9) or intermittently fasted (‘IF’, n = 9) use short torpor bouts to enhance growth and fat accumulation to survive winter. IF juveniles displayed more frequent and longer torpor bouts, compared with AL individuals before hibernation. Torpor frequency correlated negatively with energy expenditure and water turnover. Hence, IF juveniles gained mass at the same rate, reached similar pre-hibernation fattening and displayed identical hibernating patterns and mass losses as AL animals. We found no group differences in relative telomere length (RTL), an indicator of ageing, during the period of highest summer mass gain, despite greater torpor use by IF juveniles. Percentage change in RTL was negatively associated with mean and total euthermic durations among all individuals during hibernation. We conclude that torpor use promotes fattening in late-born juvenile dormice prior to hibernation. Furthermore, we provided the first evidence for a functional link between time spent in euthermy and ageing processes over winter.
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Willson, Mary F. "Loss of Habitat Connectivity Hinders Pair Formation and Juvenile Dispersal of Chucao Tapaculos in Chilean Rainforest." Condor 106, no. 1 (February 1, 2004): 166–71. http://dx.doi.org/10.1093/condor/106.1.166.
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Abstract Loss of connectivity among forest fragments of south-temperate rainforest in Chile reduced mating success of male Chucao Tapaculos (Scelorchilus rubecula) and the probability of juvenile dispersal. Of 159 chicks banded in 2000 and 2001, 19 of 91 (21%) in poorly connected fragments stayed in their natal fragments, overall, compared to only 2 of 68 (3%) in well-connected fragments. The frequency of unmated males was consistently higher in poorly connected fragments (12 of 65 males, or 18%) compared to well-connected fragments (1 of 82 males, or 1%). Chucao populations could be maintained most readily in this increasingly agricultural matrix by a network of woodlots with dense understory, connected by wooded corridors. La Pérdida de Conectividad de Hábitat Impide la Formación de Parejas y la Dispersión de Juveniles de Scelorchilus rubecula en la Selva Lluviosa de Chile Resumen. La pérdida de conectividad entre fragmentos de bosque de la selva lluviosa austral templada en Chile redujo el éxito de apareamiento de los machos y la probabilidad de dispersión de los juveniles en el tapaculo Scelorchilus rubecula. De 159 pichones anillados en 2000 y 2001, 19 de 91 (21%) individuos presentes en fragmentos poco conectados permanecieron en sus fragmentos natales, comparado con sólo 2 de 68 (3%) individuos que permanecieron en fragmentos bien conectados. La frecuencia de machos sin pareja fue consistentemente mayor en fragmentos poco conectados (12 de 65 machos, 18%) comparada con fragmentos bien conectados (1 de 82 machos, 1%). Las poblaciones de S. rubecula podrían ser mantenidas de modo más eficiente en esta matriz creciente de agricultura mediante una red de bosques con sotobosque denso, conectados por corredores de bosque.
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Possamai, Bianca, Ana Carolina dos Passos, and Bárbara Maichak de Carvalho. "Length–weight relationships comparison between juveniles and adults of fish species from the mangroves of south Brazil." Acta Scientiarum. Biological Sciences 42 (July 1, 2020): e51310. http://dx.doi.org/10.4025/actascibiolsci.v42i1.51310.
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This study reports the length‐weight relationships (LWRs) for 8 fish species that inhabit mangroves. Many fisheries depend on mangroves, which serve as nursery and feeding areas for the juvenile stage of fishes, shrimp, and other fishery resources. In this sense, mangroves provide many ecosystem services, therefore increasing the basic biological knowledge of these ecosystems can help to understand their functioning and create conservation strategies. The majority of LWR studies do not consider juveniles, and it is important to consider these differences as juveniles can grow differently from adults. The fishes were collected from Perequê mangrove, Paraná, Brazil between 2008 and 2010. A variety of fishery gears were employed, including trammel nets, fyke nets, and traps made with plastic bottles combined with four baits. The specimens were measured (weight and length), sexed and evaluated for maturational stage. For the adults, the LWRs were calculated separately by the sex, while juvenile LWRs were estimated together. In general, there were differences in growth type between sexes and life stages. Some species showed differences compared to FishBase estimations, but this could be due to the lengths (and life stage) of the individuals used in the present study compared to FishBase. The discrepancies between adult, juvenile and FishBase estimations showed the importance of considering these aspects in studies using LWR.
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Boogert, Neeltje J., Robert F. Lachlan, Karen A. Spencer, Christopher N. Templeton, and Damien R. Farine. "Stress hormones, social associations and song learning in zebra finches." Philosophical Transactions of the Royal Society B: Biological Sciences 373, no. 1756 (August 13, 2018): 20170290. http://dx.doi.org/10.1098/rstb.2017.0290.
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The use of information provided by others is a common short-cut adopted to inform decision-making. However, instead of indiscriminately copying others, animals are often selective in what, when and whom they copy. How do they decide which ‘social learning strategy’ to use? Previous research indicates that stress hormone exposure in early life may be important: while juvenile zebra finches copied their parents' behaviour when solving novel foraging tasks, those exposed to elevated levels of corticosterone (CORT) during development copied only unrelated adults. Here, we tested whether this switch in social learning strategy generalizes to vocal learning. In zebra finches, juvenile males often copy their father's song; would CORT-treated juveniles in free-flying aviaries switch to copying songs of other males? We found that CORT-treated juveniles copied their father's song less accurately as compared to control juveniles. We hypothesized that this could be due to having weaker social foraging associations with their fathers, and found that sons that spent less time foraging with their fathers produced less similar songs. Our findings are in line with a novel hypothesis linking early-life stress and social learning: early-life CORT exposure may affect social learning indirectly as a result of the way it shapes social affiliations. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.
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Gray, Lindsey J., Gregory A. Sword, Michael L. Anstey, Fiona J. Clissold, and Stephen J. Simpson. "Behavioural phase polyphenism in the Australian plague locust ( Chortoicetes terminifera )." Biology Letters 5, no. 3 (March 4, 2009): 306–9. http://dx.doi.org/10.1098/rsbl.2008.0764.
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Swarming and the expression of phase polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust ( Chortoicetes terminifera ) regularly forms migratory bands and swarms, but is claimed not to express phase polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual's lifetime in response to a change in population density.
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Small, Stacy L., Frank R. Thompson, Geoffrey R. Geupel, and John Faaborg. "Spotted Towhee Population Dynamics in a Riparian Restoration Context." Condor 109, no. 4 (November 1, 2007): 721–33. http://dx.doi.org/10.1093/condor/109.4.721.
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Abstract We investigated factors at multiple scales that might influence nest predation risk for Spotted Towhees (Pipilo maculatus) along the Sacramento River, California, within the context of large-scale riparian habitat restoration. We used the logistic-exposure method and Akaike's information criterion (AIC) for model selection to compare predator search, predator abundance, restoration, and temporal effects hypotheses. Our candidate models represented restoration, temporal, nest activity, nest concealment, agriculture, and flood effects. Restoration sites did function as breeding habitat, with nest survival comparable to mature forest sites and some young being produced. The best-supported models contained the covariates cowbird young in host nest and calendar date. All supported models contained the covariate cowbird young, the only variable with a strong effect. In contrast to our prediction, nest survival increased with cowbird young in the nest, implicating adult cowbirds in nest predation events. Nest survival declined throughout the breeding season and increased marginally with nest concealment. We calculated the finite rate of population increase (λ), using a model that incorporated nest success estimates for parasitized and unparasitized nests, double brooding, the locally observed cowbird parasitism rate for Spotted Towhees, number of young fledged from successful parasitized and unparasitized nests, adult survival and a range of juvenile survival values, estimated as percentages of adult survival. Values of λ did not approach the replacement level of one, indicating that this population is not self-sustaining. We recommend extensive habitat restoration in the floodplain landscape, ideally in conjunction with cowbird control, to reduce nest predation and parasitism pressures.
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Koyama, Akihiko, Taiga Hirata, Yuki Kawahara, Hiroki Iyooka, Haruka Kubozono, Norio Onikura, Shinji Itaya, and Tomoko Minagawa. "Habitat suitability maps for juvenile tri-spine horseshoe crabs in Japanese intertidal zones: A model approach using unmanned aerial vehicles and the Structure from Motion technique." PLOS ONE 15, no. 12 (December 23, 2020): e0244494. http://dx.doi.org/10.1371/journal.pone.0244494.
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The tri-spine horseshoe crab, Tachypleus tridentatus, is a threatened species that inhabits coastal areas from South to East Asia. A Conservation management system is urgently required for managing its nursery habitats, i.e., intertidal flats, especially in Japan. Habitat suitability maps are useful in drafting conservation plans; however, they have rarely been prepared for juvenile T. tridentatus. In this study, we examined the possibility of constructing robust habitat suitability models (HSMs) for juveniles based on topographical data acquired using unmanned aerial vehicles and the Structure from Motion (UAV-SfM) technique. The distribution data of the juveniles in the Tsuyazaki and Imazu intertidal flats from 2017 to 2019 were determined. The data were divided into a training dataset for HSM construction and three test datasets for model evaluation. High accuracy digital surface models were built for each region using the UAV-SfM technique. Normalized elevation was assessed by converting the topographical models that consider the tidal range in each region, and the slope was calculated based on these models. Using the training data, HSMs of the juveniles were constructed with normalized elevation and slope as the predictor variables. The HSMs were evaluated using the test data. The results showed that HSMs exhibited acceptable discrimination performance for each region. Habitat suitability maps were built for the juveniles in each region, and the suitable areas were estimated to be approximately 6.1 ha of the total 19.5 ha in Tuyazaki, and 3.7 ha of the total 7.9 ha area in Imazu. In conclusion, our findings support the usefulness of the UAV-SfM technique in constructing HSMs for juvenile T. tridentatus. The monitoring of suitable habitat areas for the juveniles using the UAV-SfM technique is expected to reduce survey costs, as it can be conducted with fewer investigators over vast intertidal zones within a short period of time.
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Ditmer, Mark A., David L. Garshelis, Karen V. Noyce, Andrew W. Haveles, and John R. Fieberg. "Are American black bears in an agricultural landscape being sustained by crops?" Journal of Mammalogy 97, no. 1 (October 14, 2015): 54–67. http://dx.doi.org/10.1093/jmammal/gyv153.
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Abstract Human-altered landscapes are thought to reduce habitat quality for many forest-dependent species, but some omnivorous, opportunist species take advantage of human-related food sources, such as garbage and crops. It is unknown, however, whether anthropogenic foods can sustain populations in areas with relatively little natural habitat. We studied (2007–2012) a population of American black bears ( Ursus americanus ) at the western periphery of their range in Minnesota, in a landscape that was heavily impacted by agriculture (~50%). We estimated the dietary contributions of corn and sunflowers (2–4% of the landscape) versus seasonally available natural foods (spring vegetation, ants, deer, fruit, and nuts) with stable isotope analyses (δ 13 C and δ 15 N) of 110 hair samples from 51 bears. We identified associations between diet and sex, age, body size and condition, reproductive status, space use, habitat connectivity, and natural food abundance. At the population level, adult males and adult females without cubs consumed considerable crops in fall (95% credible intervals: males = 19–46% of diet, females = 10–40%), but females with cubs and juvenile bears rarely consumed crops. Individual estimates of crop consumption were positively correlated with the proportion of GPS-collar locations in crop fields. Females, but not males, decreased crop consumption in years with high availability of natural fall foods. Further, the degree of crop consumption was more closely tied to local crop availability and landscape composition in females than in males. Weight and fat were positively correlated with crop use for both sexes, and males’ use of crops also increased with their physical stature, suggesting that crops provided substantial caloric benefits to bears and that social dominance may have influenced foraging decisions. However, a large segment of this bear population (44% of sampled bear–years) made little use of crops, and crops accounted for more than half the fall diet for only 14% of the population. Whereas some bears clearly benefited from consumption of crops, we conclude that a population of bears could be sustained in this largely agricultural region even without crops as a food source.