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Letteratura scientifica selezionata sul tema "Dunnarts"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 2 febbraio 2022

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Articoli di riviste sul tema "Dunnarts"

Bleicher, Sonny S., e Christopher R. Dickman. "On the landscape of fear: shelters affect foraging by dunnarts (Marsupialia, Sminthopsis spp.) in a sandridge desert environment". Journal of Mammalogy 101, n. 1 (15 febbraio 2020): 281–90. http://dx.doi.org/10.1093/jmammal/gyz195.

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Abstract Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing the risk of predation for small prey species. The postfire effect of predation has especially deleterious effects in Australian habitats owing to the presence of invasive mammalian predators, the red fox (Vulpes vulpes) and feral cat (Felis catus), that rapidly exploit burned habitats. Here, we investigated whether the provision of artificial shelter could alleviate the risk of predation perceived by two species of small marsupial, the dunnarts Sminthopsis hirtipes and S. youngsoni, in open postfire habitat in the sandridge system of the Simpson Desert, central Australia. We installed artificial shelters constructed from wire mesh that allowed passage of the dunnarts but not of their predators at one site, and measured and compared the perceived risk of predation by the dunnarts there with those on a control site using optimal patch-use theory (giving-up densities, GUDs). GUDs were lower near artificial shelters than away from them, and near dune crests where dunnarts typically forage, suggesting that the shelters acted as corridors for dunnarts to move up to the crests from burrows in the swales. Foraging was lower near the crest in the control plot. Two-day foraging bouts were observed in dunnart activity, with recruitment to GUD stations occurring a day earlier in the augmented shelter plot. Despite these results, the effects of the shelters were localized and not evident at the landscape scale, with GUDs reduced also in proximity to sparse natural cover in the form of regenerating spinifex grass hummocks. Mapping dunnart habitat use using the landscape of fear (LOF) framework confirmed that animals perceived safety near shelter and risk away from it. We concluded that the LOF framework can usefully assess real-time behavioral responses of animals to management interventions in situations where demographic responses take longer to occur.

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Read, John L., Matthew J. Ward e Katherine E. Moseby. "Factors that influence trap success of sandhill dunnarts (Sminthopsis psammophila) and other small mammals in Triodia dunefields of South Australia". Australian Mammalogy 37, n. 2 (2015): 212. http://dx.doi.org/10.1071/am14020.

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Optimised detection and sensitivity of fauna-monitoring programs is essential for the adaptive management of threatened species. We describe the influence of trap type, trapping duration and timing on the detection rates of small vertebrates, in particular the nationally endangered sandhill dunnart (Sminthopsis psammophila) in its two primary populations in South Australia. A total of 118 and 155 sandhill dunnarts were captured from the Middleback and Yellabinna regions, respectively, from five trapping sessions between 2008 and 2012. Wide deep pitfall traps (225 mm diameter × 600–700 mm deep) captured significantly more adult sandhill dunnarts than shorter, narrower pitfalls (150 mm diameter × 500 mm deep) or Elliott traps. Deep pitfall traps also captured significantly more hopping mice (Notomys mitchellii) but smaller mammal species were equally trapable in deep or short pitfall traps. Capture rates declined through successive nights of trapping. Capture rates of sandhill dunnarts were greatest in one study region when the moon illumination was less than 40% compared with fuller moon phases but were not affected by moon illumination in the other study region. The results suggest that higher capture rates of sandhill dunnarts will be achieved when using wide, deep pitfall traps on dark nights during the first two nights of trapping. Trapping in summer detected more juvenile sandhill dunnarts than trapping in winter.

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Haythornthwaite, Adele S. "Microhabitat use and foraging behaviour of Sminthopsis youngsoni (Marsupialia:Dasyuridae) in arid central Australia". Wildlife Research 32, n. 7 (2005): 609. http://dx.doi.org/10.1071/wr04126.

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In this study, fluorescent pigment tracking was used to determine the microhabitat use and foraging behaviour of a small insectivorous marsupial, Sminthopsis youngsoni (the lesser hairy-footed dunnart), in the dunefields of the Simpson Desert, south-western Queensland. In total, 25 successful trails were traced over the duration of this study, between March 1996 and April 1998. Nocturnal foraging trails were identified, then the distance travelled by the dunnart through each microhabitat type (nine in all) was measured and accumulated for each trail and compared with surrounding available microhabitats along control trails. This provided an index of selectivity of microhabitat use. Terrestrial invertebrates were collected from both actual and control trails to measure food availability. Dunnarts strongly selected open microhabitats when foraging, with the periphery of spinifex hummocks (up to 20 cm from the edge of a spinifex hummock) being favoured. Spinifex itself was avoided unless shelter was sought (i.e. immediately after release). Potential invertebrate prey captured along the actual trails travelled by dunnarts tended to occur in greater numbers and were larger than those captured along the control trails, indicating that dunnarts can accurately locate resource-rich areas in which to forage. Clearly, the foraging strategies used by this species enable it to successfully exploit patchy and unpredictable food resources, thereby ensuring its continued persistence and relative abundance in an unstable environment.

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Langman, C., S. Orgeig e C. B. Daniels. "Alterations in composition and function of surfactant associated with torpor in Sminthopsis crassicaudata". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 271, n. 2 (1 agosto 1996): R437—R445. http://dx.doi.org/10.1152/ajpregu.1996.271.2.r437.

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Cold profoundly influences lung compliance in homeothermic mammals. Much of this effect has traditionally been attributed to the inactivation of the surfactant system. However, many mammals undergo large fluctuations in body temperature (heterothermic mammals). Here, the surfactant lipid composition and lung compliance of warm-active dunnarts (Sminthopsis crassicaudata) and the homeothermic mouse (Mus musculus) [body temperature (Tb) = 35-37 degrees C] were compared with those of dunnarts killed after 1,4 or 8 h of torpor (Tb < 20 degrees C). Lung compliance was measured before and after the removal of surfactant, and tissue compliance was determined by inflating the lung with saline. Relative to total phospholipid (PL), mouse surfactant contained proportionately less phosphatidylinositol but more cholesterol (Chol) and phosphatidylglycerol than that of the dunnart. Lung compliance was lower in dunnarts than in mice, consistent with an allometric effect. Surfactant levels, including total PL, Chol, and disaturated phospholipid (DSP) increased during torpor. The relative proportions of Chol and DSP increased after 4 and 8 h, respectively. In marked contrast to previous studies on the behavior of isolated lungs from homeothermic mammals, in our study the lung compliance of dunnarts remained unchanged throughout torpor. Tissue compliance decreased at 1 and 4 h of torpor, but this decrease was abolished by 8 h. It appears that the surfactant of the dunnarts counteracted the negative effect of tissue compliance at 1 and 4 h, an effect not present in homeothermic mammals. However, because lung compliance was maintained at 1 h of torpor in the absence of a compositional change in surfactant lipids, the changes in lipid composition observed at 4 and 8 h of torpor are thought to relate to functions of surfactant other than that of maintaining lung compliance.

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Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels e David Palmer. "Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata". Journal of Applied Physiology 84, n. 1 (1 gennaio 1998): 146–56. http://dx.doi.org/10.1152/jappl.1998.84.1.146.

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Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels, and David Palmer. Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata. J. Appl. Physiol. 84(1): 146–156, 1998.—Torpor changes the composition of pulmonary surfactant (PS) in the dunnart Sminthopsis crassicaudata [C. Langman, S. Orgeig, and C. B. Daniels. Am. J. Physiol. 271 ( Regulatory Integrative Comp. Physiol. 40): R437–R445, 1996]. Here we investigated the surface activity of PS in vitro. Five micrograms of phospholipid per centimeter squared surface area of whole lavage (from mice or from warm-active, 4-, or 8-h torpid dunnarts) were applied dropwise onto the subphase of a Wilhelmy-Langmuir balance at 20°C and stabilized for 20 min. After 4 h of torpor, the adsorption rate increased, and equilibrium surface tension (STeq), minimal surface tension (STmin), and the %area compression required to achieve STmin decreased, compared with the warm-active group. After 8 h of torpor, STmin decreased [from 5.2 ± 0.3 to 4.1 ± 0.3 (SE) mN/m]; %area compression required to achieve STmindecreased (from 43.4 ± 1.0 to 27.4 ± 0.8); the rate of adsorption decreased; and STeqincreased (from 26.3 ± 0.5 to 38.6 ± 1.3 mN/m). ST-area isotherms of warm-active dunnarts and mice at 20°C had a shoulder on compression and a plateau on expansion. These disappeared on the isotherms of torpid dunnarts. Samples of whole lavage (from warm-active and 8-h torpor groups) containing 100 μg phospholipid/ml were studied by using a captive-bubble surfactometer at 37°C. After 8 h of torpor, STmin increased (from 6.4 ± 0.3 to 9.1 ± 0.3 mN/m) and %area compression decreased in the 2nd (from 88.6 ± 1.7 to 82.1 ± 2.0) and 3rd (from 89.1 ± 0.8 to 84.9 ± 1.8) compression-expansion cycles, compared with warm-active dunnarts. ST-area isotherms of warm-active dunnarts at 37°C did not have a shoulder on compression. This shoulder appeared on the isotherms of torpid dunnarts. In conclusion, there is a strong correlation between in vitro changes in surface activity and in vivo changes in lipid composition of PS during torpor, although static lung compliance remained unchanged (see Langman et al. cited above). Surfactant from torpid animals is more active at 20°C and less active at 37°C than that of warm-active animals, which may represent a respiratory adaptation to low body temperatures of torpid dunnarts.

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Lang, Carol J., Anthony D. Postle, Sandra Orgeig, Fred Possmayer, Wolfgang Bernhard, Amiya K. Panda, Klaus D. Jürgens, William K. Milsom, Kaushik Nag e Christopher B. Daniels. "Dipalmitoylphosphatidylcholine is not the major surfactant phospholipid species in all mammals". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 289, n. 5 (novembre 2005): R1426—R1439. http://dx.doi.org/10.1152/ajpregu.00496.2004.

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Pulmonary surfactant, a complex mixture of lipids and proteins, lowers the surface tension in terminal air spaces and is crucial for lung function. Within an animal species, surfactant composition can be influenced by development, disease, respiratory rate, and/or body temperature. Here, we analyzed the composition of surfactant in three heterothermic mammals (dunnart, bat, squirrel), displaying different torpor patterns, to determine: 1) whether increases in surfactant cholesterol (Chol) and phospholipid (PL) saturation occur during long-term torpor in squirrels, as in bats and dunnarts; 2) whether surfactant proteins change during torpor; and 3) whether PL molecular species (molsp) composition is altered. In addition, we analyzed the molsp composition of a further nine mammals (including placental/marsupial and hetero-/homeothermic contrasts) to determine whether phylogeny or thermal behavior determines molsp composition in mammals. We discovered that like bats and dunnarts, surfactant Chol increases during torpor in squirrels. However, changes in PL saturation during torpor may not be universal. Torpor was accompanied by a decrease in surfactant protein A in dunnarts and squirrels, but not in bats, whereas surfactant protein B did not change in any species. Phosphatidylcholine (PC)16:0/16:0 is highly variable between mammals and is not the major PL in the wombat, dunnart, shrew, or Tasmanian devil. An inverse relationship exists between PC16:0/16:0 and two of the major fluidizing components, PC16:0/16:1 and PC16:0/14:0. The PL molsp profile of an animal species is not determined by phylogeny or thermal behavior. We conclude that there is no single PL molsp composition that functions optimally in all mammals; rather, surfactant from each animal is unique and tailored to the biology of that animal.

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Knight, K. "DUNNARTS' DEVELOPMENT ADAPTS". Journal of Experimental Biology 215, n. 9 (11 aprile 2012): iii. http://dx.doi.org/10.1242/jeb.073072.

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Yousef, A., e L. Selwood. "Embryonic development in culture of the marsupials Antechinus stuartii (Macleay) and Sminthopsis macroura (Spencer) during preimplantation stages". Reproduction, Fertility and Development 5, n. 4 (1993): 445. http://dx.doi.org/10.1071/rd9930445.

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Forty-nine blastocysts from 11 brown antechinus, Antechinus stuartii, and 96 blastocysts from 17 stripe-faced dunnarts, Sminthopsis macroura, were used to develop a culture system for embryos during preimplantation stages. Blastocysts of brown antechinus were collected on Days 6-9 for unilaminar stages, Days 16-21 for bilaminar stages and Days 20 and 21 for trilaminar stages. Blastocysts of stripe-faced dunnarts were collected on Day 6 for unilaminar stages, Days 6-8 for bilaminar stages and Day 8 for trilaminar stages. Culture media were Dulbecco's modified Eagle's medium (DMEM) with 4.5% glucose and Whittingham's T6 medium both of which were supplemented with 5, 10, 12.5 and 20% fetal calf serum (FCS). Antechinus serum (5%) and bovine serum albumin (0.1%, 0.2%) were also added to some media. Human amniotic fluid (HAF) and Monomed media were also tested. Blastocysts were cultured at 35 degrees C in 5% CO2 in air. DMEM + 10% FCS and HAF supported normal development for the longest periods and over the greatest range of stages. Developmental failure of blastocysts in vitro during expansion of the unilaminar blastocyst and formation of the bilaminar blastocyst suggests that these stages may be dependent on uterine signals. When cultured in DMEM + 10% FCS, the rate of development of bilaminar and trilaminar blastocysts into organogenesis was 4 h slower than in vivo in the stripe-faced dunnart and about 6 h slower than in vivo in the brown antechinus. Embryos of stripe-faced dunnarts were cultured to within 18 h of birth.

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Webb, Jonathan K., David Pearson e Richard Shine. "A small dasyurid predator (Sminthopsis virginiae) rapidly learns to avoid a toxic invader". Wildlife Research 38, n. 8 (2011): 726. http://dx.doi.org/10.1071/wr10206.

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Context Invasive species are a leading cause of extinctions, yet predicting their ecological impacts poses a formidable challenge for conservation biologists. When native predators are naïve to invaders, they may lack appropriate behaviours to deal with the invader. In northern Australia, the invasion of the highly toxic cane toad (Rhinella marina) has caused serious population declines of reptilian and mammalian predators that are ill equipped to deal with toad toxins. Cane toads recently invaded the Kimberley region of Western Australia, where they potentially threaten several species of small dasyurid predators. Aims We investigated whether red-cheeked dunnarts (Sminthopsis virginiae) attack cane toads, and if so, whether individuals subsequently learn to avoid toads as prey. Methods We quantified feeding and learning behaviours in toad-naïve red-cheeked dunnarts from the north Kimberley in Western Australia. Key results All toad-naïve dunnarts attacked toads during their first encounter. Most dunnarts bit the toad on the snout, killed it by biting the cranium, and consumed the toad snout-first, thereby initially avoiding the toad’s parotoid glands. Most dunnarts partially consumed toads before discarding them, and only one animal showed visible signs of toad poisoning. All dunnarts rapidly learnt to avoid toads as prey after one or two encounters. Predators rejected toads as prey for the duration of the study (22 days), suggesting long-term retention of the knowledge that toads are noxious. Conclusions Our results show that red-cheeked dunnarts rapidly learn to avoid cane toads as prey. Implications Our study was limited by small sample sizes, but our results suggest that small dasyurids can adapt to the cane toad invasion via taste aversion learning.

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Woolley, P. A. "Diurnal resting sites of the nocturnal dasyurid marsupial Sminthopsis douglasi in Bladensburg National Park, Queensland". Australian Mammalogy 39, n. 1 (2017): 121. http://dx.doi.org/10.1071/am16013.

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An attempt has been made to determine where Julia Creek dunnarts (Sminthopsis douglasi), small nocturnal dasyurid marsupials, rest during the day under differing seasonal conditions. A short-term study was carried out in Bladensburg National Park, near the southern edge of its known distribution on the Mitchell grass downs in Queensland. Radio-collared individuals were located in cracks and holes. None of the males and females (including one with young in the pouch) were found to use the same resting site over periods of up to nine days, suggesting that they may be nomadic. Climatic factors may have affected the size of the dunnart population over the course of the study.

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Più fonti

Tesi sul tema "Dunnarts"

Bjursell, Alice. "Identifying the reproductive state of female Julia Creek dunnarts (Sminthopsis douglasi) by behavioural observations". University of Southern Queensland, Faculty of Sciences, 2006. http://eprints.usq.edu.au/archive/00004243/.

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[Abstract]: The Julia Creek dunnart (Sminthopsis douglasi) is an endangered carnivorous marsupial. A recovery plan for the species has been initiated by Queensland Parks and Wildlife Service, which includes captive breeding.An important factor in breeding S. douglasi is the identification of oestrus. The current method to identify oestrus consists of examining urine samplesfor presence of cornified cells. To collect urine, the animals have to be removed from their cages and restrained. This method is stressful for theanimals, as well as time consuming. The aim of this study was to identify specific behaviour of S. douglasi associated with oestrus, which could be readily observed without the need for handling the animal. This wouldprovide a non-invasive way of identifying oestrus, which would facilitate breeding the species in captivity and planning conservation programs.Behaviour of S. douglasi was observed throughout the night by video recording. The most striking result was the increase in activity of the female when she was in oestrus compared to non-oestrus. The most informativebehaviour to observe was entry by the female into the nest box and the frequency with which she entered the area closest to the wall of the enclosure. A discriminant function analysis generated an equation with anover-all predictive power (OPP, the probability of making an accurate identification of reproductive state) of 89%. This result was obtained by watching two random five-minute periods of activity. The equation was tested and verified with new individuals and attained a similar level of OPP. However, the equation was less accurate when the observed female’s social context was changed from being housed adjacent to a male, to being accompanied by another female or housed singularly. Consistent with thesensitivity of activity levels as an indicator, the distance run in an exercise wheel was also a good predictor of oestrous state. Females ran a significantly longer distance in their exercise wheel when in oestruscompared to non-oestrus (p<0.001).

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Hayter, Dawn. "Reproductive and social behaviour of the dunnart, sminthopsis crassicaudata /". Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09SB/09sbh426.pdf.

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Hocking, Michael. "Social interactions and reproductive behaviour of the fat-tailed dunnart, Sminthopsis crassicaudata, in captivity /". Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09SPS/09spsh685.pdf.

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Libri sul tema "Dunnarts"

Mitchell, Abbie, e Astred Hicks. Hollow Is a Home. CSIRO Publishing, 2019. http://dx.doi.org/10.1071/9781486308064.

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Do you know what a tree hollow is? To you and me, a tree hollow is just a hole, cavity or tunnel in a tree or branch. But to an animal, that hollow may be a bedroom, hiding place, nursery or shelter. It is the ultimate tree house! Come and take a peek inside the amazing world of tree hollows and discover more than 340 species of incredible Australian animals that call hollows home. With colour photos of glorious gliders, darting dunnarts, minute microbats and many more, this book is full of fun facts about animals that use tree hollows as places for resting, nesting or hiding. Find out how hollows are created, why they are threatened, and meet scientists who spend their time hollow-hunting. There are also plenty of tips on how you can spot hollows yourself, help to protect the environment and encourage habitat for hollow-dependent animals. Perfect for primary-aged readers.

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Dunnas. Mustér, CH: Romania, 1993.

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Dunnan, Nancy. Dunnan's Guide To Your Investment$ 2001: The Year-Round Investment Sourcebook for Managing Your Personal Finances (Dunnan's Guide to Your Investments). Collins, 2000.

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Dunnan, Nancy. Dunnan's Guide To Your Investment$ 2001: The Year-Round Investment Sourcebook for Managing Your Personal Finances (Dunnan's Guide to Your Investments). Collins, 2000.

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Dunnan's Guide to Your Investment$ 2000: The Year-Round Investment Sourcebook for Managing Your Personal Finances (Dunnan's Guide to Your Investments, 2000). Collins, 2000.

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Dunnan, Nancy. Dun & Bradstreet Guide to $Your Investments$: 1995 (Dunnan's Guide to Your Investments). Perennial, 1995.

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Dunnan, Nancy. Dun & Bradstreet Guide to $Your Investments$: 1997 (Dunnan's Guide to Your Investments). HarperCollins Publishers, 1997.

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Capitoli di libri sul tema "Dunnarts"

Dwyer, Tim, Kim Marriott e Michael Wybrow. "Dunnart: A Constraint-Based Network Diagram Authoring Tool". In Graph Drawing, 420–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-00219-9_41.

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