Journal articles on the topic 'Mammal decline'
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1
Lawes, Michael J., Brett P. Murphy, Alaric Fisher, John C. Z. Woinarski, Andrew C. Edwards, and Jeremy Russell-Smith. "Small mammals decline with increasing fire extent in northern Australia: evidence from long-term monitoring in Kakadu National Park." International Journal of Wildland Fire 24, no. 5 (2015): 712. http://dx.doi.org/10.1071/wf14163.
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Small mammal (<2 kg) numbers have declined dramatically in northern Australia in recent decades. Fire regimes, characterised by frequent, extensive, late-season wildfires, are implicated in this decline. Here, we compare the effect of fire extent, in conjunction with fire frequency, season and spatial heterogeneity (patchiness) of the burnt area, on mammal declines in Kakadu National Park over a recent decadal period. Fire extent – an index incorporating fire size and fire frequency – was the best predictor of mammal declines, and was superior to the proportion of the surrounding area burnt and fire patchiness. Point-based fire frequency, a commonly used index for characterising fire effects, was a weak predictor of declines. Small-scale burns affected small mammals least of all. Crucially, the most important aspects of fire regimes that are associated with declines are spatial ones; extensive fires (at scales larger than the home ranges of small mammals) are the most detrimental, indicating that small mammals may not easily escape the effects of large and less patchy fires. Notwithstanding considerable management effort, the current fire regime in this large conservation reserve is detrimental to the native mammal fauna, and more targeted management is required to reduce fire size.
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Woinarski, J. C. Z., M. Armstrong, K. Brennan, A. Fisher, A. D. Griffiths, B. Hill, D. J. Milne, et al. "Monitoring indicates rapid and severe decline of native small mammals in Kakadu National Park, northern Australia." Wildlife Research 37, no. 2 (2010): 116. http://dx.doi.org/10.1071/wr09125.
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Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was established in northern Australia’s largest and best-resourced conservation reserve. Aims. The present study aims to detect change in the native small-mammal fauna of Kakadu National Park, in the monsoonal tropics of northern Australia, over the period of 1996–2009, through an extensive monitoring program, and to consider factors that may have contributed to any observed change. Methods. The small-mammal fauna was sampled in a consistent manner across a set of plots established to represent the environmental variation and fire regimes of Kakadu. Fifteen plots were sampled three times, 121 plots sampled twice and 39 plots once. Resampling was typically at 5-yearly intervals. Analysis used regression (of abundance against date), and Wilcoxon matched-pairs tests to assess change. For resampled plots, change in abundance of mammals was related to fire frequency in the between-sampling period. Key results. A total of 25 small mammal species was recorded. Plot-level species richness and total abundance decreased significantly, by 54% and 71%, respectively, over the course of the study. The abundance of 10 species declined significantly, whereas no species increased in abundance significantly. The number of ‘empty’ plots increased from 13% in 1996 to 55% in 2009. For 136 plots sampled in 2001–04 and again in 2007–09, species richness declined by 65% and the total number of individuals declined by 75%. Across plots, the extent of decline increased with increasing frequency of fire. The most marked declines were for northern quoll, Dasyurus hallucatus, fawn antechinus, Antechinus bellus, northern brown bandicoot, Isoodon macrourus, common brushtail possum, Trichosurus vulpecula, and pale field-rat, Rattus tunneyi. Conclusions. The native mammal fauna of Kakadu National Park is in rapid and severe decline. The cause(s) of this decline are not entirely clear, and may vary among species. The most plausible causes are too frequent fire, predation by feral cats and invasion by cane toads (affecting particularly one native mammal species). Implications. The present study has demonstrated a major decline in a key conservation reserve, suggesting that the mammal fauna of northern Australia may now be undergoing a decline comparable to the losses previously occurring elsewhere in Australia. These results suggest that there is a major and urgent conservation imperative to more precisely identify, and more effectively manage, the threats to this mammal fauna.
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Lyman, R. Lee. "Terminal Pleistocene change in mammal communities in southeastern Washington State, USA." Quaternary Research 81, no. 2 (March 2014): 295–304. http://dx.doi.org/10.1016/j.yqres.2013.10.019.
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AbstractSmall mammal communities in western North America experienced declines in taxonomic richness across the late Pleistocene to Holocene transition (PHT), a recent natural global warming event. One community also experienced a decline in evenness and others replaced one species with a congener. Variability in response of small mammal communities to PHT warming is apparent. At the presently arid and xeric Marmes site in the Columbia Basin of southeastern Washington State, megafauna were absent by about 13,000 cal yr BP, evenness of small mammals declined about 11,700 cal yr BP and again about 11,400 cal yr BP whereas richness declined about 11,400 cal BP. Regional faunal turnover was, however, minimal among small-bodied taxa. Local mammal communities are depauperate as a result of megafaunal extinctions and subsequent decreases in small-mammal richness and evenness. The latter chronologically corresponds with a decrease in primary productivity driven by increasing warmth and aridity. More faunas must be studied in order to fully document the range of variability in the responses of mammalian communities to PHT warming. Documentation of patterns in those responses will facilitate understanding and enhance predictive accuracy with respect to responses of mammalian communities to modern global warming.
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Ibbett, M., J. C. Z. Woinarski, and M. Oakwood. "Declines in the mammal assemblage of a rugged sandstone environment in Kakadu National Park, Northern Territory, Australia." Australian Mammalogy 40, no. 2 (2018): 181. http://dx.doi.org/10.1071/am17011.
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There has been marked recent decline in the terrestrial mammal fauna across much of northern Australia, with most documentation of such decline for lowland areas. Here we report changes in the assemblage of small mammals in a rugged sandstone environment (Nawurlandja, in Kakadu National Park) over intermittent sampling between 1977 and 2002. Four native mammal species were commonly recorded in the original sampling: sandstone antechinus (Pseudantechinus bilarni), northern quoll (Dasyurus hallucatus), Arnhem rock-rat (Zyzomys maini) and common rock-rat (Z. argurus). Trap success rates declined significantly for the northern quoll, Arnhem rock-rat and all species combined, but increased for the common rock-rat. Despite being recorded commonly in the initial (1977–79) study, no Arnhem rock-rats were recorded in the most recent (2002) sampling. Trap success rates for northern quoll declined by ~90% from 1977–79 to 2002. The reasons for change are not clear-cut. Notably, all sampling occurred before the arrival of cane toads (Rhinella marina), a factor that has caused severe decline in northern quoll numbers elsewhere. Fire was more frequent in the sampling area in the period preceding the 2002 sampling than it was in the period preceding the initial (1977–79) sampling, and this may have contributed to change in mammal abundance.
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Wayne, A. F., B. A. Wilson, and J. C. Z. Woinarski. "Falling apart? Insights and lessons from three recent studies documenting rapid and severe decline in terrestrial mammal assemblages of northern, south-eastern and south-western Australia." Wildlife Research 44, no. 2 (2017): 114. http://dx.doi.org/10.1071/wr16178.
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Context Since European settlement in 1788, much of the Australian terrestrial mammal fauna has declined or become extinct. The pattern of, and reason for, that decline was little documented, and is now difficult to decipher. Many mammal species are still declining, providing (an unfortunate) opportunity to better document the process, identify the causal factors and attempt to redress the problem. Aim We compare trends in mammal abundance reported in three recent longitudinal studies in conservation reserves in Australia. The studies were not established with the intention of documenting mammal decline, but marked simultaneous decline of co-existing species was the most striking feature of their results. Methods Long-term monitoring in Kakadu National Park, Northern Territory (2001–04 and 2007–09), the Upper Warren region of Western Australia (since 1974) and the Great Otway National Park, Victoria (since 1975) principally relied on trapping, but also some spotlighting and sand plots, to document changes and trends in abundance in their respective mammal assemblages. Key results Decline was reported in most mammal species, across taxonomic groups, diets and size classes, but mostly involved species <5500g. The studies differed in their monitoring protocols and varied in the degree to which potential causal factors were monitored, thereby constraining interpretation of the drivers of declines. Inappropriate fire regimes and predation by feral cats are likely contributing factors in at least two study areas, and periods of markedly below-average rainfall are implicated in two areas. Conclusions We conclude the following: (1) conservation reserves in Australia may be failing to maintain at least some elements of the biodiversity that they were established to protect, and substantially enhanced management is required to redress this problem; (2) with current threats, mammal assemblages in Australia may be highly unstable; (3) substantial increase in effective long-term biodiversity monitoring programs in an adaptive management framework is needed; and (4) such monitoring programs will be more insightful if they also monitor factors driving population change. Implications Native mammal species declines and community disassembly may be occurring elsewhere. Long-term monitoring is critical for assessing trends in biodiversity and if done well, it can guide more effective and efficient management to deliver better conservation outcomes.
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Stokeld, Danielle, Alaric Fisher, Tim Gentles, Brydie Hill, Barbara Triggs, John C. Z. Woinarski, and Graeme R. Gillespie. "What do predator diets tell us about mammal declines in Kakadu National Park?" Wildlife Research 45, no. 1 (2018): 92. http://dx.doi.org/10.1071/wr17101.
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Context Small- and medium-sized native mammals have suffered severe declines in much of northern Australia, including within protected areas such as Kakadu National Park. Several factors have been implicated in these declines but predation, particularly by feral cats (Felis catus), has been identified as potentially the most direct cause of decline for many species. Aims We evaluated how prey frequency changed in cat and dingo scats in Kakadu from the early 1980s to 2013–15, with this period spanning a severe decline in the small- and medium-sized mammal fauna. Methods Chi-square test of independence and Fisher’s exact test were used to compare prey frequencies between dingoes and cats, and among years to assess significance of temporal change. Key results Small-sized native mammals were the prey item occurring at the highest frequency in scats for both dingoes and cats in the 1980s. Prey content in dingo and cat scats differed in the 2010s with macropods predominating in the scats of dingoes, and medium-sized native mammals predominating in cat scats. The frequency of occurrence of small-sized native mammals declined in both dingo and cat scats between the 1980s and 2010 sampling periods, while the frequency of occurrence of medium-sized native mammals remained constant in dingo scats and increased in cat scats. Conclusions Small mammals were a major component of the diets of both dingoes and cats in Kakadu in the 1980s, when small mammals were much more abundant. Despite marked reduction from the 1980s to the 2010s in the capture rates of both small- and medium-sized native mammals, some species continue to persist in the diets of cats and dingoes at disproportionally high frequencies. Both predators continue to exert predatory pressure on mammal populations that have already experienced substantial declines. Implications Although predation by feral cats is a major threat to small- and medium-sized native mammals, dingoes may also play an important role in limiting their recovery. Disturbance from fire and grazing by introduced herbivores has been shown to augment predatory impacts of feral cats on native mammals. Predation more generally, not just by feral cats, may be exacerbated by these disturbance processes. Management programs that solely focus on mitigating the impact of feral cats to benefit threatened species may be inadequate in landscapes with other significant disturbance regimes and populations of predators.
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Woinarski, John C. Z., Andrew A. Burbidge, and Peter L. Harrison. "Ongoing unraveling of a continental fauna: Decline and extinction of Australian mammals since European settlement." Proceedings of the National Academy of Sciences 112, no. 15 (February 9, 2015): 4531–40. http://dx.doi.org/10.1073/pnas.1417301112.
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The highly distinctive and mostly endemic Australian land mammal fauna has suffered an extraordinary rate of extinction (>10% of the 273 endemic terrestrial species) over the last ∼200 y: in comparison, only one native land mammal from continental North America became extinct since European settlement. A further 21% of Australian endemic land mammal species are now assessed to be threatened, indicating that the rate of loss (of one to two extinctions per decade) is likely to continue. Australia’s marine mammals have fared better overall, but status assessment for them is seriously impeded by lack of information. Much of the loss of Australian land mammal fauna (particularly in the vast deserts and tropical savannas) has been in areas that are remote from human population centers and recognized as relatively unmodified at global scale. In contrast to general patterns of extinction on other continents where the main cause is habitat loss, hunting, and impacts of human development, particularly in areas of high and increasing human population pressures, the loss of Australian land mammals is most likely due primarily to predation by introduced species, particularly the feral cat, Felis catus, and European red fox, Vulpes vulpes, and changed fire regimes.
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García-Aguilar, María C., Jaime Luévano-Esparza, and Horacio de la Cueva. "Mammal decline in the Middle America." Journal for Nature Conservation 28 (November 2015): 127–32. http://dx.doi.org/10.1016/j.jnc.2015.10.001.
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Short, J., and A. Smith. "Mammal Decline and Recovery in Australia." Journal of Mammalogy 75, no. 2 (May 31, 1994): 288–97. http://dx.doi.org/10.2307/1382547.
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Moore, T. L., L. E. Valentine, M. D. Craig, G. E. St J. Hardy, and P. A. Fleming. "Does woodland condition influence the diversity and abundance of small mammal communities?" Australian Mammalogy 36, no. 1 (2014): 35. http://dx.doi.org/10.1071/am13007.
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Loss of mammal species in Australia in the last 200 years has been attributed to many factors including habitat removal and altered fire regimes. Decline in tree condition could contribute further to the ongoing decline of mammals. Eucalyptus wandoo trees are currently undergoing a decline in condition that can result in a loss of canopy and other changes to the habitat. This paper examines the relationships between E. wandoo tree condition, habitat characteristics and small mammal species richness and abundance. Live-capture trapping was conducted at 24 E. wandoo sites at Dryandra State Forest and Wandoo Conservation Park, Western Australia. Condition and microhabitat variables of E. wandoo were recorded for each site. Generalised additive mixed models revealed a range of habitat and tree condition characteristics that influenced small mammal abundance and species richness, including site litter cover, crown dieback, understorey vegetation cover and tree density. The availability of coarse woody debris played a large role in explaining the abundance of Cercartetus concinnus and Antechinus flavipes, along with other microhabitat and tree condition variables, such as tree leaf litter and crown dieback. Epicormic growth, crown density and the distance to the drift fence from E. wandoo trees were the common variables in the best model for the abundance of Sminthopsis griseoventer. The decline in condition of E. wandoo and the subsequent modifications to the microhabitat are correlated with changes in the small mammal community. A better understanding of how the decline of E. wandoo impacts small mammal communities could improve management practices in E. wandoo woodlands.
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Woinarski, J. C. Z., A. Fisher, M. Armstrong, K. Brennan, A. D. Griffiths, B. Hill, J. Low Choy, et al. "Monitoring indicates greater resilience for birds than for mammals in Kakadu National Park, northern Australia." Wildlife Research 39, no. 5 (2012): 397. http://dx.doi.org/10.1071/wr11213.
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Context A previous study reported major declines for native mammal species from Kakadu National Park, over the period 2001–09. The extent to which this result may be symptomatic of more pervasive biodiversity decline was unknown. Aims Our primary aim was to describe trends in the abundance of birds in Kakadu over the period 2001–09. We assessed whether any change in bird abundance was related to the arrival of invading cane toads (Rhinella marina), and to fire regimes. Methods Birds were monitored at 136 1-ha plots in Kakadu, during the period 2001–04 and again in 2007–09. This program complemented sampling of the same plots over the same period for native mammals. Key results In contrast to the decline reported for native mammals, the richness and total abundance of birds increased over this period, and far more individual bird species increased than decreased. Fire history in the between-sampling period had little influence on trends for individual species. Interpretation of the overall positive trends for bird species in Kakadu over this period should be tempered by recognition that most of the threatened bird species present in Kakadu were unrecorded in this monitoring program, and the two threatened species for which there were sufficient records to assess trends – partridge pigeon (Geophaps smithii) and white-throated grass-wren (Amytornis woodwardi) – both declined significantly. Conclusions The current decline of the mammal fauna in this region is not reflected in trends for the region’s bird fauna. Some of the observed changes (mostly increases) in the abundance of bird species may be due to the arrival of cane toads, and some may be due to local or regional-scale climatic variation or variation in the amount of flowering. The present study provides no assurance about threatened bird species, given that most were inadequately recorded in the study (perhaps because their decline pre-dated the present study). Implications These contrasting trends between mammals and birds demonstrate the need for biodiversity monitoring programs to be broadly based. The declines of two threatened bird species over this period indicate the need for more management focus for these species.
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McCleery, Robert A., Adia Sovie, Robert N. Reed, Mark W. Cunningham, Margaret E. Hunter, and Kristen M. Hart. "Marsh rabbit mortalities tie pythons to the precipitous decline of mammals in the Everglades." Proceedings of the Royal Society B: Biological Sciences 282, no. 1805 (April 22, 2015): 20150120. http://dx.doi.org/10.1098/rspb.2015.0120.
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To address the ongoing debate over the impact of invasive species on native terrestrial wildlife, we conducted a large-scale experiment to test the hypothesis that invasive Burmese pythons ( Python molurus bivittatus ) were a cause of the precipitous decline of mammals in Everglades National Park (ENP). Evidence linking pythons to mammal declines has been indirect and there are reasons to question whether pythons, or any predator, could have caused the precipitous declines seen across a range of mammalian functional groups. Experimentally manipulating marsh rabbits, we found that pythons accounted for 77% of rabbit mortalities within 11 months of their translocation to ENP and that python predation appeared to preclude the persistence of rabbit populations in ENP. On control sites, outside of the park, no rabbits were killed by pythons and 71% of attributable marsh rabbit mortalities were classified as mammal predations. Burmese pythons pose a serious threat to the faunal communities and ecological functioning of the Greater Everglades Ecosystem, which will probably spread as python populations expand their range.
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Ohlberger, Jan, Daniel E. Schindler, Eric J. Ward, Timothy E. Walsworth, and Timothy E. Essington. "Resurgence of an apex marine predator and the decline in prey body size." Proceedings of the National Academy of Sciences 116, no. 52 (December 16, 2019): 26682–89. http://dx.doi.org/10.1073/pnas.1910930116.
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In light of recent recoveries of marine mammal populations worldwide and heightened concern about their impacts on marine food webs and global fisheries, it has become increasingly important to understand the potential impacts of large marine mammal predators on prey populations and their life-history traits. In coastal waters of the northeast Pacific Ocean, marine mammals have increased in abundance over the past 40 to 50 y, including fish-eating killer whales that feed primarily on Chinook salmon. Chinook salmon, a species of high cultural and economic value, have exhibited marked declines in average size and age throughout most of their North American range. This raises the question of whether size-selective predation by marine mammals is generating these trends in life-history characteristics. Here we show that increased predation since the 1970s, but not fishery selection alone, can explain the changes in age and size structure observed for Chinook salmon populations along the west coast of North America. Simulations suggest that the decline in mean size results from the selective removal of large fish and an evolutionary shift toward faster growth and earlier maturation caused by selection. Our conclusion that intensifying predation by fish-eating killer whales contributes to the continuing decline in Chinook salmon body size points to conflicting management and conservation objectives for these two iconic species.
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Grayson, Donald K. "Moisture History and Small Mammal Community Richness during the Latest Pleistocene and Holocene, Northern Bonneville Basin, Utah." Quaternary Research 49, no. 3 (May 1998): 330–34. http://dx.doi.org/10.1006/qres.1998.1970.
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Precipitation and net primary productivity are positively correlated in arid environments. Both variables are, in turn, correlated with mammal species richness, but this relationship is not necessarily positive. With increasing precipitation in arid areas of low to moderate productivity, mammal richness increases linearly; as rainfall and productivity increase beyond this point, mammal richness is known to decline in some areas, producing a relationship that has been termed “unimodal” or “humped.” In the Great Basin of the arid western United States, studies of the relationship between rodent species richness and precipitation have revealed only a positive relationship between these two variables. It has, however, been argued that if areas of higher precipitation were to be sampled within this region, the decline phase would become evident. When latest Pleistocene and Holocene small mammal assemblages from the northern Bonneville Basin (central Utah) are examined across a temporal moisture gradient, species richness declines as moisture declines. Since the Great Basin was significantly moister during the latest Pleistocene and Early Holocene than it has been since that time, the unimodal response model does not appear to apply to this region.
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Meyer, Stefan, Bruce C. Robertson, B. Louise Chilvers, and Martin Krkošek. "Marine mammal population decline linked to obscured by-catch." Proceedings of the National Academy of Sciences 114, no. 44 (October 9, 2017): 11781–86. http://dx.doi.org/10.1073/pnas.1703165114.
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Declines of marine megafauna due to fisheries by-catch are thought to be mitigated by exclusion devices that release nontarget species. However, exclusion devices may instead conceal negative effects associated with by-catch caused by fisheries (i.e., unobserved or discarded by-catch with low postrelease survival or reproduction). We show that the decline of the endangered New Zealand (NZ) sea lion (Phocarctos hookeri) is linked to latent levels of by-catch occurring in sub-Antarctic trawl fisheries. Exclusion devices have been used since 2001 but have not slowed or reversed population decline. However, 35% of the variability in NZ sea lion pup production is explained by latent by-catch, and the population would increase without this factor. Our results indicate that exclusion devices can obscure rather than alleviate fishery impacts on marine megafauna.
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Brodie, Jedediah F., Sara Williams, and Brittany Garner. "The decline of mammal functional and evolutionary diversity worldwide." Proceedings of the National Academy of Sciences 118, no. 3 (January 4, 2021): e1921849118. http://dx.doi.org/10.1073/pnas.1921849118.
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Biodiversity is declining worldwide. Because species interact with one another and with their environment, losses of particular organisms alter the function of ecosystems. Our understanding of the global rates and specific causes of functional decline remains limited, however. Species losses also reduce the cumulative amount of extant evolutionary history (“phylogenetic diversity” [PD]) in communities—our biodiversity heritage. Here we provide a global assessment of how each known anthropogenic threat is driving declines in functional diversity (FD) and PD, using terrestrial mammals as a case study. We find that habitat loss and harvest (e.g., legal hunting, poaching, snaring) are by far the biggest drivers of ongoing FD and PD loss. Declines in FD in high-biodiversity countries, particularly in Southeast Asia and South America, are greater than would be expected if species losses were random with respect to ecological function. Among functional guilds, herbivores are disproportionately likely to be declining from harvest, with important implications for plant communities and nutrient cycling. Frugivores are particularly likely to be declining from both harvest and habitat loss, with potential ramifications for seed dispersal and even forest carbon storage. Globally, phylogenetically unique species do not have an elevated risk of decline, but in areas such as Australia and parts of Southeast Asia, both habitat loss and harvest are biased toward phylogenetically unique species. Enhanced conservation efforts, including a renewed focus on harvest sustainability, are urgently needed to prevent the deterioration of ecosystem function, especially in the South American and equatorial Asian tropics.
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Sullivan, Thomas P., and Druscilla S. Sullivan. "Long-Term Changes in Abundance and Composition of Forest-Floor Small Mammal Communities in a Landscape with Cumulative Clearcutting." Ecologies 3, no. 4 (October 2, 2022): 446–66. http://dx.doi.org/10.3390/ecologies3040032.
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Responses of forest-floor small mammals to clearcutting are species-specific with generalists occupying a range of habitats, and specialists persisting on clearcuts for variable periods. We investigated the responses in abundance and species composition of small mammal communities to cumulative clearcutting of coniferous forests on a landscape that had four independent clearcutting events (Periods 1 to 4) over a 42-year interval from 1979 to 2020 in south-central British Columbia, Canada. We ask if the small mammal communities have changed significantly over these decades owing to removal of old-growth forest by clearcut harvesting. Hypotheses (H) predicted that the small mammal community would (H1) increase in abundance, species richness, and diversity on new clearcuts owing to the availability of early seral post-harvest habitats from cumulative clearcutting; and (H2) have higher mean abundance, species richness, and species diversity in clearcut than uncut forest sites, owing to availability of vegetative food and cover. A third hypothesis (H3) predicted that abundance of (i) early seral vegetation (herbs and shrubs) and (ii) small mammal populations, will be greater in ungrazed clearcut sites than in those grazed by cattle (Bos taurus). Mean total numbers of small mammals on new clearcuts declined in Periods 3 and 4, and hence did not support the abundance part of H1. Much of this decline was owing to low numbers of the long-tailed vole (Microtus longicaudus) and meadow vole (M. pennsylvanicus). Two generalist species: the deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), contributed to high mean species richness and diversity in Periods 2 and 3 before these metrics declined in Period 4, and hence partly supported H1. The similarity in mean total numbers of small mammals in Periods 2 to 4 did not support the abundance prediction of H2 that total numbers would be higher in clearcut than uncut forest sites. Higher mean species richness (Periods 2 and 3) and diversity (Period 3) measurements on clearcut than forest sites, particularly in the early post-harvest years, did support these parts of H2. The vegetation part (i) of H3 was not supported for herbaceous plants but it was for shrubs. The small mammal part (ii) of H3 that populations would be higher in ungrazed than grazed clearcut sites was supported for abundance but not for species richness or diversity. The decline and near disappearance of both species of Microtus was possibly related to the reduction in plant community abundance and structure from grazing (at least for shrubs) and potentially from drought effects associated with climate change. Loss of microtines from these early seral ecosystems may have profound negative effects on various ecological functions and predator communities.
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Beirne, Christopher, Laura Waring, Robbie A. McDonald, Richard Delahay, and Andrew Young. "Age-related declines in immune response in a wild mammal are unrelated to immune cell telomere length." Proceedings of the Royal Society B: Biological Sciences 283, no. 1825 (February 24, 2016): 20152949. http://dx.doi.org/10.1098/rspb.2015.2949.
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Senescence has been hypothesized to arise in part from age-related declines in immune performance, but the patterns and drivers of within-individual age-related changes in immunity remain virtually unexplored in natural populations. Here, using a long-term epidemiological study of wild European badgers ( Meles meles ), we (i) present evidence of a within-individual age-related decline in the response of a key immune-signalling cytokine, interferon-gamma (IFN γ ), to ex vivo lymphocyte stimulation, and (ii) investigate three putative drivers of individual variation in the rate of this decline (sex, disease and immune cell telomere length; ICTL). That the within-individual rate of age-related decline markedly exceeded that at the population level suggests that individuals with weaker IFN γ responses are selectively lost from this population. IFN γ responses appeared to decrease with the progression of bovine tuberculosis infection (independent of age) and were weaker among males than females. However, neither sex nor disease influenced the rate of age-related decline in IFN γ response. Similarly, while ICTL also declines with age, variation in ICTL predicted neither among- nor within-individual variation in IFN γ response. Our findings provide evidence of within-individual age-related declines in immune performance in a wild mammal and highlight the likely complexity of the mechanisms that generate them.
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Short, Jeff. "Mammal decline in southern Western Australia – perspectives from Shortridge's collections of mammals in 1904–07." Australian Zoologist 32, no. 4 (December 2004): 605–28. http://dx.doi.org/10.7882/az.2004.006.
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I., Mahakata, and Bishi T.M. "Protected Area Downsizing; Challenges and Ecological Implications on Large Mammal and Biodiversity Conservation in Chirisa Safari Area (CSA)." African Journal of Environment and Natural Science Research 4, no. 4 (December 4, 2021): 134–49. http://dx.doi.org/10.52589/ajensr-jp7jscdn.
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Protected area (PA) downsizing has been documented worldwide, but associated challenges on biodiversity and large mammal conservation in Chirisa Safari Area (CSA) are poorly understood. This study assesses the challenges associated with CSA downsizing on large mammals and biodiversity conservation. Field observations and face-to-face interviews were done with park management of CSA and SWRI from the 28th May 2021 to 10th June 2021. Analysis of station records on illegal activities, human-wildlife conflict (HWC) reports and land cover changes from 2010 to 2020 was also done. Poaching, encroachment by local people and veld fires, habitat fragmentation and HWC were sighted as major threats to large mammal biodiversity conservation in CSA. Analysed land cover and land use changes show evidence of the expansion of cultivation land and human settlements into areas that previously served as wildlife habitats. These changes have implications on large mammal and biodiversity conservation in CSA related to species migration, population decline, habitat loss and conflicts. We recommend that further research be undertaken in other areas affected by downsizing in Zimbabwe to aid knowledge in explaining its effect on large mammals and biodiversity conservation in adjacent PAs.
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Kelly, Luke T., Dale G. Nimmo, Lisa M. Spence-Bailey, Michael F. Clarke, and Andrew F. Bennett. "The short-term responses of small mammals to wildfire in semiarid mallee shrubland, Australia." Wildlife Research 37, no. 4 (2010): 293. http://dx.doi.org/10.1071/wr10016.
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Context. Wildfire is a major driver of the structure and function of mallee eucalypt- and spinifex-dominated landscapes. Understanding how fire influences the distribution of biota in these fire-prone environments is essential for effective ecological and conservation-based management. Aims. We aimed to (1) determine the effects of an extensive wildfire (118 000 ha) on a small mammal community in the mallee shrublands of semiarid Australia and (2) assess the hypothesis that the fire-response patterns of small mammals can be predicted by their life-history characteristics. Methods. Small-mammal surveys were undertaken concurrently at 26 sites: once before the fire and on four occasions following the fire (including 14 sites that remained unburnt). We documented changes in small-mammal occurrence before and after the fire, and compared burnt and unburnt sites. In addition, key components of vegetation structure were assessed at each site. Key results. Wildfire had a strong influence on vegetation structure and on the occurrence of small mammals. The mallee ningaui, Ningaui yvonneae, a dasyurid marsupial, showed a marked decline in the immediate post-fire environment, corresponding with a reduction in hummock-grass cover in recently burnt vegetation. Species richness of native small mammals was positively associated with unburnt vegetation, although some species showed no clear response to wildfire. Conclusions. Our results are consistent with the contention that mammal responses to fire are associated with their known life-history traits. The species most strongly affected by wildfire, N. yvonneae, has the most specific habitat requirements and restricted life history of the small mammals in the study area. The only species positively associated with recently burnt vegetation, the introduced house mouse, Mus domesticus, has a flexible life history and non-specialised resource requirements. Implications. Maintaining sources for recolonisation after large-scale wildfires will be vital to the conservation of native small mammals in mallee ecosystems.
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Fusco, Diana A., Matthew C. McDowell, Graham Medlin, and Gavin J. Prideaux. "Fossils reveal late Holocene diversity and post-European decline of the terrestrial mammals of the Murray–Darling Depression." Wildlife Research 44, no. 1 (2017): 60. http://dx.doi.org/10.1071/wr16134.
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Context Establishing appropriate faunal baselines is critical for understanding and abating biodiversity declines. However, baselines can be highly reliant on historical records that come from already disturbed ecosystems. This is exemplified in the Murray–Darling Depression bioregion of Australia, where European settlement (and accompanying marked land-management changes and the introduction of many species) triggered rapid declines and losses of native species, often before their documentation. Aims We aim to establish the mammal fauna present when Europeans settled the Murray Mallee and Murray–Darling Depression bioregion and determine the extent of mammal loss since European settlement. Methods We describe a dated vertebrate assemblage from Light’s Roost in the lower Murray Mallee region of South Australia. We compare our data with those of modern fauna surveys and historical records to document the extent of change in the mammal fauna since European settlement. Key results Radiocarbon ages showed that the assemblage was accumulating, at a minimum, within an interval from 1900 to 1300 years ago. Since this time, the Murray–Darling Depression has lost half of its flightless terrestrial mammals. Species lost include the mulgara (Dasycercus blythi/cristicauda), which places this taxon within only 40km of Lake Alexandrina, the hitherto-disputed type locality for D. cristicauda. Fossils provided the principal evidence for nearly half of the Murray Mallee fauna and over three-quarters of the fauna are represented in the fossil record. Conclusions Late Holocene assemblages provide important archives of species biogeography and diversity. Our revised faunal baseline indicated that the pre-European fauna of the Murray–Darling Depression was more diverse than hitherto understood and its reduction appears largely caused by the impacts of European settlement. Implications Baselines for species distributions derived from historical records and modern faunal surveys are likely to be incomplete and warrant revision, particularly for smaller and more cryptic species. Deficiencies in regional records mask the extent of mammal declines caused by European colonisation and associated agricultural practices, and thus vulnerability to anthropogenic disturbance.
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Ripple, William J., Katharine Abernethy, Matthew G. Betts, Guillaume Chapron, Rodolfo Dirzo, Mauro Galetti, Taal Levi, et al. "Bushmeat hunting and extinction risk to the world's mammals." Royal Society Open Science 3, no. 10 (October 2016): 160498. http://dx.doi.org/10.1098/rsos.160498.
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Terrestrial mammals are experiencing a massive collapse in their population sizes and geographical ranges around the world, but many of the drivers, patterns and consequences of this decline remain poorly understood. Here we provide an analysis showing that bushmeat hunting for mostly food and medicinal products is driving a global crisis whereby 301 terrestrial mammal species are threatened with extinction. Nearly all of these threatened species occur in developing countries where major coexisting threats include deforestation, agricultural expansion, human encroachment and competition with livestock. The unrelenting decline of mammals suggests many vital ecological and socio-economic services that these species provide will be lost, potentially changing ecosystems irrevocably. We discuss options and current obstacles to achieving effective conservation, alongside consequences of failure to stem such anthropogenic mammalian extirpation. We propose a multi-pronged conservation strategy to help save threatened mammals from immediate extinction and avoid a collapse of food security for hundreds of millions of people.
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Fricke, Evan C., Chia Hsieh, Owen Middleton, Daniel Gorczynski, Caroline D. Cappello, Oscar Sanisidro, John Rowan, Jens-Christian Svenning, and Lydia Beaudrot. "Collapse of terrestrial mammal food webs since the Late Pleistocene." Science 377, no. 6609 (August 26, 2022): 1008–11. http://dx.doi.org/10.1126/science.abn4012.
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Food webs influence ecosystem diversity and functioning. Contemporary defaunation has reduced food web complexity, but simplification caused by past defaunation is difficult to reconstruct given the sparse paleorecord of predator-prey interactions. We identified changes to terrestrial mammal food webs globally over the past ~130,000 years using extinct and extant mammal traits, geographic ranges, observed predator-prey interactions, and deep learning models. Food webs underwent steep regional declines in complexity through loss of food web links after the arrival and expansion of human populations. We estimate that defaunation has caused a 53% decline in food web links globally. Although extinctions explain much of this effect, range losses for extant species degraded food webs to a similar extent, highlighting the potential for food web restoration via extant species recovery.
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Collen, Ben, Louise McRae, Stefanie Deinet, Adriana De Palma, Tharsila Carranza, Natalie Cooper, Jonathan Loh, and Jonathan E. M. Baillie. "Predicting how populations decline to extinction." Philosophical Transactions of the Royal Society B: Biological Sciences 366, no. 1577 (September 12, 2011): 2577–86. http://dx.doi.org/10.1098/rstb.2011.0015.
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Global species extinction typically represents the endpoint in a long sequence of population declines and local extinctions. In comparative studies of extinction risk of contemporary mammalian species, there appear to be some universal traits that may predispose taxa to an elevated risk of extinction. In local population-level studies, there are limited insights into the process of population decline and extinction. Moreover, there is still little appreciation of how local processes scale up to global patterns. Advancing the understanding of factors which predispose populations to rapid declines will benefit proactive conservation and may allow us to target at-risk populations as well as at-risk species. Here, we take mammalian population trend data from the largest repository of population abundance trends, and combine it with the PanTHERIA database on mammal traits to answer the question: what factors can be used to predict decline in mammalian abundance? We find in general that environmental variables are better determinants of cross-species population-level decline than intrinsic biological traits. For effective conservation, we must not only describe which species are at risk and why, but also prescribe ways to counteract this.
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Ojeda, Ricardo A., Rubén M. Barquez, Jutta Stadler, and Roland Brandl. "Decline of Mammal Species Diversity Along the Yungas Forest of Argentina." Biotropica 40, no. 4 (February 22, 2008): 515–21. http://dx.doi.org/10.1111/j.1744-7429.2008.00401.x.
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Avenant, Nico. "The potential utility of rodents and other small mammals as indicators of ecosystem 'integrity' of South African grasslands." Wildlife Research 38, no. 7 (2011): 626. http://dx.doi.org/10.1071/wr10223.
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Context The expansive grassland biome is one of the most extensively transformed in South Africa, yet no strategy for monitoring its integrity is in place. A grassland health program, incorporating different ecosystem levels, was recently initiated. The suitability of three taxonomic groups as indicators has been tested so far: vegetation (by calculating an ecological index value, El), insects (using the South African grassland scoring system, SAGraSS) and small mammals (this study). All of these methods aim to be rapid and easy to perform. Whereas SAGraSS still needs further refinement, several factors already indicate the importance of including small mammal community parameters in integrity assessments. Aims This contribution reports on more than 12 years of results from various studies on small mammals in the Free State Grasslands, with the aim of exploring the utility of small mammal survey for assessment of ecosystem integrity. Methods The hypothesis was based on the outcomes of several short-term studies conducted in the grassland biome. Combining all previous results, this paper re-evaluates the parameters of trap success, species richness, diversity, evenness and individual species as bio-indicators. Key results By combining data from many sites and years, the effect of seasonal and inter-annual variations in habitat and population parameters was diminished, and a more general picture of small mammal community structure revealed. New insights were gleaned into the status of several indicator species. By providing a summary of small mammal community parameter scores and indices, the study establishes a benchmark for future small mammal assessments and monitoring. To be effective, small mammal surveys in the grassland biome of southern Africa should be carried out in autumn and early winter. Conclusions This study suggests that small mammal species richness and diversity decline with habitat degradation; that the generalist rodent Mastomys coucha dominates community numbers at low ecological integrity; that the number of specialist species increases towards ecological climax; and that specific species act as indicators during the successional process. Implications This study should benefit the monitoring, conservation and management of grassland ecosystems, make environmental impact assessments more effective, and identify new topics for ecological research.
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Faith, J. Tyler, John Rowan, Andrew Du, and Paul L. Koch. "Plio-Pleistocene decline of African megaherbivores: No evidence for ancient hominin impacts." Science 362, no. 6417 (November 22, 2018): 938–41. http://dx.doi.org/10.1126/science.aau2728.
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It has long been proposed that pre-modern hominin impacts drove extinctions and shaped the evolutionary history of Africa’s exceptionally diverse large mammal communities, but this hypothesis has yet to be rigorously tested. We analyzed eastern African herbivore communities spanning the past 7 million years—encompassing the entirety of hominin evolutionary history—to test the hypothesis that top-down impacts of tool-bearing, meat-eating hominins contributed to the demise of megaherbivores prior to the emergence ofHomo sapiens. We document a steady, long-term decline of megaherbivores beginning ~4.6 million years ago, long before the appearance of hominin species capable of exerting top-down control of large mammal communities and predating evidence for hominin interactions with megaherbivore prey. Expansion of C4grasslands can account for the loss of megaherbivore diversity.
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Menkhorst, Peter W. "Blandowski’s mammals: Clues to a lost world." Proceedings of the Royal Society of Victoria 121, no. 1 (2009): 61. http://dx.doi.org/10.1071/rs09061.
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Wilhelm Blandowski was the first zoologist employed by the Victorian Government, being appointed Officer of the Museum of Natural History by Governor La Trobe on 1 April 1854. Although he remained in this position for less than four years he left an important legacy by beginning the documentation of Victoria’s mammalian fauna before the full impact of European pastoralism and feral animals had become apparent. In particular, the 1856-57 zoological survey expedition to the lower Murray-Darling region provided a unique insight into the mammalian community that existed there before European occupation triggered a sudden decline in mammal species diversity, as happened progressively across the southern two thirds of Australia over the subsequent 90 years. Of the 34 mammal taxa recorded by the Blandowski Expedition, ten are extinct, nine no longer occur in the region, four are still present but with greatly reduced and fragmented distributions, seven have broad distributions in the region little changed since Blandowski’s time, although severely fragmented, and the remaining four have probably expanded their distributions. The contributions of Blandowski and his assistant Gerard Krefft to our understanding of the nature and causes of these mammal declines are examined and discussed. Unfortunately, the surviving contemporary documentation of the Expedition and the associated specimens is inadequate to shed much light on the factors that triggered the initial mammal declines, but the results do not support recent suggestions that predation by the introduced house cat Felis catus was pivotal.
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Lyngdoh, Adrian Wansaindor, Honnavalli N. Kumara, Santhanakrishnan Babu, and P. V. Karunakaran. "Community Reserves: Their significance for the conservation of mammals in a mosaic of community-managed lands in Meghalaya, Northeast India." PLOS ONE 18, no. 1 (January 26, 2023): e0280994. http://dx.doi.org/10.1371/journal.pone.0280994.
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Community Reserves (CRs) have been advocated for increasing the protected area coverage in northeast India where the land is primarily owned and managed by local indigenous institutions. To understand the significance of these reserves for the conservation of mammals, we investigated the diversity and abundance of mammals in five CRs in the Khasi Hills of Meghalaya as well as interviewed 75 local villagers to assess the hunting practices and perceptions of the Indigenous Khasis on mammals. We employed 60 camera traps in the CRs and undertook a recce survey (day-time and night-time) for capturing the diversity in the CRs. We used photo-capture rate and encounter rate as indices of relative abundance in the CRs. We used an exact multinomial test to test differences of opinion among the respondents of the five CRs. We found a relatively low abundance of mammals in the CRs, yet they persist. A total of 28 species were detected through camera trapping and recce survey and an additional 12 species were reported by respondents to also occur in the CRs. Among the respondents, it was believed that the decline in mammal populations was largely driven by habitat loss and degradation (82.67%) while only a few believed it was also driven by hunting (5.33%). Respondents also believed that the presence of the reserves and awareness programs taken under them had also led to a reduction in hunting (20%) in their area. Although, some attributed it to a general decline in wildlife populations and forest cover (21.33%). Thus, despite these CRs being small (<2 km2) and isolated, they still harbour mammal species and are important for retaining remnant forest patches in a landscape that is highly fragmented.
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Johnson, Christopher N., Joanne L. Isaac, and Diana O. Fisher. "Rarity of a top predator triggers continent-wide collapse of mammal prey: dingoes and marsupials in Australia." Proceedings of the Royal Society B: Biological Sciences 274, no. 1608 (October 31, 2006): 341–46. http://dx.doi.org/10.1098/rspb.2006.3711.
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Top predators in terrestrial ecosystems may limit populations of smaller predators that could otherwise become over abundant and cause declines and extinctions of some prey. It is therefore possible that top predators indirectly protect many species of prey from excessive predation. This effect has been demonstrated in some small-scale studies, but it is not known how general or important it is in maintaining prey biodiversity. During the last 150 years, Australia has suffered the world's highest rate of mammal decline and extinction, and most evidence points to introduced mid-sized predators (the red fox and the feral cat) as the cause. Here, we test the idea that the decline of Australia's largest native predator, the dingo, played a role in these extinctions. Dingoes were persecuted from the beginning of European settlement in Australia and have been eliminated or made rare over large parts of the continent. We show a strong positive relationship between the survival of marsupials and the geographical overlap with high-density dingo populations. Our results suggest that the rarity of dingoes was a critical factor which allowed smaller predators to overwhelm marsupial prey, triggering extinction over much of the continent. This is evidence of a crucial role of top predators in maintaining prey biodiversity at large scales in terrestrial ecosystems and suggests that many remaining Australian mammals would benefit from the positive management of dingoes.
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Goldingay, Ross L. "Population monitoring of an urban gliding mammal in eastern Australia." Australian Mammalogy 40, no. 2 (2018): 214. http://dx.doi.org/10.1071/am17029.
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Long-term monitoring is an important element of species conservation. This study describes changes in the size of a squirrel glider (Petaurus norfolcensis) population over a 10-year period. The population occupied a 45-ha forest remnant within the urban area of Brisbane. Gliders were tagged from 25 nights of trapping during 2006–08 and from 16 nights of trapping in 2015. Population modelling was used to estimate adult population size. This suggested the adult population comprised 30–40 individuals at the beginning and end of the 10-year period. It reached a peak of 70 individuals in mid-2007. These data suggest that the study area contains a small population that is prone to interannual variation but there was no evidence of it being in decline. Survival estimates during 2006–08 were equivalent to those estimated for a larger population in Victoria. Population monitoring should be continued to determine how resilient this population is to population decline and to investigate factors that may cause decline. This study provides an example of an approach that could be used to monitor threatened populations of the squirrel glider.
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Penton, Cara E., Leigh-Ann Woolley, Ian J. Radford, and Brett P. Murphy. "Overlapping den tree selection by three declining arboreal mammal species in an Australian tropical savanna." Journal of Mammalogy 101, no. 4 (August 25, 2020): 1165–76. http://dx.doi.org/10.1093/jmammal/gyaa074.
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Abstract Tree cavities are important denning sites for many arboreal mammals. Knowledge of cavity requirements of individual species, as well as potential den overlap among species, is integral to their conservation. In Australia’s tropical savannas, development of tree cavities is enhanced by high termite activity, and, conversely, reduced by frequent fires. However, it is poorly understood how the availability of tree cavities in the tropical savannas impacts tree cavity use and selection by cavity-dependent fauna. There has been a severe decline among arboreal mammal species in northern Australia over recent decades. Investigation of their cavity requirements may illuminate why these species have declined drastically in some areas but are persisting in others. Here we examined this issue in three species of arboreal mammals (Trichosurus vulpecula, Mesembriomys gouldii, Conilurus penicillatus) on Melville Island, northern Australia. We radiotracked individuals to their den sites to evaluate whether the species differ in their den tree and tree-cavity selection. The strongest influence on den tree selection was the presence of large cavities (> 10 cm entrance diameter), with all three species using larger cavities most frequently. Conilurus penicillatus, the smallest species, differed the most from the other species: it frequently was found in smaller, dead trees and its den sites were closer to the ground, including in hollow logs. The two larger species had broader den tree use, using larger live trees and dens higher up in the canopy. Dens of C. penicillatus are likely to be more susceptible to predation and destruction by high-intensity savanna fires. This may have contributed to this species’ rapid decline, both on Melville Island and on the mainland. However, the apparent preference for larger tree cavities by all three arboreal species is concerning due to the limited availability of large trees across Australian savannas, which are subject to frequent, high-intensity fires.
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Colman, N. J., C. E. Gordon, M. S. Crowther, and M. Letnic. "Lethal control of an apex predator has unintended cascading effects on forest mammal assemblages." Proceedings of the Royal Society B: Biological Sciences 281, no. 1782 (May 7, 2014): 20133094. http://dx.doi.org/10.1098/rspb.2013.3094.
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Disruption to species-interaction networks caused by irruptions of herbivores and mesopredators following extirpation of apex predators is a global driver of ecosystem reorganization and biodiversity loss. Most studies of apex predators' ecological roles focus on effects arising from their interactions with herbivores or mesopredators in isolation, but rarely consider how the effects of herbivores and mesopredators interact. Here, we provide evidence that multiple cascade pathways induced by lethal control of an apex predator, the dingo, drive unintended shifts in forest ecosystem structure. We compared mammal assemblages and understorey structure at seven sites in southern Australia. Each site comprised an area where dingoes were poisoned and an area without control. The effects of dingo control on mammals scaled with body size. Activity of herbivorous macropods, arboreal mammals and a mesopredator, the red fox, were greater, but understorey vegetation sparser and abundances of small mammals lower, where dingoes were controlled. Structural equation modelling suggested that both predation by foxes and depletion of understorey vegetation by macropods were related to small mammal decline at poisoned sites. Our study suggests that apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously and should be considered in tandem in order to appreciate the extent of apex predators’ indirect effects.
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Woinarski, J. C. Z., S. Ward, T. Mahney, J. Bradley, K. Brennan, M. Ziembicki, and A. Fisher. "The mammal fauna of the Sir Edward Pellew island group, Northern Territory, Australia: refuge and death-trap." Wildlife Research 38, no. 4 (2011): 307. http://dx.doi.org/10.1071/wr10184.
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Context Australian islands have provided a major conservation refuge for many native mammals; however, conversely, island populations may also be highly susceptible to the introduction of novel threats. Nearby islands subject to different arrays of threats or different timing of arrival of those threats may provide a natural experiment, offering particular insight into the relative impacts of different threats to Australian mammals more generally. Aims The present study sought to document the native mammal fauna occurring on the main islands of the Sir Edward Pellew group, Northern Territory, and the changes in that fauna over a ~50-year period, and to seek to identify those factors that have contributed to such change. Methods In different combinations, the five main islands (and three smaller islands) were subject to standard wildlife survey methods in 1966–67, 1988, 2003, 2004–05, and 2009–10. Sampling procedures were not identical in all periods; however, a measure of abundance (trap success rate) could be calculated for all sampling. This conventional survey approach was complemented by documentation of ethno-biological knowledge. Key results For many species, these islands held populations of biogeographic or conservation significance. However, there has been a major loss or decline of mammal species from most islands. Extirpation is difficult to prove; however, we consider it most likely that the important regional populations of brush-tailed rabbit-rat (Conilurus penicillatus), northern quoll (Dasyurus hallucatus), northern brush-tailed phascogale (Phascogale pirata), common brushtail possum (Trichosurus vulpecula) and canefield rat (Rattus sordidus) have been lost from these islands, and that northern brown bandicoot (Isoodon macrourus), western chestnut mouse (Pseudomys nanus), pale field-rat (Rattus tunneyi) and long-haired rat (Rattus villosissimus) have been lost from most of the islands on which they formerly occurred. Some species–island combinations are known only from the ethno-biological record, and the loss of these populations probably mostly occurred in the period 30–50 years ago. Many other declines and losses occurred in the period between the second (1988) and third (2003) survey. The loss of the northern quoll from Vanderlin Island occurred in 2008. No single factor unambiguously accounts for the declines, although the introduction of cats (Felis catus) provides the best fit to the pattern of decline. A notable exception is the extirpation of northern quoll on Vanderlin Island, which is closely linked to the colonisation of that island by cane toads (Rhinella marina). Conclusions The Sir Edward Pellew group of islands have lost much of their formerly high conservation significance for native mammals over the past 50 years, mostly because of introductions of cats, and to a lesser extent, natural colonisation of the islands by cane toads. Implications The present study has provided some insight into the relative impacts of a range of factors that have been considered as possibly implicated in the decline of native mammals on the northern Australian mainland, with most support being offered here for a primary role for predation by feral cats. The study has also demonstrated the need for better quarantining of islands with significant conservation values. The comprehensive natural colonisation of these islands by cane toads offers a further lesson, of most importance to managers of islands in north-western Australia currently just beyond the range of toads.
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Taye, Dessalegn, and Melaku Wale. "Diversity of Large and Medium Sized Mammals and Their Challenges in Abay (Blue Nile) Gorge in the Amhara Region of Ethiopia." Aquatic Science and Technology 11, no. 1 (January 26, 2023): 1–20. http://dx.doi.org/10.52941/ast.v11i1.39.
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The diversity and threats of medium and large‐sized mammals was studied in Abay (Blue Nile) Gorge, Amhara Region, Ethiopia using direct and indirect survey techniques on transect lines crossing natural forest, riverine forest and woodlands. Footprints, camera traps and group discussions were used. Data were analyzed using detrended correspondence analysis, cluster analysis, non-metric multidimensional scaling, and diversity indices. A total of 25 medium and large mammal species belonging to 6 orders and 12 families were recorded. Order Carnivora was the most abundant followed by Artiodactyla, whereas Tubulidentata, Lagomorpha and Procaviida were rare. Leopard is threatened species. The plotting of the detrended correspondence analysis between mammal species and districts showed 61% on axis 1 and 22% on axis 2 and Gozamin district stood at the left side of the plot and Andabet, Enebise Sar Midir and Borena at the extreme right, contributing to the observed association. The mammal species were found lined up along axis 1, where Lycaon pictus and Reducna redunca were closely associated to Gozamin. The cluster analysis based on the Bray-Curtis single linkage similarity index showed differences and similarities between the mammals species composition recorded in the six districts. P. anubis, C. pygerythrus, S. grimmia, O. oreotragus, G. genetta, P. pardus pardus, H. hyaena, G. sanguinea, H. brucei, P. capensis, H. cristata stood out clearly separated from the rest of them and showed linkage at almost 50% similarity. The highest similarity (at about 96% similarity) was a cluster of four species, i.e., T. sylvaticus, T.strepsiceros, S. scrofa and K. ellipsiprymnus. Non-metric multidimensional scaling also gave clusters of similar districts but not mammal species. Species diversity (H′) ranged from low (1.1) to average (1.9). Anthropogenic impacts were associated with decline in abundance of species and populations. Conservation schemes (nature reserves) need to be launched as soon as possible.
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Estes, J. A., D. F. Doak, A. M. Springer, and T. M. Williams. "Causes and consequences of marine mammal population declines in southwest Alaska: a food-web perspective." Philosophical Transactions of the Royal Society B: Biological Sciences 364, no. 1524 (June 27, 2009): 1647–58. http://dx.doi.org/10.1098/rstb.2008.0231.
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Populations of sea otters, seals and sea lions have collapsed across much of southwest Alaska over the past several decades. The sea otter decline set off a trophic cascade in which the coastal marine ecosystem underwent a phase shift from kelp forests to deforested sea urchin barrens. This interaction in turn affected the distribution, abundance and productivity of numerous other species. Ecological consequences of the pinniped declines are largely unknown. Increased predation by transient (marine mammal-eating) killer whales probably caused the sea otter declines and may have caused the pinniped declines as well. Springer et al . proposed that killer whales, which purportedly fed extensively on great whales, expanded their diets to include a higher percentage of sea otters and pinnipeds following a sharp reduction in great whale numbers from post World War II industrial whaling. Critics of this hypothesis claim that great whales are not now and probably never were an important nutritional resource for killer whales. We used demographic/energetic analyses to evaluate whether or not a predator–prey system involving killer whales and the smaller marine mammals would be sustainable without some nutritional contribution from the great whales. Our results indicate that while such a system is possible, it could only exist under a narrow range of extreme conditions and is therefore highly unlikely.
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Goswami, Anjali, Eve Noirault, Ellen J. Coombs, Julien Clavel, Anne-Claire Fabre, Thomas J. D. Halliday, Morgan Churchill, et al. "Attenuated evolution of mammals through the Cenozoic." Science 378, no. 6618 (October 28, 2022): 377–83. http://dx.doi.org/10.1126/science.abm7525.
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The Cenozoic diversification of placental mammals is the archetypal adaptive radiation. Yet, discrepancies between molecular divergence estimates and the fossil record fuel ongoing debate around the timing, tempo, and drivers of this radiation. Analysis of a three-dimensional skull dataset for living and extinct placental mammals demonstrates that evolutionary rates peak early and attenuate quickly. This long-term decline in tempo is punctuated by bursts of innovation that decreased in amplitude over the past 66 million years. Social, precocial, aquatic, and herbivorous species evolve fastest, especially whales, elephants, sirenians, and extinct ungulates. Slow rates in rodents and bats indicate dissociation of taxonomic and morphological diversification. Frustratingly, highly similar ancestral shape estimates for placental mammal superorders suggest that their earliest representatives may continue to elude unequivocal identification.
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McKenzie, N. L., A. A. Burbidge, A. Baynes, R. N. Brereton, C. R. Dickman, G. Gordon, L. A. Gibson, et al. "Analysis of factors implicated in the recent decline of Australia's mammal fauna." Journal of Biogeography 34, no. 4 (April 2007): 597–611. http://dx.doi.org/10.1111/j.1365-2699.2006.01639.x.
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Solonen, T., and P. Ahola. "Intrinsic and extrinsic factors in the dynamics of local small-mammal populations." Canadian Journal of Zoology 88, no. 2 (February 2010): 178–85. http://dx.doi.org/10.1139/z09-138.
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We studied dynamics of local small-mammal assemblages consisting of shrews, voles, and mice by small-scale snap trapping in each spring and autumn from 1981 to 2006 in southern Finland. Our aim was to search for relative roles of possible regulatory associations within and between species, as well as to find reflections of the effects of large-scale climatic phenomena on local populations. Preceding intraspecific densities had a dominating role in seasonal changes in small-mammal numbers. Their relationships with weather-related factors indicated by the indices of the North Atlantic Oscillation (NAO) were most pronounced during winter. Relationships with the NAO indices, increasing values of which indicate milder weather in the north, were negative in voles but positive in shrews and mice. Spring densities were governed by the largely compensatory effects of the growth rate of the preceding summer and subsequent population decline during winter in the field vole ( Microtus agrestis (L., 1761)) and mice, while the effects of winter decline dominated in shrews. The bank vole ( Myodes glareolus (Schreber, 1780) = Clethrionomys glareolus (Schreber, 1780)) showed decreasing winter decline, which had a considerable positive effect on population densities.
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Grossnickle, David M., and P. David Polly. "Mammal disparity decreases during the Cretaceous angiosperm radiation." Proceedings of the Royal Society B: Biological Sciences 280, no. 1771 (November 22, 2013): 20132110. http://dx.doi.org/10.1098/rspb.2013.2110.
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Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flowering plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two analyses were performed: (i) an examination of diversity based on functional dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes in mammalian morphological and dietary disparity. Results demonstrate a decline in diversity of molar types during the mid-Cretaceous as abundances of triconodonts, symmetrodonts, docodonts and eupantotherians diminished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic expansion coinciding with the angiosperm radiation, they display small body sizes and a low level of morphological disparity, suggesting an evolutionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experienced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.
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Wattinne, Aurélia, Christophe Lécuyer, Emmanuelle Vennin, Jean-Jacques Chateauneuf, and François Martineau. "Environmental changes around the Oligocene/Miocene boundary in the Limagne graben, Massif Central, France." BSGF - Earth Sciences Bulletin 189, no. 4-6 (2018): 19. http://dx.doi.org/10.1051/bsgf/2018019.
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Continental environments are very sensitive to climatic variations. A unique opportunity to study the climate changes around the Oligocene/Miocene boundary is offered by the Limagne graben Basin (France) where this stage boundary is well constrained by fossils. Indeed, some localities of the Limagne Graben Basin are so rich in mammal remains that they have become a European reference for mammal biostratigraphy. The dominant sedimentary facies of the lacustrine deposits in the northern part of the Limagne Graben Basin are composed of poorly cemented marls and calcarenites containing various plants and animals remains (e.g. algae, fish bones and teeth, gastropods, ostracods, mammals, birds and reptiles remains) associated with stromatolites. Mammal remains, well described in this area from the literature, were used to constrain the chronostratigraphic context of this lacustrine basin, with refinement thanks to new carbon and oxygen isotope measurements, palynological and sedimentological data. In this work, the available information obtained from a classical paleoecological study has been refined by new carbon and oxygen isotope analyses of carbonates and fish teeth retrieved from the washed sediment residues. The results of this study confirm that the Oligocene/Miocene boundary in Europe was a general period of aridity, associated with a cooler climate, which could be the cause of the decline in mammal paleodiversity observed during this period. The gradual evolution from brackish to fresh waters is indicated by the presence of ostracods and gastropods, and the major development of caddisflies. This period is associated to humid climatic conditions while a gradual increase in temperature took place throughout the second part of the Aquitanian. These environmental changes were driven by strong variations of temperatures and a contrasted seasonality.
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Masters, P. "The Mulgara Dasycercus cristicauda (Marsupialia: Dasyuridae) at Uluru National Park, Northern Territory." Australian Mammalogy 20, no. 3 (1998): 403. http://dx.doi.org/10.1071/am98403.
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Since the turn of the century, a third of the mammal species of arid Australia have suffered a drastic decline in distribution and abundance. Uluru National Park has not escaped the massive loss of mammals, with over 15 species being lost from the Park in the last century, and some, including the brush-tailed possum, Trichosurus vulpecula, becoming locally extinct in the last twenty years (Baynes and Baird 1992, Reid, Kerle and Morton 1993). This suggests that the processes causing the decline are still operating. The mulgara Dasycercus cristicauda, remains extant in the vicinity of Uluru National Park but has suffered extensive range reductions and is believed to be less abundant in areas which it still occupies (Kennedy 1990, Gibson and Cole 1992, Woolley 1995). Very little is known about the field ecology of D. cristicauda and this has hindered the conservation management of the remaining populations. I report here on ecological data collected from a population at Uluru National Park between 1987 and 1990. This information was collected during a study of the effects of fire on small mammals of the area (Masters 1993).
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Radford, James Q., John C. Z. Woinarski, Sarah Legge, Marcus Baseler, Joss Bentley, Andrew A. Burbidge, Michael Bode, et al. "Degrees of population-level susceptibility of Australian terrestrial non-volant mammal species to predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus)." Wildlife Research 45, no. 7 (2018): 645. http://dx.doi.org/10.1071/wr18008.
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Context Over the last 230 years, the Australian terrestrial mammal fauna has suffered a very high rate of decline and extinction relative to other continents. Predation by the introduced red fox (Vulpes vulpes) and feral cat (Felis catus) is implicated in many of these extinctions, and in the ongoing decline of many extant species. Aims To assess the degree to which Australian terrestrial non-volant mammal species are susceptible at the population level to predation by the red fox and feral cat, and to allocate each species to a category of predator susceptibility. Methods We collated the available evidence and complemented this with expert opinion to categorise each Australian terrestrial non-volant mammal species (extinct and extant) into one of four classes of population-level susceptibility to introduced predators (i.e. ‘extreme’, ‘high’, ‘low’ or ‘not susceptible’). We then compared predator susceptibility with conservation status, body size and extent of arboreality; and assessed changes in the occurrence of species in different predator-susceptibility categories between 1788 and 2017. Key results Of 246 Australian terrestrial non-volant mammal species (including extinct species), we conclude that 37 species are (or were) extremely predator-susceptible; 52 species are highly predator-susceptible; 112 species are of low susceptibility; and 42 species are not susceptible to predators. Confidence in assigning species to predator-susceptibility categories was strongest for extant threatened mammal species and for extremely predator-susceptible species. Extinct and threatened mammal species are more likely to be predator-susceptible than Least Concern species; arboreal species are less predator-susceptible than ground-dwelling species; and medium-sized species (35 g–3.5kg) are more predator-susceptible than smaller or larger species. Conclusions The effective control of foxes and cats over large areas is likely to assist the population-level recovery of ~63 species – the number of extant species with extreme or high predator susceptibility – which represents ~29% of the extant Australian terrestrial non-volant mammal fauna. Implications Categorisation of predator susceptibility is an important tool for conservation management, because the persistence of species with extreme susceptibility will require intensive management (e.g. predator-proof exclosures or predator-free islands), whereas species of lower predator susceptibility can be managed through effective landscape-level suppression of introduced predators.
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Rabinowitz, Alan, and Saw Tun Khaing. "Status of selected mammal species in North Myanmar." Oryx 32, no. 3 (July 1998): 201–8. http://dx.doi.org/10.1046/j.1365-3008.1998.d01-37.x.
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During 1996 and 1997, data on the status of selected mammal species were collected from a remote region of North Myanmar. Of the 21 species discussed in this paper, the black muntjac, stone marten and blue sheep are new records for the country. One species, the leaf muntjac, has never been described. At least three species that once inhabited the region – elephant, gaur and Sumatran rhinoceros – are no longer present, and the tiger has been nearly extirpated. Himalayan species that are declining elsewhere, such as takin, red goral and red panda, are still relatively abundant despite hunting pressures. Musk deer are in serious decline. The wolf, while not positively confirmed, may be an occasional inhabitant of North Myanmar.
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Hone, Jim, the late Graeme Caughley, and David Grice. "An experimental study of declining populations." Wildlife Research 32, no. 6 (2005): 481. http://dx.doi.org/10.1071/wr04092.
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Wildlife population declines have been attributed to predation, habitat change, and other agents of decline. An experimental study applied predation (at three levels) and habitat (at two levels) treatments over two years and measured the patterns of decline of populations of a medium-sized mammal (European rabbits). A model of population dynamics and effects of the treatments predicted negative effects of both treatments and an interaction of the treatments. All populations declined during the study including the experimental controls. During the first seven months (first phase of the study) the rate of decline, as estimated by the observed monthly instantaneous rate of increase (r), was more negative (P < 0.05) with increasing predation levels but there was no effect (P > 0.05) of habitat manipulation on r. There were no significant effects of treatments on rabbit abundance, or density, during the first phase of the study. During the second phase of the study, of 12 months’ duration, there were no significant (P > 0.05) effects of treatments on rabbit abundance, density, or r. There were no significant (P > 0.05) interactions of treatments on any response variable during either phase of the study. The interaction predicted by the theoretical model was not supported. Estimated abundance at the end of the study was not related (P > 0.05) to initial abundance (correlation = 0.023). The implications of the results are that such experimental studies can be used to evaluate theoretical models, though such studies may require a larger number of treatment replicates, and treatments at more extreme levels, to more clearly detect the effects of agents of population decline and their interactions.
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Baylis, Alastair M. M., Rachael A. Orben, John P. Y. Arnould, Fredrik Christiansen, Graeme C. Hays, and Iain J. Staniland. "Disentangling the cause of a catastrophic population decline in a large marine mammal." Ecology 96, no. 10 (October 2015): 2834–47. http://dx.doi.org/10.1890/14-1948.1.
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Cassano, Camila Righetto, Jos Barlow, and Renata Pardini. "Forest loss or management intensification? Identifying causes of mammal decline in cacao agroforests." Biological Conservation 169 (January 2014): 14–22. http://dx.doi.org/10.1016/j.biocon.2013.10.006.
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Aisher, Alex. "Scarcity, alterity and value: Decline of the pangolin, the world's most trafficked mammal." Conservation and Society 14, no. 4 (2016): 317. http://dx.doi.org/10.4103/0972-4923.197610.
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Klenner, Walt, and Thomas P. Sullivan. "Partial and clear-cut harvesting of high-elevation sprucefir forests: implications for small mammal communities." Canadian Journal of Forest Research 33, no. 12 (December 1, 2003): 2283–96. http://dx.doi.org/10.1139/x03-142.
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Subalpine spruce (Picea) fir (Abies) forests occur throughout the Cordillera of western North America. A variety of alternative silvicultural systems to clear-cutting are being investigated in these high-elevation forests in terms of their impacts on ecosystem components. We tested the hypotheses that abundance, reproduction, and survival of populations of (i) southern red-backed voles (Clethrionomys gapperi Vigors) will decline, (ii) long-tailed voles (Microtus longicaudus Merriam) and northwestern chipmunks (Tamias amoenus J.A. Allen) will increase, and (iii) deer mice (Peromyscus maniculatus Wagner) will be similar, with respect to decreasing levels of tree retention. Small mammal populations were live-trapped from 1994 to 1998 in replicated sites of uncut forest, single tree selection, 0.1-ha patch cuts, 1.0-ha patch cuts, a 10.0-ha clearcut, and edges in an Engelmann spruce (Picea engelmannii Parry ex Engelm.) subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forest near Sicamous, British Columbia, Canada. Clethrion omys gapperi dominated the small mammal community, reaching a peak abundance of 80 animals/ha with mean values ranging from 31 to 50 animals/ha. Over the 4 postharvest years, abundance, reproduction, and survival of C. gapperi populations were consistently similar among uncut forest, single tree selection, and patch cut treatments compared with clear-cut sites where this species declined to extirpation. Microtus longicaudus and T. amoenus occurred predominantly in clearcut sites, whereas P. maniculatus was present in low numbers on all sites. With respect to small mammals, partial harvesting systems appear to provide a means for combining timber extraction with maintenance of mature forest habitat in these subalpine ecosystems.