Animal Conservation最新文献

Amphibians are among the most endangered taxa worldwide, but little is known about how their disappearance can alter the functioning and structure of freshwater ecosystems, where they live as larval stages. This is particularly true for urodeles, which often are key predators in these ecosystems. The fire salamander (Salamandra salamandra) is a common predator in European fresh waters, but the species is declining due to habitat loss and the infection by fungal pathogens. We studied the consequences of fire salamander loss from three montane streams, by comparing two key ecosystem processes (periphyton accrual and leaf litter decomposition) and the structure of three communities (periphytic algae, aquatic hyphomycetes and invertebrates) using stream enclosures with and without salamander larvae. Salamander loss did not cause changes in invertebrate abundance or community structure, except for one stream where abundance increased in the absence of salamander larvae. However, salamander loss led to lower periphyton accrual, changes in algal community structure and slower leaf litter decomposition, with no associated changes in fungal communities or microbial decomposition. The changes observed may have been caused by release of salamander predatory pressure on invertebrates, which could have promoted their grazing on periphyton, in contrast to their preference for leaf shredding in the presence of salamander. Our study demonstrates an important role of salamander larvae in montane streams through top-down control of lower trophic levels and thus in regulating key stream ecosystem processes. Our results highlight the need for improving protection measures for amphibians to prevent these alterations on ecosystem structure and function.

Half of all migratory bird species have declined over the past 30 years, with intercontinental migrants declining faster than their short-distance migratory counterparts. One potential cause of these declines is habitat loss and degradation on tropical wintering grounds, where agricultural conversion of natural habitats and intensification of traditional, low-intensity agricultural systems are frequently occurring. Although the broad patterns of wintering migrant abundance are well understood along most flyways, how species' habitat associations vary across disturbance gradients in agricultural landscapes remains a key question, with implications for landscape-level farm management and restoration activities. We used 328 point count locations and associated habitat assessments targeted at a cohort of eight severely declining Afro-Palaearctic migratory passerines in the Guineo–Congolian transition zone of Western Africa to model the probability of the presence of migrants within grass, shrub, forb and forest-covered areas. We found support for the widespread use of early successional habitats retained within traditionally managed farmland by migrants. Most species utilize scrubland on fallows within the agricultural mosaic, especially Spotted Flycatcher, Garden Warbler, Melodious Warbler, Whinchat and Common Nightingale. Only Pied Flycatcher relied upon mature forested areas. The avoidance of mature forested habitats by most species suggests that habitat requirements of severely declining migrant birds must be explicitly considered within conservation and restoration schemes, via mechanisms to retain low-intensity farming, especially short-term abandoned fallows that regenerate scrubby areas within the agricultural matrix. Any habitat management within the agricultural matrix should be considered in the context of the needs of local communities.

Urbanization forms one of the most drastic alterations of the environment and poses a major threat to wildlife. The human–induced modifications of the landscape may affect individual's fitness resulting in population declines. Research on how urbanization affects fitness traits has shown mixed results. However, studies typically contrasted data from a single species from few urban and non-urban sites collected over short timeframes. Examining multiple species across a broad urbanization gradient enables a more robust comparison and understanding of how different species are impacted by urbanization-knowledge crucial for generating population predictions, which are essential for conservation management. Here, we use data from a nation-wide citizen science project to examine variation in survival and relative body mass and size (wing length) of common passerine birds, collected along an urbanization gradient in the Netherlands over an 8-year period. Urbanization was measured as the distance from the city's border and the proportion of impervious surface area. Although the overall association between urbanization and survival was slightly negative, there was support for lower survival closer to the city in three species (chiffchaff Phylloscopus collybita, European robin Erithacus rubecula, European greenfinch Chloris chloris) and higher survival closer to the city in two (great tit Parus major and house sparrow Passer domesticus) of the 11 species examined. The contrasting survival successes among species suggest that ongoing urbanization may lead to shifts in community structure and loss of biodiversity. Impacts of urbanization on relative mass and size also exhibited varying effects, albeit less pronounced, and these effects were not correlated with the effects on survival. This implies that body mass and size cannot be used as indicators for urban-associated patterns of survival. Our results further imply that effective conservation management targeting bird communities should involve a range of diverse actions, as focusing on single measures is unlikely to simultaneously impact multiple species due to the variation in responses to urbanization.

Anticoagulant rodenticides (ARs) are an effective tool used to suppress rodent populations in urban and agricultural settings to reduce human disease risk and economic loss, but widespread use has resulted in adverse effects on predators globally. Attention has largely been focused on impacts of ARs on raptors, although there is increasing evidence that mammalian carnivores are also impacted. We conducted a literature review to assess the extent to which ARs have been documented in wild mammalian carnivores globally and identify potential overlap with imperiled carnivores. We found a small but growing body of literature documenting exposure to ARs in 8 Carnivora families, with Mustelidae (64% of studies), Canidae (44%) and Felidae (23%) most represented. At least 11 different AR compounds were documented in carnivores, and authors claimed that exposure caused mortality of at least one individual in 33.9% of species studied. ARs were listed as a threat for 2% of Red List carnivores, although we found that 19% of Red List carnivores had ranges that overlap countries that have documented AR exposure in carnivores. Collectively, our review highlights the need to prioritize conservation attention on the potential role of ARs on global carnivore declines. We suggest (1) expanding AR monitoring and research outside of the northern hemisphere, (2) supporting long-term AR monitoring to understand the spatial and temporal variation of AR use and exposure risk, (3) expanding research across trophic levels and across the urban–wildland gradient and 4) research to further our understanding of the point at which morbidity and mortality occur.

Mitigation translocations move wildlife from specific areas due to conflict with humans over land use at the site. A critical decision when carrying out mitigation translocation is the acceptable distance across which animals can be moved. This decision trades off logistical expediency of unrestricted translocation with the risk of reducing translocation success due to environmental mismatch between origin and translocation site conditions. In this study, we used a large dataset of 502 individually identifiable carcasses to examine the role of geographic origin and translocation distance in the relative survival of 2822 translocated subadult and adult gopher tortoises (Gopherus polyphemus), a species experiencing large-scale mitigation translocation, at a recipient site in the Florida panhandle, USA. We hypothesized that if climate or habitat differences between the origin and translocation site influenced survival, tortoises translocated from within the Florida panhandle would have the highest survival. To the contrary, we found that survival slightly increased with increasing climatic difference between origin and recipient site, driven by higher survival of tortoises coming from central Florida sites compared to those from the panhandle and north Florida. This suggests that environmental mismatch due to long-distance translocation is not a main driver of mortality. These models also indicated an effect of season, with a survival advantage to tortoises translocated in the spring and late fall, relative to summer translocations, and a negative effect of initial density on survival. Finally, we also estimated the upper bound on annual survival in three well-monitored groups to be quite low (92–95%) for several years following release, suggesting caution when considering large translocated populations to be viable without first assessing adult survival. Our unexpected results highlight the importance of investigating species-specific sensitivities to translocation distances and indicate the limitations of assumed linear effects of translocation distance on outcomes.

Understanding the impacts of habitat conversion on species assemblages across multiple biodiversity dimensions (taxonomic, functional, and phylogenetic) and spatial scales is pivotal for implementing effective conservation strategies. Here, we surveyed phyllostomid bats using mist nets in riparian and unflooded forests, flooded savannahs, and conventional rice fields to investigate how changes in habitat quality affect multifaceted diversity from two Colombian farming systems in the Orinoco Llanos: traditional farmlands with high-intensity agriculture (mainly rice production) and Civil Society Nature Reserves with greater ecosystem protection. We used a unified framework based on Hill numbers for quantifying bat taxonomic, functional, and phylogenetic diversity and modeled the relationship of these diversity facets with landscape variables (habitat cover and patch density) across three spatial scales (0.5, 1.5, 3 km) using Bayesian generalized linear mixed-effect models. Our results indicate that increasing human activity toward rice monocultures representative of traditional farmlands negatively affected all diversity facets. In contrast, forested habitats associated mainly with riparian forests within private reserves contained higher taxonomic, functional, and phylogenetic diversity than savannahs and rice fields. However, the differences between riparian forests and rice crops were significant only for phylogenetic diversity, indicating loss of evolutionary history after habitat conversion. At the landscape scale, forest cover was a significant predictor for functional (0.5- and 3-km scale) and phylogenetic diversity (0.5 km), and bats responded negatively at the 3-km scale to rice patch density from a functional diversity perspective. Increasing habitat quality through preserving forest cover and patches should minimize the harmful effects of habitat conversion on multidimensional bat biodiversity. Furthermore, the conservation of riparian forests and the creation of more wildlife-friendly farming, as practiced in the reserves, should be prioritized to ensure high levels of bat taxonomic, functional, and phylogenetic diversity across Orinoco countryside landscapes.