Animal Conservation最新文献

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.

Conservation reintroductions play a vital role in the recovery of threatened species, and clear goals and objectives are essential for evaluating their effectiveness. In this study, we assessed short-term success (<18 months) of trial reintroductions of the Extinct in the Wild blue-tailed skink (Cryptoblepharus egeriae) and Lister's gecko (Lepidodactylus listeri) on Christmas Island. Our evaluation criteria focused on body condition, reproduction, habitat suitability, survival and population growth. In 2018 and 2019, 170 C. egeriae and 160 L. listeri were translocated from a local captive breeding facility to a 2600 m² outdoor fenced enclosure designed to exclude a predatory snake. Despite body condition declining immediately following release for both species, it had improved by 6 months post-release. We also detected successful reproduction in both species. Apparent survival was high for C. egeriae but low for L. listeri, and population growth was only evident in C. egeriae. We were unable to determine whether low survival of L. listeri in the release site was due to high post-release dispersal (beyond the exclosure) or mortality. Both species selected habitats that contained high rock and log cover and avoided areas with low ground cover. Appropriate assessment criteria, as utilized in this study, enable objective and timely evaluations of reintroduction success, thereby facilitating the improvement and refinement of reintroduction protocols. Our study showed that C. egeriae can establish (in the short- to medium-term) in a site from which a principal threat has been excluded and undergo rapid population growth, whereas under current conditions L. listeri cannot. However, we also demonstrate that such medium-term success may not lead to long-term success, as the rapid increase in C. egeriae population was reversed between 29 and 31 months after release because the barrier used to exclude an invasive predator, the wolf snake (Lycodon capucinus), was breached.

Reinforcements are a well-established tool for alleviating small population pressures of inbreeding and genetic diversity loss. Some small populations also suffer from specific threats that pose a discrete selective pressure, like diseases. Uncertainty about reinforcing diseased populations exists, as doing so may increase disease prevalence and disrupt potential adaptive processes. However, without assisted gene flow, isolated populations are at high risk of extinction. Tasmanian devils (Sarcophilus harrisii) are a useful case study to test whether reinforcements can alleviate small-population pressures where there is an ongoing disease pressure. We investigated demographic, genome-wide and functional genetic diversity, and disease consequences of reinforcing a small population (<20 animals) that was severely impacted by devil facial tumour disease. Released animals from one source population successfully bred with incumbent individuals, tripling the population size, improving genome-wide and functional diversity and introducing 26 new putatively functional alleles, with no common alleles lost and no increase in disease prevalence. Results suggest, in the case of Tasmanian devils, reinforcements can alleviate small-population pressures without increasing disease prevalence. Because no common functional alleles were lost, it is likely that any adaptive processes in response to the disease may still occur in the reinforced population, perhaps even with greater efficiency due to reduced genetic drift (due to larger population size). Our study is presented as a comprehensive worked example of the IUCN's guidelines for monitoring reinforcements, to showcase the value of genetic monitoring in a richly monitored system and provide realistic approaches to test similar questions in other taxa.

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.

Reintroductions of threatened species is a conservation strategy utilised around the world. Unfortunately, many translocated individuals have poor rates of survival post-release. If released individuals are unable to socially integrate into wild populations, they might lose the safety of the group or fail to learn critical skills. We examined the effects of age and captivity on sociality and migration survival for the critically endangered orange-bellied parrot (Neophema chrysogaster). As part of recovery efforts, adult birds are released in spring to contribute to breeding and juveniles are released in autumn prior to migration. Historically, captive-bred adults have low rates of migration survival, whereas captive and wild juveniles survive at comparable rates. We investigated both the long-term impacts of captivity on sociality and how sociality impacted migration survival by constructing social networks and comparing captive and wild birds of different age classes. We found no differences between captive and wild birds, suggesting that released birds integrated into the population. However, juveniles were more strongly connected and demonstrated greater network stability than adults. While we found no impact of sociality on survival, our results provide evidence of different migration strategies previously described for juveniles and adults: adults depart in small groups and juveniles depart as a larger flock a few weeks later. We suggest that the low migration survival of captive-bred adults may be attributable to this cohort missing the juvenile flocking phase. These results suggest that a juvenile developmental phase may be impactful in this species for future survival.

Assisted colonization to locations predicted to remain climatically suitable in the future is increasingly necessary to mitigate climate change effects in ectotherms such as reptiles. However, these future-suitable locations are often currently cooler than those from which individuals are sourced. While species-wide paradigms prevail, responses to thermal regimes may vary across a species range, affecting daily activity, colonization and survival in a new environment. Additionally, hydro-regulatory behaviours are severely understudied, despite the need for understanding trade-offs between thermoregulation and hydro-regulation for successful assisted colonization strategies. We investigated behavioural responses to temperature and relative humidity in two latitudinally distinct lineages of pygmy bluetongue (Tiliqua adelaidensis), a cryptic, burrow-dwelling endangered lizard, in the Mid-North of South Australia. From spring 2020 to autumn 2021 we took monthly field-based approach distance and behavioural footage at the source locations and at a southerly translocation site. Behaviours were matched to site-specific microclimate data prior to principal component and generalized linear mixed model analysis. We found lineage differences in behaviour that persisted after translocation; southern lineage lizards showed significantly less daily activity and were active at lower temperatures and higher humidity than northern lineage lizards. Southern lineage lizards allowed a human observer to approach closer as base-of-burrow humidity increased, while northern lineage lizards were quicker to retreat into burrows, at both source and translocation sites. Novel, non-invasive field-based activity curves successfully identified lineage differences in humidity and temperature ranges for surface activity, implying environmental preferences of target populations that were reinforced by the models. Specifically, we found evidence for thermoregulation and adaptation/acclimation to higher temperatures in northern lizards and hydroregulation and adaptation/acclimation to cooler, more humid conditions in southern lizards. The limited behavioural plasticity shown by translocated individuals over the season demonstrates the importance of understanding lineage-level behaviours, hydro-regulation, and micro-climate when selecting individuals for assisted colonization.

Degradation of natural and semi-natural habitats is often initiated and facilitated by expansions in anthropogenic infrastructures. Identifying and reducing the impact of anthropogenic structures on the wildlife that these habitats support is vital for biodiversity conservation. In Iceland, the number of summer houses has increased over the past two decades, from ~10 000 to 15 000, and >7000 additional plots for summer house construction have been approved. Most of this housing infrastructure development is in the Icelandic lowlands, which support internationally important populations of several ground-nesting bird species. To explore the effects of summer house infrastructure on the distribution of ground-nesting birds, we conducted surveys at 292 points within 71 sites with varying density of houses and associated infrastructure (tracks, decking, etc). Significant reductions in abundance with increasing housing density occurred in five (Golden Plover (Pluvialis apricaria), Black-tailed Godwit (Limosa limosa), Redshank (Tringa totanus), Whimbrel (Numenius phaeopus) and Meadow pipit (Anthus pratensis)) of the seven study species, while one species (Snipe (Gallinago gallinago)) showed no change and one (Redwing (Turdus iliacus)) increased. The differences in abundance between plots with no houses and plots with high house densities (>0.5 houses ha⁻¹) ranged from 34 to 95%, despite the housing infrastructure covering only ~6% of the area of these plots. These findings suggest that even relatively low densities of anthropogenic structures in natural or semi-natural areas can have substantial impacts on wildlife in the surrounding areas and highlight the urgent need for effective planning regulations to limit the expansion of anthropogenic structures into currently undisturbed habitats, particularly in areas of high biodiversity value.

Blue whales (Balaenoptera musculus) are the largest living animal and, like other baleen whales, became endangered due to whaling. Here, we used population genomics to infer the number, distribution and other characteristics of subspecies and populations. We used the largest DNA dataset in blue whales, both in terms of genomic markers (16,661 SNPs and mtDNA) and geographic coverage (n = 276 for SNPs; n = 531 for mtDNA). We found greatest divergence among the eastern Pacific, Indo-western Pacific and Antarctic blue whales. There were indications that natural selection in different environments promoted divergence among these groupings. Within these regions, there was divergence between the eastern North and eastern South Pacific, and among the eastern Indian Ocean, the western South Pacific and the northern Indian Ocean. There was no divergence within the Antarctic. These findings are consistent with the current classification of Antarctic and Indo-western Pacific blue whales in the Southern Hemisphere as different subspecies but call into question the subspecies taxonomy of eastern Pacific blue whales. The study shows that opposite breeding seasons on either side of the equator do not necessarily inhibit connectivity across the equator, and reinforces that population structure needs to be well understood to conserve the diversity within species.

Understanding factors that influence population-level responses to emerging threats in declining species is crucial for informed conservation action. In amphibian species impacted by the chytrid fungus (Batrachochytrium dendrobatidis), a pathogen that has caused amphibian declines globally, a commonly reported pattern is that more severe population declines tend to occur at higher elevations. Previous research has suggested that this pattern could be driven by reduced environmental suitability for chytrid fungus at lower elevations. However, delayed amphibian maturation, which is common in cold, high elevation populations, could also increase vulnerability to population decline. Here, we tackle this key knowledge gap, focusing on the critically endangered corroboree frogs (Pseudophryne corroboree and P. pengilleyi), which have experienced a pattern of extirpation at higher elevations, with remnant populations persisting at lower elevations. First, we quantify the age structure of two extant low elevation P. pengilleyi populations and museum specimens (both species) collected before the emergence of chytrid fungus in Australia. Male age to maturation varied from 1 to 3 years, with the extant population with higher chytrid prevalence displaying severe age structure truncation. Second, we use population simulations to calculate elasticity values under a range of scenarios with varying ages to maturation and chytrid-associated mortality. When the population growth rate was fixed at 1, adult survival became increasingly important as age to maturation increases, particularly under a scenario of high chytrid-associated mortality. Our simulation results indicate that delayed maturation could be a previously underappreciated factor associated with an increased risk of amphibian population decline and that earlier maturation could contribute to population persistence. Our study highlights the importance of examining variation in life history traits to better understand population-level responses to novel threats and guide the development of appropriate conservation actions.