Animal Conservation最新文献

Fishing gear entanglements can compromise health and lower survival and reproductive output of wildlife, which can slow population growth or cause population declines. However, entanglements may go unobserved, making it difficult to quantify their effects on individuals' vital rates and a population's trajectory. Fishing gear entanglements are a leading cause of death for North Atlantic right whales, Eubalaena glacialis, an endangered species whose population has declined substantially over the last decade. Key sources of observation error have not been addressed when quantifying the effects of entanglement on this species. We formulated a hidden Markov model that integrated 28 years of photo identification records, visual health assessments, entanglement assessments, and hormone assays to estimate body condition dynamics, and entanglement, survival, and reproductive rates of female North Atlantic right whales. The model also accounted for observation errors, including entanglements and reproductive events that were unobserved. Whales entangled in fishing gear were drastically more likely to experience declines in body condition and had lower survival rates than whales that were not entangled. Additionally, only whales in good body condition became pregnant. Between 1994 and 2021 entanglements reduced the expected number of calves born by 12.9% (95% credible interval: 8.2%–19.6%) and the expected number of females alive at the end of 2021 by 18.5% (95% credible interval: 8.6%–29.4%). Fishing gear entanglements have reduced the North Atlantic right whale population's capacity to recover and have increased the importance of the health and survival of the remaining living whales. Therefore, reducing the risk of fishing gear entanglements is likely necessary for the population to recover.

Translocation outcomes in connected habitats are often uncertain, as individuals dispersing outside managed areas are exposed to threats. Post-release monitoring can reduce uncertainty by revealing how dispersal and habitat selection influences establishment and population growth which inform future translocations. We undertook post-release monitoring to identify habitat selection patterns following a translocation of toutouwai (North Island robin, Petroica longipes) to a large, contiguous forest habitat. Post-release monitoring aimed to estimate survival, dispersal, and territory establishment to inform management decisions and future release site selection. We created species distribution models using monitoring data to identify differences in habitat selection during the post-release dispersal and territory establishment phases. Toutouwai dispersed across 1312 ha but established territories within only 113 ha and 1 km from the release location. Site fidelity was higher than predicted, and there was no difference in dispersal or habitat selection across demographic groups. Critically, high site fidelity suggested that the extent of managed habitat was sufficient to protect dispersing individuals. Habitat selection preferences were stronger during territory establishment and were associated with lower slopes, higher water deficit and proximity to water reservoirs. Species distribution modelling allowed for predictions of high-quality core habitat where dispersal and territory establishment were more likely, resulting in targeted management to improve population growth. Our results show that initial dispersal in connected habitats may be much larger than suggested by territory data alone, and that management may need to protect larger areas to support successful establishment. We demonstrate how effective post-release monitoring can inform predictions of habitat quality and dispersal and guide management actions to improve translocations outcomes.

A major side effect of urbanization is the increased availability of food for wildlife in peri-urban areas. Most research has focused on highly adaptive exploiter species that thrive under such conditions, overlooking avoider species, which are often predated upon by exploiters. Moreover, peri-urban areas are often grazed by livestock, mainly to reduce the frequency and intensity of fires, a practice that can also adversely affect vulnerable wildlife species. We examined the long-term effects of excess food provided to discourage exploiter species, namely golden jackal (Canis aureus) and wild boar (Sus scrofa), from foraging on farmland and in human residencies. Both species prey on endangered mountain gazelles (Gazella gazella) in our peri-urban study area, which is nested within a mosaic of settlements and agricultural lands in Mediterranean Israel. Because the park is routinely subjected to seasonal cattle ranching, we included cattle stocking rate (mean ± SD: 51.77 ± 18.21 cow grazing days/ha) as an alternative factor, into our analysis. We used Generalized Linear Mixed Models to analyze an extensive dataset, comprising 724 surveys conducted over 17 years, and modeled gazelle encounter rates in response to excess food and cattle ranching, while controlling for environmental factors. Our results suggest that anthropogenic excess food through diversionary feeding led to decreasing gazelle densities, probably through increased predation by exploiter species. When diversionary feeding ceased after 12 years, gazelle encounter rates increased. We argue that this increase corresponds to population recovery, although it could be consistent with alternative mechanisms such as altered space-use and movement patterns. To conserve vulnerable and endangered wildlife species in urban and peri-urban areas, managers should reduce the availability of anthropogenic food for predators and scavengers. Furthermore, moderate cattle ranching (i.e., seasonal with low stocking rates) could mitigate potential adverse impacts of cattle ranching on mountain gazelle populations.

To supply the high demand for wildlife as exotic pets, animals may be illegally and unsustainably harvested from the wild and laundered as captive bred. Consequently, there is considerable interest in wildlife forensic tools that are capable of verifying captive origins. Stable isotope analysis is an emerging tool for verifying captive and wild origins by identifying key differences in dietary intake. While previous studies have effectively classified origins by differences in their stable isotope ratios, these studies are often limited to species with small population sizes and geographic ranges, masking potential variation caused by different environments and diets. We tested the accuracy of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analyses to verify captive and wild origins using bird species that are common in pet trade, and have widespread distributions and generalist diets. Through a citizen science project in South Australia, we collected naturally dropped feathers from four native Australian cockatoo (Cacatuidae) species: Galahs (Eolophus roseicapilla); and three Cacatua species; sulphur-crested cockatoos (Cacatua galerita), little corellas (C. sanguinea) and long-billed Corellas (C. tenuirostris). We compared isotope ratios of captive and wild birds and calculated the classification accuracy of using stable isotopes to determine origin. Stable isotope values were significantly different between captive and wild adult birds, where captive birds had significantly higher δ¹³C and δ¹⁵N than wild birds. Captive and wild origins of individual Eolophus could be classified with relatively high accuracy (88%). However, Cacatua showed low repeatability and large overlaps between the origin groups, which reduced their classification accuracy (74%). Stable isotope analysis can be a potential classification tool in wildlife trade; however, before on-ground implementation, we recommend that variation from different diets across a species' geographical range be more thoroughly investigated to better understand and explain the full range of possible δ¹³C and δ¹⁵N values.

Ectotherms are particularly threatened by climate change because they are strictly reliant on environmental conditions for homeostasis. Increasing environmental temperatures may approach the species' critical thermal maximum, with deleterious effects on individual thermoregulation capacities. This study tests the hypothesis developed in a recent work that under ongoing global warming populations living in sites at the warm edge of the species' thermal niche will suffer a disruption of the thermoregulation process, with detrimental effects at the individual and population level. We collected individual measurements and temperature data for Mediterranean endemic rock lizards, across the entire distribution range of the species and during two different sampling periods ~20 years apart to compare thermoregulation coefficient (C), body condition index (BCI) and population size under different climatic conditions. We found that C and BCI vary across space and time following a linear pattern along the thermal niche gradient (Niche Margin Effect, NME) until a threshold temperature, beyond which the NME is disrupted. This threshold temperature indicates the warm edge of the species' thermal niche. A slightly higher temperature marks the threshold at which we observed significant population declines over the 20-year study period in the warmest sites. This suggests a lagged response of population trends to climate warming. This study suggests a mechanism of disruption of homeostatic processes when the warm margin of the thermal niche is reached and indicates that individual parameters such as thermoregulation coefficient and body condition, rather than demographic trends, are key indicators for an early detection of population extinction risk. The multipopulation approach implemented in our study allows to identify the niche edge that underlies species' vulnerability to global warming, and to identify populations suffering negative effects of climate change before demographic collapse. This might allow to plan appropriate mitigation measures and management strategies to avoid local extinctions.

Freshwater ecosystems are among the most threatened globally. Understanding how environmental variables influence the gene flow of freshwater species can help identify landscape features requiring conservation management. We used landscape genetic resistance modelling to assess the influence of climate, topography and vegetation cover on genetic structure and gene flow in platypus (Ornithorhynchus anatinus) in an urban region of south-east Queensland, Australia. Thirty DNA samples were genotyped using the DArTseq platform, and data were filtered to produce a panel of 5478 neutral single nucleotide polymorphism (SNP) markers. We used fastSTRUCTURE, partial redundancy analysis and maximum likelihood analyses to understand platypus genetic structure and landscape influences on gene flow. Between one and three genetic clusters were detected using fastSTRUCTURE. Partial redundancy analysis identified Topographic Wetness Index and antecedent rainfall as driving genetic differentiation between samples. A maximum likelihood population effects model suggested gene flow was spatially structured by Normalised Difference Vegetation Index at a fine scale (100 m) and antecedent rainfall at a landscape scale (1 km). Thus, less vegetated areas appear to restrict the gene flow of platypus in urban systems. Rainfall, vegetation cover and topographic wetness are also important for maintaining platypus gene flow across landscapes. Our research recommends conservation management through restoration of water flow and riverine vegetation to help maintain platypus connectivity and increase gene flow among populations.

Ecotourism is branded as transforming wildlife biodiversity conservation; yet, its positive and negative effects are not always assessed in wild populations. Wildlife viewing with feeding is a popular form of ecotourism, but its potential health impacts on wildlife are becoming increasingly evident. Shark feeding is a global phenomenon; however, impact studies on species' persistence (i.e. survival and reproduction) are lacking. In this study, we expand upon previous work on shark tourism and use physiological indicators to assess the sub-lethal health and fitness consequences of shark feeding. Blood cellular, biochemical and endocrinological parameters were sampled from 117 adult wild blacktip reef sharks, Carcharhinus melanopterus, at feeding and non-feeding sites around Mo'orea, French Polynesia, to compare general condition, nutritional status, a metabolism proxy and reproductive investment on the respective sites. In addition to sex- and season-specific differences observed in multiple physiological parameters, we found lower haematocrit levels (condition) at feeding sites for both sexes, as well as lower insulin levels (metabolism proxy) in male sharks at feeding sites. Further impacts of feeding on physiology were found in interaction with the breeding season: adult females using feeding sites had lower glucose levels (nutritional status), as well as lower 17β-oestradiol levels during the breeding season (reproductive investment) compared to non-feeding sites. Male sharks using feeding sites during the breeding season exhibited higher levels of testosterone compared to non-feeding sites. Our results suggest that tourism feeding activity in Mo'orea provides poor nutrition and/or unpredictable food, especially for site-attached females during the energy-intensive breeding season. We highlight how physiological indicators reveal negative health and fitness impacts of shark feeding, with the reproductive impacts potentially having longer-lasting consequences for population dynamics, making feeding an ecological trap. Animal sex and season should be considered when evaluating feeding impacts, and stricter regulations for the nutritional content of the food given to sharks are needed in ecotourism management.

Suites of coevolved traits related to reproduction and demography enable species to persist in the face of environmental change. In the case of biological invasions, the suite of life history traits, “life history strategies,” can be linked to successful establishment after an introduction. Conservation translocations share many similarities with biological invasions, yet studies examining the relationship between life history and translocation outcome are scarce. We collected data on key life history traits for all herpetofauna profiled in the IUCN Global Conservation Translocation Perspectives series to examine how life history can predict outcomes and difficulties of conservation translocations. For reptiles, our model showed that age at maturity showed a significant positive association with higher probabilities of more successful outcomes, while increased clutch/litter size and lifespan predicted less successful outcomes. We found no relationship between any life history trait and translocation outcome for amphibians. Our results showed that difficulties with conservation translocations are related more to phylogeny than life history. Amphibian translocations faced more difficulties due to the physical environment of release sites, but reptile translocations experienced more socio-political difficulties. These relationships provide important insights for conservation practitioners that can be used in the feasibility and planning stages of translocations to anticipate and avoid challenges facing this complex and increasingly common form of conservation intervention.