Animal Conservation最新文献

Humans and large aquatic predators compete for fish and negative interactions are widely reported as ‘human–wildlife conflicts’. When aquatic predators are perceived to damage fisheries or fishing equipment, lethal control can occur. The perceptions and reality of damage are infrequently compared, but this relationship is key to determining how negative outcomes can be mitigated. We examine coexistence between people and six large aquatic piscivores (two caiman, two dolphins, two otters) in Amazonian Peru. We determine the extent of damage to fishing equipment caused by each species and compare this to the amount of damage perceived by fishers. Giant otter populations have recently recovered in some areas, so we expected different perceptions relating to experiences with otters. We trained fishers to complete fishing registers (n = 278, 1173 h of fishing) to record damage to nets by wildlife. We interviewed 302 people from three sites to determine perceptions of damage by predators, and attitudes towards giant otters. Rates of damage to nets reflected the presence and populations of different aquatic predators at each site, but when present, dolphins and caimans damaged nets more than otters, which rarely damaged nets. People living where giant otters had recently recovered perceived higher relative levels of damage to nets by them and had more negative attitudes about them, compared to people from areas where giant otters had been present for longer, aquatic predators were more abundant, and community resource management was longer-established. Better knowledge and more experience with a species may lead to more accurate perceptions of damage and increased tolerance. Where humans and animals compete for natural resources, conflict mitigation rarely includes better resource management. If tolerance of predators is greater where predators are common, and resources have not been overexploited, resource management may yield greater gains for stakeholders than other commonly prescribed forms of mitigation.

Roads can impact population abundance due to mortality from collisions with vehicles, habitat degradation and loss of connectivity. Some species, however, can be unaffected or even positively affected by roads and roadside environments. Despite this, there is scarce information on population-level responses to roads. To fill this knowledge gap, we sampled medium and large mammals with camera traps near two paved roads with low and high traffic volumes in agricultural landscapes in the Brazilian Cerrado. We used Royle-Nichols' occupancy models to investigate the effects of road proximity on the local abundance of 12 mammal species with varying susceptibility to roadkill. We found that road proximity affected only three species, all of which had high roadkill rates. While two of these species exhibited lower abundance near roads, the third showed the opposite response. For most species, irrespective of their roadkill rates, variations in local abundance were strongly correlated with habitat quality and connectivity. Species' life-history traits, individual behaviour and the impact of roads and traffic on populations over time may explain these idiosyncratic responses.

Desert spring systems of the American southwest hold high local fish endemism and are ranked among the most threatened ecosystems in the world. The prioritization of conservation resources to protect species living within these arid landscapes requires knowledge of species abundance and distribution. The plight of Conchos pupfish (Cyprinodon eximius) is representative of freshwater fishes the world over, including population extirpations caused by human poisoning of streams and reservoir construction, to the extent that the species was once considered extinct in the USA. We developed a distance-sampling framework to monitor Conchos pupfish abundance and coupled this approach with species distribution modeling to guide conservation actions. Our multiscale approach included surveying abundances within 5-m transects at three reaches of the Devils River, where the last known USA populations persist. We combined this fine-scale analysis with species distribution modeling for stream segments across the range of the species in Mexico and USA. Modeling revealed Conchos pupfish abundance among transects was negatively correlated with current velocity and detection was negatively correlated with water depth. Estimated abundance at a reach where the species was previously reintroduced was greater than other reaches combined in November 2019, lowest in March 2021 when reach water levels were very low, then equivalent with other reaches by October 2021 after water returned to the reach. Modeled Conchos pupfish distribution illustrated a high probability of occurrence on the periphery of the species' overall range within Texas, USA and broadly across Chihuahua, Mexico, where proposed protected areas might benefit the species. Our study provides conservation guidance by establishing (1) baseline and trajectory values for abundance, (2) transect locations where abundances might be managed within existing protected areas, (3) reaches where high abundances could be used for future repatriation, and (4) stream segments where future surveys might be conducted to assess conservation opportunities.

The clearing and fragmentation of tropical forests is the single biggest threat to primate populations who depend on this habitat for survival. In contrast to primates that live in continuous, undisturbed forests, primate communities of fragmented forests need to adapt to decreased food availability and increased inter- and intraspecific competition typical of these degraded and anthropogenically disturbed habitats. Some primate species are highly sensitive to habitat fragmentation, whilst other species can adapt and even thrive in fragmented and degraded forests. Here, we assessed how forest fragmentation and associated edge effects impact the population density of four species of nocturnal lemur in the Sahamalaza-Iles Radama National Park, North West Madagascar. We conducted 118 transect walks over a 3-year period covering a total distance of 107 km to collect encounter rate (N/km) and population density (N/Ha) data for each species, which we then compared between the edge and core areas of a continuous forest and a fragmented forest. Our results were highly species-specific, with the population densities of two species (Lepilemur sahamalaza and Microcebus sambiranensis) increasing in edge and fragmented habitat, whilst we observed the opposite for Cheirogaleus medius. Mirza zaza density appeared consistent between the continuous and fragmented forest and in both edge and core areas. We also found evidence of species-specific population density relationships with fragment size, core area and fragment shape; however, further work is needed to support these findings. This study demonstrates that some nocturnal lemurs can adapt to degraded habitats and thrive within fragmented forests, whilst other species are less capable of doing so.

Accurate abundance estimates are essential for the development of effective conservation management strategies, yet they are difficult to produce for small populations that are elusive and sparsely distributed throughout their range. For such populations it is challenging to collect a representative dataset sufficient for robust estimation of detectability and abundance. Over a one-year study, we used two methods to estimate abundance of a Nationally Critical, widely dispersed Bryde's whale population in the Hauraki Gulf, Aotearoa/New Zealand; (i) distance sampling from systematic line-transect aerial surveys (n = 22 surveys, 9,944 km, total sightings 21–24 whales), and (ii) mark-recapture (MR) using photo-identification images collected from a platform-of-opportunity and small-boat surveys (218 sampling occasions, 27 whales). From the aerial surveys, we estimated an average of 15 whales (95% CI = 6, 30; CV = 37%) at the sea-surface at any time. For the boat-based surveys, we developed a custom MR model to address seasonal and individual heterogeneity in capture probabilities and obtained an estimate of 72 distinct whales (95% CI = 38, 106; CV = 24%) in the population. These two approaches provide different perspectives on the abundance and dynamics of Bryde's whales. The aerial surveys estimate the average number of individuals present at any one time, whereas the MR model estimates the total number of animals that used the Gulf during the study. Although neither sampling method is optimal for estimating the abundance of this small, dispersed population, the use of two complementary approaches informs conservation managers about patterns of abundance and distribution over different temporal and spatial scales. It is common to have limited resources for marine research where model assumptions cannot be met. Here, we highlight pragmatic strategies showing how models can be customized to the population of interest to assist with monitoring species of conservation concern.

The proliferation of forest edges and invasive predators have been identified as two primary threats to carnivore populations globally. These threats often occur in unison, facilitated by anthropogenic activities (e.g., fragmentation), and together may pose a greater influence than when they occur separately. Targeted conservation actions for forest carnivores, including Madagascar carnivores, have been hindered by a failure to understand the relative contributions of these factors in driving species declines. To fill this gap, we conducted an extensive camera survey along the edge of intact, continuous protected rainforests in eastern Madagascar to evaluate the extent invasive predators and forest edge separately and in combination affect native carnivore space use. We hypothesized that structural vegetation changes at the forest edge interact with invasive predator trap success and occurrence to reduce native carnivore space use near the forest edge and separately have less influence than when combined. In contrast to findings in fragmented and degraded forests of Madagascar, we found hard forest edge and invasive predators alone do not indiscriminately reduce native carnivore space use in continuous intact forest. Instead, we found free-roaming dogs and cats interact with their surrounding environment (i.e., forest edge) in unique ways that shape species response differently than within interior forest. At the forest edge, vegetational changes of increasing shrub cover and the occurrence of dogs reduce space use of three of four native carnivores. However, we found greater effects of proximity to villages, especially with high invasive predator activity (free-roaming cats). Ultimately, native carnivores showed variable sensitivities to pressures we examined, providing support for species-specific management actions to maximize conservation outcomes. We encourage future studies to consider evaluating the magnitude of separate and combined threats to carnivores. In doing so, conservationists can better identify when threats can be managed in isolation and when they require simultaneous mitigation.

Determining the effectiveness of conservation actions is a priority in conservation biology, especially in island ecosystems which can host large numbers of endemic and often threatened species. In this study, we have brought together a genetic, body condition and breeding success assessment with the aim of evaluating the viability of a newly founded population of the endangered Gran Canaria blue chaffinch (Fringilla polatzeki), the forest passerine species with the most restricted distribution in the Western Palearctic. The species occurs exclusively in the Canary pine forests (Pinus canariensis) of the island of Gran Canaria, with the Inagua nature reserve harbouring the highest number individuals. In 2010, a translocation program was initiated within the same island in the nearby pine forests of La Cumbre with the goal of establishing a viable breeding population. Genetic results revealed that La Cumbre shows genetic parameters (diversity, inbreeding, and relatedness) similar to the core source of Inagua, which contrasts with the reduced genetic diversity expected due to the small size of the newly founded population. The biometric and body condition results (wing and tarsus length, body mass, and length asymmetry of the tail feathers), together with the breeding success (nest survival and number of fledglings per successful breeding attempt), were also similar in both populations. Overall, these findings suggest that the translocation program has been successful and provide insights on the effectiveness of the actions performed. Our evaluation also delivers future avenues for the conservation planning in other upland forest endangered avian species inhabiting island ecosystems, especially those threatened by the effects of global warming.

Many Australians who work outdoors (notably, farmers and graziers) routinely kill venomous snakes. We argue that this attitude is misguided and dangerous. Despite their fearsome reputation, venomous Australian snakes pose little risk to human health (snakes kill an average of less than three people per year in Australia). Also, snakes confer a substantial benefit by consuming agricultural pests such as rodents. We estimate the magnitude of that benefit with data on snake diets, feeding rates and abundances. The most valuable rodent-controllers are Brownsnakes (genus Pseudonaja), which are rodent-specialists as adults and are abundant in agroecosystems across much of Australia. We calculate that a free-living adult Eastern Brownsnake consumes at least 50 mice per year (probably twice that number), and that population densities of Brownsnakes in agricultural areas can exceed 100 per km². Thus, Brownsnakes remove thousands of mice per square kilometre of farmland per year. That offtake plausibly reduces rodent densities because Brownsnakes take all age classes and both sexes of rodents by hunting in burrows. Tolerating Brownsnakes also would benefit the environment (e.g. less reliance on toxic chemicals) and the health of humans and domestic pets (fewer rodent-mediated diseases) and counter-intuitively, might reduce rates of snakebite (because many bites occur when a snake is attacked). In summary, a societal policy of coexisting with highly venomous snakes would confer multiple benefits to Australian farmers.

Insectivorous bats in temperate zones have evolved strategies such as migration or hibernation to overcome challenges of reduced resource availability and increased energy demand during winter. In the southeastern United States Coastal Plain, bats are either year-round residents and remain active during winter or are migrants from colder areas seeking milder temperatures. Southeastern Coastal Plain forests also may represent important areas for remnant populations of species impacted by white-nose syndrome. Working pine (Pinus spp.) forests comprise a large proportion of southeastern Coastal Plain forests, yet winter bat habitat associations and how forest management affects bat use remain understudied. Hence, we used hierarchical multispecies spatial occupancy models to evaluate factors influencing winter bat occupancy and foraging habitat associations in working forests of the southeastern Coastal Plain. From January to March 2020–2022, we deployed Anabat Swift acoustic detectors and measured site- and landscape-level covariates on six working landscapes. We detected five species of bats and three species groups at 93% (224/240) of sites. We observed higher species richness at sites with high proportions of contiguous forest and low levels of basal area. At the species level, occupancy patterns were influenced by site and landscape covariates, which had varying effects on species with distinct foraging strategies. Temperature was an important predictor of detectability. Our findings offer new insights into the ecology of bats in working forest landscapes during winter, where we highlight positive responses in occupancy with contiguous forests and lower levels of basal area, as in previous summer work. By providing valuable information on winter community composition and foraging habitat associations, we hope to guide management decisions for forest attributes important to these species, thus increasing conservation opportunities within working forests.

Coastal bottlenose dolphin populations are highly vulnerable due to their small population sizes and proximity to human activities. Long-term studies in the UK have monitored populations protected within Special Areas of Conservation (SACs) since the 1990s, but a small community of bottlenose dolphins inhabiting the coastal waters of southern England has received much less attention. The English Channel is one of the most heavily impacted marine ecosystems worldwide and increasing anthropogenic pressures pose a severe threat to the long-term viability of this population. Conservation measures to protect these animals have been hindered by a lack of knowledge of population size, distribution and ranging behaviour. This study aimed to fill these knowledge gaps. A citizen science sighting network yielded 7458 sighting reports of bottlenose dolphins between 2000 and 2020. Resightings of identified individuals were used to estimate abundance, distribution, and ranging behaviour. Social structure analysis revealed a discrete interconnected group of animals in shallow coastal waters, which did not appear to mix with conspecifics identified further offshore. A Bayesian multi-site mark–recapture analysis estimated that this population comprises around 48 animals (CV = 0.18, 95% HPDI = 38–66). These dolphins ranged between North Cornwall and Sussex, with an average individual range of 530 km (68–760 km). Areas of high-modelled habitat suitability were found to overlap with high levels of anthropogenic pressure, with pollution and boat traffic identified as the most pervasive threats. Although adult survival rates indicated that the population was relatively stable from 2008 to 2019 (0.945 (0.017 ± SE)), the small population size implies a significant risk to their long-term viability and resilience to environmental change. By highlighting the most deleterious anthropogenic activities and regions of conservation significance, our results will be useful for developing management policies for threat mitigation and population conservation, to protect this vulnerable group of dolphins.