The collapsing populations of large herbivores will have extensive ecological and social consequences.

No abstract

No abstract

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.

Extinction risk in vertebrates has been linked to large body size, but this putative relationship has only been explored for select taxa, with variable results. Using a newly assembled and taxonomically expansive database, we analyzed the relationships between extinction risk and body mass (27,647 species) and between extinction risk and range size (21,294 species) for vertebrates across six main classes. We found that the probability of being threatened was positively and significantly related to body mass for birds, cartilaginous fishes, and mammals. Bimodal relationships were evident for amphibians, reptiles, and bony fishes. Most importantly, a bimodal relationship was found across all vertebrates such that extinction risk changes around a body mass breakpoint of 0.035 kg, indicating that the lightest and heaviest vertebrates have elevated extinction risk. We also found range size to be an important predictor of the probability of being threatened, with strong negative relationships across nearly all taxa. A review of the drivers of extinction risk revealed that the heaviest vertebrates are most threatened by direct killing by humans. By contrast, the lightest vertebrates are most threatened by habitat loss and modification stemming especially from pollution, agricultural cropping, and logging. Our results offer insight into halting the ongoing wave of vertebrate extinctions by revealing the vulnerability of large and small taxa, and identifying size-specific threats. Moreover, they indicate that, without intervention, anthropogenic activities will soon precipitate a double truncation of the size distribution of the world's vertebrates, fundamentally reordering the structure of life on our planet.

Aim Predators often have important roles in structuring ecosystems via their effects on each other and on prey populations. However, these effects may be altered in the presence of anthropogenic food resources, fuelling debate about whether the availability of such resources could alter the ecological role of predators. Here, we review the extent to which human-provided foods are utilised by terrestrial mammalian predators (> 1 kg) across the globe. We also assess whether these resources have a direct impact on the ecology and behaviour of predators and an indirect impact on other co-occurring species.Location Global.Methods Data were derived from searches of the published literature. To summarise the data we grouped studies based on the direct and indirect effects of resource subsidies on predators and co-occurring species. We then compared the types of predators accessing these resources by grouping species taxonomically and into the following categories: (1) domesticated species, (2) mesopredators and (3) top predators.Results Human-provided foods were reported to be utilised by 36 terrestrial predator species in 34 different countries. In the presence of these resources we found that: (1) predator abundance increased, (2) the dietary preferences of predators altered to include the food subsidy, (3) life-history parameters such as survival, reproduction and sociality shifted to the benefit or detriment of the predator, and (4) predators changed their home ranges, activity and movements. In some instances, these modifications indirectly affected co-occurring species via increased predation or competition. Main conclusionsThe availability of human-provided food to predators often results in behavioural or population-induced changes to predators and trophic cascades. We conclude that there is an urgent need to reduce the access of predators to food subsidies to minimise human-wildlife conflicts and to preserve the integrity of ecosystem functioning in human-influenced landscapes world-wide.

Carnivore predation on livestock often leads people to retaliate. Persecution by humans has contributed strongly to global endangerment of carnivores. Preventing livestock losses would help to achieve three goals common to many human societies: preserve nature, protect animal welfare, and safeguard human livelihoods. Between 2016 and 2018, four independent reviews evaluated >40 years of research on lethal and nonlethal interventions for reducing predation on livestock. From 114 studies, we find a striking conclusion: scarce quantitative comparisons of interventions and scarce comparisons against experimental controls preclude strong inference about the effectiveness of methods. For wise investment of public resources in protecting livestock and carnivores, evidence of effectiveness should be a prerequisite to policy making or large-scale funding of any method or, at a minimum, should be measured during implementation. An appropriate evidence base is needed, and we recommend a coalition of scientists and managers be formed to establish and encourage use of consistent standards in future experimental evaluations.

Large carnivores are persecuted globally because they threaten human industries and livelihoods. How this conflict is managed has consequences for the conservation of large carnivores and biodiversity more broadly. Mitigating human-predator conflict should be evidence-based and accommodate people's values while protecting carnivores. Despite much research into human and large-carnivore coexistence strategies, there have been few attempts to document the success of conflict-mitigation strategies on a global scale. We conducted a meta-analysis of global research on conflict mitigation related to large carnivores and humans. We focused on conflicts that arise from the threat large carnivores pose to livestock. We first used structured and unstructured searching to identify replicated studies that used before-after or control-impact design to measure change in livestock loss as a result of implementing a management intervention. We then extracted relevant data from these studies to calculate an overall effect size for each intervention type. Research effort and focus varied among continents and aligned with the histories and cultures that shaped livestock production and attitudes toward carnivores. Livestock guardian animals most effectively reduced livestock losses. Lethal control was the second most effective control, although its success varied the most, and guardian animals and lethal control did not differ significantly. Financial incentives have promoted tolerance of large carnivores in some settings and reduced retaliatory killings. We suggest coexistence strategies be location-specific, incorporate cultural values and environmental conditions, and be designed such that return on financial investment can be evaluated. Improved monitoring of mitigation measures is urgently required to promote effective evidence-based policy.