A global review of the conservation threats and status of mustelids

First evidence of widespread positivity to anticoagulant rodenticides in grey wolves (Canis lupus)

Second-generation Anticoagulant Rodenticides (ARs) can be critical for carnivores, due to their widespread use and impacts. However, although many studies explored the impacts of ARs on small and mesocarnivores, none assessed the extent to which they could contaminate large carnivores in anthropized landscapes. We filled this gap by exploring spatiotemporal trends in grey wolf (Canis lupus) exposure to ARs in central and northern Italy, by subjecting a large sample of dead wolves (n = 186) to the LC-MS/MS method. Most wolves (n = 115/186, 61.8 %) tested positive for ARs (1 compound, n = 36; 2 compounds, n = 47; 3 compounds, n = 16; 4 or more compounds, n = 16). Bromadiolone, brodifacoum and difenacoum, were the most common compounds, with brodifacoum and bromadiolone being the ARs that co-occurred the most (n = 61). Both the probability of testing positive for multiple ARs and the concentration of brodifacoum, and bromadiolone in the liver, systematically increased in wolves that were found at more anthropized sites. Moreover, wolves became more likely to test positive for ARs through time, particularly after 2020. Our results underline that rodent control, based on ARs, increases the risks of unintentional poisoning of non-target wildlife. However, this risk does not only involve small and mesocarnivores, but also large carnivores at the top of the food chain, such as wolves. Therefore, rodent control is adding one further conservation threat to endangered large carnivores in anthropized landscapes of Europe, whose severity could increase over time and be far higher than previously thought. Large-scale monitoring schemes for ARs in European large carnivores should be devised as soon as possible.

Support for the size-mediated sensitivity hypothesis within a diverse carnivore community

Carnivore community dynamics are governed by a complex set of often interacting biotic, abiotic and anthropogenic factors that are increasingly volatile as a result of global change. Understanding how these changing conditions influence carnivore communities is urgent because of the important role carnivores play within ecosystems at multiple trophic levels, and the conservation threats that many carnivores face globally. While a great deal of research attention has historically been focused on large carnivores within ecosystems, the size-mediated sensitivity hypothesis has recently been proposed where the smallest carnivore in a system is likely to be the most responsive to the diverse suite of ongoing environmental and anthropogenic changes within ecological communities. We deployed camera traps at 197 sites over 4 years to monitor a diverse suite of mammalian carnivores within the Blue Ridge Mountains of western North Carolina and then used a two-step occupancy modelling-structural equation modelling framework to investigate the relative support for four primary hypothesized drivers (interspecific competition/predation, habitat complexity, food availability and anthropogenic disturbance) on carnivore occurrence. We found that each of the 10 carnivores in our system responded differently to conditions associated with each of these four hypothesized drivers, but that small and medium-sized carnivores had a greater number of significant (p < 0.05) pathways by which these conditions were influencing occupancy relative to large carnivores. In particular, the smallest carnivore observed in our study was the only species for which we found support for each of the four hypothesized drivers influencing occupancy. Collectively, our study supports the size-mediated sensitivity hypothesis and suggests that small carnivores are ideal sentinel species for global change. We echo recent calls for adopting a middle-out approach to investigations into carnivore community dynamics by refocusing sustained monitoring and research efforts on smaller carnivores within systems.

Conservation status of the world’s carnivorous mammals (order Carnivora)

The conservation of carnivores (order Carnivora) can lead to the conservation of other species as well as entire ecosystems since they play an important ecosystemic role. However, their predatory behaviour has caused many of these species to experience marked population declines worldwide and they may therefore face greater anthropogenic threats than other animal groups. To examine the conservation status, population trends, distribution patterns, habitats and threats of all extant species belonging to this order (N = 290), we collected data from the International Union for the Conservation of Nature's Red List. In addition, we calculated the Red List Index (RLI) to measure the change in extinction risk of species over time. Carnivores are more threatened than mammals in general (26.9% of endangered species vs. 22.7%) and have a significantly higher proportion of species with declining populations (48.3% vs. 31.9%). Eupleridae, Ursidae and Felidae families have the worst conservation status. Between the 1990s and 2000s, most families suffered a considerable decline in their RLI value, the most notable being Felidae. The greatest numbers of threatened carnivore species are found in forest, shrubland and grassland habitats. East and South Asia hold great numbers of carnivore species as well as the highest proportion of threatened and declining species. Hunting and trapping of terrestrial animals, along with habitat loss (caused by deforestation and agricultural expansion), pose the main threats to the Carnivora order. Our findings indicate that, within mammals, the conservation of carnivores should be a priority, and conservation measures directed at this group should be undertaken or increased as a matter of urgency.