After historical declines in population sizes and ranges, we compare and contrast the recent history and contemporary variation in the status of Great Britain's eight native mammalian carnivore species from the 1960s to 2017. Wildcat Felis silvestris conservation status is unfavourable and is masked by hybridisation with domestic cats Felis catus. Red foxes Vulpes vulpes remain widespread but are currently declining. European otter Lutra lutra, European pine marten Martes martes and European polecat Mustela putorius populations are characterised by rapid recovery. Otters have almost completely recolonised Great Britain, polecats have expanded their range throughout southern Britain from refugia in Wales and pine martens have expanded their range from the Scottish Highlands. European badgers Meles meles have generally increased in population density. Status assessments of stoats Mustela erminea and weasels Mustela nivalis are data‐deficient but available evidence suggests that stoats may have increased while weasels may have declined. Anthropogenic processes influencing carnivore status include legal protections, habitat quality, reintroductions, predator control, pollutants, hybridisation and diseases and their associated control practices. Population effects of contaminants, such as anticoagulant rodenticides, remain poorly characterised. The widespread interface with domestic and feral cats makes the wildcat's situation precarious. Recent declines in rabbit Oryctolagus cuniculus populations are a concern, given that several carnivore species depend on them as food. We conclude that, with the exception of the wildcat, the status of Great Britain's mammalian carnivores has markedly improved since the 1960s. Better understanding of the social aspects of interactions between humans and expanding predator populations is needed if conflict is to be avoided and long‐term co‐existence with people is to be possible.
The Western polecat Mustela putorius has a widespread European distribution and is currently listed as Least Concern by the IUCN Red List of Threatened Species. Reports are increasing of polecat population declines in several countries, although a paucity of data means population trends are poorly understood. This paper reviews and summarises information on the polecat’s status and range-wide population trends. Information and opinion were gathered for 34 countries, from individuals and organisations studying polecats and from reviewing the literature and national Red Lists. Where trends were identified, the polecat population is known or suspected to be declining in 20 countries, reported to be stable in five countries, stable or increasing in one country, and increasing in two countries. For many countries, data are so limited in quantity or spatial scale, or at risk of bias, that trends could not be identified or confidence in trend assessments is low. The main drivers of polecat decline are poorly understood, but might include habitat degradation; changes in prey availability; competition with invasive carnivores; poisoning; conflict with human interests; harvesting and killing of polecats; and hybridisation. Robust survey methods and systematic monitoring programmes are urgently needed to gather up-to-date data on polecat population trends across the species’ range.
As a result of legal protection and population recovery, European polecats (Mustela putorius) in Great Britain are expanding into areas associated with greater usage of second-generation anticoagulant rodenticides (SGARs). We analysed polecat livers collected from road casualties from 2013 to 2016 for residues of five SGARs. We related variation in residues to polecat traits and potential exposure pathways, by analysing stable isotopes of carbon (δC) and nitrogen (δN) in their whiskers. 54 of 68 (79%) polecats had detectable residues of at least one SGAR. Bromadiolone (71%) was the most frequently detected compound, followed by difenacoum (53%) and brodifacoum (35%). Applying historical limits of detection to allow comparison between these new data and previous assessments, we show that in the 25 years from 1992 to 2016 inclusive, the rate of detection of SGARs in polecats in Britain has increased by a factor of 1.7. The probability of SGAR detection was positively related to increasing values of δN, suggesting that polecats feeding at a higher trophic level were more likely to be exposed. Total concentrations of SGARs in polecats with detectable residues were higher in polecats collected in arable compared to pastoral habitats, and in the west compared to the east of Britain. The number of compounds detected and total concentrations of SGARs increased with polecat age. There was no evidence of regional or seasonal variation in the probability of detecting SGARs, suggesting that the current risk of exposure to SGARs does not vary seasonally and has increased (from that in the 1990s) throughout the polecat's range. We recommend quantification of current practices in rodenticide usage, particularly in the light of recent regulatory changes, to enable assessment and mitigation of the risks of secondary exposure to rodenticides in non-target wildlife.
Understanding the mechanisms of coexistence between ecologically similar species is an important issue in ecology. Carnivore coexistence may be facilitated by spatial segregation, temporal avoidance, and differential habitat selection. American martens Martes americana and fishers Pekania pennanti are medium‐sized mustelids that occur sympatrically across portions of North America, yet mechanisms of coexistence between the two species are not fully understood. We assessed spatial and temporal partitioning in martens and fishers in the Upper Peninsula of Michigan, USA, using camera trap data collected during winter 2013–2015. To investigate spatial segregation, we used a dynamic occupancy model to estimate species’ occupancy probabilities and probabilities of persistence and colonization as a function of covariates and yearly occupancy probability for the other species. Temporal segregation was assessed by estimating diel activity overlap between species. We found weak evidence of spatial or temporal niche partitioning of martens and fishers. There was high overlap in forest cover selection, and both marten and fisher occupancy were positively correlated with deciduous forests (excluding aspen [ Populus tremuloides ]). There was strong temporal overlap ( ; CI = 0.79–0.82) with both species exhibiting largely crepuscular activity patterns. Co‐occurrence of martens and fishers appears to be facilitated by mechanisms not investigated in this study, such as partitioning of snow features or diet. Our results add additional insights into resource partitioning of mesocarnivores, but further research is required to enhance our understanding of mechanisms that facilitate marten and fisher coexistence.
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