Non-invasively determined multi-site variation in pine marten Martes martes density, a recovering carnivore in Europe

Mink on the brink: comparing survey methods for detecting a critically endangered carnivore, the European mink Mustela lutreola

Monitoring rare and elusive species is critical in guiding appropriate conservation management measures. Mammalian carnivores are challenging to monitor directly, due to their generally nocturnal and solitary lifestyle, and relatively large home ranges. The European mink Mustela lutreola is a critically endangered, small, semi-aquatic carnivore and is one of the most threatened mammal species in Europe. In northern Spain, the European mink population is monitored regionally using different methods and approaches, making assessment of national population status difficult. There is an urgent need to 1) assess the efficacy of survey methods and 2) identify a standard monitoring methodology that can be deployed rapidly and inexpensively over large areas of the mink’s range. We deployed four methods—camera trapping, hair tubes, live trapping, and environmental DNA (eDNA) from water samples—to compare the probability of detecting European mink when present at 25 sampling sites within five 10 × 10 km2, and the economic cost and time required for each method. All four methods successfully detected European mink but the probability of detection varied by method. Camera trapping and hair tubes had the highest probability of detection; however, eDNA and live trapping detected mink in one 10 × 10 km2 where the latter two methods did not. For future European mink monitoring programs, we recommend a combination of at least two methods and suggest that camera traps or hair tubes are combined with live trapping or eDNA (depending on the scale and aims of the study), to gather critical information on distribution, occupancy and conservation status.

Not out of the woods yet: genetic insights related to the recovery of the pine marten (Martes martes) in Ireland

In this study, the history of the pine marten (Martes martes) in Ireland is reviewed, revealing that the population has undergone several retractions and expansions over the last few hundred years. Here, we consider the genetic legacy of this flux in fortunes and its likely impacts upon the conservation and future recovery of the species. Using nuclear DNA markers (microsatellites), we found that the genetic diversity present in Ireland today is like that of other Irish carnivores, but there is evidence of a genetic bottleneck and low effective population size that might result in further reductions of diversity in the future. There is a lack of genetic structure, showing that the population has not been fragmented genetically, despite the low percentage of woodland in Ireland. We also reviewed the mitochondrial DNA diversity present in the Irish population and showed that there is only one contemporary and one extinct haplotype present; a reduced diversity relative to other Irish carnivores. The Irish haplotypes, both extant and extinct, are shared or are genetically similar to haplotypes commonly present in southern Europe today. We discuss the possibility of reinforcing the Irish population with animals from these sources to help supplement and maintain genetic diversity for future generations.

The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations

Shared enemies may instigate or modify competitive interactions between species. The dis-equilibrium caused by non-native species introductions has revealed that the outcome of such indirect interactions can often be dramatic. However, studies of enemy-mediated competition mostly consider the impact of a single enemy, despite species being embedded in complex networks of interactions. Here, we demonstrate that native red and invasive grey squirrels in Britain, two terrestrial species linked by resource and disease-mediated apparent competition, are also now linked by a second enemy-mediated relationship involving a shared native predator recovering from historical persecution, the European pine marten. Through combining spatial capture–recapture techniques to estimate pine marten density, and squirrel site-occupancy data, we find that the impact of exposure to predation is highly asymmetrical, with non-native grey squirrel occupancy strongly negatively affected by exposure to pine martens. By contrast, exposure to pine marten predation has an indirect positive effect on red squirrel populations. Pine marten predation thus reverses the well-documented outcome of resource and apparent competition between red and grey squirrels.