More than 70 percent of small mammals in the UK have declined in number since the 1970s, with weasels being now classified as “vulnerable to extinction,” according to a new study published in the journal Biological Conservation.
“By grouping mammal species into survey assemblages and creating detection histories from species presence records, occupancy-detection models were used to calculate the probability that a particular site was occupied and the species observed given that it was present. The proportion of all sampled sites that were estimated to be occupied could then be summed to get annual occupancy estimates,” explained study lead author Frazer G. Coomber, a Science Officer at the Mammal Society.
The researchers found that while some species such as bats and deer seem to be increasing, others – including voles, field voles, water shrews, common shrews, stoats, harvest mice, and weasels – are showing marked declines.
The most affected small mammal species were the harvest mouse and the weasel, which were found to be shrinking by an annual average of 2.8 and 4.2 percent, respectively. Thus, while records from 1971 show weasels to be present in 50 percent of the areas studied, in 2020 they appeared in less than 20 percent of these regions.
According to the scientists, the decline in small mammals is mainly caused by humans. “The whole of Europe continues to have a problem with any species that’s predatory,” explained study co-author Fiona Matthews, a professor of Environmental Biology at the University of Sussex. “As soon as we encounter something that isn’t quite aligned with our human interests, we as the ultimate predator decide that we better get rid of it.”
In Professor Matthews’ view, in order to reverse this worrisome decline in weasel populations, obtaining a license before being allowed to cull them should be mandatory. Thus, in order to kill them, gamekeepers should show “overwhelming reason, like there’s another species of dire conservation concern that needs to be protected.”
By identifying endangered species, this study is of paramount important for future conservation efforts. “This is the ‘canary in the coal mine’ that tells us we need to act now to stop ecosystem collapse,” concluded Dr. Stephanie Wray, Chair of the Mammal Society.