New Research Shows Alarming Decline in Small Mammals in the UK

New Research Shows Alarming Decline in Small Mammals in the UK - The Mammal Society

Novel research finds alarming declines of some mammal species in the UK.
Five of seven species of small mammals assessed found to have declined in occupancy (areas where present) by an average of 1.2-2.8% each year between 1970 and 2016.
Some species previously thought not to be at risk, including weasels, stoats, and several species of vole and shrew, now of high concern requiring immediate conservation action.

In the first study of its kind in the UK, researchers have demonstrated a worrying decline in small mammals in Britain. The species found to be the worst affected are the harvest mouse and weasel, which were found to be shrinking in occupancy (area of land where they are present) by an average of 2.8% and 4.2% each year, respectively. The scale of decline found for the weasel, which primarily feeds on voles and mice, is enough to justify it being classified as ‘Vulnerable to extinction’ under IUCN Regional Red List Criteria.

The paper, published in Biological Conservation and authored by a team of researchers from the Mammal Society, University of Sussex, and the UK Centre for Ecology & Hydrology, assesses trends of two thirds of the UK’s land mammals from 1970 to 2016. The results are based on estimating each species “occupancy”, which refers to the proportion of sampled areas in which a species is recorded as present.

Dr Frazer Coomber, Science Officer at the Mammal Society said: “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.”.

One quarter of native British mammals were found to be at risk of extinction in the 2020 Red List for Britain’s Mammals, however this new study shows even further loss. While some species groups appear to be increasing (e.g. bats and deer) these new analyses highlight for the first time the declines in bank voles, field voles, water shrews, common shrews, stoats and weasels. All of these species were historically abundant, being found particularly in hedgerows, scrub and long grass.

Access the paper Using biological records to infer long-term occupancy trends of mammals in the UK, Coomber et al., (2021), published in Biological Conservation