Fifth of Britain’s wild mammals ‘at high risk of extinction’
The wildcat and mouse-eared bat are on the brink, but deer are spreading and otters bouncing back, according to a comprehensive analysis.
At least one in five wild mammals in Britain faces a high risk of extinction within a decade and overall populations are falling, according to the most comprehensive analysis to date.
Most at risk are the Scottish wildcat and the once-widespread black rat, while there is only a single male greater mouse-eared bat left. Also falling in number are hedgehogs, rabbits and water voles. However, some species have thrived since the last national analysis in 1995, including otters, no longer poisoned by pesticides, and deer, which lack a natural predator.
More than half the 58 wild land mammals known to breed in Britain are rodents or bats, and one in eight is an alien species, such as the thriving grey squirrel and mink. The most numerous species is the field vole at 60 million, followed by the mole, at 41 million. But both are easily outnumbered by people, at 64 million, and their livestock, with 44 million sheep and cattle and 181 million chickens.
The main cause is the destruction of wild places by roads, buildings and intensive farming, which combine to reduce and fragment habitat. The impact of invasive species and disease are also important, said Prof Fiona Mathews, at the University of Sussex and chair of The Mammal Society, which produced the new report at the request of the government.
“We have almost been sleepwalking,” she said. “This is happening on our own doorstep, so it falls upon all of us to try and do what we can to ensure that our threatened species do not go the way of the lynx, wolf and elk and disappear from our shores forever.” Changes to farming subsidies and much better research on effective conservation measures are needed, she said.
The report analysed more than 1.5 million mammal sightings from all over Britain, many by volunteers and citizen scientists. The scientists then added data from more than 500 published studies to produce estimates of population size and range. They also used internationally agreed criteria to produce a red list of the most endangered species.
There are only 200 wildcats left, making it critically endangered. The black rat may in fact already be extinct, as few wildlife volunteers seek them out – its place has been taken by more than 7 million brown rats.
The single greater mouse-eared bat remaining lives wild in West Sussex, where it hibernates. “Unless we can find some lady friends for him soon [from continental Europe], he is going to be extinct,” said Mathews. “He’s 16 now, so he’s getting on a bit. They can live up to the mid-20s.”
The hedgehog population is just over 500,000, but that is two-thirds lower than in 1995 and results from
a combination of factors: loss of hedgerows, pesticides killing their insect food, road deaths and potentially more predation from badgers. The new analysis estimates badger numbers have doubled to more than 550,000 in the last two decades, though about 30,000 were culled in 2017 in an attempt to curb tuberculosis in cattle.
Rabbits are also declining, in part due to a viral haemorrhagic disease that originated in China, but still number 36 million. In contrast, there are just 132,000 water voles – down from one million in 1995 – and their decline makes them critically endangered in Wales and endangered in England. Red squirrels are also endangered in England, as invasive greys force them out with disease and competition for food.
Little data exists for most of the 18 bat species. But while common and soprano pipistrelles are numerous, the barbastelle bat is dependent on ancient woodland. “The HS2 [railway] is probably not helping,” said Mathews. Nathusius’ pipistrelle bat may also be troubled by having to run a growing gauntlet of offshore wind farms on their migration from continental Europe.
The wild mammals doing well in modern Britain are the carnivores that are no longer persecuted by hunters, such as polecats and pine martens, and wide roaming deer. Otters have bounced back, after the banning of organophosphate pesticides, but still number just 11,000. Pine marten numbers have also grown – to 3,700 – and may increasingly migrate from their Scottish stronghold to England, but the tiny population south of the border means they are classified as critically endangered.
Beavers and wild boar have become established since 1995, but their populations remain small at 168 and 2,600 respectively. All six species of deer are expanding, with red deer now the most common.
“We live in one of the most densely populated countries in Europe,” said Mathews. A 2016 State of Nature report found Britain to be “among the most nature-depleted countries in the world”. She said ending farm subsidies that just reward the area of land held would help, and paying attention to wild mammals outside nature reserves.
She said many wild mammals survived in the margins, such as hedgerows, railway embankments and brownfield sites: “We need to stop thinking of wildlife as being something that happens somewhere else and we just put a [protected area] ring around it.”
Natural England, the government’s wildlife body and which commissioned the research, is attempting to bring 20 species of birds, insects and other animals back from the brink using a £4.6m grant from the National Lottery.
“It’s fantastic to see a comprehensive assessment of the current vulnerability to extinction of our mammals – the work clearly capitalises on the best available data,” said Nathalie Pettorelli, at the Zoological Society of London. She said the data was often scarce and significant assumptions were made: “That said, these caveats are more likely to underestimate the number species at risk than overestimate.”