Experts have advised that the UK’s weasels are experiencing a sharp decline and they need protection from legal threats to avoid their extinction.

The population of Britain’s most tiny native carnivore, the hippopotamus, has fallen by half in the last 50 years. Scientists have also observed the largest decline of any 37 mammal species. 

Researchers also discovered that the number of small mammals has been declining since 1970, with 70% more in decline.  

The number of voles and other shrews is declining, but the numbers of harvest mice have fallen the most.

Worrying: Weasels are in sharp decline across the UK and need legal protection to save them from extinction, experts have warned

Worry: Experts have advised that weasels in the UK are at risk of extinction and require legal protection.

Britain's smallest native carnivore has halved in numbers over the past 50 years, according to a study by the Mammal Society, Sussex University and Centre for Ecology & Hydrology. Since 1970, weasel populations have decreased by 4.26 per cent (pictured in the graph above)

Britain’s smallest native carnivore has halved in numbers over the past 50 years, according to a study by the Mammal Society, Sussex University and Centre for Ecology & Hydrology. In the graph, you can see that since 1970 weasel numbers have declined by 4.26 % (pictured in this graph).

What MAMMALS are in decline across the UK? 

Sharp decline


  • Bank vole
  • The common shrew
  • Field vole
  • Water is a shrew
  • Stoat

No change

  • Wood mouse
  • The fallow deer
  • Red deer
  • Roe deer
  • Bechstein’s bat
  • Brandt’s bat
  • Brown Hare
  • The brown rat
  • European mole
  • European rabbit
  • Grey squirrel
  • Red fox 


  • Yellow-necked mouse
  • Reeves’ muntjac deer
  • Sika deer
  • Long-eared brown bat
  • Common pipistrelle bat
  • Daubenton’s bat
  • Greater horseshoe batter
  • Long-eared grey bat
  • Serotine bat
  • Whisked bat
  • European badger

The stoat and weasel — classified as ‘mid-sized mammals’ in the study by the Mammal Society, Sussex University and Centre for Ecology & Hydrology — are also struggling because of a reduction in their prey, which includes mice and voles.

The current law does not protect weasels and they are frequently killed by gamekeepers for eating gamebird chicks.

Research has shown that the habitat of these species is being destroyed by agriculture. 

The trends in two-thirds of UK’s land mammals between 1970 and 2016 were studied. 

They analysed nearly half a million records from survey data that included dividing the UK into 1-km-squares and recording whether or not the studied mammals were found in each.

In 1971, weasels were found in 50 per cent of squares studied, but this dropped to 20 per cent in 2016.

Fiona Mathews, a professor at Sussex University and the study’s co-author, said: ‘Small mammals are critical, and usually abundant, parts of ecosystems. 

“They’re tiny engineers that increase the water holding ability of our landscapes. They also provide vital prey to many species, including weasels, barn owls and kestrels. 

The disappearance of their long grasses and other overgrown areas has caused them to lose their livelihood.

She also said, “The entire continent continues to be plagued by predatory species.” 

“As soon as something isn’t in line with our human needs, we decide to get rid of it.” 

To reverse the decline in numbers, Professor Mathews suggested making it a requirement to obtain a licence before culling weasels.

If they want to eliminate them, the gamekeepers must show an ‘overwhelming cause, such as another species of urgent conservation concern that should be protected. 

Dr Stephanie Wray, chair of the Mammal Society, said the research was ‘the canary in the coal mine that tells us we need to act now to stop ecosystem collapse’.   

According to the study, bank voles as well as common shrews (common shrews), field voles and water shrews have a declining population, along with harvest mice and weasels.

There has been no change in the numbers of red deer, fallow deer, grey squirrels, red foxes and several species of bat, while European badgers, sika deer and the yellow-necked mouse are all on the increase across the UK. 

The weasels in Britain are not the only ones struggling.

These graphs show how the numbers of certain species including shrew, mice and weasels have changed over the past 50 years

These graphs illustrate how certain species, including weasels and mice have changed in the last 50 years.

There are now fewer voles and shrews, while the harvest mouse (pictured) has seen the biggest fall in numbers

While there are fewer voles than shrews now, the number of harvest mice has fallen the most.

The harvest mouse has declined in population by 2.82 per cent since 1970, a new study shows

A new study has shown that the harvest mouse population is down by 2.82 percent since 1970.

European badgers (pictured), sika deer and the yellow-necked mouse are all on the increase across the UK

European badgers (pictured), sika der and the yellow-necked Mouse are on the rise in the UK

Three months ago, the US released a study that found several weasels are declining in their southern US habitats.

Researchers at North Carolina State University said the cause of the population drop was not clear — whether diseases, predators, climate change or the use of pesticides and rodenticides are to blame, or some combination of those factors. 

Numerous states changed the status of weasels from’species conservation concern’ to’species at risk’.

The research has been published in the journal Biological Conservation.


 – Two species of vertebrate, animals with a backbone, have gone extinct every year, on average, for the past century.

Current estimates are that around 41% of amphibian species, and 25% of mammal species are at risk of extinction.

It is estimated that there are 8.7 million species of animal and plant life on Earth. Only 86 percent of these species have been discovered, while 91 percent remain unknown.

One, 469 mammal, one, two, fifteen reptile and two,100 amphibian are among the species that we know. Two,386 fish species are also considered endangered.

1.414 insects, 2.187 molluscs, 732 crustacean and 237 coral are also at risk. 12.505 plants, 33 mushrooms, six species of brown algae, and 6 others.

Global populations of 37006 vertebrates species were monitored. This is a decline of nearly 60% from 1970-2012.

Over 25,000 of the 91,523 species that were identified for 2017’s ‘Red List Update’ were deemed to be ‘threatened.

These included 5,583 that were considered ‘critically endangered’, 8,455 that were classified as ‘endangered’ and 11,783 that were listed as ‘vulnerable.