Steep decline of harbour seals in Scotland as population of larger greys continues to climb

The study involved monitoring seal numbers across Britain, including the Fife coast and the Isle of May in the outer Firth of Forth.

The university’s Sea Mammal Research Unit (SMRU) said there had been a 25 per cent drop in harbour seal numbers in The Wash, in south-east England, which is the main population centre south of the border. The location has regularly been home to around 5,000 harbour seals when surveys began in 1988 and as recently as 2018.

Researchers said some areas of Scotland have seen harbour seal numbers decline or are at “drastically depleted levels compared to 20 years ago”.

NatureScot said there was “substantial research” underway to understand the harbour seal declines north of the Border.

Researchers have said it could be linked to the increasing population of the larger grey seals. There are concerns the greys, which have exploded in numbers, kill or partially eat harbour seals and their own pups.

The Mammal Society said conflict between the two species can happen when they compete for resources - either space to haul out on land or competition for prey.

Ron Morris, of the Fife Seal Group that monitors numbers mainly in the Firth of Forth and up the Fife coast, said harbour seal numbers in the area have clearly declined, with greys on the rise.

“With the increase in grey seals in this area, it seems the harbour seals are getting displaced,” he told The Scotsman. “My impressions are that as the grey seal has become more numerous in the Firth of Forth, the harbour seal is getting pushed further and further east.”

From rough counts on the ground, Mr Morris said there were about 50 harbour seals in the Firth of Forth, yet about 20 years ago, there were some 150.

The UK is home to over a third of the world’s grey seal population, according to SMRU. The animals’ increase, since the cessation of culls in the 1970s and the ban of hunting in the early 1980s, has often been hailed as a conservation success story.

Indeed, SMRU aerial surveys revealed the number of grey seals in south-east England had risen over 20-fold in the past 20 years from less than 2,000 to over 40,000.

Surveys conducted recently, however, have indicated a decline in the number of grey seal pups born on the UK east coast. The reasons are unknown, but recent marine heat waves and a disease outbreak are potential factors.

Researchers said it could also be down some individual grey seal males killing the pups.

SMRU said it is investigating how many grey seals exhibit this behaviour to understand whether or not this may be significantly impacting harbour seal populations.

Dr Debbie Russell, deputy director of SMRU said: “The apparent drop in grey seal pups need to be investigated further. SMRU will be continuing their aerial survey program in August 2025 to survey key grey and harbour seal haul-outs.”

She said SMRU were scheduled to survey all major grey seal breeding colonies in Scotland and east England this year to generate estimates of pups born across colonies, which will help indicate which declines at some colonies on the east coast are offset by increases at others, and the nature of the declines.

SMRU is calling on the public to help them in its research by sending in images and videos of seal observations. They can be reported to SMRU by emailing [email protected]