Intertidal mammals

The UK is home to 38% of the world’s grey seals. 

Around 4% of grey seals in the south-west get caught in fishing gear. 

Seals can rest while keeping half of their brain awake to stay alert for danger.  

What we need to do

About

Devon is home to a wide range of marine mammals, including whales, dolphins, porpoises and seals. These species are all an integral part of the county’s rich coastal ecosystem.  The majority, however, live in deeper waters and its only seals which are often found in Devon’s intertidal habitats. 

The UK has two species of seal: grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina), also known as common seals. Grey seals are larger and can be identified by their more dog-like faces.   

Seals need remote, quiet beaches and islands as haul-out areas, where they can rest, breed, digest food, moult and socialise throughout the year. Although the two species can use the same sites, they usually prefer to use separate areas.  

Seals have a varied diet that includes fish, crabs, lobsters, shrimp, squid, cuttlefish, and octopus. While they are opportunistic feeders and eat what’s available, they tend to prefer small bait fish such as sandeels and dragonets. 

Devon’s seal populations have rebounded from historic lows, particularly following the introduction of legislation such as the Conservation of Seals Act in 1970. Despite this, grey and harbour seals remain vulnerable and require ongoing protection (see Key Pressures and Opportunities below). 

Both species are found in Devon’s coastal waters and are listed as Devon Species of Conservation Concern. However, Devon is particularly significant for grey seals, which are more commonly seen in the region. Grey seals breed locally, with well-established haul-out sites near Lundy Island and the Dart Estuary and are therefore designated as a Focus Species. Populations of both species will benefit from the actions set out below. 

Key pressures and opportunities

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Climate change

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Warming seas are affecting the distribution of species which are critical food for seals, such as sandeels and dragonets. Rising sea levels and extreme weather events flood haul-out sites, meaning the seals have to move and sometimes separating pups from their mothers.  

Oceans absorb carbon dioxide from the atmosphere. Increasing amounts of carbon dioxide are causing ocean acidification, which affects the overall health of marine ecosystems.   

Climate change can increase toxic algal blooms, such as those that produce domoic acid, which harm marine mammal’s nervous systems.  

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Water quality

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Seals can absorb pollutants in the water, leading to a buildup of toxins in their blubber. These toxins can harm reproduction, cause physical abnormalities and immune disorders and affect the seal’s long-term survival.  

There is widespread concern about sewage pollution in Devon. This has led to significant public pressure on water companies, with MPs and local communities demanding better management and cleanup efforts. 

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Litter and plastics

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Seals can get caught up in fishing gear that has been lost or dislodged from its moorings following a storm. This ghost netting can cause serious injuries and affects about 4% of seals in the south-west of England, the second highest rate globally.  

Other plastic litter, such as bags, bottle caps and packaging materials also cause serious harm. Plastic breaks down into microplastics which have been found in seal faeces, blood and tissues. Microplastics can cause a range of health problems in seals, including intestinal injuries and blockages. 

Although now banned, PCBs (polychlorinated biphenyls, a group of man-made chemicals) are still polluting our seas. They cause immunosuppression and reduced reproductivity in male grey seals.  

Community campaigns, such as Plastic Free North Devon, are working to reduce plastic pollution and raise awareness about its environmental impacts. 

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Habitat loss

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Coastal development and human activities can cause coastal squeeze and the loss of critical haul-out and breeding sites.  

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Human disturbance

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Human activities such as using watercraft, flying drones and dog walking can disturb grey seals, especially at their haul-out, foraging and breeding sites.  Disturbance can cause seals to flee into the water, leading to stress, energy loss, injury and even death.  

Frequent disruptions interfere with essential activities such as resting, breeding, and nurturing pups. Continuous disturbance can cause chronic stress in grey seals, weakening their immune systems and making them more susceptible to disease.  

Disturbing heavily pregnant adult females, particularly in the summer, can harm their unborn pups. An increase in the death rate of grey seals under the age of one is thought to be connected to an increase in human disturbance. 

The impact of artificial sound on seals and their hearing is unknown and understudied. 

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Fishing

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Fish stocks are now lower than they have ever been, reducing the prey available to grey seals. Seals have historically fed on discards from fishing boats and today are also often fed by visitors on wildlife tour boats. As a result, many seals associate watercraft with food, increasing the risk of seal bycatch.  

85% of UK bycatch occurs in the south-west of England and most seals caught are young grey seals. This is likely due to the region’s extensive use of tangle and trammel nets, which are more prone to accidentally capturing seals. It is an offence to intentionally or recklessly kill, injure or take a seal. 

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Disease

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Avian flu, particularly the H5N1 strain, can infect seals, causing respiratory problems and disorientation. This virus can quickly make the seals very ill and can be fatal.  

Mouth rot is a bacterial infection that causes painful ulcers and inflammation in seals’ mouths. The condition makes it difficult for seals to eat, leading to malnutrition and weakened immune systems. Severe cases can make the seals very ill and may be fatal.   

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Community action

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Community action can help seals by raising public awareness about the threats they face, advocating for stronger protective laws, organising beach cleans to reduce pollution, supporting rescue and rehabilitation efforts and engaging in citizen science to monitor seal populations. 

What we need to do and where

Priority

Increase the abundance and distribution of seals in Devon’s coastal waters, particularly grey seals, a Focus Species.  

Focus species

Grey seal

Halichoerus grypus
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Ecology 

Adult grey seals can be up to two metres long  and weigh over 230 kilograms. They are excellent divers and can stay underwater for 20 minutes, sometimes going as deep as 300 metres to find food.  Females can live for 25 to 35 years and, if healthy, can have a single pup from the age of six until the end of their lives. Males have an average life expectancy of 25 years.  

Most male grey seals do not breed, but some become dominant ‘beachmasters’ that females mate with in exchange for protection during the pupping season. Males become beachmasters through a process of intense competition and physical confrontation, with the largest and most aggressive males typically winning. 

Devon distribution  

Although grey seals are globally rare, they can frequently be seen around all of the Devon coast and have been recorded in Devon’s estuaries.  

Lundy is the most significant site for grey seals in Devon, with a population of around 250 individuals. The island is in the Marine Conservation Zone (MCZ) and its clear waters and plentiful food make it an ideal habitat for grey seals.  

Seals tend to prefer remote and quiet beaches for hauling out, which can limit their presence in areas such as East Devon. However, their distribution is also influenced by factors such as food availability and suitable haul-out or breeding sites, meaning they can still be found in busier locations like Brixham. 

Actions for all Intertidal mammals

These actions will benefit both species of seal. 

Protect seal haul-out areas from disturbance    

  • Restrict the use of recreational drones in sensitive areas. This is primarily the responsibility of the landowner. However, in areas designated as SSSIs, Natural England (NE) has the authority to prohibit drone use. 
  • Increase general awareness (e.g. signage) about drone restrictions, particularly in sensitive areas and along the South West Coast Path. 
  • Promote campaigns such as Give Seals Space. 

Create new haul-out areas  

Create seal friendly haul-out areas on near or offshore structures (piers and offshore wind farms) to compensate for coastal habitat lost due to climate change.   

Reduce pollution, including plastics 

  • Restrict the sale and use of flying ‘frisbee’ rings and other items that can easily trap and strangle grey seals.   
  • Raise awareness about the British Divers Marine Life Rescue network for seals in trouble.   
  • Support community pollution and plastic projects, such as Plastic Free North Devon, and beach cleans to reduce marine litter. 

Reduce seal bycatch and entanglement 

  • Encourage the use of modified tangle and trammel nets with escape panels or acoustic deterrents. 
  • Improve port-side disposal facilities to prevent gear loss and encourage responsible waste management. 
  • Monitor and mitigate seal injuries in inshore mackerel fisheries. 

Research, survey and monitoring 

Expand and support existing monitoring programmes to record seal populations, their health and behaviour.   

Legislation and policy 

  • Designate sensitive haul-out sites as County Wildlife Sites.   
  • Designate other protected areas where human access can be limited and managed all year round, especially during breeding and moulting seasons. 

Support conservation projects 

Support local conservation groups and other organisations that work to protect and monitor grey seals, such as the Seal Alliance, the Seal Research Trust and The Seal Project.  

Other relevant actions

Seals will benefit from the actions on the following pages 

Where to focus action

Estuaries and Rocky Shores, particularly Lundy – see Mapping 

Inspiration

Case studies

The seal project

The Seal Project is a conservation charity that monitors and manages the welfare of seals in South Devon. They conduct surveys, identify individual seals by their fur patterns and record their behaviours. The project also raises awareness of the importance of protecting seals and avoiding disturbances.  

Where to visit

Watch seals from an accredited wildlife-watching boat, such as those certified by the WiSe Scheme or the Marine Wildlife Awareness Accreditation Scheme (MWAAS) in North Devon, supported by the Marine Management Organisation. 

When watching seals, please follow the Marine and Coastal Wildlife Code: advice for visitors. If you’re hoping to photograph seals, please follow advice from the Seal Alliance.  

The Seal Alliance have also produced a best-practice guide to watching seals. 

Find out more

Organisations and charities 

The Seal Research Trust is a multi-award-winning, evidence-based seal conservation charity that monitors seals across 54 haul-out sites in the south-west of the UK, including Devon. 

Seal Alliance is a working coalition of organisations and individuals that protect seals and their habitats across the UK. 

The Seal Project is a charity that monitors and protects grey and common seals throughout south Devon. 

SeaGen builds robots to monitor and support nature, including seals. They’re looking for partners to support their projects or monitor a local area. 

Projects

The Seal Project received a grant from Devon Environment Foundation to install a remote access camera near Kingswear in South Devon to record seal numbers and identify individual seals in the Dartmouth estuary. The Devon Environment Foundation has an update on the project. 

Resources for businesses

Earth Action North Devon gives information and advice to small businesses to help them reduce their impact on the local and global environment. 

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