Cornwall Mammal Group
Common seal-(Phoca vitulina)
Order: Carnivora, Cornish Name: Ruen
Recognition:
Only recorded occasionally around the Cornish coast, the common seal is sometimes seen in the company of its larger relative, the grey seal. Common seals are much smaller than greys, the males reaching
about 1.5 m and weighing up to 85 kg with the females getting to about 75 kg and 1.4 m, the head is proportionally smaller than that of the grey seal. The sexes are similar and it difficult to tell them apart. The coat is brown or grey with a mottled pattern. Pups generally have short dark coats when they are born and can swim immediately. The head of the common seal is cat-like, with large dark eyes, a shorter snout and more obvious forehead than grey seals. The common seal appears more agile and lithe than the grey seal. Despite these differences it can be difficult to tell common seals from smaller grey seals in the water. At a distance the ‘Roman nose’ of the grey seal is the best clue. Also, grey seals are much more vocal and more likely to be heard ‘singing’ than
common seals. Close up, the common seal’s nostrils can be seen to be meet in a ‘V shape’, compared to the grey seal’s more parallel nostrils.
Tracks and Trails:
When hauled out on sand or mud, the common seal will leave drag marks with
flipper and claw marks alongside.
Did you know?:
Common seals are the most widely distributed of seal species with 5 sub-species found around the coastal waters of the North Atlantic and Pacific oceans as well as the North Sea and Baltic Sea. The total worldwide population is estimated to be up to 500,000.
Survey Methods:
Coast walk transects and boat surveys.
Common seals are most likely to be identified in Cornwall during grey seal surveys.
© Sue Sayer
In the UK common seals are predominantly found around the Scottish and Irish
coasts, the Wash, and some offshore sand banks. They prefer less exposed sites than
grey seals: sheltered rocky shores, estuarine mud or sandbanks. Reports of common
seals in Cornwall are sporadic, possibly due to in part to confusion with the grey
seals that dominate this stretch of coast.
Common seals are opportunistic feeders, taking whatever prey is available, but focusing on sand eels, members of the cod and herring families, and squid and octopus. Common seals may work to herd sand eels into tight schools, grabbing any fish which break away from the main body. They eat 3-4 kg of fish each day.
Limited evidence is emerging of very small numbers of common seals breeding
somewhere around the Cornish coast. At other UK sites they produce single pups in
late June or early July. Twins have been recorded, but have poor survival rates. The
pup is suckled for about 4 weeks and stays close to the mother both in and out of the
water. Once the pup is born the female mates again. The fertilised egg undergoes
delayed implantation of between 5 and 12 weeks before the start of the 10-11 month
pregnancy. The females are mature at 3-4 years, the males at 4-6 years, and they
can live for about 30-35 years.
Common seals in the UK are sometimes caught by killer whales, although this is less significant than in some of the American populations. In some areas conflicts with fisherman can result in a large proportion of local populations being shot. There is evidence that common seals are particularly susceptible to organic pollutants such as PCBs and DDT; this may affect their reproductive success but also their ability to fight infection. In 1988 and 2002 large numbers of common seals around the UK died in an outbreak of Phocine Distemper Virus, a disease which does not seem to fatally affect grey seals. Recent research suggests common seals are vulnerable to the ducted propellers of boats with dynamic positioning systems with sometimes fatal results.
Distribution:
Typically found in more sheltered water, the common seal is only rarely recorded around Cornish coast, often during surveys of grey seal colonies. Elsewhere in the UK, 80% of common seals are found around the coast of Scotland. They also occur at sites on the coast of Northern Ireland and around the Wash. The European
sub-species is found from France to Iceland and the Baltic Sea.
Records:
2007-2012: 13
2002-2007: 17
Pre-2001: 12
Total: 42
British Divers Marine Life Rescue (BDMLR) volunteers are very active in Cornwall and have been rescuing injured and sick seals for over a decade. Many of the rescued animals are treated and rehabilitated at the Cornish Seal Sanctuary at Gweek, near Helston,
before being returned to the sea.
Conservation:
Common seals are a BAP species in Cornwall and the Isles of Scilly. They are included in the Conservation of Seals Act (1970) and are one of the nine marine species identified in Annex II of the European Habitats Directive for which the UK has special responsibility. Common seal numbers have fallen alarmingly in recent years with a 60% decline in the last 6 years for reasons that are, as yet, unclear.
