Europe's Sea Mammals Including the Azores, Madeira, the Canary Islands and Cape Verde: A field guide to the whales, dolphins, porpoises and seals - Robert Still, Hugh Harrop, Tim Stenton and Luís Dias [2019, PDF]

Contents

a preference for particular haul-outs, the choice varies with factors such as
weather, time of year and prey abundance. Will form loose aggregations
in the water, but generally solitary when hunting. Males are not territorial
on land but will defend small areas of water, especially during the mating
season. It appears that Common Seal has a polygynous mating pattern,
insofar as most males will mate with a single female each season, although
some will have more than one mate. However, spatial disputes at haul-outs
are regular which can be marked with growls, head thrusts and flipper-
waving. moult: Pups typically shed their white lanugo within the womb,
and the few that are born with it lose it within a few days. The pup has a
subdued version of the adult coat, which will come through fully at the
following year’s moult. Adults moult at the end of the breeding season
with each individual moult taking 3–4 weeks. Moult timing varies,
with yearlings moulting first (sometimes as early as June, well before
the main moulting period), followed by females, then younger males and finally older males. communication: Not particularly vocal. At haul-outs growls, presumed to be threats, sometimes heard. Other sounds recorded include barks, honks, grunts, roars and moans. Pups will call to their mothers with a baby-like ‘waa-waa’. Underwater males are quite vocal, producing low frequency (1·2 kHz) roars for territorial and display purposes. breeding: Generation time approximately 15 years, assuming a first reproduction age of 8 years. Males reach maturity at around 4–5 years but are probably older before they breed successfully. Females are mature at 3–4 years and give birth to a single calf every year after a 10–11 month gestation period that includes a delayed implantation of up to 12 weeks. Newborns are 70–100 cm long, weigh 9–11 kg and are able to join their mothers in the water immediately after birth. They are nursed for 3–5 weeks. Mothers become less attentive towards their pups during the latter period of nursing before eventually leaving them. Pupping occurs between the last week of May and the 1st week of July, peaking around 20 June. Mating takes place post lactation, in the water, from late June into August depending on location. Post-breeding, pups will disperse but generally remain within 50km of their birth area. predation: Killer Whales and sharks are known to be predators, but a much rarer occurrence in the northeast Atlantic than elsewhere in the range Predation of pups by Grey Seals has been reported. threats: Historically, in the eastern Pacific and western Atlantic there were organized culls and bounty schemes to reduce seal numbers because of perceived competition with fisheries. However, currently only some subsistence hunting is allowed in the US. In the eastern Atlantic, hunting still occurs at managed levels in many parts of its range (e.g. around fish farms in Scotland). Viral outbreaks have killed thousands of Common Seals on both sides of the Atlantic, but most notably in Europe caused by phocine distemper virus. Because Common Seals haul out on nearshore and coastal mainland sites, they are exposed to wild predators, pets, feral animals and human waste, which can all present an increased risk of exposure to communicable diseases. They are also exposed to both major stochastic events such as oil spills, as well as ongoing background issues such as the accumulation of industrial and agricultural pollutants (e.g. organochlorines and PCBs) which, at high levels, can cause immunosuppression and reduced breeding success. They are also easily disturbed and increasing development along the coast, both industrial and commercial, may affect the health and feeding behaviour of nearby populations. Entanglement and bycatch are also a cause of low-level mortality. conservation: No direct measures are in place but various national and multinational protection measures are in place. The Svalbard population is protected under the Norwegian National Red List. The populations in France are categorized as VU on the National Red List. Hunting in the Baltic Sea was prohibited in 1970 and the population is managed and monitored by HELCOM. Denmark and Sweden have created sanctuaries. Denmark, Germany and the Netherlands are party to an agreement to manage the Wadden Sea population. In the UK they are protected under the Conservation of Seals Act and the Marine Scotland Act. protection: CMS App. II (1985); EU Habitats Directive Ann. II; Bern Convention App. III.