The seals of South Africa : Seals belong to the order Pinnipedia of which there are 33 species worldwide. These fall into two categories. Fur seals – Otariidae – or sea lions, have external ears and hind limbs that can be rotated forward to allow them to walk and climb on land. True seals – Phocidae – have hind limbs that cannot be rotated forward and have no external ears. Only one species, the cape fur seal is resident in South Africa. Other species occasionally occur as vagrants. The seals of South Africa :
CAPE FUR SEALTHE CAPE FUR SEAL – Arctocephalus pusillus.
Identification: Cape fur seals can weigh up to 350kg – the largest of all fur seals. The males have a rough mane on their powerfully developed necks and are much larger than the females, which only attain a weight of around 90kg. Both males and females are covered in thick, dark-brown to olive fur. The pups are born black and moult for the first time at 4 months.
Biology: Mature bulls come ashore in late October to establish territories which they actively defend. The females arrive later and join the bulls harem which consists of around 20 females. Pups conceived the previous year are then born and the bulls mate with the cows only 6 days after they have given birth. Within the female, the implantation of the embryo is delayed by 4 months. A gestation period of 8 months follows and thus ensures that the pups are born on a yearly cycle.
Behaviour: When on land, fur seals are skilled climbers and may be sighted in surprisingly high places. At sea they are known to travel large distances – as much as 80km a day – and may spend months offshore where they are able to dive to over 200m in search of food. The females tend to remain at the colony for most of the year, feeding at sea on fish, squid and crustaceans and returning every few days to suckle the pups. Twenty five fur seal colonies are found between Algoa Bay (Port Elizabeth) and Cape Frio (Northern Namibia) most of which are on offshore islands and sightings are guaranteed the year round. Being fantastically agile and always graceful underwater, they are a pleasure to watch when diving.
SOUTHERN ELEPHANT SEAL – Mirounga leonina.
Identification: The Largest of all seals, male elephant seals can attain 6m and 3500kg while the females are smaller at 4m and 800kg. The bulls are easily identified by the short, bulbous, trunk-like proboscis that hangs over the mouth. The elephant seals fur is grey-brown to brown but can be yellow-brown in mature males and before moulting.
Biology: The bulls come ashore in spring to establish territories. The females arrive later and join the harem. The pups conceived the previous year are born about a week later and the bulls mate with the cows 2-3 weeks after they have given birth.
Behaviour: Elephant seals have a circumpolar distribution and are largely restricted to sub-Antarctic waters as far north as the southern tip of South America. They feed mainly on fish and squid, however crustaceans are also occasionally taken. Elephant seals are mostly solitary animals. Spending most of their time at sea, data suggests that almost 90% of that time is spent underwater where they can dive to over 1400m and remain submerged for up to 2 hours. Sightings in South Africa are rare, although vagrants occasionally beach along our coastline.
THE CAPE CLAWLESS OTTER – Aonyx capensis.
Cape clawless otters are found throughout the southern and eastern coastal regions of South Africa, where they prefer areas with both fresh and salt water.
Identification: Attaining 1.5m and 18kg, the males are larger than the females. The body is dark to light-brown with a white throat and belly. Slender, and seal-like in form, cape clawless otters have a thick and tapering tail, flattened underneath to act like a rudder. The front legs have highly dexterous, clawless, fingers which enable them to probe under stones and in crevices for prey. The hind legs are partially webbed and provide most of the propulsion for swimming.
Biology: Little is known. However based on studies undertaken on other species of otter, it is believed that two or three cubs are born in the summertime following a three month gestation period. The cubs are completely weaned after an estimated 14 weeks but, stay in a family group with their mother for some years.
Behaviour: Adult clawless otters are mostly solitary animals, pairing up only for mating season. They are territorial and shy but can be found in rivers, wetlands, estuaries and coastal waters. With molars especially adapted to crushing, they feed largely on crabs, crayfish and molluscs. Octopus, small fish, frogs, rodents, insects and even birds are taken opportunistically. When not feeding, they are often playful and, if you’re lucky, they can be seen chasing each other, mock fighting and playing with stones or sticks for long periods. They have also been observed washing food items before eating. Otters are most active at dusk and at dawn, the daylight hours usually being spent in thick vegetation or in their holts.