Cape Fur Seal
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
I don't feature marine life much in this column … partly because I don't have much personal experience of it, living deep inland and only having been to the seaside a few times in my life. But today I try to make up for it a bit, by showing you a couple of Cape Fur Seals, Arctocephalus pusillus pusillus. The reason for the second 'pusillus' is that the Cape Fur Seal is not a species as such, but a subspecies of the Brown Fur Seal, the other subspecies of which, Arctocephalus pusillus doriferus, is the Australian Fur Seal! The genus name 'Arctocephalus' means 'bear-headed' and 'pusillus' means 'small'. Not that this is a small animal … a male Cape fur seal can reach about 2.4m/8' in length and a weight of 350 kg/770 lbs! An average Cape fur seal male is about 2.1 m long and 185 kg; females are much smaller, averaging 1.6 m and 75 kg.
No True Seal
There are three modern families of seal-like animals. The first, the Odobenidae, contains only one species, the Walrus. The True Seal family, the Phocidae, contains what are also known as earless seals, from small ones such as the Ringed Seal up to the enormous Elephant Seals which I'll feature here soon. Then there are the Eared Seals, also called Sea Lions, the Otariidae, which include our fur seals. They differ from true seals in numerous respects. They can use their fore and hind feet for running though their gait is rather clumsy. Their front flippers are strongly used for swimming. True seals cannot turn their hind feet forward to walk on them; they have to wriggle forward on their bellies. They use mainly their hind flippers for propulsion under water. Eared seals also, as you may gather, have visible external earlobes, while true seals don't; they only have ear holes.
The Cape fur seal is the only seal you're likely to encounter around the Southern African coastline. Like other fur seals, it likes cooler water, especially because the cold Benguela Current off the western coast of Africa is rich in oxygen and supports a wealth of marine life. Ninety percent of a seal's diet consists of fish, the rest being squid, crabs and other invertebrates. Most of the fur seals are found on the west coast of South Africa and Namibia; some are found as far east as East London and as far north as southern Angola. Fur seals fish in waters near the coast, and rest and breed on rocky islands or on rock or pebble beaches. Rarely, they can be found on sandy beaches also. They are gregarious and occur in colonies, sometimes in great numbers.
Cape fur seals are rather vulnerable on land, especially their pups. Most of them breed on islands, with only six known breeding colonies on the mainland versus nineteen on islands. Big adult males (called bulls) start laying claim to their breeding spaces in October, which is springtime in South Africa. They compete and set up territories, the first arrivals getting the best spots. Over the previous months, they've fed well and laid down a thick layer of blubber. They use this for energy as they struggle and fight, sometimes constantly for six weeks without going out to feed, seeing as how they can't afford to abandon their hard-won land for even an instant. The fighting can get very violent, bulls frequently injuring each other with deep bites. The females come onto land a few weeks after the bulls, ready to give birth to their pups. They, too, fight among each other for the best territories. Then, shortly after giving birth, they come in oestrus again and mate with the bulls, the most dominant bulls with the best territories having access to the largest number of females. Yes – they carry their pups for a whole year! So they give birth to the pups from the previous year's mating, and mate to bring into being the next year's pups. It is timed wonderfully. The next year's embryo goes into a resting stage for 4 months before it implants on the uterus wall and starts developing, to ensure the pup will be ready for birth almost on the dot a year after conception.
Typically, a female will have a single pup. On the mainland, the main enemies of the pups are jackals and hyenas. The female will try to defend them but is hampered by a lack of speed and agility on land. The seals therefore find protection in numbers. The female nurses her pup for nine months or more. For the first week of its life, the mother will remain constantly with it, but from then on, she needs to abandon her pup periodically when she goes fishing, sometimes for a few days at a time. When she returns, she calls her pup with a bleating 'm-a-a-a'. The pup answers with a lamb-like bleat. She also knows it by smell; together with remembering exactly where her territory is, this helps her find her pup amidst thousands of others. When the females are away, the pups gather together on 'playgrounds'. Initially they explore small regions around their birth places; they get more adventurous as they grow, exploring rock pools at first, and later the open sea. As their moms taper off the nursing, hunger drives them to start trying to find their own food. At the age of seven months, they are able to stay at sea for three or four days at a time. But they still get milk from their mothers for some months more.
Somewhat awkward on land, fur seals turn exquisitely graceful in the water. Their bodies, looking sometimes rather corpulent on land, turn lithe and sleek under water. Young seals have been noted as ingesting smooth pebbles and stones, perhaps as ballast to enable them to dive more easily. They can catch fast-swimming fish and dive to a depth of 400 m, staying submerged for ten minutes. They target mostly smallish fish such as mackerel, anchovy, gobies and sardines, as well as squid, octopuses and crustaceans. They've even been noted killing fair-sized sharks, eating the liver which is very rich in energy. They in turn are preyed on by large sharks and killer whales.
Like other fur seals, these have had a hard time from humans. Vast numbers were killed for their fur, but this exploitation ended with the seals, very nearly extinct, getting legal protection in 1893. At present, a small number is still killed or 'culled' by the Namibian government each year. There are calls for limiting seal numbers because they supposedly compete with fishermen. We need to remember that Planet Earth and its resources don't exist for Homo sapiens alone! I can assure you that humans take vastly greater quantities of fish out of the oceans than seals do. The seals have been doing it for longer than we; they have a much greater right to complain about us taking 'their' fish! As it is, they sometimes die from getting entangled in nets. But overall, the seal population is large and healthy, and the species not considered endangered. The situation may change very rapidly, though, so we need to remain vigilant.