The Cape Fur Seal is often referred to as the ‘dog of the ocean’. Animal Ocean reckons that they are possibly the most curious and playful mammals you will ever have the joy of interacting with in their natural environment.
These Seals are from Southern Africa
Did you know that Cape fur seals are endemic to Southern Africa? Their name says it all – find them as far north as Angola, with colonies occurring all along the coastlines of Namibia and South Africa, up to Algoa Bay near Port Elizabeth.
There are roughly 2 million Cape fur seals reside in this range. They live in large colonies and most have settled along the pristine and wild beaches of southern Namibia, as well as on islands just off the West Coast of South Africa. Seals are not nearly as agile on land as they are in the water, so they choose these secluded locations to be safe from human interference, land-based predators and habitat destruction.
Adult males can weigh up to 350kg, with females tipping the scales from 80kg to about 150kg. More than your average human male! The males like to gather females around them in a harem of sorts – one male can attract some 50 females.
Breeding and Eating
Nature is amazing – females are able to delay fertilisation for up to three months to make sure that they will only give birth to pups at the beginning of summer – normally late November/early December. These pups are born without blubber and are unable to swim, making them highly dependent on their mothers for nutrition and protection.
Cape fur seals traditionally prefer pilchards and anchovies but overfishing means that the numbers of these fish have been dwindling. So, seals have to look for alternative sources of food. Fortunately they are rather opportunistic and highly adaptable, happily snacking on anything from crayfish and shrimps to seagulls and penguins.
True Seals, Fur Seals and Sea Lions
- Fur seals have cute little ears on the sides of their heads, while true seals have no external ears.
- Fur seals also have larger front flippers, which they use to propel themselves through the water, unlike true seals who motor along using their back flippers.
- There are nine species of fur seal, of which the Cape Fur Seal is most closely related to the Australian Fur Seal.
Eyes and Fur
While Cape fur seals seem to have tiny eyes on land, they pop wide open under water, taking on something of a torch-like look. With the ability to dive to a depth of up to 200m, their intensely-developed eyes help them to see in even the murkiest conditions.
Fur seals are so called, because they have two thick layers of fur – a soft inner layer and a more bristly outer layer. Along with a layer of blubber on the inside of their skins, this fur helps keep them warm in the freezing water they like to fish and play in. Sadly, this has also made them the target of much violence, as seal fur coats were a sought-after fashion item not too many decades ago.
Various researchers have noticed that Cape fur seals like to nibble on rocks. Scientists think that they do this because: the rocky roughage helps aid digestion OR the weight provides ballast when diving underwater. There is not enough conclusive evidence to support either theory just yet!
Seals and Sharks
So, what impact are the white sharks having on Cape fur seals at Seal Island?
Shark Spotters have been researching this for yours and they say that “even though the highest predation rate on seals observed anywhere in the world is recorded at Seal Island (up to 36 in a single day), predation is unlikely to be the primary reason for seal density being controlled here.”
Because space is limited, hundreds to thousands of seal pups are washed off the island every year and they drown because they are not good swimmers when they are born. In fact, there has been little change in the size of the seal population over the past 60 years.
We have, however, identified another very important impact that white sharks have on seals. We studied two populations: the one at Seal Island, where there is a high white shark presence and associated risk of being attacked, and one at Egg Island, a small breeding colony on the west coast of South Africa with no notable predation risk from white sharks. To understand how white sharks influence seals, we tagged and tracked seals at both islands and observed the differences in behaviour between them.
One of the most interesting discoveries was the change in behaviour of seal pups when they were exposed to white sharks. Sharks arrive at the island just as the young-of-the-year start leaving on their first ‘practice’ foraging trips. The pups are pretty naive at this point, but our research results suggest that they wise up pretty quickly.
At Seal Island, tagged pups initially left and returned at all hours of the day. By the end of the high-risk season, however, they completely avoided leaving from and returning to the island at the most perilous time, the hours after sunrise. At Egg Island, where there was no noticeable predation risk, no such temporal shift was evident. Thus, it seems that exposure to predators is a primary driver of behaviour change.
Fascinating stuff! What is happening globally to seals? They are threatened by hunting in many regions as people still want their meat, blubber and fur. Climate change is another factor – the ice is melting so fast that Arctic seals are losing more pups which are separated from their mothers and dens are threatened. Oceans are also warming up, becoming more acidic and levels are rising.
According to the Seal Range State Policy and Management Review by the International Union for the Conservation of Nature (IUCN), “commercial harvesting of seals has long been a controversial issue. Animal welfare and animal rights campaigns in developed countries have resulted in bans on importing seal products, notably to the USA, EU and Russia….
“The bans have impacted negatively not only on the commercial seal fur trade, but also on the livelihoods of indigenous peoples and their rights to realise the full benefits of the seals they harvest. Expanding seal populations and their perceived impacts on fisheries are also a controversial and largely unresolved issue.”
To sum it all up – there are plenty of seals left in the world but they still need our protection! We need to care for these marine animals which are a vital part of the food chain!