False Bay West Coast #6: Seal Rock
This is the 6th of a 7-cache series which will take you to some possibly less well-known parts of this wonderfully wild but still easily accessible coastline – and fill a few gaps between existing caches!
This park ‘n’ grab cache, a small flip-topped, camo-taped tablet pot, is placed at the start of the private access gravel track which heads steeply down to Partridge Point. From the cache location are great views down to the point and beyond to the various rocky outcrops and across the bay.
The outcrops are home to two species in particular. Two of the smaller ones are nesting colonies of white-breasted cormorant and on the largest one named after its inhabitants you should be able to spot (definitely with the aid of binoculars or camera telephoto) – and if the wind is in the right direction, hear - a colony of large furry creatures.
The brown fur seal (Arctocephalus pusillus), also known as the Cape/South African/Australian fur seal, is the largest and most robust member of the fur seals. It has a large and broad head with a pointed snout that may be flat or turned up slightly.
They have external ear flaps (pinnae) and their whiskers (vibrissae) are long, and may extend backward past the pinnae, especially in adult males. The fore flippers are covered with sparse hair over about three-quarters of their length. The hind flippers are short relative to the large body, with short, fleshy tips on the digits.
There are 2 sub-species and the one found here is the southern African A.p.pusillus which is slightly larger than its Australian relative. On average males are 2.3 m long and weigh 200–300 kg. Females are smaller – on average 1.8 m long and 120 kg.
Adult males are dark grey to brown, with a darker mane of short, coarse hairs and a light belly, while adult females are light brown to grey, with a light throat and darker back and belly. Pups are born black and moult to grey with a pale throat within 3-5 months.
It lives around the southern and southwestern coast of Africa from Cape Cross in Namibia and around the
Cape of Good Hope to Black Rocks near Port Elizabeth in the Eastern Cape province.
They prefer to haul out and breed on rocky islands, rock ledges and reefs, and pebble and boulder beaches. However, some large colonies can be found on sandy beaches. They spend most of the year at sea, but are never too far from land. They have been recorded up to 160 km from land, but this is not common.
Its diet is typically 70% fish, 20% squid, and 2% crab together with other crustaceans, cephalopods and sometimes birds. Rarely they may attack and eating sharks. In one incident off Cape Point a large male was seen attacking and killing five blue sharks 1.0-1.4 m long. It was concluded that the seal likely killed the sharks to eat the fish-rich contents of their stomachs, as well as their livers as a source of energy.
The African subspecies can dive up to 204 m deep for as long as 7.5 minutes. They can also ‘sleep’ in the water by laying on their side with one side flipper ‘holding’ on to a back flipper. In this position, known as jugging, they are able to breath as the position keeps the head out of the water.
Its main predator is the great white shark (see here and here) although they are also preyed upon by various other animals, such as killer whales and vagrant southern elephant seals. On the Skeleton Coast in Namibia land-based predators include black-backed jackals (see here), brown hyenas (see here and here) and occasionally lions (see here).
Here in False Bay, the seals use various anti-predatory strategies when in shark-infested waters, including:
swimming in large groups and harassing sharks in the vicinity (see great short video here, low porpoising to increase subsurface vigilance, darting in different directions to cause confusion when attacked, using their greater agility to stay out of reach and riding near the dorsal fin to keep out of reach of the shark's jaws when attacked.
They often gather into large colonies or rookeries and while they spend most of the year at sea, they never fully evacuate the rookeries, as mothers and pups return to them throughout the year. When at sea, they travel in small feeding groups.
They start breeding mid-October, when males haul out on shore to establish territories though display, vocalisations, sparring, and sometimes actual combat. They fast and don’t resume eating until Nov-Dec after mating. When the females arrive, they fight among themselves for territories in which to give birth. Their territories are smaller than those of males and are always located within them. Females within a male's territory can be considered part of his harem. However, males do not herd the females, which are free to choose their mates and judge them based on the value of their territories.
Copulation begins 6 days after the female gives birth to their pups conceived from the previous year. Gestation typically lasts a just less than a year.
After mating, females alternate between periods foraging at sea for up to 7 days with the pups left in creches, and several days ashore nursing their pups. When a mother returns, she emits a loud call which attracts all the nearby pups, but she only responds to her pup - possibly recognized by smell. When left alone, pups gather in groups and play during the evening. They are usually weaned at 4–6 months old.
It is an inquisitive and friendly animal in the water, and often accompanies scuba divers. They swim around divers for periods of several minutes at a time, even at a depth of 60 m. On land, they are far less relaxed and tend to panic when humans come near them.
In SA they have a very robust and healthy population as harvesting of seals was outlawed in 1990. However, they are still harvested in Namibia where permits are issued for the killing of pups for their luxurious fur and adult males for their genitalia, which are considered an aphrodisiac in some countries. Seal numbers are limited there because of the supposed and disputed effect they have on the country's fish stocks.
The main places in the Peninsula where seals are found are the relatively large and flat rocky outcrops of
Seal (Duiker) Island, Hout Bay @ S 34 3 .523 E 18 19.586 (figures of 7-75,000 seals are given in different sources! – see video here), and Dyer Island/Geyser Rock @ S 34 8.270 E 18 34.961 on the north side of False Bay (60,000) which since 2001 has been popularized by the Discovery Channel series Air Jaws, which features the spectacular breaching behaviour of Great Whites near the island as they attack the seals (see extraordinary video here).
Individuals can always be seen in and around the peninsula harbours – Kalk Bay (see here), Simon’s Town (see here), Hout Bay (see here) and of course Cape Town itself at and around the V&A Waterfront (see here) .
Sadly, in Oct-Nov 2021, 100s of emaciated dead or dying young seals washed up along the shores of the Western Cape (see here). Although some annual die-off (of pups who don’t complete weaning) is normal, the quantities involved suggested that West Coast overfishing was leading to an acute shortage of food and that the seals were starving to death. In contrast, along the East Coast seal populations seem to have enough food and are thriving.
Seal Rock is also one of the several dive sites associated with the Partridge Point location – see here for detailed info on the dive and what can be seen there – apart from the seals of course!
For short videos, see here, here and here (diving with fur seals @ PP).
