Situated on the magnificent Robberg Nature Reserve, a 3.9km peninsula that extends into the ocean on the southern side of Plettenberg Bay, is a colony of approximately 4000 Cape Fur Seals (Arctocephalus Pusillus). After the extermination of the original colony in the early 1900’s, the seals only returned in the early 90’s. The population gradually increased, initially due to migration and later due to breeding. It was officially declared a breeding colony a couple of years ago, meaning that in excess of 100 pups are born there annually.
Cape Fur Seals have a defined breeding season, commencing in November and continuing for approximately 6 weeks. The season commences with the males fighting for territory, while the females give birth, generally within a week of one another. Within 6 days of giving birth, the female is ready to mate again.
However, being a mammal, she needs to provide milk for her newborn pup and therefore, if she were now to commence a pregnancy, the demands on her energy reserves would be too high. To facilitate this imbalance, fur seals utilise delayed implantation. This means that the embryo doesn’t implant in the uterus and is kept in a dormant state until the previous pup is weaned.
A few days after parturition, the mother may then return to the sea to feed, sometimes for as long as 4 days, while spending on average of 3 days with her pup so it can feed. At 4 months the pup is weaned and has begun to venture into the ocean and learn to feed itself. The mother will then devote her energy to her current pregnancy. Approximately one year after mating originally occurred, a pup is born and the breeding cycle recommences.
– by Steve Bebington