Published: 21st Jun 2018For seals, it's a case of all their birthdays coming at once...
Are your family birthdays spread through the year? Or do they cluster and make a busy period for gift-giving and parties? Spare a thought for Living Coasts’ South American fur seals. There are five of them, and they were all born between May 25th and June 21st.
Grace was born on May 26th 2001, Karel on June 21st 2003, Tunanta June 7th 2006, Gemini June 3rd 2014 and Tamar on May 25th 2017. Is it bad luck – or clever biology?
The South American fur seal (Arctocephalus australis) breeds on the coasts of Peru, Chile, the Falkland Islands, Argentina, Uruguay and Brazil. The total population may be around 250,000, but has been on a general downward trend for some time.
Each year in the wild, between October and December (the southern hemisphere spring), South American fur seals begin their breeding period. Females come into season together and males fight for territories. Females give birth anytime throughout the three months.
Seven to ten days after giving birth, mating occurs again, but implantation is delayed (it’s called embryonic diapause). This, along with a gestation period of between 8 and 12 months, ensures that wild fur seals give birth in the spring, with the better weather and a better supply of food.
Pups are weaned at about 12 months, so the mothers are ready to nurse the next one when it’s born the following spring.
It’s a strategy that means survival in the wild. At Living Coasts, where life is far easier, the seals don’t need to worry about where their next meal is coming from, but they still give birth in the (northern hemisphere) spring and early summer. It means that staff can be prepared – not so much with cards and flowers, but to look out for a new-born pup.