Saturday, August 25, 2007

Galapagos Sea Lions


The sea lion is one of the animals one first notices in the Galapagos. The young ones are especially curious and playful. They often approached us when we were snorkeling, and pulled at our fins. On one occasion a pup bit several people in the class while we were swimming. This endemic seal lion is most closely related to the California sea lion. The Galapagos sea lion is smaller than the California sea lion, but males can still weight as much as 250 kilograms (550 pounds). Females are smaller, and by comparing the photos below, you should be able to see other obvious differences.

Sea lions eat fish and squid, and may travel far out to sea to hunt. Sea lions also spend a good amount of time resting on sandy beaches.
Females typically give birth to one pup, and may still be caring for an older pup when the newest is born. There is competition between the two, and sometimes the younger one dies.
Sea lions breed annually, but gestation is only 9 months. Implantation of the fertilized egg in the uterus is delayed. About three weeks after giving birth, the female is ready to breed again, but the fertilized egg only divides a few times, then stops development and does not implant in the uterus for two months or so.
Female sea lions live about 20 years, and males a bit less. Males compete with each other for sandy beach territories, and the beach master does not feed while defending his territory. Because of this, any given male is not a beach master for longer than a couple of months. Compare the female in the picture above, with the male below. What differences do you see?

The beach master mates with the females that choose to use his beach, but females are free to move from his territory to another if they find him unsuitable. Males are much more aggressive than the females and defend their territories vigorously by first barking above and below the water. I was warned away from a territory in this manner while snorkeling and quickly swam away. No need to argue with a 500 pound animal.:)
El Nino events have had a negative impact on the populations of Galapagos sea lions. During the El Nino event of 1997-98 their population numbers feel 48%. Some simply left, but there was also high mortality. 90% of those born in 1997 died, and 67% of the dominant males died of starvation. In 1979 there were about 50,000 sea lions in the Galapagos. A survey done in 2001, found an estimated 14,000-16,000 animals. Since then some recovery has occurred, with a more recent survey finding an estimated 16,000-18,000.
For more information about sea lions, and other Galapagos organisms you can visit the website of the Darwin Foundation at:

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