What Are Sea Lions?
Sea lions are a kind of eared seal. In fact, the familiar “trained seals” that perform in zoos and circuses are sea lions. Native to the Pacific Ocean, these cheerful performers of the sea learn easily and can be trained to do such tricks as juggling balls on their noses and blowing horns.
Unlike most seals, who must wriggle on their bellies when on land, the sea lion can turn its paddle-like flippers forward and use them as feet for walking. Sleek animals with large, soft brown eyes, the big male is recognizable by the thick mane around his neck.
Both seals and sea lions are called Pinnipeds, which means “fin-footed.” They are mammals, a group of animals that includes humans that have live young, produce milk, have hair/fur on their bodies, are air breathing, and are “endothermic” or able to control their body temperature.
Both types of animals are also semi-aquatic, which means that they spend part of their lives on land, and part of their lives in the ocean. Seals and sea lions are protected by the Marine Mammal Protection Act, which requires that no one harass the animals – which includes getting too close! They also have similar diets, although a few things are different, and they use their specialized whiskers to feel the movement of their prey in the water. They are preyed upon by orcas, polar bears and sharks.
They are more adapted for life on land than seals, as they can rotate their back flippers to make it possible for them to walk and run on land. Sea lions can only dive as deep as 450m, but dives further than 200 are uncommon, and they can’t store as much oxygen in their lungs as seals can. Sea lions’ flippers have no hair or claws so that they can more easily grip the surface of rocks and many of their mating areas are on rocky terrain. The way they use their flippers to swim is different from seals – it’s actually the exact opposite.
Sea lions use their long, strong front flippers for power while they swim, and their back flippers for steering. This gives them an advantage when escaping orcas because if the orca were to bite their back flippers, they could still swim quickly to get away, where if a seal had its back flipper bitten, it would no longer have the “power” flippers to keep it moving forward. Sea lions are also usually monochromatic – or they only have one color in their fur, while seals typically have many colors.
The mating system in sea lions is polygynous, which means that there are many females per male. A ratio of 10 females per male is fairly common. The males will defend a patch of land, called a territory, and then all the females on his land are the ones that he mates with.
The older and more experienced the male: the better location he has and the more females that want to give birth and nurse their pup on his land. Both otariids and phocids (sea lions and seals) have post partum estrus, or are ready to mate immediately after giving birth. The uterus in females is shaped like a “y”, with one horn holding the full-term fetus and the other preparing to receive the new blastocyst within a few days of birth of the fetus. The females become receptive for mating between 4 and 23 days postpartum.
In the Steller sea lion, it has been noted the females that have lost a pup will adopt another. Sea lions are different from seals in that the females will continue eating while lactating, seals fast during this time, and also in that pups stay with the females between 4-12 months, depending on the species. Sea lions also tend to have a little longer life than seals – they can live to be 15-20 years old.