Sunday, August 19, 2007
Sex and the single seal
[Basking harbor seals at Bolinas Lagoon, Marin County, California]
It's a neighborly thing to do -- walking your neighbor's dog. And it doesn't have to be drudgery, especially when you live in a small seaside community like Jenner, at the mouth of the Russian River on California's Sonoma County coast. There you can take the pooch to the beach, and play retrieve the stick. This is exactly what Angel Garcia was doing when a huge Northern Elephant Seal torpedoed from the surf and seized the pit bull in its jaws. Sativa, the pooch managed to break free. For a few moments, man and dog stood defiant before the great hulk. Then they decided 'discretion is the better part of valor'.
Meet Nibbles, an elephant seal with a checkered past. Since he was an adolescent, five years ago, he has been visiting this beach and forcing himself on female harbor seals. Yes, that's what I said. He has been trying to have sex with them, and in the process he kills them. I should also mention that the oaf weighs about 10 times more than his victims. Bull dozer deaths.
At first it seemed to be accidental, the errors of confused and testosteronized youth, frustrated by the bullying of larger males. Then last year Nibbles started to kill the seals with a head bite. More recently he started to eat the dead victims. It seems rather bizarre, but as Mark Twain said, "truth is stranger than fiction". [If you haven't viewed the video, now is the time, but be forewarned -- it's gory.]
What do people make of this? The public is more likely to rush to judgment and pronounce the animal a degenerate miscreant. Biologists know that our knowledge of seal behavior may be incomplete, and that such events may not always be abnormal.
So I wrote to Daryl Boness, a good friend who is an expert on pinniped behavior.
Daryl replied that while raping and pillaging is not common among pinnipeds, elements of Nibble's bizarre behavior are known in a number of species. He has observed adult male grey seals raping female harbor seals. "While I have not witnessed the harbor seal being killed or eaten, I did get a report from someone of harbor seals being killed by a male under such conditions, but there was no indication of eating the carcass.
"However, there is a published report of male New Zealand fur seals occasionally stealing, killing and eating pups of their own species. There was no evidence of sex with the pups, but young South American fur seals will steal pups from mothers and have sex with them, which often leads to their death. Males of this species also will group together and steal females from a territorial male."
It's not pretty stuff, but there you have it. Male seals and sea lions are aggressive by nature. When you are talking about seals and sex, the word courtship seems an egregious malapropism. Copulation in pinnipeds is a brutish thing. The fumbling and bumbling sexual attentions of adolescent males are at times directed to inappropriate subjects such as immature animals. You can add to this the fact that some pinnipeds (walruses, northern sea lions, and leopard seals) prey on smaller pinnipeds, and the lines between normal and abnormal start to blur.
The point I want to make is that some aspects of animal behavior may seem immoral or indecent by human standards, but may not be abnormal.
That isn't to excuse Nibbles.
As Daryl said, "I think these young males are driven by sex hormones and things get out of hand. It is likely a learned behavior. Killing and eating the carcass is the most aberant part of it. You see lots of young grey seal males raping weaned pups on Sable Island, but you don't see them killing and eating the pups.
"Your elephant seal male may be the equivalent of a human nut case. How's that for being scientific?"
Daryl is obviously a little uncomfortable about being anthropomorphic. But I agree with him . . . we can always rely on our own species for the best examples of the bizarre and abnormal.
Campagna et al 1988. Group raids: a mating strategy of male southern sea lions. Behaviour, 107:44-60
Campagna et al 2000. Pup abduction and infanticide in southern sea lions. Marine Mammal Science, 16(2):494-500.
Mortenson, J. and Follis, M. 1997. Northern elephant seal (Mirounga angustrirostris) aggression on harbor seal (Phoca vitulina) pups. Mar. Mamm. Sci. 13(3): 526-530