For male humpbacks, trip to isles is all about mating

It’s January, and our most famous winter visitors, about 10,000 humpback whales, are stirring the sea.

Several whales I saw from the Lani­kai lookout last week were particularly active, blowing, splashing and flipping their fins. As I watched the peaceful sunrise, I was tempted to imagine that the group was a family consisting of parents and baby, maybe accompanied by an auntie or uncle with a cousin or two.

But that would be wrong. I was almost surely watching male whales fighting.

Male humpbacks migrate from Alaska to Hawaii each winter for one reason, and it’s not for a family vacation. They’re here to mate. Being typical of most mammals, the males want to spread their genes far and wide by mating with as many females as possible. Given the biological drive, it’s the male’s job to fight off other males with the same goal, which is all of them.

To make life even more competitive, there are far more sexually mature males in Hawaii waters than there are receptive females. The male-female numbers in the Alaska feeding grounds are equal, but because females give birth only once every two or three years, not all adult females make the trip south each year. For every female in estrus in Hawaii’s breeding grounds, there are two to three eager males.

From the female perspective, having a surplus of males is a good thing since female whales go for quality over quantity. Competition allows a female to pick the biggest, strongest male to father her offspring.

For males, though, spending the winter among a pack of testosterone-loaded rivals can leave smaller and weaker individuals as bloody messes. Fights can include head butts, body blows and fluke whacks, resulting in head injuries, torn fins and damaged tails.

When not wooing a female or duking it out with challengers, the life of a male humpback is lonely. His interactions with other members of his species usually last only minutes, or maybe an hour or two.

For a male, a long-term commitment is two days, the longest time Hawaii researchers recorded a male staying with a female and her calf. Usually, however, a male’s attention to a female is a few hours — a day, max. The male then moves on to the next encounter.

Or hangs out alone, singing the blues. Or maybe a rock opera with a message. No one knows for sure the meaning of humpback whales’ haunting songs. Researchers do know that the songs occur only during breeding season, that only males sing and that the songs, which the whales learn from each other, do not seem to attract females.

Knowing what we do about male whales, though, you can be sure the always changing songs have something to do with mating.

Most female humpbacks give birth in January, so from now through April it will be common to see calves swimming and frolicking near their mothers.

But when the water is white with fin slaps, tail smacks and body slams, it’s not a family of humpbacks enjoying each other’s company. It’s male whales brawling for their moment of glory. It works. The humpback whale population is growing.

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Reach Susan Scott at www.susanscott.net.