Going underwater with video cameras and sonar, scientists have gained new insights into the mating behavior of humpback whales.
They learned that female humpbacks on the prowl prefer the largest males on the breeding ground, while smaller males gravitate toward smaller females -- apparently so as "to run less risk of a big male coming over and beating you up," said Adam Pack, a biologist and psychologist at the University of Hawaii at Hilo. "It's basically making the best of a poor situation," he added.
Dr. Pack and his colleagues, who report their findings in the journal Animal Behavior, tracked 67 dyads, or pairs of male and female whales, in the Pacific Ocean off Hawaii. Although humpback mating has never been seen, it is likely that these were mating pairs, Dr. Pack said. (The whales migrate from Alaska each year to breed, fasting and relying on stored reserves to survive.)
The researchers used underwater videogrammetry to capture images of the whales at sea. The technique involves recording the whales with a camera, using a sonar device to estimate the distance of the whale from the camera as well as other measurements.
"With a little bit of geometry, we can determine the true length of the whale," Dr. Pack said. The information allowed the scientists to estimate the likelihood that a given whale had reached sexual maturity; they also used historical data.
"If you can actually photograph an underside of a whale's tail, you have a unique marking you can compare to prior pictures," Dr. Pack said. "Some of these smaller-sized females were nonetheless sexually mature."
The researchers also found that juvenile whales were pairing off in male-female dyads. Like teenagers, "they are probably learning the social conventions," Dr. Pack said.
This article originally appeared in The New York Times.