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Science Notes / Marine biology, ichthyology

Dolphins recognize other dolphin voices

It might be tough for dolphins to remember faces, considering they always look like they're smiling. But new research indicates they apparently never forget a voice.

That's one finding from a research project by University of Chicago doctoral student Jason Bruck that represents, he says, "a decoding of their whole communication system -- at least the start of that."

Bruck, who is working with dolphins at six facilities, plays recorded whistles of dolphins that had been in the same tank 20 years earlier but hadn't seen their tank mates in that time. When that happens, the dolphins swim toward the signal. When he plays the whistles of unfamiliar dolphins, the signal is ignored or, in some cases, imitated.

Based on detailed observations and multiple underwater microphones, Bruck's research also suggests that dolphins are able to determine family relationships of other dolphins through whistles, and that mother dolphins "cluck like chickens" to call their calves.

Maybe it's no surprise, but females appear better at whistle interpretation than males, Bruck said. "The ladies are keeping track of who's who, and the boys are like, 'whatever.' "

-- Chicago Tribune

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Female fish prefer strong, tough mates

Female African cichlids like their mates tough, based on a recent study of the freshwater fish. When a female cichlid sees her chosen mate win a fight, her brain's pleasure and reproductive centers activate. When she sees him lose, her brain processes an anxiety-like response, said Julie Desjardins, a Stanford University postdoctoral research associate.

In a series of experiments using 15 female and 30 male cichlids, Desjardins and an assistant put a fertile female -- whose belly looked swollen with eggs -- in the middle section of a clear, compartmentalized aquarium. Two comparable-size males were placed in sections on either side of her.

"In the wild, females that aren't full of eggs only interact" with other females, Desjardins said. "We chose females who needed someone to fertilize their eggs."

She gave each female 20 minutes over two days to choose a potential mate. The female would stare at "the one" through the clear divider and swim near him. After the two-day courtship, the scientists put the male fish in the same compartment. Naturally territorial, the males fought, in full view of the female. In eight cases, the boyfriend won and in seven he lost. The scientists then dissected the female's brain and looked for gene activity in the regions responsible for social behavior.

In females that had picked winning males, the brain areas that regulate reproductive hormones had significant spikes in gene activity.

-- Washington Post