Infanticide Reported in Dolphins
Milius, Susan, Science News
Bottlenose dolphins, the darlings of sea parks and nature tourism worldwide, have now received the distinction of being the first of the dolphin-porpoise-whale group accused of killing youngsters of their own species.
A research team in Scotland and another in the United States say that young dolphins found on the shores were probably pummeled to death by adult dolphins. The researchers cannot tell which adults attacked or why.
"There is this public ethos that dolphins couldn't do a thing like that," observes Tony Patterson of the Inverness Veterinary Centre in Scotland. Yet five carcasses of youngsters discovered in Moray Firth show a "specific and consistent pattern" of injuries typical of dolphin attacks, he says. He and his colleagues report their evidence in the July 7 Proceedings of the Royal Society of London B.
Dale G. Dunn of the Armed Forces Institute of Pathology in Washington, D.C., found the same pattern in nine dead dolphin calves retrieved from the Virginia coast during 1996 and 1997. The bodies did not look badly injured, but when he opened the carcasses, Dunn found broken bones, ripped tissue, and bruised organs. "It looks like someone had taken a baseball bat and just literally beaten these animals to death," Dunn says. He and his colleagues presented their findings at the Sixth Annual Atlantic Coastal Dolphin Conference in May in Sarasota, Fla.
In 1996, Ben Wilson from the University of Aberdeen in Scotland and H.M. Ross from Inverness, coauthors of the recent article, reported that 60 percent of harbor porpoises found dead on the northeast Scottish coast appeared to have been killed by dolphins. To identify the killers, Wilson compared teeth marks seen on some of the corpses with mammal jaws in museums.
Since then, people have caught some attacks on video, Patterson reports. One to three dolphins chase a porpoise and ram their beaks into it hard enough to toss it into the air. "When [it's] thrown high out of the water, there's massive twisting injury," Patterson says. Blubber and muscle rip away from the bones. …