Baffling behaviour of bottlenose dolphins recorded for the first time

Scientists in West Wales have been left puzzled by aggressive behaviour  displayed by female dolphins thought to be chastising her calf.

The team taking part in the Cetacean Survey Training Course in New Quay,  Cardigan Bay, watched the newborn bottlenose dolphin calf being repeatedly  tossed into the air by its mother.

The actions, never before recorded by the team, may have simply been some  unusually rough play or possibly a means of disciplining or teaching a newborn,  say the scientists.

Sea Watch research director Peter Evans said the demonstration may have been  a lesson to stay away from male dolphins since they have, on occasion, been  recorded attacking and even killing newborn calves.

“The phenomenon of aggressive behaviour against porpoises sometimes leading  to death has in the past been attributed by some scientists to misdirected  infanticide by male dolphins, since young dolphins have been observed being  attacked by adults, generally presumed to be males,” said Mr Evans.

“In this particular instance, photography made it possible to establish that  the apparently aggressive behaviour was actually made by the mother rather than  a male dolphin as might otherwise have been inferred.”

Sea Watch is the holder of the largest database of whales and dolphins in  Europe and has been researching the bottlenose dolphin population in Cardigan  Bay for more than a decade.

The unusual event occurred late in the afternoon on Sunday, just off the  coast at New Quay where several members of the training course were aboard a  survey boat from the marine research charity Sea Watch. Others witnessed the  event also from a watch post on land.

“Soon after leaving the harbour, the boat encountered a group of seven to  eight dolphins and stopped for photo identification of the individuals,” said Mr  Evans.

“The dolphin group consisted of several adults, an older calf, and a newborn  calf thought to have been only a few days old.

“The group demonstrated primarily social and percussive behaviour, involving  belly-up displays, physical contact with one another, and tail thrashing and  slapping.

“Then those aboard the boat witnessed the newborn being nudged out of the  water. Approximately five minutes later, the animal was tossed repeatedly right  out of the water, three to four times.”

Those watching on land initially thought it to be a harbour porpoise because  it looked so small against the adult dolphin, but after multiple observations,  it was confirmed to be the newborn dolphin calf.

Although other adults came close to the mother and calf, the photographs  revealed that the actual tossing was done by the calf’s mother. She was an  animal recognised as one named Tamara by Sea Watch researchers, a female that  had last given birth to another calf three years ago.

Mr Evans said reasons for the aggression cannot be known for certain.

“Maybe she was simply playing with her infant. Alternatively she could have  been scolding her young one for wandering too far from her, so as to ensure the  infant did not come too close to either a hostile male dolphin or to the survey  vessel,” he said.

“Earlier, she had repeatedly nudged the infant along in a particular  direction away from a group of other dolphins.

“All individuals in the group were later observed feeding, throwing fish into  the air, and engaging in normal swimming behaviour, so the calf appeared to be  completely unharmed, though presumably a lot wiser for its experience.”

Rachel Lambert, a volunteer for Cardigan Bay Marine Wildlife Centre (CBMWC)  watched the drama unfolding just 400 metres away with her binoculars.

“It went on for about 45 minutes, this tiny little thing being flung through  the air,” she said. “But I saw it later swimming alongside its mum, so maybe  they were just giving it a good telling off.”

Steve Hartley, CBMWC’s founder said he’d never heard of anything like this in  Welsh waters.

“There have been many instances around the world of dolphins attacking  smaller porpoises in a similar manner and ultimately killing them, and we’ve  seen this type of behaviour in Cardigan Bay,” he said.

“But this was definitely a young dolphin, not a porpoise.”

Source: Wales online

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