Metro

Bacterial infection may be cause of death for some stranded Cape dolphins

Rescuers released a common dolphin that had become stranded in Provincetown this week.
International Fund for Animal Welfare.
Rescuers released a common dolphin that had become stranded in Provincetown this week.

Wildlife experts are looking at whether a bacterial infection that can spread easily between common dolphins is severely reducing the chances of survival for the marine animals when they become stranded suddenly on Cape Cod beaches.

Since Jan. 1, staff and volunteers from the International Fund for Animal Welfare have responded to 96 individual dolphin strandings up and down the coast, a number that Brian Sharp, the welfare group’s marine mammal rescue and research program manager, said was unusually high.

“This is one of our busiest years for dolphin strandings,” he said, hours after the nonprofit group rescued a single dolphin in Provincetown. The group also responded to two separate dolphin deaths on the Cape on Thursday.

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But even more troubling than the strandings have been the deaths of some of the dolphins the team had hoped they could safely return to the sea.

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In just over two months, the team has encountered 29 dead common dolphins, and an additional 12 dolphins either had to be euthanized or died during rescue attempts due to their poor condition.

Sharp said researchers from the group have performed necropsies — autopsies for animals — on 14 common dolphins that didn’t survive. Of those animals, five dolphins showed possible signs of a bacterial infection called “Brucellosis,” which causes respiratory and other problems in the animals and can weaken their chances of survival in the event of a stranding.

“It’s not the cause of the strandings, but it may be the cause of why the animals are succumbing to the stress of the stranding and may be dying,” he said. “That’s our leading theory. . . . It might be what’s putting them over the edge.”

Researchers from the welfare group have sent blood and tissue samples from the five necropsied common dolphins to two separate labs — one at the Mystic Aquarium in Connecticut, and the other at the University of Illinois — as part of their investigation. Results are still pending.

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“We are not sure what’s going on yet, but a lot of animals are dying soon after their strandings,” Sharp said. “Even before we can do the care and treat the animals, these animals are dying.”

The welfare group has been hard at work, averaging more than one dolphin rescue response per day since the start of the year. They have worked to help a mix of common dolphins, harbor porpoises, and Risso’s dolphins, Sharp said.

“It is concerning, because we are at such a rapid pace that we are basically responding and resetting — barely resetting — before the next stranding occurs,” he said. “It’s alarming and we are looking at a lot of different factors.”

Steve Annear can be reached at steve.annear@globe.com. Follow him on Twitter @steveannear.