Dolphins may be cause of spike in porpoise deaths

Marine biologists have figured out why a growing number of dead harbor porpoises have been found on California beaches in recent years: dolphin attacks.

Now they’re trying to determine a reason for them.

Okeanis, a Moss Landing-based conservation group, shot video of bottlenose dolphins fatally attacking a porpoise. It helps explain why carcasses were found with internal bleeding, rake marks and broken bones.

The video shows male dolphins coralling the porpoise, ramming it and drowning it, then bringing the carcass to researchers on a boat and swimming away.

Scientists say about 74 dead porpoises washed up last year in the state.

Okeanis biologists are working with the Santa Barbara Museum of Natural History, Marine Mammal Center and other groups to find evidence that will shed more light on the attacks.