Monterey Bay researchers say dolphins are causing porpoise deaths For the past five years, the growing number of dead harbor porpoises washing up on California shores has been a marine mystery — until now. In September, marine biologists with Okeanis, a nonprofit conservation group based in Moss Landing, captured the only video footage taken in Monterey Bay of bottlenose dolphins attacking and killing a porpoise. Scientists suspected dolphins, which have a relatively docile reputation, have been attacking the smaller porpoises because the porpoises have been washing up on the shore with rake marks and internal bleeding, but they never had...