Rowdy dolphins fingered in California "porpicide"

It obviously was something in the water - but what? Between 2007 and 2009, researchers witnessed what they described as three deadly aquatic interactions where harbor porpoises got pounded to death by bottlenose dolphins in Monterey Bay, California.

That much is clear. What triggered the violent outbreak in the famed cove not far south from San Francisco still remains unclear.

Although this marked the first time that marine biologists were able to document these sorts of attacks in the Pacific, they remain stumped about what caused the incidents. They dismissed the usual explanations, such as interspecies competition over territory. However, one possibility is that was something on the order of guys being guys driven by high-testosterone levels, as the attacks occurred at the height of the breeding season. Or, they suggested, it might be related to "a skewed operational sex ratio" as 21 of the 23 attackers were males.

"Ultimately, we need more information about bottlenose dolphin social structure at the time of the aggression," they report in the latest edition of the journal Marine Mammal Science.