Dolphins Washing Up Dead On US East Coast

Dozens of dead dolphins have been washing up on the East Coast, as worried scientists try to find out why.

Since early July, seven times the usual number of bottlenose dolphins have been found stranded on the shores in New York, New Jersey, Delaware, Maryland and Virginia, the National Oceanic and Atmospheric Administration (NOAA) said.

"All age classes of bottlenose dolphins are involved and strandings range from a few live animals to mostly dead animals with many very decomposed," the agency said in an Unusual Mortality Event note on its website.

A chart published by NOAA showed that there have been 299 cases so far this year - compared to 111 in all of last year.

In Virginia alone, 80 animals were stranded this month, compared to less than 10 in August 2012.

Dozens of marine biologists along the Atlantic are examining stranded dolphin carcasses for clues.

NOAA said some of the dead animals had pulmonary lesions.

One animal might have contracted morbillivirus infection, preliminary testing of tissues suggests.

In 1987, more than 700 animals died, with morbillivirus identified as the main culprit.

The agency said it was evaluating all potential causes, but it added that "an infectious pathogen is at the top of the list".

"Work is underway to determine whether an infectious agent affecting these dolphins is present in collected tissue samples," it said.

Charles Potter, a marine mammal expert with the Smithsonian Natural History Museum, said there might be underlying causes.

He said on the Smithsonian's blog that heavy metals, pesticides and hydrocarbons might play a role.

Other stresses attributable to human activity, such as increased noise and competition for space and food with humans, might make the animals more susceptible to infectious pathogens, he said.