newsweek:

Ian Yarett looks at the scientists who are trying to figure out how many animal deaths can be attributed to the BP oil spill:

To tease out causes of death for the animals collected since the spill began, necropsies—animal autopsies—are being done on as many of the carcasses as possible, says Erin Fougeres, a marine- mammal biologist at the National Oceanic and Atmospheric Administration (NOAA).

There’s always the possibility that higher-than-normal reported animal casualties are due to factors other than oil exposure. For instance, NOAA says that more dolphins than usual were being stranded prior to the spill—62 of them were found stranded in March, compared with the usual 18. Additionally, people are looking a lot harder for injured or dead animals than they ordinarily would, says Robert MacLean, a veterinarian at the Audubon Nature Institute. With so many cleanup workers, government officials, and environmental advocates swarming across the outlying beaches of the Gulf Coast since the spill, animal carcasses that would otherwise have gone unnoticed are more likely to be discovered.

But then again, response workers are probably collecting only a small portion of the affected animals out there. “I think we’re only seeing the tip of the iceberg. The question is how much of the iceberg is actually submerged,” says Ziccardi, a veterinarian who has been working with injured animals in the gulf since late April. “We don’t know whether we’re finding one in five animals that are affected or one in 50.”