The oil that began leaking with the explosion of the Deepwater Horizon oil rig on April 20th continues to spill into the gulf. This oil spill is now the worst in U.S. history.

The spill is taking a heavy toll on wildlife. More than 800 dead animals, including birds, fish, and dolphins, have been found in areas affected by the spill. The number of affected animals seems to have been increasing in the last few days.

Oil is hard to clean up. Try rubbing some olive oil and canola oil on your hair to see how hard it is to clean off. Now imagine trying to clean crude oil off your whole body using your mouth. Oil-coated birds are unable to keep the oil off their feathers, but while there is oil on their feathers they are unable to fly. Rehabilitators are trying to clean some of the birds by rubbing them with vegetable oil, which breaks down the heavier oil, and then washing them with detergents. Because the oil from the spill is toxic, not all cleaned birds will survive.

Scientists are not yet sure how the deaths of so many creatures will affect the Gulf ecosystem.

See more pictures of affected wildlife on National Geographic News.

Photograph by Win McNamee, Getty Images