Oil on a marine mammals (

) makes them sick.

Yes. as stated : "Oil destroys the insulating ability of fur-bearing mammals, such as sea otters, and the water repellency of a bird's feathers, thus exposing these creatures to the harsh elements. Without the ability to repel water and insulate from the cold water, birds and mammals will die from hypothermia."

fur

Explanation:

oil on their fur makes it hard for animals to stay insulated, which causes them to develop hypothermia