Scientists are also taking skin samples from the whale, which will be tested for petroleum. The results of those tests, as well as tests on its skin and blubber to determine its gender, may take weeks to process, the oceanic agency said. Government workers are also trying to rule out other possible causes of death, like a ship strike or net entanglement.

“It is a relatively rare occurrence,” said Ms. Mase, who added that there have been only five or six whale deaths in the gulf in five years, “so we are studying this very carefully.”

NOAA sent a research ship to the area around the Deepwater Horizon a few days ago specifically to learn whether the oil spill was changing whales’ behavior and if so, in what ways.

There are an estimated 1,700 sperm whales that live in gulf waters and they are known to congregate particularly at the mouth of the Mississippi River, a rich feeding ground. Unlike other whales, which travel long distances, these live full-time in the gulf and do not usually mingle with sperm whale pods in the neighboring Caribbean and Sargasso Sea. Ms. Mase said that the dead whale was almost certainly a gulf whale.

The fate of the whales, which have frequently been spotted swimming in the oil by planes overhead, has been of intense concern to wildlife biologists. Because whales are large and very mobile, they are relatively less vulnerable to oil spills than other sea life. However, the whales are classified as endangered and the crude oil is toxic to them. Moreover, they prefer to dive and fish right off the continental shelf, where the Deepwater Horizon wellhead is located, and their sensitivity to the large plumes of oil droplets and the enormous amount of dispersants being used to combat this disaster is unknown.