For two sometime residents of Mobile Bay, Ala., the impact of the oil spill is still an unanswered question.

Bumpy and Bama are manatees who live in Florida most of the year but come to Alabama in late summer for reasons unknown. When oil first entered Mobile Bay in June, researchers feared it would contaminate the manatee habitats.

Though that has not come to pass, another danger is yet to come when the manatees return home in late fall, said Ruth Carmichael, who leads manatee research at the Dauphin Island Sea Lab in Dauphin Island, Ala. Researchers who model the spill’s progress expect subsurface oil to collect in the shipping channel, which the manatees use on their migration, Dr. Carmichael said.

“So far, they’ve been up to just being manatees, which is a good thing,” she said. “We’ve reported animals engaged in mating behaviors. We’re not seeing changes in behavior or habitat.”