Manatee died from disease brought on by cold water, necropsy shows

Dennis, the wayward manatee that wildlife groups attempted to rescue off Cape Cod over the weekend, died from "cold stress" brought on by his extended stay in cold water, officials said yesterday after performing a necropsy on the animal.

"It had burned up most of its body fat," said Charles Underwood of the US Fish and Wildlife Service's manatee rescue and rehabilitation program, which performed the necropsy and was involved in Saturday's capture of the manatee in Sesuit Harbor in Dennis. The examination also showed that the manatee had kidney failure, another sign of cold stress, he said.

Cold stress syndrome in manatees is a series of physiological symptoms and diseases that can be triggered in cold water. Studies show that water that dips into the 60s can dampen manatees' metabolism, making them lose weight and weakening their immune system. In Sesuit Harbor last week, water temperatures hovered at 65 degrees, and Dennis's body temperature Saturday was almost 15 degrees below normal.

That's why wildlife rescue groups decided to catch Dennis, take him south to rehabilitate, and release him in the warm waters of his native habitat, Florida. But he died Sunday after a 27-hour journey by truck to a rehabilitation Center at SeaWorld in Orlando.

"If this animal had been caught sooner, the prognosis would have been better," said Bob Bonde, a biologist with the US Geological Survey in Florida who has studied manatees for 30 years. "I think in hindsight, with cold-stressed animals, it would be a good idea to get them to a facility locally before having them undergo transit."

The US Fish and Wildlife program rescues about 50 manatees a year, mostly from Florida's coastal waters, as winter approaches. Most survive, said Bonde, but they are not forced to make such a long trip.

Dennis is one of 19 manatees reported to have died from cold stress this year, according to the Save the Manatee Club, a Florida advocacy group.

Wildlife groups were waiting for him to return on his own, as some have done in the past after straying from southern latitudes. Once the groups decided Dennis needed help, it took a while to gather the crew and the equipment to rescue him. The rescue's costs are still being tallied, but could exceed$10,000, including in-kind donations and staff time, said Underwood. The costs were shared by SeaWorld, the International Fund for Animal Welfare, and the federal agency.

Bonde applauded the attempt to save Dennis but said that if many more manatees begin turning up so far north, "maybe it's more desirable to protect the core of the population rather than these outliers. We may be doing a disservice biologically to the population."

Bina Venkataraman can be reached at bvenkataraman@globe.com.