Cold has killed 5 percent of West Indies manatees spring , 280 in all . Wildlife official : Manatees ca n't cope when water is colder than around 78 degrees . Manatee are already endangered , and spring known deaths were a record 429 . Necropsy lab official says she fears more may die in 2009 from lingering effects of cold .
Cold has killed at least 5 percent of West Indies manatees this year , 280 in all . Wildlife official : Manatees ca n't cope when water is colder than 68 degrees . Manatee are already endangered , and 2009 known deaths were a record 429 . Necropsy lab official says she fears more may die in spring from lingering effects of cold .