The scientists at the Florida Fish and Wildlife Research Institute just released the total number of manatees that died in 2010 -- and it's a jaw-dropping 767.

The previous record, set in 2009, was 429. That year a record 97 were killed by boaters.

But that's not what happened in 2010. Instead, what drove the pace of mortality last year was the dropping mercury. As many as 500 were killed by extremely cold temperatures. Last winter's cold snap killed 244 manatees, and another 35 were killed by the cold last month.

Cold stress also contributed to the deaths of 21 of the 96 manatees in the "perinatal" or "newborn" category. And biologists say the cold temperatures probably contributed to many of the 214 deaths in the "undetermined" category and the 68 deaths in the "unrecovered" category.

The surge in manatee deaths from such a natural cause is reminiscent of the wave of deaths in 1996, which is a major event in "Manatee Insanity." Some 150 manatees died over the course of a few months, their demise a mystery. During a tour of the state's marine mammal pathology lab, then-Gov. Lawton Chiles pointed out the scariest aspect of the deaths: "“The trouble is, even if scientists manage to pin down the cause, they may not be able to do anything about it.”

Eventually the mystery was solved. The culprit: Red Tide. As Chiles had warned, it was something no one could do anything about.

Cold, like Red Tide, is a natural occurrence that can take a toll on wildlife. The natural world is full of such perils, but generally they do not lead to extinction.

What poses a threat to the future of a species is when humans also do things that take a toll on wildlife, on top of what's done by the natural world -- things such as wiping out the mangroves that provide coastal habitat, scraping out the sea grass beds that provide food and shelter, or repeatedly clobbering slow-moving animals with fast-moving boats.<./a>