Is This What You Call A Shifting Baseline?

In news of the strange, I just read on CNN that a wayward West Indian Manatee (Trichechus manatus) has been spotted off Cape Cod. That puts this fellow about 1,200 miles north of it's more subtropical haunts in Florida and the Caribbean. I mean I'll happily go out of my way for a nice plate of Cape Cod fried clams, but this is crazy!

While certainly not the first manatee to explore chilly New England waters, the unpredictable meandering of the late summer Gulf Stream can perhaps provide a partial explanation. And there is a possibility that this manatee is a repeat wanderer by the name of Chessie, first sighted in the Chesapeake Bay in 2001.

But manatee incursions into more northern regions have also been some of the suggested outcomes of a changing global ocean climate. As I wrote about last year, short- and long-term climate changes and their impacts on ocean temperatures can influence the distribution of a variety of marine species in their range. The ecosystem consequences of these interactions are poorly understood.

One problem immediately possible for such curious, stray manatees as the one in Cape Cod is the very real danger of getting too cold.

Manatees are giant herbivores that rely on a ruminant digestive system to process the enormous volume of vegetation they take in--think big, floating cows without the bells and udders. West Indian manatees evolved in tropical and subtropical climates and lack the thick insulating blubber present in their marine mammal cousins such as the cetaceans (whales) or pinnipeds (seals and sea lions). With such thin padding, cool water (anything below 20 degrees C - 68 degrees F) can wreak havoc with their metabolism. They can have trouble digesting food and even stop eating. Without enough nutrients, these vegetarians become susceptible to skin lesions and infections, such as pneumonia, that eventually lead to death.

While sightings of manatees so far north are rare, the frequency of occurrence can also be supported through artificial "rest stops" that are created along the coast by thermal outflows from power plants. In fact it's estimated that 60 percent of Florida manatees bask in these "hot tubs" every winter instead of their natural warm springs.

Here's hoping that, after a quick stop at the Cape Cod Factory Outlet Mall in Sagamore, the southern visitor will make his or her way back home safely.