Trichechus manatus Photo Fiona Sunquist ©
If you canoe any of Florida’s rivers and spring runs or visit a spring in winter, you are likely to see manatees. These massive slow-moving aquatic mammals resemble a walrus without tusks, but are more closely related to elephants and hyraxes than other marine mammals.
Manatees have wrinkled, brownish-gray skin, often covered on the back with algae and barnacles. The head is blunt, with a broad square snout, and the upper lip is cleft and covered with bristles. They have more than 2,000 facial bristles, 600 of them in a circular region between the mouth and nose called the oral disc. Manatees use this highly sensitive area like an elephants trunk, to grasp and explore objects. Experimental tests have shown that using these bristles, manatees can detect minute differences in the size of groves and ridges on an underwater board – they performed as well as an elephant using its trunk, and almost as well as a human.
Despite thier large size, manatees rarely venture into deep, cold water, preferring to stay in shallow coastal coves, bays and large slow-moving rivers. They are very intolerant of cold, and when ocean temperatures drop below 20° C (68° F), they seek out warm-water refuges such as natural springs and places where power plants discharge warm-water effluent. During Florida’s periodic winter freezes, aggregations of 60-100 manatees are sometimes seen in the warm waters of Blue Spring near Orlando, and as many as 300 have been counted around power plants near Crystal River and Tampa Bay.
Photo Fiona Sunquist ©
Manatees are herbivores. They eat a variety of aquatic plants including water hyacinth, hydrilla, and sea grass and may even graze on bank vegetation where it overhangs the water. Manatees must consume about 8-10% of their body weight each day – for larger individuals this means eating 23-41 kg (50-90 lbs) of vegetation a day. When they are not eating, manatees often rest just below the surface, raising their snout every few minutes to breathe. This behavior puts them is great danger from speeding motorboats, which kill about 80 manatees a year and maim dozens more. The number of boat encounters is so great that almost all manatees have scars on their backs or split tails. In fact, biologists studying manatees now use the scars as a way to identify individuals.
In winter, Florida harbors the entire US population of manatees and a count in February 2006 revealed a population of about 3100 individuals. Manatees were protected as an endangered species but in November 2006 the Florida Fish and Wildlife Conservation Commission began the process of reclassifying, or ‘down listing’ them to threatened.
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