May/June 2016For Wildlife Watchers: Manateeby Rob Simbeck
Manatees can eat up to 10 percent of their body weight in sea grass a day.
On January 9, 1493, near the end of his first voyage to the new world, Christopher Columbus noted that he and his crew had seen three mermaids. They were, he said, "not half as beautiful as they are painted."
Given that they were likely manatees or their relatives, that's not surprising. There is a lot to love about manatees - they are gentle, slow-moving, graceful and curious - but you would be hard pressed to mistake one of these chubby, seal-like mammals with a mug like a walrus's for a mermaid. And yet, they are in fact members of the order Sirenia, a name taken from the sirens said to lure seamen to their deaths.
The order has four members: three species of manatee - the Amazonian, the West African, and ours, the West Indian - and the dugong, a relative found in the Indian Ocean. The Florida manatee, a subspecies of the West Indian, is the one that visits us in South Carolina from late April through mid-October, when the water is at or above 70 degrees. In the winter months, they withdraw to Florida, where, as here, they can be found in bays, estuaries, rivers and canals, able to deal with salt, fresh or brackish water.
Manatees are plant-eaters, and what looks like chubbiness is simply the ample space required for up to 150 feet of intestines that use bacteria to break down what your grandmother called roughage. That produces plenty of gas. For biologists studying manatees, which may dine or rest under ten feet of murky water, that gassiness provides a distinct advantage. Just ask Al Segars, the DNR's stewardship coordinator for the ACE Basin National Estuarine Research Reserve, and a veterinarian by training.
Florida Manatee Trichechus manatus latirostris
Description: Ten to twelve feet long, 800 to 1,200 pounds, gray/brown, gentle and slow-moving.
Habitat and Range: West Indian ranges from northern South America to mid-Atlantic Coast when water, salt, fresh or brackish, is warm.
Reproduction: West Indian ranges from northern South America to mid-Atlantic Coast when water, salt, fresh or brackish, is warm.
Viewing Tips: Near shore and in inlets in warm months.
"When we were monitoring manatees on the Cooper River, we were looking for gas bubbles to locate them," says Segars. "It's a good sign. It suggests they've been eating and their GI tract is functioning."
The alternative involves waiting for them to bob up to take a breath, normally at three- to five-minute intervals, although they can stay under for twenty. Manatees can eat up to 10 percent of their body weight in sea grass a day. Their split upper lips, with each side essentially prehensile, can grasp and manipulate the vegetation they often dig up with nails at the ends of their flippers. Large salivary glands begin digestion, kicking off a week-long journey through the long and winding road of that 150-foot-long intestine. Their teeth, six to seven on each side of the upper and lower jaw, have flat grinding surfaces, and as those in front are worn down, all of them move forward, with new ones being produced constantly from the rear.
The largest manatee on record weighed 3,600 pounds and was fifteen feet long, although around 1,200 pounds and ten feet is more common. They've got very thick skin, with a thin layer of fat beneath. They are surprisingly agile, capable of somersaults, head and tail stands, barrel rolls, and upside-down gliding. They have excellent eyesight and sensitive, cat-like whiskers thinly distributed all over their bodies.
Manatees communicate with sight, taste, touch and sound. Squeals, chirps and whistles are all part of their vocalizations when frightened, annoyed or aroused. They rarely fight, and display little fear, an insouciance borne of evolution amid ready food and no natural enemies. Frankly, humans are their main problem. The manatee's buoyancy and their love of shallow water means they are often near us. Too often, we work to draw them closer, to their detriment.
"There's a big problem with people watering and feeding them," says Segars (both are prohibited by federal law). "Everyone wants to 'befriend' them and get a video for Facebook or Youtube. It's not malice on the part of the public, but they are reinforcing the behavior of hanging around docks and marinas. That greatly increases the risk of boat strikes."
Manatees can also get caught in or eat monofilament line, which clogs their digestive systems. Herbicide runoff, pollution, development and dredging can eliminate food and habitat. One study showed that 38 percent of manatee deaths between 1995 and 2005 were caused by human-related activities.
Natural causes like cold weather and red tide, an algal bloom, can kill them too, although their attraction to warm water runoff from power plants and the like heightens their vulnerability. About 10 percent of the manatee population is found dead in Florida each year.
Manatees were first protected in Florida in 1893 and became one of the original seventy-eight species listed as threatened under the Endangered Species Preservation Act of 1966. The U.S. Fish and Wildlife Service listed the manatee as endangered a year later. Conservation efforts have helped, and they are currently doing well. Their numbers are increasing in Florida - up to 6,000 or so from fewer than 3,000 in 2007 and just a few hundred in 1967. Range-wide, in an area that includes Puerto Rico, Mexico, Central America and the Antilles, there are an estimated 7,000 more.
In 2016, after a review prompted by a petition seeking the manatee's reclassification from endangered to threatened, the USFWS proposed just that, inviting a ninety-day comment period before the final decision. Many people, including those with an economic interest in bringing swimmers and divers into contact with manatees, support the move, especially given recent population gains. Many others strongly oppose it, saying the creatures need all the protection possible. The USFWS says current protective measures would remain in place.
Segars counsels us to be wildlife watchers, not minglers.
"Wild animals do not need to be our 'friends,' " he says. "They need a healthy fear of humans. Manatees do not need fresh water from a hose; they did quite well for thousands of years without water from humans. Such behavior is not only illegal but also has a very negative impact on these animals. Enjoy them from a distance!"