The Conservation of Manatees
One early morning in the recent past found me scrolling through the depths of Facebook only to happen upon an article dating back to 2017 declaring manatees no longer an endangered species. Naturally, I wanted to know more, so I did some digging into the murky world of the gentle grey giants to learn some more about this supposed conservation victory. After hours of combing through the information available to me, I have come to the conclusion that the article I originally read was a little misleading and manatees are a difficult animal to pull free from the gaping maws of extinction.
African manatees. (image from shutterstock)
There are three distinct species of manatee with subtle differences that are worth mentioning prior to zooming out and talking about the gentle creatures as a whole. The most mysterious and least studied species of manatee is the African manatee (Trichechus senegalensis) that inhabits the coastal and fresh waterways of the West African coastline, and they are thought to be primarily nocturnal where the other species are neither diurnal nor nocturnal. African manatees are thought to travel in small groups and prefer brackish to freshwater areas full of vegetation over a more open saltwater environment, but this, like everything else about the species remains unconfirmed.
On the other side of the world, the Amazonian manatee (Trichechus inungius) can be found in tropical backwater lakes and lagoons. Amazonian manatees are the smallest of the three species of manatees and the only one that has white markings on the chest area that breaks up their gray coloring. These manatees are the only entirely freshwater species of manatee, and they prefer lakes, ponds, and waterways with dense vegetation. Historically they have been known to travel in large herds making them more social than the other species, but over hunting has drastically reduced the size of herds that they can be found in today.
Next door to the Amazonian manatee, and extending north to the southern east coast of the United States, the most well-known manatee species, the West Indian manatee (Trichechus manatus) can be found. West Indian manatees are a primarily solitary species, but can occasionally be found in small groups that rarely stay together for long periods of time, with the exception of young bachelor groups. This manatee species is the one that has provided researchers with the most information about manatees as a whole and is the one that is used to speculate about the secret lives of their more mysterious cousins.
Amazonian manatees. (image taken from facts-about.info)
One problem that manatees face is that their range is restricted to tropical waters with stable temperatures that do not drop below a certain threshold. All three species lack a thick blubber layer like whales and dolphins meaning they are more vulnerable to freezing when cold snaps happen and they are unable to escape to warmer waters. When they are forced to deal with cooler temperatures, they have been observed huddling together near power plants in Florida, but that is a short term solution to a problem they are rarely faced with.
Since their range is so small, manatees have limits in resource availability and as a result have a unique diet that is highly restricted and lacks nutrients, which is their first barrier to long term survival. These large mammals are herbivores that feed primarily on both aquatic plant and algae species and anything that grows close enough to the water for them to reach. Despite the fact that they have found a way to extend their menu to terrestrial plants, there is still a problem with a diet that is high in cellulose. This food source is highly abrasive and wears out their teeth fast enough that they have evolved “marching molars” that fall out and are replaced throughout a manatee’s life. To deal with the low nutrient content of the vegetation they feed on, manatees have developed a way to deal with cellulose like horses and cattle on the land. In addition to their herbivorous diet, there is evidence of manatees occasionally digging up plants with their flipper to eat the roots, and feeding on crustaceans and fish.
West Indian manatee. (flickr - James Scott)
Like other large mammals, manatees are slow breeders, making it difficult to recover decimated populations. Once a female manatee reaches sexual maturity, she will produce a single calf after a 12-14 month gestation period that will stay with her for an average of two years. In the best-case scenario, a single female manatee can produce one calf every three years. This long period between births slows down the rate at which a manatee population can grow, especially if members of the population are dying.
In the wild, manatees have no natural predators to chip away at their populations, so the threats to their survival primarily stem from their human neighbors. Since manatees inhabit fairly shallow waters, they are especially vulnerable to collisions with boats that leave them with horrific scars in the best of cases, but all too often these collisions end with the death of a manatee. Manatees also find unfortunate ends tangled within fishing nets and at the hands of poachers looking to profit off of their hides, bones, and meat. Humans also provide a less direct threat to manatees as they repurpose manatee habitat for the expansion of recreation, housing, and other building endeavors, and further reduce the space manatees can inhabit.
The range of manatees and the closely relates dugong. (image from savethemanatee.org)
Although manatees have been reduced from an endangered to threatened status in the United States, they are still protected as a species and conservation efforts are still in effect. The U.S. Fish and Wildlife Service (USFWS) provides information on four partners and research projects dedicated to the long term preservation of manatees. The general public can get involved with manatee conservation by volunteering their time or donating to these efforts, or help further the cause by researching and spreading awareness to others.
Manatees are part of a larger grouping that includes their entirely marine cousin that they can easily be confused with, the dugong. Unlike manatees, dugongs exclusively inhabit marine habitats, and there is only one species still alive today. The lost species of dugong inhabited cooler waters than their living counterparts and were driven to extinction by overhunting in the fairly recent past. This loss of an entire species serves as a warning to the hardworking scientists and conservation activists that are working to ensure manatees stick around for many years to come.
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