Why Manatee Populations Are Under Threat

All three manatee species are considered vulnerable to extinction.

Florida manatee
Florida manatees, a subspecies of West Indian manatee, are commonly injured by collisions with boats.

Robert Bonde / U.S. Geological Survey / Flickr / Public Domain

Manatees have long struggled to coexist with humans, and today all three manatee species are listed as vulnerable by the International Union for Conservation of Nature (IUCN). That means they aren't officially endangered, which is one category closer to extinction, but it doesn't mean they're out of danger. The West Indian manatee, the Amazonian manatee, and the African manatee each still faces "a high risk of extinction in the wild in the immediate future," according to the IUCN. Of the three, only the West Indian manatee is split into subspecies, and both of those — the Florida manatee and Caribbean manatee — are listed as endangered.

There are still a few thousand individuals in each manatee species, but their population estimates are often hindered by scant data, and even the best-case scenarios don't provide much buffer from the threats they face. There are thought to be fewer than 15,000 African manatees, according to The Zoological Society of London (ZSL), while the Amazonian manatee numbers anywhere from 8,000 to 30,000. The Florida manatee fell as low as a few hundred individuals in the 1970s, when it was added to the U.S. endangered species list, but conservation efforts have since helped it rebound to about 6,600, according to the U.S. Fish and Wildlife Service (FWS). That led the FWS to downgrade Florida manatees from endangered to threatened in 2017, despite objections from many conservationists who argue the move was premature. Less is known about the Caribbean subspecies, but its population is thought to be smaller and sparser.

silhouettes of three manatees swimming underwater
Before manatees were widely known, sailors sometimes mistook the mammals for mermaids. David Hinkel / U.S. Fish and Wildlife Service / Flickr / CC BY-2.0

Threats to Manatees

With few natural predators, manatees didn't face much selective pressure for speed or defensive measures during most of their evolutionary history. They are generally docile, slow-moving creatures with limited ability to fight or flee, leaving them especially vulnerable to humans. Archaeological evidence suggests people have hunted manatees for thousands of years, and although some manatee populations may have adapted by growing more secretive and cautious, that hasn't been enough to protect them in modern times from fast-growing human populations.

Manatees are in danger from people virtually everywhere they live, but the risks can vary widely depending on the species and location. Here's a closer look at the major threats humans pose to manatees.

Boats

Humans have a history of hunting manatees, but today, manatees are more threatened by human ignorance and carelessness than deliberate predation. People commonly wound and kill manatees by operating motorized watercraft in their habitats. This problem is most severe for West Indian manatees, particularly Florida manatees living in densely populated coastal areas.

About half of all deaths among adult Florida manatees can be attributed to human activities, according to the IUCN, and the main threat comes from watercraft. Due to their slow speed, high buoyancy, and tendency to feed on seagrass in shallow water, manatees often have little time or space to escape fast-moving boats and jet skis. A collision can hurt a manatee in two ways: blunt force from the hull of a vessel, and cutting injuries from a propeller. Watercraft collisions account for about 25% of all deaths among West Indian manatees, as well as 35% of documented deaths with a known cause.

Fishing Gear

As with many marine mammals, entanglement in fishing lines and nets poses another grave threat to manatees. Although people do target manatees in some places with traps, nets, and baited hooks, they are also widely killed by fishing gear intended for other animals. This can happen to both adults and juveniles, and unless humans find them in time to help, entangled manatees generally have slim chances of survival. Many drown, and those who manage to surface for air may still be unable to move around easily enough to survive for very long.

While incidental entanglement is a problem for all three manatee species, it seems to play the largest role for African manatees. Many entangled African manatees die before they're discovered, but even when they're found alive, most are killed rather than released, the IUCN notes, possibly because they're seen as pests that damage fishing equipment. In the Amazon, manatee calves who survive entanglement in fishing nets are sometimes kept alive to be sold as pets.

Habitat Loss

Loss of habitat has become one of the most pervasive threats to endangered species around the world, and manatees are no exception. In Florida, rapid human population growth has led to widespread coastal development near estuaries and coastal wetlands, often at the expense of vital seagrass beds and warm-water springs. Tampa Bay, for example, lost about 80% of its seagrass between 1900 and 1980, largely due to poor water quality. Development also raises the demand for groundwater supplies, threatening the warm springs where cold-intolerant manatees seek refuge in winter.

Dams are a major cause of habitat degradation for Amazonian and African manatees, according to the IUCN, sometimes isolating populations in rivers or interfering with water speeds and nutrient loads. Deforestation in the Amazon also threatens water quality in manatee habitats, as does pollution from agricultural pesticides and mercury used in gold exploration.

Illegal Hunting

Many manatee populations still haven't recovered from intensive hunting by humans in the past, leaving them more vulnerable to modern threats like boats, habitat loss, and even smaller-scale local hunting. All three species are now legally protected, but those laws are not always enforced, and illegal manatee hunting remains common in Africa and especially South America. In fact, the IUCN cites illegal hunting as the No. 1 threat for manatees in the Amazon, where hunters typically catch the animals with harpoons, then sell their meat and other parts for local consumption.

two manatees feeding in shallow water in Florida
One of the easiest ways to help manatees is to give them space and obey boating regulations. Jim Reid / U.S. Fish and Wildlife Service / Flickr / CC BY-2.0

What Can We Do to Help?

Manatees are still vulnerable to extinction throughout their range, and despite some recent conservation success in Florida, they aren't well-suited for quick recoveries due to their low reproductive rate. The gestation period of manatees lasts about year, they average only one calf every two to five years, and both males and females need about five years to reach sexual maturity. Given the array of threats working against them, manatees will need all the help they can get to avoid slipping any closer to the brink. Here are a few ways humans can lend a hand.

Be a Responsible Boater

Watercraft collisions are the main threat to Florida manatees, but they're also a risk for manatees everywhere. If you're boating in manatee habitat, assign someone to look out for manatees (or take turns). It might help to wear polarized sunglasses, according to the Florida Fish and Wildlife Conservation Commission (FWC), since they cut glare and can help reveal manatees underwater. Look for a pattern of ripples on the surface, known as "manatee footprints," caused by the animal's tail as it swims.

If you see a manatee, one of the easiest ways to help is by giving it plenty of room. Even if you only see one, it might be traveling with others — like a calf — that are out of view. Manatees can become confused by multiple boats, sometimes swimming away from one and into the path of another. Try not to pass over manatees, and don't separate mothers from their calves.

Even if you don't see manatees, avoid traveling through seagrass beds or other shallow areas where they might feed or rest, and obey all posted waterway signs, including no-wake zones. Using a "prop guard" around a boat's propeller can also reduce the risk of injury in case there is a collision.

If you do collide with a manatee, make sure to report it quickly. Boat strikes often don't kill manatees immediately, so prompt rescue efforts can save their lives. You won't be cited in Florida for accidentally hitting a manatee if you were obeying speed limits, the FWC notes.

Be a Responsible Paddler

Keeping your distance may be more immediately important for motorboats and jet skis than for canoes, kayaks, and paddleboards, but paddlers should still be careful about getting overly chummy with a threatened wild animal.

Never offer food or water to a manatee, since it alters their natural foraging behavior and is considered a form of harassment, according to the FWC. Don't touch manatees, surround them, approach them, or make loud noises near them. Your goal should be to watch from a distance and for a limited amount of time, without drawing attention to yourself. If a manatee responds to your presence, you are already too close, the FWC warns.

Manatees who frequently interact with friendly paddlers can lose their natural caution around watercraft of all kinds, including the motorized vessels that already maim and kill too many manatees.

Recycle Your Fishing Lines

Never carelessly discard your fishing lines, especially near the water, since they could create a dangerous entanglement hazard for manatees or other wildlife. If you're fishing in Florida, take advantage of the Monofilament Recovery and Recycling Program (MRRP), which aims to encourage recycling with a network of line recycling bins and drop-off locations at docks, boat ramps, and tackle shops across the state. Check the MRRP's map to find the nearest bin location.

Help Clean Up Manatee Habitat

Whether you live near a manatee habitat or just take a vacation there, you can assist their recovery by making even a minimal effort to clean up hazardous trash. That could mean joining a coordinated cleanup event at a shoreline, park, river, or roadside, or simply picking up a little trash as you walk along the beach. Your help will be especially valuable if you remove discarded fishing line, plastic bags, or other items that pose a danger for manatees.