Are Manatees Endangered and How Many Are Left in the World?

Quick Take

• Manatees have zero natural predators, and yet their numbers are collapsing. The real culprit behind their decline is far more unexpected than you'd guess. About manatees and predators →
• Their official conservation status was changed once, and scientists are now pushing hard to change it again. What triggered both shifts? Their conservation status explained →
• The one thing manatees eat most is also the reason they're so easy to kill, and it has nothing to do with being hunted. How their diet puts them at risk →
• Two separate population counts differ by thousands, but a single catastrophic year made both figures nearly irrelevant. See the population counts →

Sailors once confused manatees for mermaids. These gentle giants of the sea, rather than being mythical creatures like the half-human, half-fish of legend, are real. For some, the experience of interacting with one may seem out of this world. Accounts of people’s interactions with them fill the interwebs, but these slow-moving, plant-eating mammals are threatened by human-related impacts and natural events such as cold snaps and red tide.

Let’s learn more about these fascinating creatures and their status.

What Are Manatees?

There are three species of this aquatic mammal:

1. West Indian (Trichechus manatus): This species includes two subspecies, the Antillean manatee (T. m. manatus) and the Florida manatee (T. m. latirostris). This article concerns the latter.
2. West African (Trichechus senegalensis)
3. Amazonian (Trichechus inunguis)

The most widely known manatee species is the West Indian manatee. Nevertheless, all three species and their subspecies share the same order (Sirenia), family (Trichechidae), and genus (Trichechus); have similar physical characteristics (stout, streamlined or tapered, grayish bodies; flippers; paddle-shaped tails (no hind limbs)); are aquatic herbivores; and live in shallow, calm coastal waters, rivers, estuaries, and bays. Reproduction, social behavior, ecology, and lifespan are also similar to each other.

Their diet may come as a bit of a surprise given their large size. Manatees eat loads of seagrass, along with other vegetation. They eat an estimated 4% to 9% of their body weight in greens daily.

West Indian Manatee

The West Indian manatee inhabits the warm coastal areas of the Caribbean, extending as far north as the eastern United States and as far south as northern Brazil. Its two subspecies are divided according to where these manatees primarily live and migrate and are distinguishable from each other based on cranial measurements. Those in the United States are recognized as the Florida manatee, and those living in the Caribbean as the Antillean manatee.

These manatees are large, typically growing to 9-10 feet in length and weighing around 1,000 pounds. Some grow and weight much more than the average, up to 13 feet long and 3,500 pounds. Even their calves are large, weighing 60-70 pounds at birth.

West African Manatee

The only manatee from the Old World is the West African manatee, and it is found in coastal waters and inland waterways off West Africa from Senegal to Angola. Like its New World cousins, West African manatees are large, growing to lengths of 15 feet and weighing nearly 800 pounds.

Amazonian Manatee

Amazonian manatees live in the Amazon Basin in Brazil, Peru, Colombia, and Ecuador. The smallest (by length) manatee species, but hardly small, Amazonian manatees gros to be about 9 feet in length and weigh around 1,000 pounds. The other manatee species have 3-4 nails on their flippers, Amazonians do not, hence their species name, “inunguis,” which is Latin for nailless. These manatees also have a white patch on their chest.

Are Manatees Endangered?

While they aren’t endangered as defined legally, West Indian manatees do have protection from the U.S. federal government under the Endangered Species Act and the Marine Mammal Protection Act. All three manatee species and their subspecies are vulnerable according to the IUCN Red List of Threatened Species.

Their official designation was endangered until 2017 when they got downgraded. The reason for their significant population decline over the years and prior endangered status has largely to do with their food of choice. Since they mostly eat seagrass, these graceful creatures spend a lot of time in shallow water. And that makes them vulnerable to passing boats. Many manatees collide with the ships themselves. Others inadvertently get tangled in the motors of passing boats. These deadly encounters have led to a shocking decline in the manatee population worldwide.

Other important factors underlying their low numbers are habitat loss, toxins, and entanglement with fishing gear. As with many animals, human encroachment in their areas has led to destruction (whether intended or not). Additionally, red tides bring waves of toxins that manatees are ill-equipped to deal with. They can easily make the large sea creatures sick beyond recovery. And fishing nets are often cast in locations where manatees feed, which can cause entanglement.

How Many Are Left in the World?

There is some conflicting data about the number of manatees left globally. Most are estimates and best guesses based on direct observation. So, some counts may be slightly off if certain population groups have traveled outside the observation area. That said, researchers have established a rough estimate of the existing population.

The most recent U.S. Fish and Wildlife Service stock assessment looks at data from 2014 to 2018. It provides an estimated number of 8,810 manatees. This report also explores the known causes of manatee death. Of the 543 deaths recorded over that five-year span, just over 117 of them were human-caused. 

Another estimate of the manatee population came from a synoptic survey conducted in 2019. It recorded a total of 5,733 manatees. However, since this type of survey is subject to several factors out of researchers’ control, the numbers are considered low. 

Neither of these estimates account for a dramatic loss of manatees in 2021. Researchers discovered roughly 1,100 manatee carcasses along the coast of Florida between December 2020 and December 2021. Then, in 2022, an additional 800 manatee deaths were recorded. 

Scientists noticed that many of the carcasses were emaciated, suggesting starvation due to the loss of seagrass. Unfortunately, the most likely cause of this food loss is poor water quality.