Up Close and Personal With… Manatees

Whilst most of us probably haven’t seen a manatee, many have certainly heard of these unique looking creatures which are often used as a poster species in conservation campaigns to capture the hearts of the public. These comical and cute creatures do however face some critical issues in our oceans which are threatening the survival of some manatee populations. Let’s take a closer look into the life of a manatee and what the future holds. 

Also known as sea cows, these gentle giants live in three distinct areas of ocean and each population is considered a separate species. Some reside on the east coast of the Americas between Brazil and Florida whilst another population inhabits Africa’s west coast and its rivers. The final species actually lives in the Amazon River and their range expands across six South American countries. From this distribution we can see that manatees can survive in an astonishing range of habitats, from coral reefs to rivers, inland lagoons to mangroves. These creatures are often confused with the dugong, a similar looking species also in the same group of animals called Sirenia. However, you can distinguish the difference by looking at their tails; dugongs have fluked tails like a whale whilst manatees have broad rounded tails. 

Manatees are herbivorous mammals which feed on a mix of grasses, weeds and algae in the ocean. They often spend eight hours a day grazing on food, allowing them to eat up to 10% of their body weight a day. Considering these creatures weigh between 300-600 kilograms, that’s very impressive! Ranging from 8-13 feet in length, these animals can live for 50-60 years in the wild and during this time they will mostly be seen alone or in pairs or small groups. Manatees never leave the water but frequently need to surface to breathe in air, with 15 minutes being the longest they stay underwater when they are asleep. During the day, despite their bulkiness, they are surprisingly graceful and use their tails to swim at around five miles per hour in search of food. When not feeding or sleeping, these mammals like to spend their time at the ocean’s surface soaking in the sun’s rays. This explains why their backs are often covered in green algae as they provide a perfect sunny yet wet spot for algae and even barnacles to live. Whilst sunning themselves, the bristle like hairs on their skin help them stay alert for danger as they pick up vibrations in the water which could be the sign of a boat approaching. 

There are several facts however which show just how unique this species is. For example, manatees have only six bones in their neck compared to the normal seven in most other animals and humans. This means that manatees can only move their heads up and down but not side to side, so their whole body has to move in order to look sideways. Researchers also now believe that these creatures float on the surface by using diaphragm contractions which compress and store gas in folds in the intestine; this helps increase their buoyancy. When they want to swim deeper, they release this gas in the form of flatulence to help them sink under the waves. It has even been observed that constipated manatees are unable to dive and sometimes get stuck floating on the surface of the ocean! Somehow, even with this trait, manatees were once thought to be misidentified by tired and hallucinating sailors who mistook them for mermaids or sirens, giving birth to a whole host of legends and stories! 

Despite the modern manatee inhabiting our coasts for around one million years, their populations are now classed as vulnerable on the IUCN red list due to a range of modern human threats. These creatures have often been threatened by man because they inhabit coastal areas and inland rivers where our activities often cross over with theirs. Historically, they were hunted for hides, oil and bone but today our impact on them is more unintentional yet nevertheless still devastating. 

Boat accidents are a large cause of manatee death in some areas and many wounds inflicted by propellers are either critical or fatal. In order to reduce this threat, local authorities often impose low speed areas which gives slow-moving manatees more time to get away from any approaching boats. They also urge people not to feed these animals from boats as it encourages them to approach vessels. Many manatees are rescued each year and taken to rehabilitation centres where their strike wounds are treated and once released, the pattern of their scars is a way for researchers to identify and track individuals. 

Manatees are also one of thousands of marine species which are impacted by plastic pollution as they accidentally ingest small pieces of our waste whilst they can also become helplessly entangled in fishing nets. Those living in Florida also have to contend with the annual red tide event where a sharp increase in algae causes a boom in toxins in the water. Manatees spend all day swimming in these toxins, breathing in aerosolised particles and eating toxins which have settled on the seagrass beds. In 2018, 26% of all dead manatees in Florida died due to poisoning from the red tide. 

This year however, manatees in Florida have faced a much larger crisis with these creatures suddenly dying at an alarming rate. In 2021, 1,100 manatees died in the area, with the next deadliest year being 830 deaths in 2013. Many bodies were found in the Indian River lagoon, almost all of which showed signs of malnourishment. Manatees gather in Florida during the winter to make the most of the warmer waters, however their winter seagrass feeding ground has been massively diminished in the last year, meaning hundreds of manatees have been left without a substantial food source. It is thought that this decline in seagrass has been caused not only by an extremely severe red tide year but also by nitrogen pollution entering the water. This pollution consists of sewage and agricultural waste such as fertilisers running off the ground and into the ocean after rainfall. Once this nitrogen is in the ocean, it encourages a massive growth of algae and eventually clouds of algae block essential sunlight from marine plants such as seagrass, leaving them struggling to grow. 

Whilst conservation normally tries to leave species alone to survive in the wild, it was decided that human intervention would be critical to ensure this vulnerable species didn’t see a huge population collapse. So, in an attempt to save local manatees, wildlife experts in Florida began hand feeding them romaine lettuce and cabbage to help them survive the seagrass famine. This rare decision to use supplemental feeding sees manatees being fed just enough food to keep them going through the winter months before they disperse along the coast once more. Since December 2021, tens of thousands of pounds of lettuce have been consumed by the manatees and how do we know this; by looking at their poo. At the start of the trial, very little poo was visible in the water but a large increase in faeces has been seen which shows that the manatees are eating enough vegetation for them to process it and produce faecal material. In addition to this care, around 30 manatees showing dangerous levels of emaciation have been taken to rescue centres where they will spend several months recovering before being released. 

You may be wondering how experts are finding these creatures in order to feed them but the truth is, tracking down individuals has been fairly straightforward. Manatees hate the cold and can’t survive in waters cooler than 18 degrees Celsius and so in the winter months, they abandon their solitude and can be seen gathering in large groups in shallow inland waters. In Florida, 60% of manatees actually rely on artificially heated water to stay warm and so huge gatherings can be seen by warm water outfalls from power plants! There are so many manatees in some industrial areas, up to 1,000 individuals, that they have actually been designated as wildlife sanctuaries. Yet this dependence on the factories could be incredibly dangerous as it would only take one plant to shut down and the warm waters these manatees rely on for survival would disappear.

Despite many manatee populations being in grave trouble, we can still have hope for the future. Conservation groups have already filed lawsuits stating that authorities failed to protect critical marine habitat from pollution and argue that this example proves without doubt the extent of trouble our oceans are in. Yet we know we can save the manatee. In the 1990s, there were only around 1,200 of these creatures in Florida, yet by 2018, this number had risen to over 6,000, allowing them to move from an endangered species status to a vulnerable one; let’s keep up the hard work and make sure these unique creatures have a secure place in our future. 

By Neve McCracken-Heywood