Unknown to many people, the gentle manatees actually have close to zero natural predators in the wild. The possible predators that manatees could have are sharks, alligators, crocodiles and killer whales as these are the only creatures that are large enough to tackle a manatee. However, it has been observed that such predator-prey attacks are rare in occurrence. Sad to say, the reason that manatees have been driven toward extinction is because of humans. Below is a list of some of the more prominent reasons for the declining population of manatees.
(1) Human infrastructure
Due to growing populations and urban developments, many countries have constructed and are still constructing new infrastructure or reclaiming more land along the waterways for their own purposes. Manatees natural habitats are near the coast, in shallow waters and they are very sensitive creatures who cannot survive in water temperatures, on average, below 20 degrees Celsius. Therefore, this destruction of natural environments may destroy some of the only suitable climate habitats that manatees can live in. When the typical or otherwise only potential habitats of manatees are reduced, they will have to swim out to other locations to live, of which not all may be the freshwater supply that manatees require. Although manatees can drink saltwater due to the adaptive mechanism of their kidneys, however, it is unknown of how long a manatee can actually survive without freshwater. To make matters worse, only around 3% of the world’s water is freshwater and yet we are still polluting these systems through agricultural run-off and sewage material, making it among the most endangered habitats in the world.
In addition, a country’s water transportation system is another reason for the decreasing population size of manatees due to their collisions with boats and other types of vessels. Statistics have shown that around 38% to 50% of mortality of manatees is due to watercraft activities. Manatees are generally slow, graceful swimmers with an average speed of 5km/h to 8km/h. Hence, they may be too slow to swim away from such human equipment in the waters, resulting in injuries and death. It has been noted by a non-profit conservation group who discovered that at least 668 manatees have been killed from boat collisions from 2008 to 2014. Another impact from human’s water activities include the problem of manatees accidentally getting trapped in the commercial fishing nets or even in fishing lines.
(2) Climate change
Climate change has caused global temperatures to rise around 0.15 to 0.20 degrees Celsius for every 10 years. Due to the warmer water temperatures, it promotes growth of algae. This results in two possibilities. Firstly, such algae growth doesn’t differentiate between the harmful species or toxic-free ones. Therefore, if the toxic algae species growth increases, it may kill or causes illness to the marine animals, manatees included. Secondly, when the amount of algae is in excess, it blocks the amount of sunlight that can reach the plant species that dwell at the bottom of the waters. This causes them to decrease in number, meaning that the food source of manatees will also decrease, hence, undeniably affecting the population of manatees. Furthermore climate change has also caused rising sea levels. As mentioned above, manatees tend to live near the coastal areas. If climate change continues with its accelerated rate, many of these lower level habitats will be lost. The University of New Hamshire predicted that the increase in water levels over the next century would cut the amount of available sunlight by half and cause the seagrass to decrease in quantity by 30-40%.
(3) Pollution
Pollution in the ocean includes human littered trash, sewage and agricultural run-off. All of these that end up in the ocean waters are dangerous to manatees and every other marine animal. Besides polluting the waters, sewage and agricultural run-off have the potential to promote algae growth, whose damaging consequences can be found above under the threat of ‘Climate change’. Besides those types of pollution, a study that was published by the Proceedings of the National Academy of Sciences (PNAS), one of the world’s most referenced and extensive multidisciplinary scientific compilation of research articles, discovered that at least 88% of the surface of the ocean is covered with plastic garbage. Furthermore, this only accounts for 1% of the total amount of plastic debris that is in the ocean waters. Therefore, indicating that 99% of the plastic trash is beneath the ocean surface. All of these plastic are a danger to marine wildlife as ingestion may disrupt their biological systems, resulting in death. Taking a closer look at how Singapore has contributed to this, the International Coastal Cleanup Singapore (ICCS), which conducts annual beach clean-ups, revealed in a 2013 study that they collected 14,448kg (153, 147 pieces) of trash along the coastlines in Singapore.