Colours of Wildlife: African Manatee

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African Manatee

Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"

Manatees by Willem

This time I present to you something I haven't yet seen in the living flesh, but truly hope to – a mother and baby African Manatee, Trichechus senegalensis! The closest country to South Africa where they occur, is Angola. They're most frequent in western-equatorial Africa, in large rivers, especially the Niger, and all along the coastline, as far as southern Mauritania. They're at home in salt as well as fresh water, but likely do need access to fresh water at all times, for the sake of the salt balance in their bodies, and cannot tolerate temperatures much under 20 degrees Celsius. They can be found occasionally up to 75 km away from the shore. They are mostly about 3 m/10' in length, weighing 350 kg/770 lbs, but can grow to 4.5 m/15' and weigh over a ton. This is one of three currently-accepted manatee species, the other two being the Amazonian Manatee and the West Indian Manatee. Together with the Dugong they comprise the order Sirenia. Sirenians are the closest living relatives of the elephants!

The ancestry of sirenians can be traced back to over 50 million years ago. The first ones were medium-sized but long-bodied, short-legged herbivores that likely inhabited swamps and marshy regions, where they could both walk and wade in the water. They're very similar to ancestors of the elephants that were living at the same time. From that point their swimming abilities improved, their front legs turned to paddles and their hind legs were completely lost, while their tails lengthened and grew flat to form a paddle-shape in the manatees and flukes in the dugongs. They grew into a variety of types, but all quite similar to the living forms. The African manatee is closely related to the two American species, and likely evolved there in the Pliocene, spreading to Africa at some point by managing a fairly long oceanic crossing, while today they don't venture very far into the open ocean. The most unique sirenian was the enormous Steller's Sea Cow, which should still have been with us – it survived long enough to be discovered by scientists in the Nineteenth Century, only to go extinct soon after. The innocuous giants were easy prey for humans. Sad to say, the surviving sirenians are highly vulnerable as well, and they all count as endangered or threatened to some degree or other. If the Steller's Sea Cow were still extant, present-day sirenian diversity would have been pretty much as high as it's ever been.

Today, African manatees still survive over a large range and can be found in many rivers. Their spread upriver is limited by shallows and waterfalls, so that for instance they do not make it into the great interior portion of of the Congo River. They are found almost through the entire length of the Niger River, and they also occur in many man-made lakes. They can be found singly or in groups of up to 6. Group members bond with each other through smell, touch and sound, though I've not yet managed to find a description of the noises they make. They move around in response to the weather and fluctuating water levels in rivers. Sometimes they migrate together in large groups. They're active mostly in the evening and night, dozing in shallow water by day, only coming up for air every twenty minutes or so.

Along the coast, manatees feed in shallow water where there's seagrass and seaweeds, and inland they feed on floating or submerged aquatic plants as well as plants growing on the riverbanks, including the leaves of trees and shrubs overhanging the water. Manatees use their flexible lips to grasp and pull in the foliage. Their left and right front lips are divided and can move independently, with several sets of muscles making them very dextrous for manipulating food, or for grubbing about the river and ocean bottom. They also use their flippers to gather food and move it to their mouths. They don't have any front teeth, but they do have a hard plate at the front of their upper palate, and they have several cheek teeth to grind their food. The teeth are not very hard and strong and the enamel soon wears away. As in elephants, the old teeth then fall out and new teeth from the back of their jaws emerge and move forward to replace them.

African manatees spend about seven hours of each day feeding. To deal with all the plant food they eat, manatees have long guts and a large caecum, a pouch at the front of the large intestine, in which the ingested leaves can ferment and break down. They have micro-organisms in their guts to help the digestion of cellulose, the tough component of plant cell walls.

More so than other manatees, the African manatee does eat a substantial amount of non-plant food, primarily clams and molluscs, but they do take advantage of human fishermen, eating fish that have been immobilized in nets. They're not fast and can't easily catch free-swimming fish. Though their usual travelling speed is 5 to 8 km/h, 3 to 5 mph, they can put out a burst of speed of up to 30 km/h, 20 mph. Their natural predators are sharks and crocodiles, though it's mainly the calves that are at risk to those.

Like elephants, manatees are slow reproducers. The females mature at the age of 3 years, and can give birth every 3 to 5 years. Males only mature aged 9 to 10. From the outside, it's hard to tell the sexes apart. The female has a pair of nipples in between her front flippers, but they're not conspicuous. Manatees don't have a specific breeding season. Several males may mate with one female, competing for access to her by bouts of shoving. The female gives birth after a gestation of about 13 months. The calf, weighing about 30 kg, can swim from the start, and stays with its mother as it grows. In nature, they can reach the age of thirty, and one captive Florida manatee lived to the age of sixty nine.

Although they're slow and placid, manatees may actually be quite intelligent, similar to elephants. They have good memories, can solve problems of discrimination, and learn fairly complex tasks.

Sad to say, these peaceful beasts are at great risk from humans. They suffer debilitating and sometimes fatal collisions with boats, are impacted by pollution and man-made changes to their habitat, and are also directly hunted in many places for their meat, oil, skins and even bones, which are used to make walking sticks and spinning tops for kids. But in Senegal, the Gambia and Mauritania, the species is considered sacred. Legends say that manatees guard the secrets of the future. Other legends contend that manatees were once human. The females having 'breasts' in a similar position to those of humans, is likely the source of this idea. Manatees are identified with Maame Water, a sea goddess, symbolizing wealth and beauty, and turning over boats so that their occupants can join her undersea realm. Killing manatees in these cultures is considered taboo. Today, hunting them is actually illegal everywhere in Africa, and their trade is prohibited, but manatee meat can still be found in many markets, since the laws are hard to enforce.

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