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Manatees and dugongs: saving serene sirenians

May 28, 2020

You’ve probably heard of manatees – the gentle marine mammals that live in warm waters from Florida to South America and graze on underwater vegetation. But what about their cousins, dugongs? They look similar at first glance, but manatees have round, paddle-shaped tails, while dugong tails are notched like a whale’s. Dugongs are found in warm, shallow waters along the east coast of Africa and around many islands in Asia and the Pacific.

Manatees and dugongs make up the order Sirenia, named for the sirens of Greek mythology–beautiful women whose songs lured sailors to their deaths. In fact, it’s likely that dugongs and manatees inspired the legends of mermaids. Although sirenians are often referred to as “sea cows” because of their slow pace and near-constant grazing, their closest living relatives are actually elephants and hyraxes.

Manatees and dugongs spend their lives in the water, only surfacing to breathe every 5 to 15 minutes. The mostly solitary animals swim languidly at around 5 mph, though they can go three times that fast for short bursts.

Many human activities threaten sirenians. Dugongs are listed as vulnerable, and some subspecies are endangered. Fishers catch them (accidentally) in their nets, hit them with boats, and tear up seagrass beds where the animals feed. In some places, people hunt them for hides, oil, and bones. Their long breeding cycles and tendency to produce few offspring mean that if populations decline, they are slow to rebuild.

Manatees can be found along the eastern coast of the Americas and deep into the rivers of the Amazon basin.

Dugongs can be differentiated from manatees by their forked tails.

Manatees and dugongs can’t survive without healthy seagrass bed; an adult eats almost 70 pounds each day. This is one of the reasons Seacology supports many projects that restore and protect seagrass.

Abalone Caye Ranger Station is a critical lookout in Belize’s Port Honduras Marine Reserve, which comprises small islands, coral reefs, mangroves, and seagrass beds. It is home to many threatened sea creatures, including three species of sea turtles and West Indian manatees. The ranger station was threatened by coastal erosion until Seacology provided a grant to stabilize it. From their upgraded facility, rangers are able to more effectively patrol the area against poaching and other threats.

Bogtong Village in the Philippines created a large, diverse marine protected area that contains mangroves, coral reefs, and seagrass beds. Local residents protect the habitat through daily boat patrols, and maintain a mangrove nursery to aid in reforestation. A Seacology grant will fund an additional 200 meters of boardwalk to enhance tourism, provide a place for locals to sell handicrafts and food, and make it easier to patrol the mangroves. More tourists will deter poaching, and healthy mangroves will support the coral reefs and seagrass beds, providing shelter and sustenance for dugongs and other creatures that live there.

Off Tanzania’s coast, Kwale Island is home to the only resident population of dugongs in East Africa. Before our project there, the island lacked freshwater infrastructure, which caused serious health problems, especially for children. The villagers worked with Seacology to create a plan to protect and replant the island’s mangroves, stabilizing the marine ecosystem. In return, we funded a rainwater cistern that holds learly 160,000 gallons of water for the 2,500 people of the community, increasing water security in the drought-prone area.

The waters around Libong Island in southwest Thailand are home to about half of the country’s 200 remaining dugongs. Although the area is technically protected, enforcement has been lax. Seacology is supporting a local plan to protect 1,000 acres of dugong habitat by making it a no-take area, prohibiting dugong-killing fishing practices, and creating a patrol team. A grant is being used to build an education center to spread the word about these endangered creatures and the important ecosystem that sustains them.

Mariam, an orphaned dugong was rehabilitated at Libong Island, site of two Seacology projects.

Sirenians consume large amounts of seagrass and other underwater vegetation.