Dugongs and manatees are often confused due to their similar appearance and aquatic lifestyles. While both belong to the same taxonomic order, Sirenia, and share a common ancestry, they are distinct species. This article highlights their common traits and unique features.
Shared Traits of Sirenians
Dugongs and manatees are aquatic mammals classified within the order Sirenia, commonly known as “sea cows” due to their herbivorous grazing habits. They are the only fully aquatic herbivorous mammals. Both possess streamlined, fusiform bodies adapted for life in water, with paddle-like forelimbs and no hind limbs. Their dense bones help them manage buoyancy, an adaptation for their aquatic environment.
These animals are slow-moving and spend much of their time feeding on aquatic vegetation, primarily seagrasses. Both exhibit a thick, tough skin with sparse hair, concentrated around the muzzle, which features sensitive bristles. They also share a reproductive strategy involving a long gestation period, typically around a year, with calves staying with their mothers for up to two years.
Distinguishing Features
Despite their similarities, several distinct features differentiate dugongs from manatees. One of the most noticeable differences lies in their tail shape: dugongs have a fluked tail, resembling that of a dolphin or whale, while manatees possess a rounded, paddle-shaped tail. Their snouts and feeding adaptations also differ significantly. Dugongs have a broad, shovel-like snout that points downward, which they use to root for seagrasses on the seabed. In contrast, manatees have a shorter, more rounded snout with a divided, prehensile upper lip, allowing them to grasp vegetation more flexibly.
Differences extend to their dentition and flippers. Male dugongs, and sometimes older females, develop tusks, which are overgrown incisor teeth that remain for their lifetime. Manatees, however, lack incisor teeth in adulthood and instead have a unique system of “marching molars” that are continuously replaced from the back of the jaw as front teeth wear down. Regarding flippers, West Indian and African manatees typically have three or four nails on their flippers, whereas dugongs and Amazonian manatees do not.
Geographic distribution and habitat preferences further distinguish them. Dugongs are found exclusively in warm coastal waters of the Indo-Pacific region, from East Africa to Australia, and are strictly marine mammals. Manatees, conversely, are found in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico, as well as along the west coast of Africa, and can inhabit freshwater, brackish, and marine environments. Manatees also tend to be slightly larger and more robust, typically measuring 8 to 13 feet long and weighing between 440 and 1,300 pounds, while dugongs are generally 8 to 10 feet long and weigh 510 to 1,100 pounds.
Conservation and Ecological Role
Both dugongs and manatees face conservation challenges, with all living species listed as vulnerable by the International Union for Conservation of Nature (IUCN) Red List. Their slow reproductive rates and long lifespans make their populations susceptible to threats. Dangers include habitat loss and degradation, primarily due to coastal development and the destruction of seagrass meadows. Other threats involve human activities such as boat strikes, which can cause serious injuries or fatalities, and entanglement in fishing gear. Climate change also poses a risk, affecting water temperatures and the health of seagrass ecosystems.
As “gardeners of the sea,” dugongs and manatees play a role in maintaining the health of seagrass beds by grazing, which helps prevent overgrowth and promotes biodiversity. Their presence indicates a healthy marine ecosystem.