Habitat – tropical coastlines
Niche – large herbivore
Favorite Food – sea grasses
Length – between 8 and 13 feet
Weight – up to 2,000 pounds (one ton)
Status – Vulnerable to Extinction
Threats – collisions with boat propellers, tangling in fishing nets, pollution
Although they may not live up to the imaginations of the sailors who once mistook them for mermaids, dugongs are fascinating creatures of the warm oceans of the world. For starters, they are the only true marine mammal herbivores, feeding on rich beds of sea grass on the floors of offshore waters. They are large, heavyset marine mammals with short front flippers and a crescent-shaped tail that resembles the fluke of a whale. They are related to manatees, but are the only remaining species in their particular order of mammals.
As its alternate name “sea cow” implies, much of the dugong’s daily routine is devoted to eating. Unlike cows that use multi-chambered stomachs to digest grasses, dugongs instead depend on a very long gut in order to break down sea grasses, which contain a great deal of cellulose and are hard to digest. In order to get sufficient nutrients out of their food, dugongs eat up to 15% of their body weight in sea grass every day.
Dugongs have the advantage of no competition for their food. The only other creatures in the sea that feed exclusively on sea grass are certain sea turtles, but the turtles eat the blades of the grass rather than the stem. However, munching tough plants on the sea floor has a drawback – the abrasive sand and tough grass easily wears down a dugong’s teeth. As a result, dugongs have evolved a way to counteract this rapid wear by constantly shedding their front teeth and replacing them with a new row from the back of the mouth.
Dugongs have few predators in the wild, which helps to explain their natural curiosity and gentle nature. They will often come to investigate a solo diver or small boat, although they are easily scared by loud noises or commotion in the water. They fend off predators mostly with their sheer size and their ability to absorb punishment through a tough hide and thick bones. Their blood also clots very quickly, allowing them to rapidly plug wounds and reduce blood loss.
Despite being among the gentlest animals in the sea, dugongs have been mercilessly exploited by man. Their numbers are so low today in large part due to hunting for their meat, oil, and tusks in decades past. They are slow and easy to capture, especially now in the age of guns and motorboats. Dugongs also produce very few offspring over their long lives, further hampering conservation efforts. Although they are protected from hunting by law in many areas, dugongs are still susceptible to collisions with boats and encounters with fishing nets from which they cannot easily escape. They are now vulnerable to extinction.