The dugong (Dugong dugon) is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow (Hydrodamalis gigas), was hunted to extinction in the 18th century. It is also the only sirenian in its range, which spans the waters of at least 37 countries throughout the Indo-Pacific, though the majority of dugongs live in the northern waters of Australia between Shark Bay and Moreton Bay. The dugong is the only strictly marine herbivorous mammal, as all species of manatee use fresh water to some degree.
Like all modern sirenians, the dugong has a fusiform body with no dorsal fin or hind limbs, instead possessing paddle-like forelimbs used to manoeuvre. It is easily distinguished from the manatees by its fluked, dolphin-like tail, but also possesses a unique skull and teeth. The dugong is heavily dependent on seagrasses for subsistence and is thus restricted to the coastal habitats where they grow, with the largest dugong concentrations typically occurring in wide, shallow, protected areas such as bays, mangrove channels and the lee sides of large inshore islands. Its snout is sharply downturned, an adaptation for grazing and uprooting benthic seagrasses.
A Vulnerable species is one which has been categorized by the International Union for Conservation of Nature (IUCN) as likely to become Endangered unless the circumstances threatening its survival and reproduction improve. There are currently 4728 animals and 4914 plants classified as Vulnerable, compared with 1998 levels of 2815 and 3222, respectively.
Vulnerability is mainly caused by habitat loss or destruction. Vulnerable species are monitored and are becoming threatened. However, some species listed as "vulnerable" may in fact be quite abundant in captivity, examples being the blue poison dart frog.
According to the IUCN they use several criteria to enter species to this Vulnerable category.
A taxon is Vulnerable when it is not Critically Endangered or Endangered but is facing a high risk of extinction in the wild in the medium-term future, as defined by any of the following criteria (A to E):
A) Population reduction in the form of either of the following:
1) An observed, estimated, inferred or suspected reduction of at least 20% over the last 10 years or three generations, whichever is the longer, based on (and specifying) any of the following:
a) direct observation
b) an index of abundance appropriate for the taxon