Dugongs

 

Paul Anderson, Kevin Crane, Paul Anderson

Dugongs occur in tropical and subtropical waters around the world.

Dugongs are large grey mammals which spend their entire lives in the sea. Fully grown, they may be three metres long and weigh 400 kilograms. Dugongs swim by moving their broad whale-like tail in an up and down motion, and by use of their two flippers. They come to the surface to breathe through nostrils near the top of their snouts. Dugongs' only hairs are the bristles near the mouth.

Dugongs are subject to a range of human threats throughout their global distribution, including entanglement in shark nets for bather protection, entanglement in fishing nets (e.g. mesh and gill nets), entanglement in marine debris (see the Threat Abatement Plan for the impacts of marine debris on vertebrate marine life), loss and degradation of important habitat such as seagrass meadows, unsustainable traditional use and collisions with boats (also known as boat strikes).

Legislative protection

Environment Protection and Biodiversity Conservation Act 1999

In Australia, dugongs are protected under the Australian Government's Environment Protection and Biodiversity Act 1999 (EPBC Act), which lists them as marine and migratory species, and various State and Northern Territory legislation.

EPBC Act Status and Documents - Dugong dugon — Dugong

Dugongs are an integral part of the traditional culture of many coastal indigenous peoples throughout the world. Dugongs may be legally hunted by Aboriginal and Torres Strait Islander people under section 211 of the Native Title Act 1993 for personal, domestic or non commercial communal needs.

International conventions

Internationally, dugong are listed on Appendix I of the Convention on International Trade in Endangered Species of Wilde Fauna and Flora (CITES), and on Appendix II of the Convention on Migratory Species (the CMS). Australia is a signatory to both these conventions. More recently, an international Memorandum of Understanding (MoU) on the Conservation and Management of Dugongs and their Habitats throughout their Range  was developed under the CMS. Australia is a signatory to the MoU which entered into force on 31 October 2007. The MoU is designed to facilitate national level and transboundary actions that will lead to the conservation of dugong populations and their habitats.

Habitat and biology

Habitat

Dugongs undertake long-distance movements, which means Australia shares populations with other neighbouring countries. In Australia, dugongs occur in the shallow coastal waters of northern Australia from the Queensland/New South Wales border in the east to Shark Bay on the Western Australian coast. They are also found in other parts of the Indian and Pacific Oceans in warm shallow seas in areas where seagrass is found.

Shelter

Dugongs are usually found in shallow waters protected from large waves and storms. They may also swim in deeper water, further offshore, in areas where the continental shelf is wide, shallow and protected.

Breeding

Female dugongs give birth underwater to a single calf at three to seven year intervals. The calf stays with its mother, drinking milk from her teats and following close by until one or two years of age. Dugongs reach adult size between 4 and 17 years of age. These low breeding rates, long-term care of their calves, long time between calves, as well as their dependence on seagrass, make dugongs vulnerable to human threats.

Diet

Dugongs are sometimes called 'sea cows' because they graze on seagrasses. These marine plants look like grass growing on a sandy sea floor in shallow, warm water. Dugongs need to eat large amounts of seagrass.

Defence

Dugongs are slow-moving and have little protection against predators. Being large animals, however, only large sharks, saltwater crocodiles and killer whales are a danger to them. Young dugongs hide behind their mothers when in danger.

Indigenous culture and dugongs

Dugongs have important cultural and social values for Aboriginal and Torres Strait Islander people living in coastal areas of northern Australia. Hunting these species is important for maintaining family relations (kinship) and social structure, has important ceremonial and community purposes and also provides valuable protein in regions where fresh food is expensive and difficult to obtain.

Indigenous communities are working collaboratively with government agencies and scientists to develop and implement community-based management for sustainable hunting of dugongs. This work is primary supported through the Australian Government's Caring for Our Country and Working on Country programs.

Under the Native Title Act 1993, Traditional Owners have the right to take marine resources, including hunting of dugongs for personal, domestic or non-commercial communal needs and in exercise and enjoyment of their native title rights and interests.

Resources