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  Seaweek 2004    

Dugongs
Text courtesy of GBRMPA
 
Dugongs are the world's only fully vegetarian marine mammal and the only sea cow in Australian seas. Dugongs, like whales and dolphins spend their lives at sea.

Australian dugongs range from Shark Bay in Western Australia around the north to Moreton Bay in Queensland. It is believed there are 80,000 dugongs in Australian waters, approximately 14,000 of them on the Great Barrier Reef.

Dugongs are a fish-like shape, with flippers and a tail and can grow up to three metres long and weigh up to 400 kilograms. Their skin is thick and smooth.


Drawing courtesy Wet Paper

Their nostrils are located near the front of their head enabling them to breath with most of their body beneath the surface. Unlike other mammals, dugongs cannot hold their breath under water for very long. Their mouths are large, and the upper lip is covered in bristles which are used to find and grasp seagrass. Dugongs' ears and eyes are found on the side of the head, and their movements are slow and graceful.

Reproduction
Dugongs live for approximately 70 years. Female dugongs first breed between the ages of six and seventeen years old. They produce calves every two and a half to five years. Breeding commences when the female is in oestrous (on heat). Groups of male dugongs will follow the female around and will mate only with her. The female will produce a single calf after a 14-month pregnancy. Most calves are born between September and October, and remain with their mother for around 18 months.

Feeding
Dugongs along the Great Barrier Reef feed mostly on small, delicate seagrasses, which are low in fibre, high in nitrogen and easily digestible. A dugong can dig up an entire seagrass plant including the roots. Dugongs do not have a chambered stomach, but rely on an extremely long intestine and bacteria living within it to digest the cellulose of seagrass.

Threats
Dugongs are considered 'threatened' and are protected in the waters of the Great Barrier Reef Marine Park.

Dugongs have played an important part in traditions and cultures of Aboriginal and Torres Strait Islander people for thousands of years, and are still hunted under controlled conditions today.

The greatest threat to dugongs is the loss of their habitat. As a result of increased siltation and nutrients from human activities on the land, such as dumping of dredge wastes, urbanisation, industry and agriculture, seagrass beds are diminishing. Nets are also a threat to dugongs who can become entangled and drown in certain types of fishing nets. In some locations fishing nets are restricted in order to establish dugong protection areas. Shark nets erected to protect beaches have also been responsible for drowning dugongs in Queensland. Many of these nets have been replaced with drum lines.

 

What you can do

To help ensure dugongs are not killed or injured:

· Make sure you give dugongs plenty of space in the water
· Do not chase, grab, try to ride or block the path of a dugong
· Take all rubbish home with you
· Report injured or dead dugongs to the Marine Animal Hotline on 1300 360 898

To protect dugong habitat and feeding grounds:

· Keep drains and gutters clear and free of chemicals and rubbish
· Limit the use of pesticides and fertilisers
· Take care not to spill when fuelling boats or changing engine oil
· Dispose of all litter and waste appropriately
· Use garden beds or vegetation strips to capture rainwater on your land

 
Search site

Seaweek 2004 Home
1 Get started for
Seaweek 2004
2 Harmful Marine Debris
3 The EAC (East Australian Current)
4 Fish Fact File
5 Dugongs
6 Ghost Fishing -
Reducing the impact of fishing on non target species
7 First View - Giant Crab at home on the Slope
8 I live in the sea: Turtles the ancient mariners of the sea
9 I live in the sea: Sharks & Rays - they're more scared of us!
10 Sea stars
11 Marine algae
12 Sea jellies
13 Crustaceans
14 Echinoderms
15 Marine reptiles
16 Fisheries and Aquaculture
17 Whales & Dolphins
18 Protection of precious wetlands - success in New Zealand
19 Seaweek Discoveries in Vic Marine National Parks
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