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Dugong

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Dugong
Dugong.jpg
Scientific Classification
Binomial Name

Dugong dugon

Dugong-fish.jpg

The dugong is a large sea animal that is about 11 feet long and 2,000 pounds. It is completely herbivorous and almost exclusively eats seagrass. [1] Although the dugong surfaces about every minute, [2] it is capable of holding its breath for up to 6 minutes. Dugongs and sirenians are thought to be the reason for the tales of mermaids. [3] Australia has the highest amount of dugong population. [4]

Contents

Anatomy

Dugongs are large sea animals typically ranging in weight from 510-1,100 pounds. They are similar to a manatee but their tail is fluked like a whale’s, [5] their skin is smoother than a manataee's and the dugong’s body is more streamlined. Though they are 11 feet long, [6] they are similar to a 6’ tall human, because of their curved shape [7] and their excessive weight of over 2,000 pounds. [8]

Dugong calves are born a cream color and they darken with age into a darker gray color. Their skin is thick, and tough yet smooth at the same time. The upper lip is cleft, the lower lip has horny pads and together they are very strong. An adult has 10-14 teeth. The teeth do not have enamel, they have no nasal bones and the braincase is small. Babies and adults use their tail for propulsion but adults using it for steering purposes as well. Dugongs get calluses [9] on their small paddle-like flippers [10] from ‘walking’ on them while feeding in sea grass meadows. [11] Males have ivory tusks that they use for rivalry and getting food. Their skin is rough and covered in short, thick hairs. Dugongs do not reach full size until they are between 9 and 17 years. [12]

Reproduction

A contributing factor to the reason dugongs are an endangered species is because of the gestation period and the late age of sexual maturity. The mother will be pregnant for 12-14 months [13] and she will give birth to only 1 calf. In rare cases she will have twins. [14] They have more than one breeding partner and they do not have an exclusive breeding season. [15] They do not have a limitation to when they breed, they have a limitation to how often the female is able to carry a new baby. A female will give birth to a baby every 3-7 years. [16] In dugongs, they do not reach sexual maturity until they are 9-10 years old and even sometimes not even until they are 15. Calves lactate for 18 months even though they will start eating some vegetation at about 3 months. They stay with their mothers for about 18 months before going off on their own. [17]

Ecology

A dugong skimming the surface of the sea floor.

Dugongs are found in 43 countries along the western Pacific and Indian Oceans. They are specifically found in East Africa, the Persian Gulf to Japan, the Philippines and Australia. They tend to live in bays, channels, and inshore islands where food is plentiful. [18] They come up to the top of the shallow water every one or two minutes in order to breathe. [19]

Dugongs are herbivorous animals that eat day and night. [20] As they graze on seagrass, they leave behind trails of bare sand and uprooted vegetation. [21] Dugongs shake their heads to ‘clean’ their food before they eat it and to remove sand. Occasionally they have been known to eat algae and even crabs. [22]

Dugong communicate vocally. A baby dugong has a cry similar to that of a sheep, [23] adults use squeaks and squeals as (most likely) short range communication.[24]

Human Impact

A dugong enjoying a snack.

In the past, when dugongs were more plentiful on earth, they had been known to live in herds of hundreds. Now the number in herds has been reduced to about groups of 6. Dugongs and manatees are a target for hunters because of their meat, (similar to veal) [25] oil, skin, bones and teeth.[26] Although dugongs are prey for sharks, killer whales and crocodiles humans tend to harm them more than other animals.[27] They do not have good defense mechanisms.[28]

Although they are endangered and protected by law in many parts of the world,[29], hunting of dugongs is permitted in Northern Australia and Papua New Guinea.[30] Dugongs are very languid creatures, closely related to the manatee. [31] In order for a dugong to survive its normal life expectancy of around 70 years, it must be kept in a safe environment away from human activities, in a constant warm temperature with abundant food. Such environments are becoming increasingly harder to find.[32]

The numbers of these animals have become so small that commercial hunting slowly ceased in most regions not because people were concerned about them but because there were so few of them that it wasn’t realistic to spend the time hunting for them. As the human population grows, sirenians' habitats are getting taken over as well. They depend on seagrass and algae, but the beds of this vegetation is becoming destroyed by sedimentation. As people water-ski and use boats, these mammals get are harmed.[33] Even if all the factors that are harming manatees and dugongs were taken away, they cannot reproduce fast enough to completely save themselves.[34]

Gallery

References

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