Dugong why are dugongs endangered

Dugong populations in Madagascar are poorly studied, but due to widespread exploitation it is thought they may have severely declined, with few surviving individuals.

This population may belong to a different group than that distributed among the inner isles. There are less than individuals scattered throughout Indian waters. It is 1, kilometres mi from the population in the Persian Gulf, and 1, kilometres 1, mi from the nearest population in India. Former populations in this area, centered on the Maldives and the Laccadive Islands , are presumed to be extinct.

Recoveries of seagrass beds along former ranges of dugongs, such as the Chilika Lake have been confirmed in recent years, raising hopes for re-colorizations of the species. A small population exists today along the southern coast of China , [ citation needed ] where efforts are being made to protect it, including the establishment of a seagrass sanctuary for dugong and other endangered marine fauna ranging in Guangxi. In Thailand, the present distribution of dugongs is restricted to six provinces along the Andaman Sea , [61] and very few dugongs are present in the Gulf of Thailand.

The waters around Borneo support a small population, with more scattered throughout the Malay archipelago. All the islands of the Philippines once provided habitats for sizeable herds of dugongs. They were common until the s, when their numbers declined sharply due to accidental drownings in fishing gear and habitat destruction of seagrass meadows.

Today, only isolated populations survive, most notably in the waters off the Calamian Islands in Palawan , Isabela in Luzon , Guimaras , and Mindanao. The dugong became the first marine animal protected by Philippine law, with harsh penalties for harming them. Litters of plastic waste single-use sachets, plastic bottles , fast food to-go containers etc. As these materials may be mistaken as food by dugongs, these may lead to death due to plastic ingestion.

Overpopulation and lack of education of all coastal fisherfolk in the Philippines regarding marine trash are clearly harming the coastal environment not only in Palawan but also across the islands of the Philippines. Populations also exist around the Solomon Islands archipelago and New Caledonia , stretching to an easternmost population in Vanuatu. A highly isolated population lives around the islands of Palau. A single dugong lives at Cocos Keeling Islands although the animal is thought to be a vagrant.

Today, possibly the smallest and northernmost population of dugongs exists around the Ryukyu islands, and a population formerly existed off Taiwan. On Aragusuku Island, large quantities of skulls are preserved at an utaki that outsiders are strictly forbidden to enter. Populations around Taiwan appear to be almost extinct, although remnant individuals may visit areas with rich seagrass beds such as Dongsha Atoll.

Some theorize that populations existed independently, for example, that the Okinawan population were isolated members derived from the migration of a Philippine subspecies. It has been confirmed that dugongs once inhabited the water of the Mediterranean [82] [83] possibly until after the rise of civilizations along the inland sea.

This population possibly shared ancestry with the Red Sea population, and the Mediterranean population had never been large due to geographical factors and climate changes. Dugongs are long-lived, and the oldest recorded specimen reached age A large number of infections and parasitic diseases affect dugongs. Detected pathogens include helminths , cryptosporidium , different types of bacterial infections, and other unidentified parasites.

Although they are social animals , they are usually solitary or found in pairs due to the inability of seagrass beds to support large populations.

Communication between individuals is through chirps, whistles, barks, and other sounds that echo underwater. Different sounds have been observed with different amplitudes and frequencies, implying different purposes. Visual communication is limited due to poor eyesight, and is mainly used for activities such as lekking for courtship purposes. Mothers and calves are in almost constant physical contact, and calves have been known to reach out and touch their mothers with their flippers for reassurance.

Dugongs are semi-nomadic , often traveling long distances in search of food, but staying within a certain range their entire life. It is thought that these movements are caused by changes in seagrass availability. Their memory allows them to return to specific points after long travels. Daily movement is affected by the tides. In areas where there is a large tidal range, dugongs travel with the tide in order to access shallower feeding areas.

In Moreton Bay, dugongs often travel between foraging grounds inside the bay and warmer oceanic waters. At higher latitudes dugongs make seasonal travels to reach warmer water during the winter.

Occasionally individual dugongs make long-distance travels over many days, and can travel over deep ocean waters. Dugongs, along with other sirenians , are referred to as "sea cows" because their diet consists mainly of seagrass.

When eating they ingest the whole plant, including the roots, [17] although when this is impossible they will feed on just the leaves. In other southern areas of both western and eastern Australia, there is evidence that dugongs actively seek out large invertebrates. This does not apply to dugongs in tropical areas, in which fecal evidence indicates that invertebrates are not eaten. Most dugongs do not feed on lush areas, but where the seagrass is more sparse. Additional factors such as protein concentration and regenerative ability also affect the value of a seagrass bed.

Seagrasses of a lower seral are preferred, where the area has not fully vegetated. Only certain seagrass meadows are suitable for dugong consumption, due to the dugong's highly specialized diet. There is evidence that dugongs actively alter seagrass species compositions at local levels. Dugongs may search out deeper seagrass. Feeding trails have been observed as deep as 33 metres ft , and dugongs have been seen feeding as deep as 37 metres ft. Dugong feeding may favor the subsequent growth low-fibre, high-nitrogen seagrasses such as Halophilia and Halodule.

Due to their poor eyesight, dugongs often use smell to locate edible plants. They also have a strong tactile sense , and feel their surroundings with their long sensitive bristles. They have been known to collect a pile of plants in one area before eating them. This leaves furrows in the sand in their path. A dugong reaches sexual maturity between the ages of eight and eighteen, older than in most other mammals. Mating behaviour varies between populations located in different areas.

This greatly increases the chances of conception. Females give birth after a to month gestation , usually to just one calf. Dugongs have historically provided easy targets for hunters, who killed them for their meat, oil, skin, and bones. As the anthropologist A. In some areas it remains an animal of great significance, [18] and a growing ecotourism industry around dugongs has had an economic benefit in some countries.

There is a 5,year-old wall painting of a dugong, apparently drawn by neolithic peoples, in Tambun Cave , Ipoh , Malaysia. This was discovered by Lieutenant R.

L Rawlings in while on a routine patrol. Dugongs feature in Southeast Asian, especially Austronesian , folklore. Because of this, it is considered bad luck if a dugong is killed or accidentally dies in nets or fish corrals in the Philippines, some parts of Sabah Malaysia , and northern Sulawesi and the Lesser Sunda Islands Indonesia. Dugongs are predominantly not traditionally hunted for food in these regions and they remained plentiful until around the s.

Conversely, dugong "tears" are considered aphrodisiacs in other parts of Indonesia , Singapore , Malaysia , Brunei , Thailand , Vietnam , and Cambodia.

They are actively hunted in these regions, in some places to near-extinction. In Palau , dugongs were traditionally hunted with heavy spears from canoes.

Although it is illegal and there is widespread disapproval at killing dugongs, poaching remains a major problem. Dugongs are also widely hunted in Papua New Guinea , the Solomon Islands , Vanuatu , and New Caledonia ; where their meat and ornaments made from bones and tusks are highly prized in feasts and traditional rituals. However, hunting dugongs is considered taboo in some areas of Vanuatu.

Some aborigines regard dugongs as part of their Aboriginality. Local fishermen in Southern China traditionally revered dugongs and regarded them as "miraculous fish". They believed it was bad luck to catch them and they were plentiful in the region prior to the s. Beginning in the s, a wave of immigrants from other regions that do not hold these beliefs resulted in dugongs being hunted for food and traditional Chinese medicine.

This led to a steep decline in dugong populations in the Gulf of Tonkin and the sea around Hainan Island. Carved ribs of dugongs in the shape of butterflies a psychopomp are found throughout Okinawa.

They were commonly hunted throughout Japan up until around the s. Dugongs have also played a role in legends in Kenya, and the animal is known there as the "Queen of the Sea".

Body parts are used as food, medicine, and decorations. In the Gulf states, dugongs served not only as a source of food, but their tusks were used as sword handles.

Dugong oil is important as a preservative and conditioner for wooden boats to people around the Gulf of Kutch in India, who also believe the meat to be an aphrodisiac. During the Renaissance and the Baroque eras, dugongs were often exhibited in wunderkammers.

They were also presented as Fiji mermaids in sideshows. Dugong numbers have decreased in recent times. For a population to remain stable, 95 percent of adults must survive the span of one year.

The fact that they live in shallow waters puts them under great pressure from human activity. Research on dugongs and the effects of human activity on them has been limited, mostly taking place in Australia. In many countries, dugong numbers have never been surveyed. As such, trends are uncertain, with more data needed for comprehensive management.

The last major worldwide study, made in , concluded that the dugong was declining and possibly extinct in a third of its range, with unknown status in another half. Kenya has passed legislation banning the hunting of dugongs and restricting trawling, but the dugong is not yet listed under Kenya's Wildlife Act for endangered species.

Mozambique has had legislation to protect dugongs since , but this has not been effectively enforced. The United Arab Emirates has banned all hunting of dugongs within its waters, as has Bahrain. The UAE has additionally banned drift net fishing. India and Sri Lanka ban the hunting and selling of dugongs and their products. Japan has listed dugongs as endangered and has banned intentional kills and harassment.

Hunting, catching, and harassment are banned by the People's Republic of China. The first marine mammal to be protected in the Philippines was the dugong, although monitoring this is difficult. Palau has legislated to protect dugongs, although this is not well enforced and poaching persists. Indonesia lists dugongs as a protected species; [12] however, protection is not always enforced and souvenir products made from dugong parts can be openly found in markets in Bali. Vanuatu and New Caledonia ban hunting of dugongs.

Dugongs are protected throughout Australia, although the rules vary by state; in some areas, indigenous hunting is allowed. Most currently live in established marine parks , where boats must travel at a restricted speed and mesh net fishing is restricted. Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include hunting, habitat degradation , and fishing-related fatalities.

Most issues with industrial fishing occur in deeper waters where dugong populations are low, with local fishing being the main risk in shallower waters. In areas such as northern Australia, hunting remains the greatest impact on the dugong population. Vessel strikes have proved a problem for manatees, but the relevance of this to dugongs is unknown.

Ecotourism has increased in some countries, although the effects remain undocumented. It has been seen to cause issues in areas such as Hainan due to environmental degradation. These are nursery areas for many fish species and thus important for food security in the region. Stephanie found that dugongs around Madagascar were particularly threatened - more so than previously thought. Part of a dugong skull in the Museum's marine mammal collections. Stephanie took 62 samples from these specimens.

The type of analysis that Stephanie did is called phylogeography. It is a way of studying how and why populations of animals and plants are spread across a certain area, done by looking at the genetics of those organisms.

Often, researchers can tell if populations of animals have migrated, or been split in two by continents moving. Phylogeography is a relatively new way of studying nature, because it relies on DNA analysis, which has become much easier since the s. Stephanie looked into the genetic history of dugongs across their original range. She used 14 different museum collections, taking DNA samples from the bones or teeth of dugongs.

The oldest specimen she used dates back to Stephanie took samples from 62 specimens from the Natural History Museum collections, along with samples from other institutions around the world.

Richard Sabin, Principal Curator of Marine Mammals at the Museum, says, 'The dugong samples from the mammal collection in the Life Sciences department made a substantial contribution to the overall study. The results now help us to understand how dugong populations are connected and how genetically different they are from each other.

Alongside a drop in their numbers comes the risk of a loss of genetic diversity. As animal populations are significantly reduced, this results in genetic bottlenecking. In other words, it is a drastic shrinking of the gene pool. When an animal population is affected by sudden habitat loss or intensive hunting, lots of gene variations are lost very quickly.

It is a problem facing most animals on the brink of extinction, such as rhinos , and it is an issue because a species needs a wide range of healthy DNA in a population to be able to cope with any changes it might face in the future. Lack of diversity makes it harder for a species to keep evolving, adapting and ultimately surviving.

But Stephanie's analysis found that it is likely that valuable genetic diversity among dugongs has already been lost during the last years. She found unique and previously unidentified dugong lineages in the Indian Ocean - meaning it is likely there were once even more unique lineages that have already disappeared.

Stephanie also found that there isn't much gene flow between some populations of dugong in different regions. Perhaps the most important result was that all the dugongs that live around Madagascar are particularly genetically isolated, so may be even more at risk from human activity than previously thought and deserve a higher conservation status.

These mammals can stay underwater for six minutes before surfacing. Dugongs spend much of their time alone or in pairs, though they are sometimes seen gathered in large herds of a hundred animals. Female dugongs have one calf after a yearlong pregnancy, and the mother helps her young reach the surface and take its first breath. A young dugong remains close to its mother for about 18 months, sometimes catching a ride on her broad back.

These languid animals make an easy target for coastal hunters, and they were long sought for their meat, oil, skin, bones, and teeth. Dugongs are now legally protected throughout their range, but their populations are still in a tenuous state.

Some believe that dugongs were the inspiration for ancient seafaring tales of mermaids and sirens. All rights reserved. Common Name: Dugong. Scientific Name: Dugong dugon. Type: Mammals. Diet: Herbivore. Group Name: Herd.

Size: 8 to 10 feet. Weight: to 1, pounds. Size relative to a 6-ft man:.