A future for the dugong - ResearchOnline@JCU ResearchOnline@JCU Contacts A future for the dugong Marsh, Helene, Penrose, Helen, and Eros, Carole (2003) A future for the dugong. In: Gales, Nick, Hindell, Mark, and Kirkwood, Roger, (eds.) Marine Mammals: fisheries, tourism and management issues. CSIRO Publishing, Collingwood, VIC, Australia, pp. 383-399. PDF (Published Version) Restricted to Repository staff only View at Publisher Website: 2 Abstract The dugong (Dugong dugon) is the only herbivorous mammal that is strictly marine and is the only extant species in the Family Dugongidac. The other members of the order Sirenia, the three species of manatee, all use fresh water to varying degrees (Reynolds and Odell 1991). The only other recent Sirenian, Steller's sea cow, Hydrodamalis gigas, was hunted to extinction within 27 years of its discovery in the eighteenth century (Stejneger 1887).

All extant members of Order Sirenia (induding the dugong) are listed as vulnerable to extinction (Hilton-Taylor 2000). All populations of the dugong are also listed on Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Prospects for the survival of the dugong are the best among the Sirenia, because each manatee species has a more localised distribution than that of the dugong (Reynolds and Odell 1991). In addition, the estimates of dugong abundance in Australia which total to a mean of about 85000 individuals (Marsh et al. 1999) are much greater than have been recorded or suggested for any species of manatee. Item ID: A Method for Capturing Dugongs (Dugong dugon) in Open Water "Throughout the dugong's (Dugong dugon) Indo- Pacific range, there have been marked declines in population sizes over the past few decades (Marsh et al., 1996Marsh et al., , 2003).

In many areas with small or declining populations, there is an urgent need to obtain location-specific data pertaining to populations, demography, life history, and movements . " [Show abstract] [Hide abstract] ABSTRACT: We developed a method to rapidly and safely live capture wild dugongs based on the “rodeo method” employed to catch marine turtles. This method entails close pursuit of a dugong by boat until it is fatigued. The dugong is then caught around the peduncle region by a catcher leaping off the boat, and the dugong is restrained at the water surface by several people while data are collected. Our sampling protocol involves a short restraint time, typically < 5 min. No ropes or nets were attached to the dugong to avoid the risk of entanglement and subsequent drowning. This method is suitable for shallow, open-water captures when weather and water conditions are fair, and may be adapted for deeper waters.

Full-text · Article · Jun 2006 Dugong - Dugong dugon - Details - Encyclopedia of Life See also: Evolution of sirenians The word "dugong" derives from the Tagalog term dugong which was in turn adopted from the Malay duyung, both meaning "lady of the sea". [3] Other common local names include "sea cow", "sea pig" and "sea camel". [4] Dugong dugon is the only extant species of the family Dugongidae , and one of only four extant species of the Sirenia order, the others forming the manatee family. [5] It was first classified by Müller in 1776 as Trichechus dugon, [6] a member of the manatee genus previously defined by Linnaeus . [7] It was later assigned as the type species of Dugong by Lacépède [8] and further classified within its own family by Gray [9] and subfamily by Simpson . [10] Dugongs and other sirenians are not closely related to other marine mammals , being more related to elephants .

[11] Dugongs and elephants share a monophyletic group with hyraxes and the aardvark , one of the earliest offshoots of eutherians . The fossil record shows sirenians appearing in the Eocene , where they most likely lived in the Tethys Ocean . The two extant families of sirenians are thought to have diverged in the mid-Eocene, after which the dugongs and their closest relative, the Steller's sea cow , split off from a common ancestor in the Miocene . The Steller's sea cow became extinct in the 18th century. No fossils exist of other members of the Dugongidae. [12] Molecular studies have been made on dugong populations using mitochondrial DNA . The results have suggested that the population of Southeast Asia is distinct from the others. Australia has two distinct maternal lineages, one of which also contains the dugongs from Africa and Arabia. Limited genetic mixing has taken place between those in Southeast Asia and those in Australia, mostly around Timor . [5] One of the lineages stretches all the way from Moreton Bay to Western Australia , while the other only stretches from Moreton Bay to the Northern Territory .

[11] There is not yet sufficient genetic data to make clear boundaries between distinct groups. [5] There are claims mentioning that several subspecies such as in Okinawan waters exist either historically or presently. Anatomy and morphology[ edit ] The dugong's body is large with a cylindrical shape that tapers at both ends. It has thick, smooth skin that is a pale cream colour at birth, but darkens dorsally and laterally to brownish-to-dark-grey with age. The colour of a dugong can change due to the growth of algae on the skin. [13] The body is sparsely covered in short hair, a common feature among sirenians which may allow for tactile interpretation of their environment. [14] These hairs are most developed around the mouth, which has a large horseshoe shaped upper lip forming a highly mobile muzzle. [12] This muscular upper lip aids the dugong in foraging. [13] Bones in the forelimb can fuse variously with age. The dugong's tail flukes [15] and flippers [11] are similar to those of dolphins.

These flukes are raised up and down in long strokes to move the animal forward, and can be twisted to turn. The forelimbs are paddle-like flippers which aid in turning and slowing. [12] The dugong lacks nails on its flippers, which are only 15% of a dugong's body length. [12] The tail has deep notches. [16] A dugong's brain weighs a maximum of 300 g (11 oz), about 0.1% of the animal's body weight. [12] With very small eyes, [17] dugongs have limited vision, but acute hearing within narrow sound thresholds. Their ears, which lack pinna , are located on the sides of their head. The nostrils are located on top of the head and can be closed using valves. [11] Dugongs have two teats , one located behind each flipper. [12] There are few differences between sexes; the body structures are almost the same. [13] A male's testes are not externally located, and the main difference between males and females is the location of the genital aperture in relation to the umbilicus and the anus .

The lungs in a dugong are very long, extending almost as far as the kidneys , which are also highly elongated in order to cope with the saltwater environment. [12] If wounded, a dugong's blood will clot rapidly. [13] The skull of a dugong is unique. [16] The skull is enlarged with sharply down-turned premaxilla , which are stronger in males. The spine has between 57 and 60 vertebrae . [12] Unlike in manatees, the dugong's teeth do not continually grow back via horizontal tooth replacement. [18] The dugong has two incisors ( tusks ) which emerge in males during puberty. The female's tusks continue to grow without emerging during puberty, sometimes erupting later in life after reaching the base of the premaxilla. [12] The number of growth layer groups in a tusk indicates the age of a dugong, [5] and the cheekteeth move forward with age.

The full dental formula of dugongs is 2.0.3.33.1.3.3, meaning they have two incisors, three premolars, and three molars on each side of their upper jaw, and three incisors, one canine, three premolars, and three molars on each side of their lower jaw. [16] Like other sirenians, the dugong experiences pachyostosis , a condition in which the ribs and other long bones are unusually solid and contain little or no marrow. These heavy bones, which are among the densest in the animal kingdom , [19] may act as a ballast to help keep sirenians suspended slightly below the water's surface. [20] An adult's length rarely exceeds 3 metres (9.8 ft). An individual this long is expected to weigh around 420 kilograms (926 lb). Weight in adults is typically more than 250 kilograms (551 lb) and less than 900 kilograms (1,984 lb).

[21] The largest individual recorded was 4.06 metres (13.32 ft) long and weighed 1,016 kilograms (2,240 lb), [12] and was found off the Saurashtra coast of west India . [22] Females tend to be larger than males. [12] Distribution and habitat[ edit ] Dugong on the sea floor at Marsa Alam , Egypt Dugongs are found in warm coastal waters from the western Pacific Ocean to the eastern coast of Africa, [15] along an estimated 140,000 kilometres (86,992 mi) of coastline [2] between 26° and 27° degrees to the north and south of the equator . Their historic range is believed to correspond to that of seagrasses from the Potamogetonaceae and Hydrocharitaceae families. The full size of the former range is unknown, although it is believed that the current populations represent the historical limits of the range, [5] which is highly fractured.

[13] The dugong is the only strictly-marine herbivorous mammal, as all species of manatee utilise fresh water to some degree. Recorded numbers of dugongs are generally believed to be lower than actual numbers, due to a lack of accurate surveys. Despite this, the dugong population is thought to be shrinking, [5] with a worldwide decline of 20 per cent in the last 90 years. They have disappeared from the waters of Hong Kong , Mauritius , and Taiwan, as well as parts of Cambodia , Japan, the Philippines and Vietnam. Further disappearances are likely. [11] Dugongs are generally found in warm waters around the coast [15] with large numbers concentrated in wide and shallow protected bays. Large numbers also exist in wide and shallow mangrove channels and around leeward sides of large inshore islands, where seagrass beds are common.

[5] They are usually located at a depth of around 10 m (33 ft), [13] although in areas where the continental shelf remains shallow dugongs have been known to travel more than 10 kilometres (6 mi) from the shore, descending to as far as 37 metres (121 ft), where deepwater seagrasses such as Halophila spinulosa are found. [5] Special habitats are used for different activities. It has been observed that shallow waters are used as sites for calving, minimising the risk of predation. Deep waters may provide a thermal refuge from cooler waters closer to the shore during winter. [5] The Middle-East and Africa[ edit ] Populations of dugongs exist in the water of 37 countries and territories. [11] In the late 1960s, herds of up to 500 dugongs were observed off the coast of East Africa and nearby islands. Current populations in this area are extremely small, numbering 50 and below, and it is thought likely they will become extinct.

The eastern side of the Red Sea is the home of large populations numbering in the hundreds, and similar populations are thought to exist on the western side. In the 1980s, it was estimated there could be as many as 4,000 dugongs in the Red Sea. The Persian Gulf has the second-largest dugong population in the world, inhabiting most of the southern coast, [5] and the current population is believed to be around 7,500. [17] In Mozambique , most of local populations remaining are rather very small where the largest (about 120 individuals) occur at Bazaruto Island , [23] but they have become rare in historical habitats such as in Maputo Bay and on Inhaca Island . [24] [25] Northern Indian Ocean[ edit ] A highly isolated breeding population exists in the Marine National Park, Gulf of Kutch , [26] the only population remaining in western India. It is 1,500 kilometres (932 mi) from the population in the Persian Gulf, and 1,700 kilometres (1,056 mi) from the nearest population in India.

Former populations in this area, centred on the Maldives and the Laccadive Islands , are presumed to be extinct. A population exists in the Gulf of Mannar Marine National Park and the Palk Strait between India and Sri Lanka , but it is seriously depleted. Dugongs are also found in the Andaman and Nicobar Islands and is the state animal of this territory.[ citation needed ] Once distributed throughout the coastal belt in Sri Lanka, the dugong number declined in last two decades due to heavy hunting by the fishermen. Now only the north-eastern coastal belt is home for the rest of dugong population around Sri Lanka.[ citation needed ] It is listed as an endangered species on the southern coast of Pakistan.[ citation needed ] Continental China, Vietnam, and Cambodia[ edit ] See also: Wildlife of China A very small remnant population still exists today along the coast from Guangdong , Leizhou Peninsula , and Hainan Island , to the Gulf of Tonkin . Today, dugongs off southern China are centred on Hainan Province, excluding the west coast of the island of Hainan.

[27] The Chinese government has funded a sanctuary for dugong and mangrove conservation ranging from Hepu County to Shankou in Guanxi , [28] also aiming to secure local Chinese White Dolphins . [29] In Vietnam, dugongs have been restricted mostly to the provinces of Kiên Giang and Bà Rịa–Vũng Tàu , including Phu Quoc Island and Con Dao Island , [30] which had been hosts to large numbers in the past. [31] On Phu Quoc, the first 'Dugong Festival' was held in 2014, [32] and there have been several land-based observations on Côn Đảo in recent years as well. [33] The Côn Đảo National Park in Vũng Tàu has been declared as a suitable site to observe them. [34] Nonetheless, dangerously low levels of awarenesses for conservation of marine organisms in Vietnam and Cambodia may result in increased intentional or unintentional catches, and illegal trade is a potential danger for local dugongs.

[31] Japan, Taiwan, and the Philippines[ edit ] Today, possibly the smallest and northernmost population of dugongs exists around the Nansei Shoto islands, and a population formerly existed off Taiwan. [5] An endangered population of 50 or fewer dugongs, possibly as few as only three individuals, survives. [35] around Okinawa . [36] Historically, the Yaeyama Islands held the largest concentration of dugongs, with more than 300 individuals. On Aragusuku Island , large quantities of skulls are preserved at an utaki that outsiders are strictly forbidden to enter. [37] [38] Amami Oshima was the northernmost edge of the historic range, where a single animal was confirmed in the 2000s, over 40 years after the last previous records. [39] A vagrant strayed into port near Ushibuka, [40] Kumamoto, and died due to poor health. Dugongs in these areas were literally wiped out by historical hunts as payments to the Ryukyu Kingdom and devastating mass illegal hunts and fisheries used dynamite to destroy whole coral systems after the World Wars.

There have been two theories about the biological origins of this population. One is that these stocks had been isolated and were an endemic Philippine subspecies. [41] This, however, is contrary to the idea of "the only method to restore the Okinawan population is to wait until vagrants from the Philippines stray into and re-colonize the areas".[ clarification needed ] The other is that one super-population constantly migrates or mixes throughout the range of the Ryukyu Archipelago, Taiwan, and the Philippines. [42] The population around the Andaman and Nicobar Islands are known only from a few records, and although the population was large during British rule, it is now believed to be small and scattered with the largest population vicinity to Palawan . All the islands of the Philippines are believed to have once provided habitats for dugongs, which were common until the 1970s. Taiwanese populations seem to be almost extinct, although remnant individuals may visit areas with rich seagrass beds such as Dongsha Atoll . [43] It is unclear whether populations in these areas once consisted a super-population or underwent constant mixing.

There are occasional records of vagrants at the Northern Mariana Islands as well.[ citation needed ] South Asia and South Pacific[ edit ] Dugong with attached remora off Lamen Island , Vanuatu The Gulf of Thailand also used to have a large population, but they have not recently been sighted in the west of the gulf, and the population in the east is thought to be very small. Dugongs are believed to exist in the Straits of Johor in very small numbers. The waters around Borneo support a small population, with more scattered throughout the Malay archipelago . Populations exists around the Solomon Islands archipelago and New Caledonia , stretching to a westernmost population in Vanuatu . A highly isolated population lives around the islands of Palau . [5] Australia[ edit ] Australia is home to the largest population, stretching from Shark Bay in Western Australia to Moreton Bay in Queensland . [11] The population of Shark Bay is thought to be stable with over 10,000 dugongs. Smaller populations exist up the coast, including one in Ashmore reef .

Large numbers of dugongs live to the north of the Northern Territory , with a population of over 20,000 in the gulf of Carpentaria alone. A population of over 25,000 exists in the Torres Strait such as off Thursday Island , although there is significant migration between the strait and the waters of New Guinea . [5] The Great Barrier Reef provides important feeding areas for the species; [44] this reef area houses a stable population of around 10,000, although the population concentration has shifted over time. Large bays facing north on the Queensland coast provide significant habitats for dugong, with the southernmost of these being Hervey Bay and Moreton Bay . [11] Extinct Mediterranean population[ edit ] It has been confirmed that dugongs once inhabited the water of the Mediterranean [45] [46] 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 . [47] The Mediterranean is the region where the Dugongidae originated in the mid-late Eocene , along with Caribbean Sea .

[48] [49] Ecology and life history[ edit ] A mother and calf in shallow water Dugongs are long lived, and the oldest recorded specimen reached age 73. [5] They have few natural predators, although animals such as crocodiles, killer whales, and sharks pose a threat to the young, [11] and a dugong has also been recorded to have died from trauma after being impaled by a stingray barb. A large number of infections and parasitic diseases affect dugongs. Detected pathogens include helminths , cryptosporidium , different types of bacterial infections, and other unidentified parasites. 30% of dugong deaths in Queensland since 1996 are thought to be because of disease. [5] Although they are social animals, they are usually solitary or found in pairs due to the inability of seagrass beds to support large populations. [13] Gatherings of hundreds of dugongs sometimes happen, [15] but they last only for a short time. [13] Because they are shy, and do not approach humans, little is known about dugong behaviour.

[13] They can go six minutes without breathing (though about two and a half minutes is more typical), [50] and have been known to rest on their tail to breathe with their heads above water. [15] They can dive to a maximum depth of 39 metres (128 ft); they spend most of their lives no deeper than 10 metres (33 ft). 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. [13] Dugongs are semi-nomadic, often travelling long distances in search of food, but staying within a certain range their entire life. [13] Large numbers often move together from one area to another. 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.

[11] Dugong movements mostly occur within a localised area of seagrass beds, and animals in the same region show individualistic patterns of movement. 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. [5] One animal was seen as far south as Sydney . [12] Although they are marine creatures, dugongs have been known to travel up creeks, and in one case a dugong was caught 15 kilometres (9.3 mi) up a creek near Cooktown . [11] Feeding[ edit ] Typical dugong feeding area in Moreton Bay Dugongs, along with other sirenians, are referred to as " sea cows " because their diet consists mainly of sea-grass.

When eating they ingest the whole plant, including the roots, [11] although when this is impossible they will feed on just the leaves. [5] A wide variety of seagrass has been found in dugong stomach contents, and evidence exists they will eat algae when seagrass is scarce. [12] Although almost completely herbivorous , [13] they will occasionally eat invertebrates such as jellyfish , sea squirts , and shellfish . [11] Dugongs in Moreton Bay, Australia, are omnivorous, feeding on invertebrates such as polychaetes [51] or marine algae when the supply of their choice grasses decreases. 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 faecal evidence indicates that invertebrates are not eaten. [5] Most dugongs do not feed from 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.

[11] The chemical structure and composition of the seagrass is important, and the grass species most often eaten are low in fibre, high in nitrogen, and easily digestible. [5] In the Great Barrier Reef, dugongs feed on low-fibre high-nitrogen seagrass such as Halophila and Halodule , [11] so as to maximize nutrient intake instead of bulk eating. 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 specialised 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 (108 ft), and dugongs have been seen feeding as deep as 37 metres (121 ft). [5] Dugongs are relatively slow moving, swimming at around 10 kilometres per hour (6.2 mph). [48] When moving along the seabed to feed they walk on their pectoral fins.

[16] 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. [13] They will dig up an entire plant and then shake it to remove the sand before eating it. They have been known to collect a pile of plants in one area before eating them. [16] The flexible and muscular upper lip is used to dig out the plants. This leaves furrows in the sand in their path. [13] Reproduction and parental care[ edit ] Dugong mother and offspring from East Timor A dugong reaches sexual maturity between the ages of eight and eighteen, older than in most other mammals. [52] The way that females know how a male has reached sexual maturity is by the eruption of tusks in the male since tusks erupt in males when testosterone levels reach a high enough level. [53] The age when a female first gives birth is disputed, with some studies placing the age between ten and seventeen years, while others place it as early as six years. [5] There is evidence that male dugongs lose fertility at older ages.

[12] Despite the longevity of the dugong, which may live for 50 years or more, females give birth only a few times during their life, and invest considerable parental care in their young. [52] The time between births is unclear, with estimates ranging from 2.4 to 7 years. [5] Mating behaviour varies between populations located in different areas. [13] In some populations, males will establish a territory which females in heat will visit. [5] In these areas a male will try to impress the females while defending the area from other males, a practice known as lekking . [13] In other areas many males will attempt to mate with the same female, [5] sometimes inflicting injuries to the female or each other. [11] During this the female will have copulated with multiple males, who will have fought to mount her from below. This greatly increases the chances of conception. [13] Females give birth after a 13–15 month gestation , usually to just one calf. [52] Birth occurs in very shallow water, with occasions known where the mothers were almost on the shore.

[12] As soon as the young is born the mother pushes it to the surface to take a breath. [15] Newborns are already 1.2 metres (4 ft) long and weigh around 30 kilograms (66 lb). [11] Once born, they stay close to their mothers, possibly to make swimming easier. [12] The calf nurses for 14–18 months, although it begins to eat seagrasses soon after birth. [5] A calf will only leave its mother once it has matured. [13] Importance to humans[ edit ] A cave painting of a dugong – Tambun Cave, Perak , Malaysia Dugongs have historically provided easy targets for hunters, who killed them for their meat, oil, skin, and bones. They are often considered as the inspiration for mermaids , [15] and people around the world developed cultures around dugong hunting. In some areas it remains an animal of great significance, [12] and a growing ecotourism industry around dugongs has had economic benefit in some countries.

[13] There is a 5,000-year-old wall painting of a dugong, apparently drawn by neolithic peoples, in Tambun Cave , Ipoh , Malaysia. [54] This was discovered by Lieutenant R.L Rawlings in 1959 while on a routine patrol. During the Renaissance and the Baroque eras, dugongs were often exhibited in wunderkammers . They were also presented as Fiji mermaids in sideshows . Dugong meat and oil have traditionally been some of the most valuable foods of Australian aborigines and Torres Strait Islanders . Some aborigines regard dugongs as part of their Aboriginality. [11] 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 to people in India,[ citation needed ] and its meat is believed to be an aphrodisiac . Dugong ribs were used to make carvings in Japan.

In Southern China dugongs were traditionally regarded as a "miraculous fish", and it was bad luck to catch them. A wave of immigration beginning at the end of the 1950s resulted in dugongs being hunted for food. In the Philippines dugongs are thought to bring bad luck, and parts of them are used to ward against evil spirits. In areas of Thailand it is believed that the dugong's tears form a powerful love potion, while in parts of Indonesia they are considered reincarnations of women. In Papua New Guinea they are seen as a symbol of strength. [5] Dugongs' or sea cows' hides have been thought [55] to have been used as coverings in the building of the Old Testament portable worship tent known as the Tabernacle . See also: Dugong hunting in Australia Dugong numbers have decreased in recent times. For a population to remain stable, 95 per cent of adults must survive the span of one year. The estimated percentage of females humans can kill without depleting the population is 1–2%. [11] This number is reduced in areas where calving is minimal due to food shortages.

Even in the best conditions a population is unlikely to increase more than 5% a year, leaving dugongs vulnerable to over-exploitation. 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. [5] The only data stretching back far enough to mention population trends comes from the urban coast of Queensland, Australia. The last major worldwide study, made in 2002, concluded that the dugong was declining and possibly extinct in a third of its range, with unknown status in another half. [2] The IUCN Red List lists the dugong as vulnerable, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora regulates and in some areas has banned international trade. [12] Regional cooperation is important due to the widespread distribution of the animal, and in 1998 there was strong support for Southeast Asian cooperation to protect dugongs.

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 1955, but this has not been effectively enforced. Many marine parks have been established on the African coast of the Red Sea, and the Egyptian Gulf of Aqaba is fully protected. 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 is 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. The dugong is a national animal of Papua New Guinea, which bans all except traditional hunting. 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. [5] Dugongs are listed under the Nature Conservation Act in the Australian state of Queensland as vulnerable. Most currently live in established marine parks, where boats must travel at a restricted speed and mesh net fishing is restricted. [11] In Viet Nam, an illegal network targeting dugongs had been detected and was shut down in 2012. [32] Human activity[ edit ] Despite being legally protected in many countries, the main causes of population decline remain anthropogenic and include hunting, habitat degradation, and fishing-related fatalities. [4] Entanglement in fishing nets has caused many deaths, although there are no precise statistics. Most issues with industrial fishing occur in deeper waters where dugong populations are low, with local fishing being the main risk in shallower waters. [5] As dugongs cannot stay underwater for a very long period, they are highly prone to deaths due to entanglement. [17] The use of shark nets has historically caused large numbers of deaths, and they have been eliminated in most areas and replaced with baited hooks.

[11] Hunting has historically been a problem too, although in most areas they are no longer hunted, with the exception of certain indigenous communities. In areas such as northern Australia, hunting remains the greatest impact on the dugong population. [5] Vessel strikes have proved a problem for manatees, but the relevance of this to dugongs is unknown. [5] Increasing boat traffic has increased danger, [11] especially in shallow waters. Ecotourism has increased in some countries, although effects remain undocumented. It has been seen to cause issues in areas such as Hainan due to environmental degradation. [5] Modern farming practise and increased land clearing have also had an impact, and much of the coastline of dugong habitats is undergoing industrialisation, with increasing human populations. [11] Dugongs accumulate heavy metal ions in their tissues throughout their lives, more so than other marine mammals. The effects are unknown. Socio-political needs are an impediment to dugong conservation in many developing countries. The shallow waters are often used as a source of food and income, problems exacerbated by aid used to improve fishing. In many countries, legislation does not exist to protect dugongs, and if it does it is not enforced.

[5] Oil spills are a danger to dugongs in some areas, as is land reclamation . In Okinawa the small dugong population is threatened by United States military activity. Plans exist to build a military base close to the Henoko reef, and military activity also adds the threats of noise pollution, chemical pollution, soil erosion, and exposure to depleted uranium . [5] The military base plans have been fought in US courts by some Okinawans, whose concerns include the impact on the local environment and dugong habitats. [36] [56] It was later revealed that the government of Japan was hiding evidence of the negative effects of ship lanes and human activities on dugongs observed during surveys carried out off Henoko reef. [57] Environmental degradation[ edit ] If dugongs do not get enough to eat they may calve later and produce fewer young. [11] Food shortages can be caused by many factors, such as a loss of habitat, death and decline in quality of seagrass, and a disturbance of feeding caused by human activity. Sewage, detergents, heavy metal, hypersaline water, herbicides, and other waste products all negatively affect seagrass meadows.

Human activity such as mining, trawling, dredging, land-reclamation, and boat propeller scarring also cause an increase in sedimentation which smothers seagrass and prevents light from reaching it. This is the most significant negative factor affecting seagrass. [5] One of the dugong's preferred species of seagrass, Halophila ovalis , declines rapidly due to lack of light, dying completely after 30 days. Extreme weather such as cyclones and floods can destroy hundreds of square kilometres of seagrass meadows, as well as washing dugongs ashore. The recovery of seagrass meadows and the spread of seagrass into new areas, or areas where it has been destroyed, can take over a decade. Most measures for protection involve restricting activities such as trawling in areas containing seagrass meadows, with little to no action on pollutants originating from land. In some areas water salinity is increased due to wastewater , and it is unknown how much salinity seagrass can withstand. [5] Current imminent threat to the habitat is the case of Oura bay area in Henoko, Okinawa, Japan, where a small population of dugong inhabit.

[58] Despite it being the northern limit of Dugong, their habitat is about to be destroyed by land reclamation conducted by Japanese Government in order to build a US Marine base in the ocean. In August 2014, preliminary drilling surveys are being conducted in the grazing habitat. [59] It is expected to seriously damage the dugong population's habitat, leading them into local extinction. [60] Capture and captivity[ edit ] The Australian state of Queensland has sixteen dugong protection parks, and some preservation zones have been established where even aborigines are not allowed to hunt. [11] Capturing animals for research has caused only one or two deaths; [5] dugongs are expensive to keep in captivity due to the long time mothers and calves spend together, and the inability to grow the seagrass that dugongs eat in an aquarium. [11] Only one orphaned calf has ever been successfully kept in captivity. [13] Worldwide, only five dugongs are held in captivity. A female from the Philippines lives at Toba Aquarium in Toba, Mie , Japan. [5] A male also lived there until it died on 10 February 2011.

[61] Another is at Underwater World, Singapore , due to its mother being killed when it was a calf. [62] A third resides in Sea World Indonesia, [63] after having been rescued from a fisherman's net and treated. [64] The last two, a male and a female, are kept at Sydney Aquarium , where they have resided since they were juveniles.[ citation needed ] Manatee - New World Encyclopedia Manatee Fossil range: Early Miocene to Recent Antillean Manatee Trichechus manatus Trichechus senegalensis Manatee is the common name for large, herbivorous, fully aquatic marine mammals comprising the family Trichechidae, characterized by a nearly hairless body with paddle-like front flippers, small eyes, no external ear, and absence of hind limbs (although there are vestigial pelvic bones). There is one genus recognized in the family, Trichecus, which includes three extant species. Manatees are found in both freshwater and marine environments in parts of the Americas and Africa. Manatees, which sometimes are known as sea cows, are part of the order Sirenia along with dugongs .

Sirenians are one of four groups of marine mammals, the others being cetaceans ( whales , dolphins , and porpoises ), sea otters, and pinnipeds ( walruses , earless seals , and eared seals ). The sirenians and cetaceans are completely aquatic, while pinnipeds spend considerable time on land, including giving birth and raising their young, and sea otters can mate and raise their young entirely at sea. Sirenia is thought to have evolved from four-legged land mammals over 60 million years ago, with the closest living relatives being the Proboscidea (elephants) and Hyracoidea ( hyraxes ) (Domning 1994). Manatees are important to the food chains in their aquatic habitats, consuming a wide variety of different aquatic plants and algae and, although the adults have few predators, manatees are consumed by sharks , crocodiles , and orcas. They have long been tied to culture. They traditionally have been hunted for their meat and to make various products (war shields, canoes , shoes) and their bones were ground to treat asthma and earache.

In West African folklore, the manatee was considered sacred and thought to have been once human; killing one was taboo and required penance (Cooper 1992). Today, manatees are now considered endangered and protected. One of their main sources of mortality today is collisions with boats and propellers. Contents 7 Credits Description The body of the manatee is largely hairless, somewhat oval in cross section, and with short, flexible and paddlelike forelimbs, a broad, horizontally flattened tail, and no hind limbs, although the pelvic musculature has the presence of vestigial pelvic bones. With the exception of the Amazonian manatee, Trichechus inunguis, there are three or four nails on the end of the forelimbs; Amazonian manatees lack the nails in the forelimbs. There is a small, hard to see external ear opening, but no pinna (external ear). Testes are internal, and mammary glands are paired, with a single nipple in each axilla (Odell 2004). A group of 3 manatees The upper lips of manatees are split and described as prehensile (Odell 2004).

In many ways, the upper lip acts like a shortened trunk, somewhat similar to an elephant's. They use the lip to gather food and eat, as well as using it for social interactions and communications. Their small, widely spaced eyes have eyelids that close in a circular manner. Manatees are also believed to have the ability to see in color. The main visual difference between manatees and dugongs are the tails. A manatee tail is paddle-shaped, while a dugong tail is forked, similar in shape to a whale's. Like horses , manatees have a simple stomach, but a large cecum, in which they can digest tough plant matter. In general, their intestines are unusually long for animals of their size. Adult manatees have no incisor or canine teeth, just a set of cheek teeth, which are not clearly differentiated into molars and premolars. Uniquely among mammals, these teeth are continuously replaced throughout life, with new teeth entering at the back of the jaw and replacing old and worn teeth at the front, with the older teeth falling out from further forward in the mouth.

Thought to be their close cousins, the elephants also have teeth that get replaced, but they have a limited set of these replacement teeth. At any given time, a manatee typically has no more than six teeth (Best 1984). Generally, manatees have a mean mass of 400 to 550 kilograms (900-1200 pounds]]) and mean length of 2.8 to 3.0 meters (9-10 feet), with maximums of 3.6 meters and 1,775 kg seen (the females tend to be larger and heavier). When born, baby manatees have an average mass of 30 kilograms. The body color generally is gray to brownish, but may have algae and other epiphytes that result in another appearance (Odell 2004). Florida manatees (T. m. latirostris) have been known to live up to 60 years. They have few natural predators, but are preyed upon by sharks , crocodiles , orcas, and alligators .

Much of the knowledge about extant manatees is based upon research done in Florida and cannot necessarily be attributed to all types of manatees. The name manatí comes from the Taíno , a pre-Columbian people of the Caribbean , meaning "breast" (Winger 2000). Distribution and habitat Approximate distribution of Trichechus; T. manatus in green; T. inunguis in red; T. senegalenis in orange Manatees inhabit the shallow, marshy coastal areas and rivers of the Caribbean Sea and the Gulf of Mexico (T. manatus, West Indian manatee), the Amazon Basin (T. inunguis, Amazonian manatee), and West Africa (T. senegalensis, West African manatee). There has been a proposal for recognition of a fourth species, the Ddwarf manatee (T. bernhardi), for a population found in the Brazilian Amazon (van Roosmalen 2008), although some strongly consider it to just be an immature Amazonian manatee, as backed up by DNA evidence (Hammer 2008). Florida manatees (T. m.

latirostris) have been known to live up to 60 years, and they can move freely between different salinity extremes; however, Amazonian manatees (T. inunguis) never venture out into salt water. Studies in Florida suggest that Florida manatees must have some access to fresh water for proper osmoregulation. Florida is usually the northernmost range of the West Indian manatee as their low metabolic rate makes cold weather endurance difficult. They may on occasion stray up the mid-Atlantic coast in summer. Half a manatee's day is spent sleeping in the water, surfacing for air regularly at intervals no greater than 20 minutes. Manatees typically inhabit warm, shallow, coastal estuarine waters and cannot survive below 15°C (288 K; 60°F). Their natural source for warm waters during the winter is warm-spring fed rivers. The West Indian manatee migrates into Florida rivers such as the Crystal River, the Homosassa River, and the Chassahowitzka River. The head springs of these rivers maintain a water temperature of 22°C (299 K; 72°F) year round.

During the winter months, November to March, approximately 400 West Indian manatees (according to the National Wildlife Refuge) congregate in the rivers in Citrus County, Florida. Manatees have been spotted as far north as Cape Cod, and as recently as the late summer of 2006, one made it up to New York City and Rhode Island 's Narragansett Bay, as cited by The Boston Globe. According to Memphis, Tennessee's The Commercial Appeal newspaper, one manatee was spotted in the Wolf River harbor near the Mississippi River in downtown Memphis, Tennessee, on October 23, 2006, though it was later found dead ten miles downriver in McKellar Lake (Charlier 2006). Manatees often congregate near power plants, which warm the waters. Some have become reliant on this source of artificial heat and have ceased migrating to warmer waters. Some power plants have recently been closing and the U.S. Fish and Wildlife Service is trying to find a new way to heat the water for these manatees. The main water treatment plant in Guyana has four manatees that keep storage canals clear of weeds.

Manatees spend most of their time grazing in shallow waters and at depths of 1 to 2 meters (3-7 feet). Behavior, diet, and reproduction On average, most manatees swim at about 5 to 8 kilometers per hour (1.4 to 2.2 meters/second or 3 to 5 miles per hour). However, they have been known to swim up to 30 kilometers/hour (8 meters/second; 20 miles per hour) in short bursts. Manatees are herbivores and eat over 60 different plant species such as mangrove leaves, turtle grass, and types of algae , using their divided upper lip. An adult manatee will commonly eat up to nine percent of its body weight (approx 50 kilograms) per day. Manatees have been known to eat small amounts of fish from nets (Powell 1978). Manatees emit a wide range of sounds used in communication, especially between cows and their calves, yet also between adults to maintain contact and during sexual and play behaviors. They may use taste and smell, in addition to sight, sound, and touch, to communicate.

Manatees are capable of understanding discrimination tasks, and show signs of complex associated learning and advanced long term memory (Gerstein 1994). They demonstrate complex discrimination and task-learning similar to dolphins and pinnipeds in acoustic and visual studies (Dierauf and Gulland 2001). Manatees typically breed only once every other year, since gestation lasts about 12 months, and it takes a further 12 to 18 months to wean the calf. Only a single calf is born at a time and aside from mothers with their young or males following a receptive female, manatees are generally solitary creatures (Best 1984). Species and population size A manatee in captivity. The population of manatees in Florida (T. manatus) is thought to be between 1,000 and 3,000, yet population estimates are very difficult. The number of manatee deaths in Florida caused by humans has been increasing through the years, and now typically accounts for 20 percent-40 percent of recorded manatee deaths (FWRI 2008).

There were near 300 registered and confirmed manatees in Florida killed by human activity in 2006; the majority of these, that happened to be discovered by Florida Fish and Wildlife, have been caused by boat strikes. Accurate population estimates of the Florida manatee are notoriously difficult and have been called scientifically weak. With widely varying counts from year to year, some areas show possible increases yet others decreases, with very little strong evidence of increases except in 2 areas. However, population viability analysis studies carried out in 1997, found that decreasing adult survival and eventual extinction is a probable future outcome for the Florida manatees, unless they are aggressively protected (Marmontel et al. 1997). Manatee counts are highly variable without an accurate way to estimate numbers. In Florida in 1996, a winter survey found 2,639 manatees; in 1997, a January survey found 2,229; and a February survey found 1,706 (Dierauf and Gulland 2001). Fossil remains of manatee ancestors show they have inhabited Florida for about 45 million years.

The Amazonian manatee (T. inunguis) is a species of manatee that lives in the freshwater habitats of the Amazon River and its tributaries. Their color is brownish gray and they have thick, wrinkled skin, often with coarse hair, or "whiskers." Its main predator is also man. The Brazilian government has outlawed the hunting of the manatee since 1973 in an effort to preserve the species. Deaths by boat strikes, however, are still common. The African manatee (T. senegalensis) is the least studied of the three species of manatees. Photos of African Manatees are very rare; although very little is known about this species, scientists think they are similar to the West Indian manatees. They are found in coastal marine and estuarine habitats, and in fresh water river systems along the west coast of Africa from the Senegal River south to the Kwanza River in Angola, including areas in Gambia, Liberia, Guinea-Bissau, Guinea, Sierra Leone, Côte d'Ivoire, Ghana, Mali, Nigeria, Cameroon, Gabon, Republic of the Congo, and Democratic Republic of the Congo.

Although crocodiles and sharks occasionally kill manatees in Africa, their only significant threats are from humankind due to poaching, habitat loss, and other environmental impacts. They live as high upriver on the Niger as Gao, Mali. Although rare, they occasionally get stranded as the river dries up at the end of rainy season and are cooked for a meal. The name in Sonrai, the local language, is "ayyu." Vulnerability and conservation Antillean Manatee Although manatees have few natural predators, all three species of manatee are listed by the World Conservation Union as vulnerable to extinction . On June 8, 2006, the Florida Fish and Wildlife Conservation Commission voted to reclassify the manatee on Florida's list, to a "threatened" status in that state (FWC 2008). While none of the state laws protecting manatees have changed, many wildlife conservationists are not pleased with the removal decision. Manatees remain classified as "endangered" at the federal level. A sign advising boaters of no-wake manatee zone The current main threat to manatees in the United States is being struck with boats or slashed with propellers.

Manatees are slow-moving, non-aggressive, and generally curious creatures. They enjoy warmer waters and are known to congregate in shallow waters, and frequently migrate through brackish water estuaries to freshwater springs. Their slow-moving, curious nature, coupled with dense coastal development, has led to a number of violent collisions with fast moving recreational motor boats and their propellers, leading frequently to maiming, disfigurement, and even death. Sometimes manatees can live through collisions with boats, but have severe injuries. On some manatees off the Florida coast, a large portion of manatees exhibit scars on their backs and they are now even classed by humans from their scar patterns. There are findings of upwards of 50 scars and disfigurements from boat strikes on a single manatee (Dierauf and Gulland 2001; Kennedy 2006). In other cases, the wounds are fatal, whether as a result of internal injuries or because the cuts often lead to infections (Dierauf and Gulland 2001; Kennedy 2006).

According to marine mammal veterinarians, "The severity of mutilations for some of these individuals can be astounding—including long term survivors with completely severed tails, major tail mutilations, and multiple disfiguring dorsal lacerations. These injuries not only cause gruesome wounds, but may also impact population processes by reducing calf production (and survival) in wounded females— observations also speak to the likely pain and suffering endured" (Dierauf and Gulland 2001). In an example, Dierauf and Gulland (2001) cited one case study of a small calf "with a severe dorsal mutilation trailing a decomposing piece of dermis and muscle as it continued to accompany and nurse from its mother… by age 2 its dorsum was grossly deformed and included a large protruding rib fragment visible" (Dierauf and Gulland 2001). These veterinarians go on to state that "the overwhelming documentation of gruesome wounding of manatees leaves no room for denial.

Minimization of this injury is explicit in the Recovery Plan, several state statutes, and federal laws, and implicit in our society's ethical and moral standards" (Dierauf and Gulland 2001). One problem is that young Manatees are curious—this one is checking out a kayak There are other anthropogenic risks for manatees. Manatees occasionally ingest fishing gear (hooks, metal weights, and so on) while feeding. These foreign materials generally do not seem to harm manatees, with the notable exception of monofilament line or string. This can clog the animal's digestive system and slowly kill the animal. Manatees can also be crushed in water control structures (navigation locks, floodgates, among others), drown in pipes and culverts, and are occasionally killed from entanglement in fishing gear, primarily crab pot float lines. Manatees are also vulnerable to red tides—blooms of algae , which leach oxygen from the water. Trichechus sp. Hunting traditionally has posed a risk. Manatees were commonly hunted for their meat by natives of the Caribbean , although this is much less common today (Nunez 2008).

When Christopher Columbus arrived in the region, manatee hunting was an established trade. Native Americans hunted manatees to make war shields, canoes , and shoes, though the manatee was predominantly hunted for its abundant meat. The primary method of hunting the manatee was somewhat crude, as the hunter would use dugout canoes to approach targeted manatees. The indigenous hunter would then use various methods of baiting in order to attract a manatee close enough to hit the animal near the head with an oar-like pole, temporarily stunning the manatee. Many times the creature would flip over, leaving it vulnerable to further attacks. Manatees were also hunted for their valuable bones, which were used to make "special potions." Up until the 1800s, museums paid as much as $100 for manatee bones or hides. Though hunting manatees was banned in 1893, poaching continues today. In the United States, it is illegal under federal and Florida law to cause the manatees injury or harm (Dierauf and Gulland 2001).

While humans are allowed to swim with manatees in one area of Florida (STMC 2008), there have been numerous charges of people harassing and disturbing the manatees in various ways, in addition to the concern about repeated motorboat strikes. References Best, R. 1984. Manatee. Pages 292-298 in D. Macdonald, The Encyclopedia of Mammals. New York: Facts on File. ISBN 0871968711 . Charlier, T. 2006. Manatee's corpse recovered; goes to zoo for analysis. The Commercial Appeal December 13, 2006. Cooper, J. C. 1992. Symbolic and Mythological Animals. London: Aquarian Press. ISBN 1855381184 . Dierauf, L. A., and F. M. D. Gulland. 2001. CRC Handbook of Marine Mammal Medicine. Boca Raton, FL: CRC Press. ISBN 0849308399 . Domning, D. P., 1994.

Paleontology and evolution of sirenians: Status of knowledge and research needs. Proceeding of the 1st International Manatee and Dugong Research Conference, Gainesville, Florida.

Question: Because all species of the manatee use fresh water in varying ways, what is the only strictly marine herbivorous mammal?
Answer: Dugong