Cumulative Dugong Population Of The Philippines example essay topic

Dugong Research Scientific name: Dugong Dugong Status: Vulnerable to extinction since 1982 (IUCN) Appendix I of CITES Taxonomy: Class Mammalia Order SireniaFamily DugongidaeGenus Dugong Species dugonCommon Name dugong or sea cow Local Name du yong or baby dag at Description: The dugong is one of the 24 species of marine mammals present in the Philippine waters. The dugong is the only representative of the order Sirenia to be found in the country. It is a truly unique aquatic animal, being the only herbivorous mammal whose preferred habitat is the sea. Like people and other mammals, the dugong is warm-blooded, has hairs, breathes air and the mother suckles their young. It has been noted that stories on mermaids are attributed to this unique animal due to its striking resemblance - fish-like tail, brownish smooth skin, mammary glands, woman-like genitalia and even its's uc kling baby. An adult dugong can grow to more than three meters in length and can weigh more than 400 kg.

Newborns are a little over a meter, while mature animals measure at least 2.5 meters in length (Marsh et al. 1984). The dugong's body is torpedo-shaped with whale-like flukes. The neck is short and indistinct. The flippers are small and short are used for manoeuvring and as a support during feeding or resting at the sea bottom. The color of an adult dugong is greyish bronze, which becomes lighter ventrally.

Neonates and juveniles are lighter and are browner in color. The skin is tough, heavily scarred and usually colonized with barnacles in older animals. Short / stiff hair and fine / thin hair is sparsely distributed throughout the back of the animal. Hair is almost absent in the abdomen but are large, thick and abundant in the snout region. The upper lip forms the disc, which is horseshoe in shape and is covered with a lot of thick and long vibrissae used for probing. A unique feature is around 25-35 mm thick (not as thick compared to other marine mammals, since protection from the cold is not a great problem for this warm and shallow water species).

The eyes are round, small and dark and are closed by lids with a sphincter action. Underwater vision is assumed to be similar to that of a masked scuba diver. The dugongs produce a mucoid secretion from a gland under the eyelid, which are excreted when the eyes are exposed to air. The ears lack a pinna e and appear as small holes on the sides of the head; hearing is observed to be very keen. The nose is situated ante ro-dorsally to facilitate breathing while the rest of the body remains submerged.

Another feature is the valves attached to the floor of the nasal cavity that opens and closes the nostrils to prevent water from entering. The bone of the dugong is very dense and thick which is suggested to play an important role in the buoyancy control system and protection of the animal. The skull has enlarged pre-maxilla that is deflected downward. Vertebrae usually number 59. Dugongs also possess tusks, which are used purely for social activities and not for feeding. The tusks are erupted in mature males and in some old females past their reproductive years.

Tusks produce annual growth layers, which are very useful in determining the age of dugongs. Six sets of molars are present which erupt on each side of the jaw. Dugongs swim slowly, are shy and evasive. They move along coasts and between islands. Their movement is affected by tide, weather, season, availability of food and human disturbance. They need to breathe air on the surface of the water every one to four minutes.

The dugong is a very gentle animal that peacefully lives in our seas without causing harm to people or other marine life. Evolution: Siren ians have evolved from four-legged hoofed mammals of the early Eocene Epoch, a geological time, which was about 53 million years ago. These herbivorous stem animals called sub ungulates are also the ancestors of elephants and hyraces, making the two the closest relatives of dugongs and manatees. Through millions of years, the land-dwelling ungulates have evolved to a life adapted to the sea. Their hind limbs degenerated, they developed a tail, their front legs became paddle-like, their external ear disappeared, and their hairy coat sparse, all in favor of the aquatic environment. The earliest known siren ian was found in Jamaica.

The fossilized skull was dated from the latter part of the early Eocene Epoch. Though more of its fossils are yet to be discovered, there are speculations that this animal moved from land and water. Fossil records of Sirenia are extensive and are distributed pan tropically. About a dozen genera were known from the Miocene Epoch (25-5 million years ago) to the late Pliocene Epoch (about 2 million years ago). Tropical condition was widespread during the Miocene Epoch, coinciding with a peak in siren ian diversity and abundance. The most widespread genus was Metaxytherium.

It is considered to have given rise to a new subfamily of dugong ids, which includes the Steller's sea cow (Barnes et al., 1985). Dugongs and manatees have risen from the same primitive dugong id ancestor. They formed the different phyletic lines from each other in the Late Eocene or Early Oligocene Epoch 35 million years ago. The modern dugong's closest relative among the siren ia lie within the dugong id subfamily called Rytiodontinae (Dugonginae). This subfamily appears to have originated by the late Oligocene (30 million years ago).

The most recently discovered dugong ancestor was recovered from Florida. It was aged less than 2 million years old (Late Pliocene Epoch). Behavior: a) Feeding Dugongs are benthic grazers of a wide range of sea grasses (the only true flowering plants of the sea). Dugongs also feed on different types of algae and several macro invertebrates. Since sea grass is very low in nutrients, dugongs have to consume large amounts of it. Therefore the dugong spends most of its time feeding.

A captive dugong in Japan has been observed to consume up to 25 kg. of sea grass (wet weight) in a day, or approximately 8% of its body weight. The highly specialized and flexible snout of the dugong is used for prehension. The upper lip can change shape as it is used. The mouth is directed ventrally to allow the dugong to feed off the sea bottom with its body in a horizontal position. The flippers are used as a support when feeding. This has led to the thickening and staining of the part of the flipper constantly touching the sea floor.

Because of the characteristic grazing habit of the dugong, distinguishable paths in the sand are created where sea grasses have been uprooted. These paths are referred to as feeding trenches or trails. A dugong grazing continuously could produce a 14 m trail, but most are much shorter because the dugong often surfaces to breathe. These trails are used in identifying the feeding areas of the dugongs.

The dental pads of the dugong are determined to be very effective in macerating sea grasses and transporting it to the inner part of the mouth. It complements the function of the cheek teeth. The digestive system is comparable to that of hind-gut digesting land herbivores (like elephants and horses). Digestion of cellulose by enteric bacteria occurs in the caecum and large intestines. The abundance and type of sea grass present is one element influencing the feeding habits of the dugong. Dugongs can consume all types of sea grass, but prefers small, soft sea grasses that are low in fiber but high in nutrients and digestibility (e.g. sp. and Halodule sp.

). Other factors include: a) The time of day- dugongs are thought of as nocturnal feeders, though diurnal feeding has been commonly observed. b) The rise and fall of tide- dugongs go with the rising tide and prefer to feed when the water is high (sea grass beds are often exposed at low tide and shallow water can lead to stranding and are very close to the shore). Dugongs also feed on deepwater sea grass (60 ft). b) Breathing, swimming and movement The dugong cannot stay submerged for long periods, constantly needing to breathe every 1 to 2 minutes. The longest recorded for dugong in captivity is 8.26 minutes. Only a couple of seconds is needed at the surface, taking a single or several breaths before making a dive. Studies in Australia show that dugongs stay submerged longer in deeper water but will stay longer on the surface in between dives.

Dugongs swim in a very slow pace, about 5 km per hour. Movement is sluggish and leisurely when undisturbed. Dugongs are also seen apparently inactive at the surface of the water (idling) or resting on the sea bottom. Dugongs are considered to be more active at daytime. Daily movements of dugongs are influenced by the tide and weather, food and disturbances.

Seasonal movement on the other hand may be determined by changing temperature, monsoon season, abundance and season of sea grass and anthropogenic disturbances. Dugong satellite tracking reveal that they maintain certain home ranges in areas with expensive sea grass beds. Extent of habitat is unknown but is assumed to be tens and thousands of kilometers. This will depend on habitat shape and sea grass available. c) Social Organization Dugongs in the wild can be seen singly, in mother and calf pairs, small groups or herds of hundreds of animals, sometimes up to 600. A large herd is now a rarity in most of the dugong's range and recent sightings have been limited to Australia, Arabian Gulf and Somalia. Since herding is evident, it can be inferred that dugongs are social animals.

This also suggests that some form of communication between them is present. Dugongs can produce sounds and are observed in both young and adult animals. Bird-like chirps (1-8 k Hz) have been recorded. This may be significant in mother-calf bonding.

Life History and Reproduction Dugongs are long-lived animals with a low reproduction rate. This has led scientists to conclude that dugongs are very prone to extinction. Age determination indicates that the dugong can live well over 70 years old. Breeding generally occurs throughout the year but peaks transpire during the season when sea grass is most abundant. In some Australian herds, mating takes place in areas of concentrated use of the dugongs within their home range.

In the Philippines, no observations have been made yet. Males and females can be easily differentiated from each other by the position of genital apertures. The penis of the male is found inside a genital slit centrally located between the anus and the umbilicus. The shaft is extruded only when the male is excited. The testes are located inside the abdomen. The female's genital slit on the other hand, is located in close proximity with the anus.

Both male and female are sexually mature at about 9-17 years when they measure at least 2.5 m in length. Gestation lasts for 12-13 months and a single calf is born. Majority of the Births occur when sea grass growth is at its peak so that neonates can take of the high nutrients available from the young and flourishing sea grass. Births are said to occur in very shallow water. Neonates start sucking on sea grass in just a few weeks while they still suckle from their mother. The auxiliary mammary of the sea cow is well endowed and continually produces milk for about 18 months.

During this period an intimate cow-calf tie is displayed. The calf stays close to the mother at all times. A dugong up to 1.8 m in length may still suckle from its mother. This tie is undoubtedly essential for the calf to stay alive. Calving occurs every 3-7 years only, making the dugongs very slow reproducers. Range, Distribution and Population The common conditions necessary to sustain dugongs around the world are warm water with temperature ranging from 18 - 38 o C throughout the year, abundant sea grass, and shelter from high winds and heavy waves.

Dugongs occur in shallow coastal waters with a depth range of about 2-10 m though it is not unusual to find a dugong in waters up to 37 m deep. The dugongs are found in the tropical and subtropical waters of the world confined within the longitudinal range between 170 oEast in the New Her brides and 30 oEast at the head of the Gulf of Suez and a latitudinal range 26 oN orth to 27 o South of the equator (Marsh, 1993). The actual population size of the dugongs throughout its range is unknown. Aerial surveys are needed to estimate a population of the dugongs along coasts, but due to its low repeatability and the specialized skill and high cost demanded, no accurate count on the number of dugongs in the world has been made. Dugongs occur in the Indian and West Pacific oceans only, with around 42 countries harbouring them in their coasts.

In 1979, Nishiwaki gave a rough estimate of the dugong population worldwide to be 30,000 based only from interviews and reported exploitation. He also presumes that the cumulative dugong population of the Philippines, Molucca and West Australia is 7,000 with Palawan having around 1,000 dugongs. Australia is the only country to have a thorough and systematic aerial survey of their local dugong population. Recent estimates reveal that the partial dugong population in Australia's coast alone may reach 85,000. Australia has the largest population of dugongs in the world making Nishiwaki's estimate too low. In addition, The Arabian Gulf and Red Sea total number of dugongs counted 9,000.

Thus the world-wide population of the dugongs are estimated to be over 100,000 animals. The status of the dugong is still unclear. However, there are a lot of evidence suggesting the depletion of their population world-wide. In the country, Palawan is the only place in the country where reports are regularly received and confirmed. Palawan could be the only major refuge in the country left for the dugong. Historical records indicate that dugongs were common around the Philippine islands.

Herds up to 20 have been sighted in Palawan waters in the 1960's. Today, it is very rare to find dugong forming relatively large herds in the country though groups of four to five are still reported in Palawan (Leatherwood et al., 1992; PCP reports). From recent surveys conducted by PCP, dugongs are more commonly seen singly or in pairs, usually mother and calf. Exploitation Dugongs have very few natural predators which includes crocodiles, sharks and killer whales. Man is still the most important single factor affecting dugong populations. The oldest confirmed record of the dugong in the Philippines came from an archaeological site in Butuan City (Bautista, 1990).

The ribs recovered, which were dated from the 9th to 12th century A.D., indicate that dugongs were utilized as food. Even earlier, dugong bones were recovered from what is now called the Dugong Cave in Quezon, Palawan. The numerous bones found suggests that the animal was used for ritual offerings in the early Metal Age [500-200 B.C.] (Fox, 1970). Spanish records from the 18th century mentioned dugongs being captured in the Eastern coast of Luzon and their vertebrae were transferred to be bartered in Palau, exemplifying the commercial significance of the species (De Elera, 1915). In 1913, the flesh of the dugong was said to be highly valued as food by the people of Zam bales (Seale, 1915).

Therefore, the utilization and exploitation of this species is not of recent origin in the Philippines. Though dugongs were hunted using nets, prongs, hooks and spears (Al zina, 1668), harpoon and dynamite (Leatherwood et al., 1992), and javelin (Blair & Robertson, 1950), it is not surprising that in more recent times, they have also been caught using dynamite. Dynamite has caused a huge number of dugongs to be killed (Yaptinchay, 1994). Its excessive use until today, affects not only our dugong population, but also destroys their habitat as well. Today, direct takes of the dugongs are not as common. Almost all of the catches today are incidental, although fishers will not pass off any opportunity to catch a dugong...

Respondents in surveys conducted in Palawan attributed fishnets as the most common device to capture dugongs. Dugongs are susceptible to net entrapment and eventually die from suffocation and stress a few minutes after getting entangled (Marsh and Anderson, 1983; Anderson, 1981; Heinsohn et al., 1976). Types of nets responsible for dugong nets are bottom set and drift gill net [pants], beach seine, purse seine and bag net [baring] (Kataoka et al., 1995). A fishing gear called fish corral or "bak lad" in the local language, which are usually situated on sea grass beds, has caused live entrapment of the dugongs (Yaptinchay, 1995). The dugongs are usually maintained alive for several days before being slaughtered.

Others die from sun exposure and dehydration during low tide. There were also several cases where the dugong caught would be kept alive in the hope of getting a large amount of money. Stranding of injured dugongs and calves after typhoons have also been reported. Utilization The slaughter of dugongs in areas where they are abundant cannot be overemphasized. Most of the reports come from Palawan. There were also unconfirmed reports of slaughter from Biol, Davao del Sur, Mindoro, Quezon and Palawan, Isabela, and reports of exploitation in the Antique and the Gui maras- Negros area.

The dugong is a prized delicacy. Captured dugongs are slaughtered because they provide high quality meat that tastes and looks like beef or pork. Many claim that the meat is so delicious and tastes even better than beef. The meat (which may reach up to 100 kilograms or more) is oftentimes distributed among families in the village. The meat is usually prepared by sun drying or cooked like beef or pork. It is priced at P 10.00-30.00 per kilo.

It was previously open sold in markets up until the time it was prohibited. Now, anyone who is caught responsible for the exploitation of the dugong is charged at least P 500.00. Other parts are used as follows. Body Part Local Uses Flippers For treatment of any disease Hair For treatment of indigestion and asthma Hide / Blubber Food (chi charon / soup), cure for kidney disorders, dried to make whips and canes, source of oil for export, used as scent base and candle Bones For treatment of asthma, relapse, stomach cramps and indigestion in humans (bones scrapings are added to a glass of drinking water); bone shavings are sprinkled on smoldering shells and smoke is inhaled by the mother and her newborn (this warrants a smooth recovery of the mother and wards off diseases that may afflict the infant); bones are grounded and mixed with feeds for protection against animal diseases (pests and parasites); aphrodisiac Teeth Same medicinal uses as bones; serve as a good luck charm; made into pendants Tusk Medicinal; used to drive bad spirits away; made into jewelry used to determine a safe journey Liver mixed with oil For treatment of rheumatism Male Genitalia Aphrodisiac and medicinal Gall Bladder For treatment of cholera, stomach ache, diarrhea Dugong penis Dried for treatment of gas pains, diarrhea, tooth ache Ecological Role of Dugongs The dugong is a truly unique animal, being the only herbivorous mammal whose preferred habitat is the sea. Dugongs, therefore, are primary consumers, occupying the second tropic level in the food web.

The role of dugongs in the ecosystem is not yet fully understood. They occupy a special niche in the sea grass ecosystem because they are the largest herbivore found there. They participate in this ecosystem directly by consuming sea grasses and indirectly, by competing with other organisms for sea grasses as the food source, e.g. with green turtles, or by removing sea grasses which provide shelter and substrate for other organisms (Heinsohn et al., 1977). Heinsohn et al. (1977) also states that dugongs stimulate energy flow and nutrient cycling by the rapid return and metabolism of the sea grass as fecal and excretory products. This in turn will provide a nutrient and energy base for the detritus of dead and decomposing sea grasses.

In Moreton Bay, where large dugong herds graze on vast sea grass beds, "cultivation grazing" occurs where dugongs feed in a single area for a month. This not only reduces sea grass abundance and biomass, but also affects species composition, age composition and nutrient status of sea grass species. It may also be responsible for spatial of sea grass communities (Preen, 1992). The dugong has also been observed to play host to commensal c such as remoras, bat fishes and pilot fishes. Underwater observations of a wild dugong in Busuanga, Palawan, showed fish species such as goat fishes, emperors, parrot fishes and rabbit fishes immediately approaching the grazed area as soon as the dugong transfers to another site.

Apparently, faunal assemblages cause the root and rhizome system of the plants to become exposed during grazing by the dugong. This provides an opportunity for fishes to feed on these associated fauna. Conservation The following are major reasons responsible for the difficulty in the protection of the dugong: ^other breed very slowly; a depleted population will have a problem recovering. ^other is a lack of sufficient data regarding population size, cause of mortality, birth rate, seasonal distribution and movement, and habitat requirement. This information is essential in formulating sound and effective conservation strategies. ^people use the same areas that dugongs need to survive, increasing the chances of conflicts between the two. Habitat destruction, exploitation, pollution and various disturbances all affect the dugong population. ^o Insufficient information dissemination campaigns, lack of concern by residents and officials living near dugong habitats, laws are not sufficiently implemented and most of all, lack of funds. Conservation efforts The Department of Natural Resources (DENR) issued Administrative Order No. 55 in 1991 to protect the animal from exploitation.

The killing, collecting, trading and possessing of the dugong except for scientific purposes is punishable by law. The Protected Areas and Wildlife Bureau of DENR has been conducting distribution and habitat surveys and at the same time undertaking information and education activities on dugong conservation. Further, an Inter-agency Task Force on Marine Mammals in the Philippines was created and mandated to conduct a nation-wide survey of dugongs and other marine mammals. Members of this inter-agency task force come from relevant government institutions, the academe, as well as private and non-government organizations. At present, studies on the dugong are being undertaken in order to gather as much information on its behaviour and habitat.

Ka bang Kalikasan ng Pilipinas or KKP is conducting a Dugong Research and Conservation Project in Dimakaya Island, Northern Palawan, Philippines. Among the studies and activities being done on the island are: the identification and characterization of sea grass areas; the development of an information and education campaign among the people of Dimakaya; and, the conduct of information seminars among the surrounding local communities to increase awareness on dugong conservation. Dugong rescues have also been successful, having at least five (5) dugong releases mostly in the Palawan area since 1992 to present. KKP is going to launch dugong rescue fund to help organizations and communities in other parts of the archipelago to release fund to help organizations and communities in other parts of the archipelago to release back dugongs accidentally trapped in fish corrals or caught in fish nets. KKP's Dugong Conservation Program was implemented July 1997 and focused on a nation-wide campaign to save the dugong. After an initial poster-making contest for children with the theme "Save the Dugong for Me", follow-up activities are conducted for school children all over the country.

A dugong puppet show and activity book was made available to children in key provinces of the Philippines. In addition, KKP aims to work towards the declaration of dugong-protected areas in critical areas identified as dugong habitats.

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