Tim SandersonAnth 111In Malay orang means “person” and utan is defined as “forest’. ThusOrangutan literally means “Person of the Forest”.Orangutans are found in thetropical forests of Sumatra and Borneo. They are the most arboreal of the greatapes and move amongst the safety of the trees from one feeding site to the next.
They are so well adapted to arboreal life that they cannot place their feet onthe ground, instead they walk on the outside of their curved foot.There is a scattered population of orangutan in Indonesian Borneo,Malaysia Borneo and northern Sumatra. The different habitats have isolated theorangutan reproductively and geographically from one another creating a “degreeof difference” or two subspecies. There are several different characteristicsbetween the two subspecies of orangutans and it has recently been suggested thatthey may be a separate species. The Borneo male has relatively large cheekpads, a tremendous laryngeal sac and a square shaped face. The Sumatran malehas small pads and laryngeal sac, a ginger coloured moustache, a pronouncedbeard, and a diamond shaped face. Individuals can also be distinguishedchromosomally, biochemically, and by their cranial characteristics.
There is a great deal of individual variety in the orangutan. “Eachorang-utan had a distinct personality and in dealing with such highlyintelligent animals in captivity, the keeper’s knowledge of the individual wasprobably more important than the knowledge of the overall behaviour patterns “(Markham, 1980). Orangutan males, however, appear to be totally intolerant ofone another, especially the Borneo males who are even aggressive towards femalesand infants. Male orangutans’ participation in social groups is limited tosexual “consortship” with females. However, the Sumatran males tend to stay withfemales for a longer period of time usually until the birth of the infant.
They may stay longer with their partner because of the presence of largepredators absent in the Borneo habitat. The orangutan has a menstrual cycle of29-30 days, menstruation lasting 3-4 days. The Gestation period lasts slightlyless than nine months. Offspring pass through three stages, infancy (0-4),juvenile (4-7), and adolescents (7-10). Mother young relationship lasts for along time, the young usually stay with their mother until they are mature.Female Orangutans are not sexually mature or fully grown until the age of twelveand will not have their first offspring until they are at least fourteen. Malesbecome sexually mature and fully grown at the age of fifteen. The cheek flangesof the male easily recognize the differences between adults and semi-adults.
Theflanges in the Boreal male curve out ward from the face and develop around theage of eight and are not completely grown until the age of fifteen. Sumatraflange development begins at the age of ten and is not complete until the earlytwenties. The flange in the Sumatra orangutan lie flat against the face andgive a wide facial appearance especially in the mid facial region. The lifeexpectancy of orangutans in the wild is not known, but captive orangutans havebeen known to live up to fifty years.Orangutans are sexually dimorphic. Males are approximately twice thesize of females and weigh about 220 lbs. and reach a height of five feet.
It isbelieved that the males larger size may be an adaptation for mating becausethere is strong competition among males for females. The pendulous laryngealsac, when inflated, increases the tone of the animals voice, producing “longcalls”.In both subspecies (Borneo and Sumatran) calling acts as ” a spacingmechanism between the males and also advertise the location of the highestranking male to the mature females.” (Rijksen,1978). The long call of the Borneomale is long and drawn out where as the Sumatran is much shorter and has afaster tempo.
The difference may be attributed to the larger throat pouch theBorneo has. The reason for the different calls is unclear. They may be relatedto the terrain each subspecies inhabits. The faster call of the Sumatran may bemore effective in the rugged, mountainous terrain. The longer call of theBorneo may be due to the wide distribution of this race.A large portion of an orangutans day is spent looking for and consumingfood.
Their diet primarily consists of fruit but they also eat leaves, bark,flowers, insects, and birds eggs. One of their preferred foods is the fruit offof the durian tree, it is supposed to taste like sweet garlic. After they havefinished eating and bedtime comes around the orangutans build themselves a newnest forty to fifty feet up in a tree made of boughs.Like the other great apes (chimpanzees and gorillas), orangutans arehighly intelligent. Tests have indicated that their intelligence is relativelysimilar. Wild orangutans use their intelligence to solve problems usuallyrelated to arboreal living and food gathering. In captivity, however, they havebeen trained to perform tricks and to use sign language. They have also madetools to throw at humans, get food, and gain leverage.
Today, the total number of orangutans ranges between 20-27,000. Theyare now endangered primarily because their habitat continues to be destroyed andthe practice of killing the mother in order to capture a baby for animal trade.Even though they are protected by international laws, it is difficult to enforcethem.Orangutans are inhabit the forests on the islands Sumatra and Borneo.Through evolution and reproductive and geological isolation two sub species haveemerged (Borneo and Sumatra). They generally live alone with the exception ofthe long term relationship between a female and her young.
When orangutans domeet one another they are very tolerant and aggression is rare, unless twomature males meet each other. Males maintain their distance from on anotherwith “long calls”, these also advertise their location to adult females.Orangutans are generally fruit eaters, because fruit is abundant in the foreststhey inhabit. They lead a very solitary life.The population continues todecline because of habitat loss, and fewer than 30,000 orangutans are thought toremain in the wild.Category: Science