Study Of Gorillas


Study Of Gorillas Essay, Research Paper

Los Angeles Zoo OBJECTIVE The purpose of this observation was to study the activities and behavior of some selected primates, and to discuss the differences and similarities of these primates. It would have been ideal to examine three primates from each continent, but at the Los Angeles Zoo, the primates there only represented Africa, South America and what the Los Angeles zoo calls “Eurasia.” For this study I observed three different primates from Africa, two primates from South America, and two primates from “Eurasia”. I wasn’t able to observe any primates from Australia or Northern America at the zoo. RESULTS The primates that I observed from Africa were the Colobus Monkey, the Ringed tailed Lemur, and the Western low land Gorilla which are all Old World Primates. The primates I observed from South America were the Howler monkey, and the Uakari. The primates that were observed from “Eurasia” were the Orangutan and the Siamang. HABITAT The primates of South America have been undergoing loses to their habitat and the study of non-human primates play an important role to public health. They are valuable to helping discover new vaccines, and they are also beneficial to helping humans understand diseases such as diabetes, malaria, AIDS, yellow fever, mental disorders, and some forms of cancer. Therefore the availability of non-human primates for biomedical purposes is very important, but there has been major threats to their environment both in South America and in Africa. The major factor contributing to the decline of the non-human primate populations is habitat destruction. More than 90% of all primates dwell in tropical forests, and as these forests continue to disappear, so do these primates. The primates are having to make major adaptations, as their habitats are constantly changing because of agriculture activities. Of the 76 species of New World Monkeys in the world, as of 1990, 28 of these species are on the endangered list. Of the 20 primates at the Los Angeles Zoo, 9 of then are endangered species. DISCUSSION/CONCLUSION SOUTH AMERICA Howler Monkey Howler monkeys are in the class Aloutta and are simian new world monkeys. They eat tough green vegetation and have strong dentition to eat through their foods. Howlers can be found in the Andean forest, at altitudes of 2,800 m above sea level. These primates moved among branches and trees, but they didnt display the jumping or hoping like the Colobus and the Lemurs did. In fact they didnt move fast in the trees, and when they moved from branch to branch, they would pull the branch inward that they were moving to, then they would swing on it. Ukari The Ukari is known as Cacajao calvus, a New World Monkey, and are expected to be found dwelling in tropical regions of Columbia. There are usually found in the forests of the low lands, under 1000 m above sea level. AFRICA Western Low Land Gorilla The Western low land Gorilla is among the largest Gorillas of the four great apes; which are the Gorilla, Orangutan, Large Chimpanzee and the Pigmy Chimpanzee. They usually grow about 6′2″ and over 400 lbs. They roam the dense moist forest of Africa in groups of 2-30 members. Their time is divided between feeding and resting. At night these gorillas make night nests from vegetation. These are peaceful animals and will not attack unless they are molested. These primates were among the slowest moving primates that I observed at the zoo. The gorilla I observed was in the same location with four other similar gorillas. The one I observed was a smaller female who was doing a lot of scratching. When I first noticed her she was scratching her forearm and her nose. This gorilla later walked across to the other side of the exhibit. She sat down in the grass with her back facing the crowd, eating off the ground. She was picking in the grass at small objects, picking them up and eating them. She was sitting next to the largest gorilla, who was probably the father, but there was no interaction among the two. After about five minutes of sitting stationary, the gorilla walked back to the original location, then walked behind a large rock out of sight. The large father gorilla that the female was sitting next to earlier, never moved from his sitting position against the rock wall. in the middle of the exhibit. The only part of his body that moved was his head and neck. When one of the other gorillas were moving around, the father would just look around to see what was going on, but would never get up and walk. The first female came back into vision, eating some grass. When she was finished eating the grass that was in her hand, she would grab some more grass from the ground using her mouth instead of her hands. After she grabbed plenty of grass with her mouth, she walked off on all four limbs, out of sight. At the same time that this gorilla was walking off, another female was laying on her back on the grass masturbating. This is called rhythmic genital rubbing(rgr) and it is very common in captive gorillas.(Michael p523) I also observed a male engaging in rhythmic pelvic movements(rpm) against a rock. The rgr can be done by one gorilla to another, and also by the same sex. The menstrual cycle of these gorillas is 31 days. Ring Tailed Lemur The scientific name for the lemur is lemur catta, and it resides in the arid, rocky regions of Madagascar. It enjoys eating fruits, insects and eggs. The Lemurs are only found on the island of Madagascar, off the eastern coast of Africa. Although they have dog-like faces, their long bushy tails, mobile limbs, grasping hands and feet, and digits bearing nails makes them primates. The reason why they only inhabit Madagascar is not fully understood. It is believed that these primates where marooned on this island when it started to separate from the African mainland. (Tatersall p110) Lemurs are lower primates, and are the only lower primates active in the day(diurnal). Most all higher primates are diurnal. Lemurs have smaller brains relative to body size than do higher primates. They also have roomier nasal cavities than higher primates, with complex internal structures. The eyes of the Lemurs a forward-facing, and the left and right visual fields dont overlap. Many of the lower primates like the lemurs have scent glands. With their large nasal cavities lemurs explore their environment with their noses. When a lemur would chose fruit to eat they will smell it rather than chose it by its appearance. The lemurs were one of the fastest moving primates that I saw at the zoo. They not only jumped from tree to tree but they were extremely mobile on land. They rarely stood still for more than a few seconds and they moved on all four limbs, They were dwelling in a large free area, where they had the option to jump right out the exhibit into the walk way. They appeared to be very furry animals with stripes through its tail. Colobus Monkey Colobus are from the central and eastern parts of Africa. They are strictly leaf eaters and they have saculated chambered stomachs for digesting the coarse vegetables they consume. When they are born they are pure white, but with-in six months they take on the dark adult color, and they have been hunted for their furs. The adult Colobus monkeys have long white tails, and a white ring of fur around the edges of their faces. They are about raccoon size, with a tail that appears to be longer than their body. Their backs are partially white and there fur are very bushy. I observed these monkeys mostly engaging in swinging and jumping, but unlike the lemurs they were in a smaller confined environment that was covered with a fence above them. There were several logs hanging from the fence above with chains inside their zoo habitat. There was a lot of branches with much green vegetation spread all over their entire habitat, which they frequently were eating. There was also a bucket of pealed mangos on the floor near the back. The Colobus monkey were smaller than the ring tailed lemur, and they ate more than any of the primates I observe. They were the most active of all the monkeys, maybe contributing to their frequent eating habits. I observed a Colobus trying to pull a small branch with leafs on it, so he can eat. He appeared to not have enough strength in its small body to pull the branch loose. While standing on a log, he gripped the branch with both of his hands, then used it as a vine to swing. It detached immediately and he then landed on a lower level log. I thought that his method was an intelligent way to use his body weight to break off the branch. After he landed on the lower level log he began to eat all the leaves off the branch. Another monkey was sitting on a log on its hind legs eating a mango. Another monkey jumped on the same log and tried to unsuccessfully take the mango away, and the first one didnt want to share its fruit, so it jumped away to a lower log and ate in solitude. EURASIA Orangutan Orangutans are in the class pongo pygmaeus and are one of the four great apes. They walk on the palms of their hands similar to how human infants crawl but they cant travel rapidly in this fashion too long. This quadrupedal locomotion is so tiring to the primates, that they will start to somersault to their destination. The only way that Orangutans can travel long distances without exhausting themselves are by means of using trees. The Orangutan and the Siamang both have this characteristic in common, and are both from Asia, and when they are required to travel in large open areas between batches of trees, they become easy prey for any carnivores, because their rate of progression becomes very slow. Orangutans engage in human like activities like face-to-face copulation, comprehension of speech, tool manufacturing and imitation. Orangutans are similar to Gorillas in the area of intelligence and communication. These similarities are due to their common ancestry. They both also use gestural communication. Gorillas and Orangutan males posses the largest canines and display the lowest degree of male-male bonding, and have the highest degree of competition for females. Males have been observed having sex with unreceptive females and sometimes rapraping the female when she tries to escape. These rapes usually last 10 minutes but in captivity these rapes vary in time and the females adapt to their mates, becoming less timid.(Michael p261) Siamang The Siamang was a primate I found at the zoo in Eurasia and its class is Hylobates syndactylus. Most of all Siamang primates are found in Malayan forests, They are dark brown with a woolly texture fur that covers their entire body. Unlike the low land gorillas I observed, Siamangs males bond only with females. Homosexual contact is not common among Siamangs. The Siamang locomotion on the ground is very rare, and they have non anatomically adapted bipeds, whose main mode of transportation is brachiation. At the zoo they where in a tropical looking setting with many trees, branches and vines. I observe them climbing and swinging most of the time, and when they would stop swinging they would remain stationary on a supported branch. I didnt notice them eating as much as the other primates. Bibliography 1. Michael, R.,1973, Comparative Ecology and Behavior of Primates, Academic Press, London. 2. Quiatt, D., 1994, Homonid Culture in Primate Perspective, University Press of Colorado, Niwot, Colorado. 3. Tattersall, I., 1993 January, Scientific America, Madagascars Lemurs, pp110-117. 4. Waal, F., 1989, Peacemaking among Primates, Harvard University Press, London England.

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