Gorillas have been termed as the largest living primates, which inhabit the African forests. They are also ground-dwelling, as well as being herbivores. Due to their similarity in DNA to that of humans, they are seen as the closest human living relatives.
Both the tropical and subtropical forests offer habitats to the gorillas. There are three species of gorillas; Western Gorilla, Lowland Gorillas, they inhabit dense forests, lowland swamps, and sea-level low marshes.
The lowland gorillas are considered to be an endangered species. Their numbers in the wild have been decreasing at a very alarming rate. Human activities have led to the exploitation of gorillas and their habitats. This means that they are under severe threat from poaching, conflict & habitat destruction. Their remaining populations if not protected and their habitats conserved, they may be on the verge of extinction.
There are two species of lowland gorillas; the western lowland gorilla (Gorilla gorilla gorilla) and the Eastern lowland gorilla (Gorilla beringei graveri). The Mountain Gorilla falls under the major class of Eastern Lowland Gorilla. Mountain gorillas are the darkest in color, followed by the Eastern gorilla, and the western gorillas respectively. The thickest body hair is found in the mountain gorillas. Lowland gorillas are more slender than mountain gorillas that are bulkier. They in addition have shorter hair, and arms that are longer.
In terms of the distribution, the Western Lowland Gorilla is found in montane primary and secondary forests. Also found in the lowland swamps. In Africa, western lowland gorillas are found in Angola, Cameroon, Central Africa Republic, Gabon, Equatorial Guinea, and the Democratic Republic of Congo.
The Eastern Lowland Gorilla, which is a subspecies of the Eastern Gorilla, inhabits the Democratic Republic of Congo forests along the border with Uganda & Rwanda only. (The Columbia Encyclopedia, 6th Edition).
Gorillas live in varying habitats. This is due to their adaptations to the environment or the habitat in which they exist. The habitat of the lowland gorilla includes the montane primary and secondary forests, lowland swamps, and marshes. Equatorial forests in central Africa offer a great home to the gorillas.
Their behavior varies slightly with the species. They also have behavior flexibility that promotes their co-existence with each other. Gorillas live in social groups known as troops. The group size is between 5-30 individuals. Each troop is lead by a ‘silverback.’ A silverback is a strong dominant male in the troop. The ‘silverback’ name comes from the patch of silver hair on the back of the male gorilla. The dominant male is more than 12 years old. Sexually mature males of up to 11 years of age are known as the ‘Black backs.’
The silverback is the leader of the troop and enjoys the troop’s attention. It has its other roles that include; making all the decisions on behalf of the troop, mediating conflicts that may arise, determining the movement of the troop, leading others to the feeding sites, and providing security for the troop. The ‘black backs’ give backup protection for the troop. These are young mature males in the troop, who instead of a silverback have a black back. They become the silverbacks after they form other troops and become completely mature.
After birth, offsprings remain in the troops that their mothers belong to. This they do until they can become mature and fully independent. At seven to eight years old, female gorillas become sexually mature. They do not breed until they are ten years or older. The gestation period lasts 8½ months. After birth, the young can walk within 3-6 months. At 3 years of age, their mothers wean the young. They remain in the troop where they learn and undertake other troop activities until they become sexually mature. After reaching their sexual maturity (between ages 7 and 10), young gorillas disperse from their natal troops to seek new troops or mates. They emigrate to go and form new troops. Females can either form new troops or join other troops of unrelated individuals. The males can form a bachelor group until they can form a troop with the females or even fight with the Silverback If a Blackback wins over the Silverback, then he can take over the troop.
Females disperse into a new group of their choice. Males also move out to form new troops. During their development, young gorillas play very often. The silverback tolerates them in their play and even participates in the play of both the older juveniles and black back males. Young gorillas older than 3 years make nests, which they use for day and night resting. The nests are made by sitting in one place, then pulling down and tucking branches, or leaves around themselves. Young gorillas exhibit arboreal behavior compared to adults. Gorillas have a lifespan of about 35 years in the wild and up to 54 years in zoos.
Their home ranges vary from 2.7 to 5.5.km² for Eastern Lowland Gorilla and 7-14km² for the Western Lowland Gorilla. Their home ranges are influenced by the availability of food. For example, fruits form a very important component of a gorilla’s meal. During the season where fruits are in plenty, the troops may not travel great distances in search of food. Where there is a scarcity of fruits or even plants, gorillas may cover quite a large distance in search of food. The Silverback makes the decisions on when to feed, where to feed, and how far the troop should go in search of food. The troop feeds early in the morning and in the evenings. The gorillas rest during the midday hours. This gives them more time to rest and play (for the young), before returning back to feed in the evening.
Aggressive behavior has been observed in the gorillas. The Western lowland gorilla is non-aggressive, quiet, and peaceful unless it is provoked. Males, however, show aggressive behavior, when they are fighting over the acquisition of females. The males will often fight over who should mate with the females. This is known as reproductive aggressive behavior. In the troop, the Silverback has full rights to mate with the females and may only give the blackbacks the chance to mate with the females. This may even result in the killing of an unrelated male. This aggressive behavior may cause the female to go into estrous. This facilitates an increased reproduction rate in the gorillas.
An adult dominant male protects the troop from the intruders. The male shows defense aggressiveness, by standing on his legs and slapping his chest using his cupped or flat hands. Great roaring and screaming accompany this. If the intruder refuses to retrieve after this, the male then rears his head back violently a number of times.
In addition, the male may drop on all fours and charge towards the intruder if the intruder further refuses to retrieve. They do not hit the intruder when they charge towards them. Order is maintained in the group and the possibility of injury is reduced in this form of aggressiveness. This can be looked at as behavior flexibility. The larger males always win against smaller males, since they are much larger physically and can easily injure the smaller males. The fact that it is also the leader of the troop and it should protect the troop increases its aggressiveness towards the smaller males or the intruders. Reproductive aggressiveness is exhibited in the gorillas.
In reproductive behavior, only the dominant males in a troop mate with the females. The dominant male has full rights to mate with the females. The younger males may mate with the females, only when given a chance by the dominant male. The males’ fight over the acquisition of mates. This may result in the death of some males due to the injury afflicted on them during the fighting. The Silverback male has full rights to the females in his troop. The other sub-adult males may also be allowed to mate with the females and this may be a mechanism of the males to avoid injuring each other.
Both males and females leave their natal groups after their sexual maturity. They then form new groups with other individuals from other troops. The gestation period of the gorillas is 8½ months. The females have an interval of 3-4 years between births and this has contributed to a low reproduction rate in the gorillas as compared to the other primates. After birth, the mothers stay with the infants for a period of between 3-4 years. Both males and females disperse from their natal groups after reaching their sexual maturity (7-10 years). Recently, gorillas have been seen to show a trait that is unique to both humans and bonobos. They were observed to engage in face-to-face sex (http. //www.msnbc.msn.com/id/23148063/).
Communication behavior is observed in the gorillas. Gorillas communicate using various forms of expression. One of the ways is through auditory signals. This is whereby they use vocalizations or voices, for example roaring and screaming. Another form of communication is through visual signals. This includes the use of gestures, body postures, or facial expressions. Individuals can be able to pass messages from each other through their body language. For example, the slapping of the chest, when showing its aggressiveness. They also use olfactory signals, which is the use of odors.
Gorillas scream or roar when approached by an intruder. This alerts the individuals of the troop that they should be vigilant since an intruder has been spotted. Breaking of branches and baring of teeth is done in case of an intruder. (Glass, Bonnie, 2001. Evolution of the Human)
Their foraging behavior indicates that the gorillas are predominantly herbivorous. They eat mostly leaves. They eat a few leaves from a single plant in order to allow the re-growth of the plant for their future survival. They in addition consume fruits, seeds, and insects. Fruits form a very important component of a gorilla’s diet when the fruits are easily available. They eat stems of herbs, shrubs, and vines. Sometimes they may eat insects, and they have been observed to have a preference for the ants.
The consumption per day of the male gorilla is about 32 kilograms. The females consume about two-thirds of the amount consumed by the male. Gorillas feed during the morning hours and in the evenings. Resting and taking a nap are done during the midday hours before they resume eating in the evening. They cover a small area of the forest at any given time. Where the food might be scarce, they travel a long distance to search for the food. The gorillas wake up just after sunrise to search for food, rest for few hours then go back to forage again after midday. The silverback regulates the time of the troop waking up, eating, and sleeping. (Looking at Ape Diets).
Eastern Lowland gorillas depend on fruits, for example, fruits comprise 25% of their total diet when fruits are abundant. They also feed on insects, and eastern Lowland gorillas have a preference for ants. Their large home range is a result of traveling long distances in search of fruits (btw 2.7 to 6.5km²) when they are not in abundance in a particular area.
Fruits are very important in a western lowland gorilla’s diet. Fruits are found across their range, widely available during the fruit abundance season. For example, forest habitats may offer a variety of fruit types due to the great diversity.
Behavior flexibility contributes to the gorilla’s social behavior. The lowland gorilla inter-unit interaction can occur frequently. This interaction helps reduce the aggressiveness of the individuals towards each other. The gorillas’ behavior can also be more variable in nature.. The inter-group encounters include the avoidance of aggressive conflicts, which may result in serious injuries. By the inter-group interactions, the individuals can be able to tolerate each other’s presence and this avoids their aggressiveness to each other. There is also a peaceful intermingling of groups.
The Social organization of the gorillas has been studied Gorillas live in groups known as troops, which are made up of between 5-30 individuals. The composition of the troop includes a silverback male, one or more black males, and several adult males together with their infant and juvenile offspring. After sexual maturity, both males and females disperse from their natal groups, to go and form a new group. This prevents inbreeding. (Groves, Colin, 2005)
A female may change groups a number of times in her life, this can be termed as transfer of the female from one troop to the other. Dispersed males may spend a few years as solitary males before forming a new group. When non-related females join a lone male, a new group may be easily formed. A female makes a choice on which troop she should join in relation to the factors such as the fitness of the dominant male in that troop.
The silverback male is the most dominant male. He is the leader of the group, which gives him exclusive rights to mate with the females. The silverback makes all the decisions of the troop (when to wake up, eat and sleep). He also mediates disputes that may arise in the troop and leads others to the feeding sites. Sites that provide abundant food for the whole troop are given more preference. Scarcity of food will result in the decision of the male to select other sites that provide more food. He provides security to the troop, and will aggressively defend the troop from intruders. The black backs (young males) provide a backup defense to the dominant male when the need arises.
The members of a troop communicate through vocalizations, body gestures, facial expressions, and odors. They wake up early after sunrise to feed as a group, during the mornings and later in the evenings. Some gorillas may make loud noises during copulation. The middle of the day is spent, sleeping, playing, or a silverback. At night, gorillas sleep in nests that are made of leaves and branches. The mothers sleep together with their infants.
Also, at midday, the adults take a rest and normally take a nap. While the adults take a rest, the young wrestle and play games. Infant play behavior is even tolerated by the silverback that may even participate in the play of both older juveniles and the black back males. This assists the young in their growth and development.
Conservation of the gorillas is very important considering that, they have been classified as endangered species. They are unique in that they are the closest living relatives of human beings. Their DNA has been said to be 97% similar to that of human beings. Many decades ago, gorillas enjoyed living in the vast tracts of forests. This has changed with human activities endangering their existence. It is estimated that the number of gorillas in the wild has declined so drastically over the years. Various factors have contributed to this.
The ever-increasing human population has put so much pressure on the habits of the declining primates. Expanding populations demand increased resources in order to support these populations. Resources have been therefore overexploited to satisfy the ever-increasing human needs. Natural resources provide a means of earning income to the communities that surround the gorilla’s inhabited areas. The logging of trees has resulted in the devastating effects of deforestation. Water catchments areas that act as a water source for both the community and the species diversity in the habitats are drying up. Roads have been created for logging trees in their habitats. This has promoted intensive logging of the forests. Advanced technology is being used to cut down the trees and transport them to the market. This has in turn encouraged other exploitation methods, For example, logging opens new roads for people to burn charcoal from the trees in that habitat, in order to get fuel.
Hunters kill and capture gorillas for meat or pets (young ones). Poachers have killed large numbers of gorillas in order to benefit from their meat. The Bushmeat market has led to the gorilla meat be sold both in city markets and restaurants. Civil wars in both Rwanda and the Democratic Republic of Congo have hindered the conservation efforts of the gorillas. Snares have also been used to kill and injure gorillas.
Low incomes for the local communities cause them to turn into killing gorillas for their meat as an alternative protein source (food). Some meat may be used in the subsistence setup while the rest is diverted to the markets. Increasing demand for meat and increasing prices encourage exploitation. Their skins can be traded in the market for use in the textile industries.
These factors have driven the gorilla populations to the verge of extinction. The outbreak of diseases like Ebola has also contributed to the death of gorillas (New Scientist.com). Creating awareness and educating the people on the importance of conserving both the species and the habitats is important in our conservation efforts. Enforcement of laws should be done to save this primate from extinction. The habitats should be protected from loggers and hunters. Deforestation of destroyed habitats, increased political stability, better public awareness, and well-protected parks would assist increase the numbers of gorillas as well as mitigate activities that undermine them.
Conclusions
Nature and its resources support human existence. It is therefore very important for us to prevent the destruction of these resources. Gorillas have been said to be the closest relatives of human beings. Their value to existing overweighs any economic gain from killing them. It is our duty to ensure that, this great ape continues to exist. Conserving its habitat, and protecting it from execution will be the only way out to save them.
References
Caught in the act! Gorillas mate face to face.
Glass, Bonnie B: (2001). Evolution of the Human.
Gorillas infecting each other with Ebola New scientist.com. Web.
Gorilla (Sixth Edition)– The Columbia Encyclopedia, bartieby.com. Web.
Groves and Colin. 20065. Mammal Species of the World. 3rd Edition, John Hopkins University Press, 181-182.
Looking at Ape diets, myths, realities and Rationalizations. Beyondveg.com. Web.