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The Zoo has two gorilla troops. One includes Jabari, the silverback, and Honi. The second is a bachelor group consisting of two young males, Louis and Kuchimba. Jabari and Louis arrived together from the St. Louis Zoo on July 13, 2004. Honi and Kuchimba arrived together from the Bronx Zoo on March 14, 2007.
Jabari: Male, born February 5, 1985 at the Brookfield Zoo in Chicago.
Louis: Male, born May 12, 1999 at the St. Louis Zoo. Jabari's son.
Kuchimba: Male, born June 29, 2002 at the Bronx Zoo to Honi.
Honi: Female, born September 7, 1994 at the Bronx Zoo. Honi is Kuchimba's mom.
PECO Primate Reserve
Scientists now think that there are two species of gorilla, the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei). Almost all gorillas in zoos are western gorillas, of a subspecies called the western lowland gorilla (Gorilla gorilla gorilla). The other western gorilla subspecies is the very rare Cross River gorilla (Gorilla gorilla diehli). The mountain gorilla (Gorilla beringei beringei), made famous by the work of Dian Fossey, is one of the two subspecies of eastern goriila. The mountain gorilla is the most studied of the four types of gorillas and is the one on which most information is based. The other type of eastern gorilla is the eastern lowland gorilla (Gorilla beringei graueri).
Gorillas are the largest and heaviest living primates. Average size varies among the different types of gorillas - the western lowland gorilla typically found in zoos is not the largest of the gorillas. Western lowland gorillas are covered with thick, dark brown-gray fur, which appears almost black, and they have a brown patch on the top of the head. As they mature, male gorillas develop silvery colored fur on their back and, hence, are known as "silverbacks." A gorilla's face is black with no fur, and the heads are conically elongated, particularly in adult males. Gorillas have the same number (32) and arrangement of teeth as humans do. However, their teeth are much larger than humans' - the canines are particularly big, especially in males.
Gorillas are primarily terrestrial. Western lowland gorillas live in tropical lowland forest.
Western lowland gorillas, although still the most abundant of the four types of gorillas, are now considered Critically Endangered in the wild, due to losses from poaching and disease. Conservationists estimate that the total population has declined by more than half (perhaps 60%) over the last 20 to 25 years. Most areas, even protected reserves, have serious poaching problems and almost half of the protected habitat has been affected by Ebola virus.
Gorillas may live as long as 50 years in zoos, with a more typical lifespan being around 34 years of age. The Philadelphia Zoo's Massa held the longevity record of 54 years at the time of his death in 1984. Wild gorillas can live 35 years or more.
Females may reach sexual maturity at about 6 years old and males at 10 years old, but both sexes may not actually reproduce until several years later. Like humans, the gorilla does not seem to have any particular breeding season, and births occur throughout the year. The female cycles every 27-35 days, and pregnancy lasts for about 8.5-9 months. Normally a single youngster weighting 4-5 pounds is born, although twins have been recorded. In contrast to many other primates, gorilla babies cannot cling to their mothers right away and have to be supported by the female. Youngsters usually nurse for 3-4 years.
Chest-beating is done by all gorillas, not just by adult males, and involves clapping either one or both hands against the chest. For adult males, chest-beating is usually a threat display, but it may also just indicate general excitement, particularly in youngsters. Aggressive displays can also include ground beating, tearing up of vegetation and short sudden sideways rushes.
Grooming appears to be infrequent compared with many other primate species. Most grooming is seen between mother and infant, but occasionally subordinate individuals groom the dominant male. Gorillas are diurnal. Each day they build sleeping nests out of tree branches and foliage, either on the ground or sometimes in a tree. Gorillas spend most of their time on the ground but will climb trees to forage for food, rest and sleep. Females and young seem to climb trees more often than males.
Unlike other primates that move on all fours, which support their weight on the palms of the hands, gorillas support their weight on the backs of the third and fourth fingers of the curled hands. This type of locomotion is called "knuckle-walking".
Males can measure 5-6 ft (152-183 cm) tall when standing erect and females stand up to 5 ft (152 cm) tall.
Males weigh 300-600 lbs (136-272 kg). Females weigh about half as much as males.
In the wild, western lowland gorillas eat mostly fruit, leaves and other plant parts. In at least some areas, gorillas may eat termites and other small insects. In the Zoo, gorillas receive nutritionally complete primate chows plus a wide variety of fresh produce including oranges, apples, carrots, grapes, kale and other types of greens. They also receive puffed cereal, popcorn, raisins and seeds that are scattered outside in the grass or inside in hay to encourage foraging behavior.
The western lowland gorilla is found in the countries of Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, and Nigeria. The mountain gorilla is found in Rwanda, Uganda and Zaire.
On the 2011 IUCN Red List for Threatened Species, the western lowland gorilla is listed as Critically Endangered.
Western lowland gorillas, as well as the other subspecies of gorillas, are considered endangered by IUCN and CITES. CITES classifies this species as most restricted and threatened with extinction. Gorillas are threatened by human population growth, expansion of agriculture, logging, mining and cattle ranching. They also are hunted for bushmeat, which is currently a major threat to their population. Recent western lowland gorilla population estimates were approximately 100,000 in the wild, mostly in the Congo and Gabon. Numbers today may be substantially lower, due to hunting pressure and disease outbreaks. The other types of gorillas survive in much smaller numbers, with estimates of 8,000-17,000 for the eastern lowland gorilla, only 150-200 for the Cross River gorilla and 600 for the mountain gorilla.
The breeding program for this species is managed on a national level by a Species Survival Plan organized by the American Zoo and Aquarium Association (AZA).
To learn more about the conservation efforts at the Philadelphia Zoo, click here.
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