Silverback Gorilla

Taxonomy

• Kingdom: Animalia  

• Phylum:  Chordate

• Class:  Mammalia

• Family: Great Apes

• Order:  Primates 

• Genus: Gorilla Isidore  Geoffroy Saint-Hilaire, 1852 

• Species: Mountain gorilla

Evolution

• SubSpecies: Gorillas. Mountain Gorillas (G. beringei beringei),Western Lowland Gorillas (G. gorilla gorilla),Eastern Lowland Gorillas (G. beringei grauri) ,Cross River Gorillas (G. gorilla diehli).

• Time of existence: About 7 million years.

• Closest living relative: chimpanzees and humans 

• 3 ancestor: Catopithecus, Aegyptopithecus

Description:  

• Physical description: The face is black and hairless, with small eyes that are close together and large, prominent nostrils. Adult males are identified by a sagittal crest along the midline of the skull and an area of white hair on the back, which is why they are known as 'silverbacks.  

• Key characteristics: It has longer hair, jaws and teeth, but slightly shorter arms, than the other subspecies, the eastern lowland gorilla. Adult males grow a patch of silver hair on their back and hips, giving them the name 'silverback'. Size: On average, adult males weigh 160 kg, and adult females 98 kg. 

• Size: Silverback gorillas are about 4-6 feet tall, the tallest silverback recorded was 1.95 cm tall with an arm span of 2.8 meters and a chest of 1.98 meters wide. 

• Weight: Silverback gorillas weigh between 300 and 500 pounds, while females are between 150 and 250 pounds.  

• Life Span: In the wild, gorillas can live to over 40 years old. 

• Differences between Males and Females: Adult male gorillas, or silverbacks, will be close to twice the size of the females, have silver hair on their back, and have large bumps on the top of their heads called sagittal crests! Even with these indicators, it sometimes may be hard to tell young males and adult females apart. 

Description of Habitat

• How much rainfall: Gorillas primarily inhabit tropical forest habitats. Tropical forests are characterized as having little variance in temperature (around 23°C) and length of daylight (around 12 hours). 

• Plants: African alpine bamboo is the only indigenous bamboo species in Rwanda's Volcanoes National Park. It is the foliage of choice for the protected area's 700-plus mountain gorillas and golden monkeys, and a significant part of its tropical montane rainforest ecosystem. 

• Animals: Gorillas share their habitat with animals such as the African forest buffalo (Syncerus caffer nanus), African gray parrots (Psittacus erithacus), African forest elephants (Loxodonta cyclotis), Giant Forest Hog (Hylochoerus meinertzhageni) and leopards (Panthera pardus). 

• Temperature: Gorillas primarily inhabit tropical forest habitats. Tropical forests are characterized as having little variance in temperature (around 23°C) and length of daylight (around 12 hours).

• Terrain: Silverback gorillas live high in the mountains in two protected parks in Africa. They are also referred to as mountain gorillas. Silverback gorillas continually wander through their home ranges of 10 to 15 square miles, feeding and resting throughout the day. 

Distribution

• Continents found: Africa is the only continent in the entire world where mountain gorillas live and survive in their natural habitats. 

• Invasive at all: NO

Diet

• What does it eat: Gorillas stick to a mainly vegetarian diet, feeding on stems, bamboo shoots and fruits. Western lowland gorillas, however, also have an appetite for termites and ants, and break open termite nests to eat the larvae. 

• How often does it eat: There are actually about 142 varieties of plants represented in the silverback's diet, including bamboo, celery, nettles, thistles and succulent herbs. When they can get them, they also love to eat any wild berries they can find. To sustain their weight, they need to eat about 60 pounds of food every day. 

• How it gets its food: Gorillas are very selective foragers. They usually only eat parts of vegetation. For example they may eat only the leaves, pith, stalk, or roots of a particular plant. They use their agile lips and hand dexterity to manipulate the vegetation for the particular portion they want to consume. 

• Any special foods: Gorillas stick to a mainly vegetarian diet, feeding on stems, bamboo shoots and fruits. Western lowland gorillas, however, also have an appetite for termites and ants, and break open termite nests to eat the larvae. 

Social Structure

• Live in packs or Solo: Each has a lowland and upland subspecies. Gorillas live in family groups of usually five to 10, but sometimes two to more than 50, led by a dominant adult male—or silverback—who holds his position for years. The bond between the silverback and his females forms the basis of gorilla social life. 

• Roles within community: Gorillas are social animals that live in groups. A gorilla group usually has a harem structure of one adult male, or silverback, living together with several adult females (three to six) and their offspring. The task of the silverback is to lead and protect the group. 

• Male or Female led group: Male

• Individuals that make up the group: Gorillas are non-territorial and live in groups called troops that generally consist of 1 to 4 adult males (called silverbacks), some juvenile males (called black backs), several adult females and young. 

• How do they interact with each other: Gorillas communicate in a variety of ways, including facial expressions, sounds, postures and gestures. When things are calmer, gorillas often greet each other by touching their noses together, and will sometimes even give a reassuring embrace. The females align themselves with their leader, openly soliciting mating. 

Reproduction

• How often they mate: Gorillas may breed year round. Females are in estrus for 1 to 2 days per month and only the dominant silverback has breeding rights. Gorillas are polygamous in nature because the dominant silverback mates with several females in his troop. 

• How many mates do they have: The dominant silverback mates with all females in the group as soon as they begin ovulation. The moment when a female gorilla is ready to mate is not evident physically like it is in chimpanzees. In most cases, it is the female who initiates the mating process as soon as she ready. 

• Time of year for mating: There is not a specific mating season so that they can mate during any time of the year. Females are in heat for 1 or 2 days a month, but before they start having sex partners they must be separated from their born troop and start searching for a “silverback” male from another group. 

• Mating rituals: The dominant silverback can also initiate mating by approaching the female and touching her or making a display with a grunt. If the female is hesitant or resistant, the silverback may charge and slap the female to give in. 

•  Number of offspring at one time: Like humans, gorillas reproduce slowly, giving birth to only one baby at a time and then raising that infant for several years before giving birth again.  

• Unique characteristics of mating: Males incite copulation by approaching a female and displaying at her or touching her and giving a "train grunt". Recently, gorillas have been observed engaging in face-to-face sex, a trait once considered unique to humans and bonobos. 

Development

• Stages of development: Their life cycle is as follows: infant->juvenile->young adult-> mature adult. When they are born (after a gestation period of nine months) they weigh only four pounds, and cling to their mother until they are two or three. 

• How old before sexual maturity: Their life cycle is as follows: infant->juvenile->young adult-> mature adult. When they are born (after a gestation period of nine months) they weigh only four pounds, and cling to their mother until they are two or three. 

• Activities and environment of stages: Gorillas typically live in the lowland tropical rainforests of Central Africa for all stages of their life.: Adult male gorillas, or silverbacks, will be close to twice the size of the females, have silver hair on their back, and have large bumps on the top of their heads called sagittal crests! Even with these indicators, it sometimes may be hard to tell young males and adult females apart. Due to this difference in size and weight, the male gorilla is almost twice as strong as the female gorilla. 

Courses of death

• Predation: The mountain gorilla's only natural predator is the leopard. However, humans are the mountain gorilla's most significant predator. Humans hunt gorillas for meat and for trophies. They also kill gorillas for eating their crops, and poachers kill adults in order to capture the infants and sell them.

• Sexual Competition: While many conflicts between them are limited to aggressive displays like chest-beating (i.e., all bark and no bite), they do occasionally fight and kill each other one-on-one. They do this because only one male mates in a group of gorillas.

• Disease: Ebola is a widespread threat to gorillas and chimps in Central Africa, and may have spread to humans from people who ate infected animals. Ebola and SARS may both have originally come from bats.HIV, the virus that causes AIDS, originated from chimps and other primates. Gorillas may have given humans pubic lice, or "the crabs." There have been suspicions that chimps at Gombe Stream National Park in Tanzania contracted polio from humans, Leendertz said. There have also been concerns that gorillas contracted yaws, a disease related to syphilis that is not sexually transmitted, from humans, Leendertz added. Gorillas and chimpanzees in West Africa have been killed by outbreaks of anthrax. This may have originated from cattle herded by humans, although Leendertz noted these may have been natural events that just exist there in the forests.

• Other causes of death: Physical trauma.

Competition:  Bwindi gorillas exhibited higher rates of aggression while foraging on fruit than on other food resources, suggesting that contest competition increases as they forage on depletable, limited, and apparently monopolizable patches, as occurs in several other primate species.

• competition inter-species: Males have competition to be the alpha male so they can mate.

• Intra species: Apart from humans, gorillas don't really have enemies. The only predator to prey on gorillas is the leopard. Walter Baumgärtel found the remains of several gorillas after they had been killed by leopards in the Virunga Volcanoes.

• What do they compete over: Females and food

• Affect of invasive species:  no invasive species( that are not humans)

IUCN Rating

• What is the rating: Critically Endangered (CR) 

• Population: around 1,004 individuals 

• Population trend: Thanks to conservation efforts, the population of mountain gorillas has increased from 620 individuals in 1989 to around 1,004 individuals today. This number is likely to be accurate, as these animals have been intensely monitored since the 1950s. 

Impact of Humans

• What impacts have occurred: The gorillas, like all endangered species, already face so many human-induced threats—loss of habitat, hunting and poaching, and diseases. 

• Potential future impacts: EXTINCTIION

• How long have they been interacting with humans: 120 years

• Effects to help them: Through our African Great Apes Programme, we are actively working to protect all four gorilla subspecies through Stopping the illegal trade in gorilla products. Increasing support for gorilla conservation among both local and international communities.