Chimpanzee

The **chimpanzee** (*Pan troglodytes*), or **robust chimpanzee**, is a species of great ape. The common chimpanzee is often called the chimpanzee (or "chimp"), but this can refer to both species in the genus *Pan*: the common chimpanzee and the closely related bonobo.

Evidence from fossils and DNA sequencing show both species of chimpanzees are the closest living relatives to modern humans.

## Description 
The common chimpanzee is more  than the bonobo. Adult chimps are 150 cm (4 ft 11 in) tall on average. In the wild, adult males weigh between 40 to 70 kg (88-154 lb), while adult females weigh 27 to 50 kg (60 to 110 lbs). 

Its gestation period is eight to nine months. Infants nurse for up to 5 years, then stay close to their mothers for several more years. They reach puberty between ages eight and 12. 

The species lives in a male-dominated strict hierarchy with an alpha male at the top. The others then each took parts of the carcass, sharing with other members of the troop in response to begging behaviours. This was a major scientific discovery: it challenged previous ideas of chimp diet and behavior.
Goodall’s Gombe data have also led researchers to take a closer look at the role that hunting plays in chimp feeding habits. One recent Gombe study, for instance, concluded that the 45 members of one troop ate *a ton of monkey meat per year*. During one hunting binge, chimps killed 71 colobus monkeys in 68 days; one chimp alone killed 42 monkeys over five years. All told, chimps may kill and eat a third of the Gombe’s *Colobus* population each year. Researchers have also found that lower-ranking males often trade the meat for mating privileges; such trades may help prevent inbreeding by keeping a single group of males from fathering the majority of a troop’s children.

She later said:During the first ten years of [my] study I had believed […] that the Gombe chimpanzees were, for the most part, rather nicer than human beings. […] Then suddenly we found that chimpanzees could be brutal—that they, like us, had a darker side to their nature.These findings revolutionized our knowledge of chimpanzee behaviour. They were further evidence of the social similarities between humans and chimpanzees.

## Aggression between groups
If they can, male chimpanzees try to kill the male members of neighbouring groups. Males work together when they spot a chance to make a lightning raid on an isolated male from another group. They kill him. During the Gombe Chimpanzee War in the 1970s, a group of chimps killed seven of their neighbours one by one, until all were gone.  

It can take years for this to happen but, when it does, the remaining females and the neighbouring territory are added to the now larger group. Attacks like this are carefully planned, done only when success is likely, and carried out in silence. Their behaviour is quite different from any other behaviour known in chimpanzees: About every two weeks, males are drawn by some unknown signal to walk very quietly, single file, into a neighbouring territory to attack a vulnerable male... the overwhelming targets are other males.

The advantage for the males that win is to breed more children. Their tribe also holds a larger territory, and so has access to more food. Several authors have drawn a connection between this behaviour and the origins of human warfare.

## Endangered status 
The common chimpanzee is listed on the IUCN Red List as an endangered species. There are between 170,000 and 300,000 individuals. They live in the forests and savannahs of West and Central Africa. The biggest threats to the common chimpanzee are habitat destruction, poaching and disease.

## References