Both species are classified as Critically Endangered by the IUCN all subspecies are classified as Critically Endangered with the exception of the mountain gorilla, which is classified as Endangered. There are thought to be around 316,000 western gorillas in the wild, and 5,000 eastern gorillas. Lowland gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda. The mountain gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from 2,200 to 4,300 metres (7,200 to 14,100 ft). Although their range covers a small percentage of Sub-Saharan Africa, gorillas cover a wide range of elevations. Gorillas' natural habitats cover tropical or subtropical forest in Sub-Saharan Africa. Gorillas tend to live 35–40 years in the wild. The eastern gorilla is distinguished from the western by darker fur colour and some other minor morphological differences. They tend to live in troops, with the leader being called a silverback. Gorillas are the largest living primates, reaching heights between 1.25 and 1.8 metres, weights between 100 and 270 kg, and arm spans up to 2.6 metres, depending on species and sex. The DNA of gorillas is highly similar to that of humans, from 95 to 99% depending on what is included, and they are the next closest living relatives to humans after chimpanzees and bonobos. The genus Gorilla is divided into two species: the eastern gorilla and the western gorilla, and either four or five subspecies. Journal reference: American Journal of Primatology, DOI: 10.1002/ajp.Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. “I agree with Diane’s assertion that females are competing with each other.” Such prestige could be one reason why pregnant females fake oestrus: group sizes are limited, and females must curry favour with a male to stick around.īy delaying the pregnancy of others, females could also gain a reproductive advantage over competitors, says Tara Stoinski, a primatologist at Zoo Atlanta in Georgia, who found that pregnant female gorillas in captivity also time their sexual advances to coincide with those of other females. Unlike male mountain gorillas, which prefer to mate with fertile females, Doran-Sheehy’s silverback went for higher-ranking females, fertile or not. Another female named UG mated throughout her pregnancy, almost always when another female was trying to become pregnant. With only lactating – and therefore sexually inactive – females remaining, MK ceased offering herself to the silverback. Strategic sexįor instance, after one female, MK, became pregnant she mated with the silverback during three consecutive oestrus cycles of another gorilla, EB, who left the group afterwards. However, females seemed to time such post-conceptive romps with the fleeting fertility of another female. Her team recorded most copulations and all births among a human-habituated group of gorillas at the Mondika research centre in the Republic of Congo for 1147 days between September 2003 and January 2007.Īll five females gave birth to one infant during the study and all engaged in sex after pregnancy, the researchers found. “It’s what’s going on with the females in the group.” “It doesn’t have all that much to do with the males,” Doran-Sheehan says. Yet paternity isn’t an issue for silverback gorillas, which usually enjoy exclusive access to a harem of females. “All of the males think they could be the father of your offspring,” Doran-Sheehy says. Bonobos treat coitus like a handshake, while female chimpanzees mate during pregnancy and outside fertile periods, or oestrus, to gain support from males and to protect against infanticide. However, Homo sapiens and Gorilla gorilla aren’t the only apes who engage in recreational sex. This kind of competitive behaviour may even help explain how humans evolved into a mostly monogamous species, she says.
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