Editing Gorilla (section)

=== Social structure {{anchor |Group life}} ===
{{redirect2 |Blackback |Silverback ||Blackback (disambiguation) |and |Silverback (disambiguation)}}
[[File:Silverback.JPG|thumb|Silverback with female]]
Gorillas live in groups called troops. Troops tend to be made of one adult male or silverback, with a harem of multiple adult females and their offspring.<ref name="Watts 1996">{{cite book |last=Watts |first=D. P. |year=1996 |chapter=Comparative socio-ecology of gorillas |editor1-last=McGrew |editor1-first=W. C. |editor2-last=Marchant |editor2-first=L. F. |editor3-last=Nishida |editor3-first=T. |title=Great ape societies |location=Cambridge, UK |publisher=Cambridge University Press |pages=16–28}}</ref><ref name="Yamagiwa 2003">{{cite journal |last1=Yamagiwa |first1=J. |last2=Kahekwa |first2=J. |last3=Kanyunyi Basabose |first3=A. |year=2003 |title=Intra-specific variation in social organization of gorillas: implications for their social evolution |journal=Primates |volume=44 |pages= 359–369 |pmid=12942370 |doi=10.1007/s10329-003-0049-5 |issue=4 |s2cid=21216499}}</ref>{{sfn|Robbins|2001|pp=29–58}} However, multiple-male troops also exist.<ref name="Yamagiwa 2003" /> A silverback is typically more than 12 years of age, and is named for the distinctive patch of silver hair on his back, which comes with maturity. Silverbacks have large canine teeth that also come with maturity. Both males and females tend to emigrate from their natal groups. For mountain gorillas, females disperse from their natal troops more than males.<ref name="Watts 1996" /><ref name="Stokes 2003" /> Mountain gorillas and western lowland gorillas also commonly transfer to second new groups.<ref name="Watts 1996" />

Mature males also tend to leave their groups and establish their own troops by attracting emigrating females. However, male mountain gorillas sometimes stay in their natal troops and become subordinate to the silverback. If the silverback dies, these males may be able to become dominant or mate with the females. This behaviour has not been observed in eastern lowland gorillas. In a single male group, when the silverback dies, the females and their offspring disperse and find a new troop.<ref name="Stokes 2003">{{cite journal |last1=Stokes |first1=E. J. |last2=Parnell |first2=R. J. |last3=Olejniczak |first3=C. |year=2003 |title=Female dispersal and reproductive success in wild western lowland gorillas (''Gorilla gorilla gorilla'') |journal=Behavioral Ecology and Sociobiology |volume=54 |pages=329–339 |jstor=25063274 |doi=10.1007/s00265-003-0630-3 |issue=4 |bibcode=2003BEcoS..54..329S |s2cid=21995743}}</ref>{{sfn|Yamagiwa|Kahekwa|2001|pp=89–122}} Without a silverback to protect them, the infants will likely fall victim to [[Infanticide in primates|infanticide]]. Joining a new group is likely to be a tactic against this.<ref name="Stokes 2003" /><ref name="Watts 1989">{{cite journal |last=Watts |first=D. P. |year=1989 |title=Infanticide in mountain gorillas: new cases and a reconsideration of the evidence |journal=Ethology |volume=81 |issue=1 |pages=1–18 |doi=10.1111/j.1439-0310.1989.tb00754.x|bibcode=1989Ethol..81....1W }}</ref> However, while gorilla troops usually disband after the silverback dies, female eastern lowlands gorillas and their offspring have been recorded staying together until a new silverback transfers into the group. This likely serves as protection from leopards.{{sfn|Yamagiwa|Kahekwa|2001|pp=89–122}}
[[File:Gorilla gorilla11.jpg|thumb|left |Silverback gorilla]]
The silverback is the centre of the troop's attention, making all the decisions, mediating conflicts, determining the movements of the group, leading the others to feeding sites, and taking responsibility for the safety and well-being of the troop. Younger males subordinate to the silverback, known as blackbacks, may serve as backup protection. Blackbacks are aged between 8 and 12 years{{sfn|Robbins|2001|pp=29–58}} and lack the silver back hair. The bond that a silverback has with his females forms the core of gorilla social life. Bonds between them are maintained by grooming and staying close together.<ref name="Watts 2003">{{cite book |last=Watts |first=D. P. |year=2003 |chapter=Gorilla social relationships: a comparative review |editor1-last=Taylor |editor1-first=A. B. |editor2-last=Goldsmith |editor2-first=M. L. |title=Gorilla biology: a multidisciplinary perspective |location=Cambridge, UK |publisher=Cambridge University Press |pages=302–327}}</ref> Females form strong relationships with males to gain mating opportunities and protection from predators and infanticidal outside males.{{sfn|Watts|2001|pp=216–240}} However, aggressive behaviours between males and females do occur, but rarely lead to serious injury. Relationships between females may vary. Maternally related females in a troop tend to be friendly towards each other and associate closely. Otherwise, females have few friendly encounters and commonly act aggressively towards each other.<ref name="Watts 1996"/>

Females may fight for social access to males and a male may intervene.<ref name="Watts 2003"/> Male gorillas have weak social bonds, particularly in multiple-male groups with apparent dominance hierarchies and strong competition for mates. Males in all-male groups, though, tend to have friendly interactions and socialise through play, grooming, and staying together,{{sfn|Robbins|2001|pp=29–58}} and occasionally they even engage in homosexual interactions.<ref>{{cite journal |first=Juichi |last=Yamagiwa |title=Intra- and inter-group interactions of an all-male group of Virunga mountain gorillas (''Gorilla gorilla beringei'' ) |journal=Primates |volume=28 |issue=1 |year=1987 |doi=10.1007/BF02382180 |pages=1–30 |s2cid=24667667}}</ref> Severe aggression is rare in stable groups, but when two mountain gorilla groups meet the two silverbacks can sometimes engage in a fight to the death, using their canines to cause deep, gaping injuries.<ref name="Fossey1983" />