Silverback

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Silverback at the San Francisco Zoo

An adult male gorilla from around the age of 12 is called a silverback because of its characteristic silvery-gray fur.

While the light coloration of the Eastern gorillas is limited to the back, it can also extend to the hips and thighs of the Western gorillas . Other special features are the long canine teeth, a particularly large throat pouch (to amplify the sound during chest drumming) and a pronounced crest that the male gorilla develops over time.

The average height of a silver back is 1.7 meters and it weighs up to 230 kilograms. Life expectancy in the wild is 35 to 40 years, the oldest animal in human care - Ozoum ( Ozzie ) in the Atlanta Zoo - is 58 years old (as of 2019). The first captive-born gorilla, an animal named Colo from the Columbus Zoo, Ohio, died in 2017 at the age of 60.

Group behavior

Dominant silverbacks are leaders of their respective families or groups, which can contain up to about 30 animals. You are responsible for the cohesion, safety and well-being of your family. They settle internal conflicts and make all necessary decisions, for example with regard to the timing and direction of their group's wandering in search of the best feeding places. They face both the challenge of another silverback trying to take over the group and the threat of human poachers. This is why they naturally have the full attention of the group, which usually gathers around the silverback. The physical proximity to him is an indication of the rank of the other members, especially that of the females. The support from the females is vital to the survival of the group - if the leader does not earn their respect, they will leave the group with their children and go in search of a more suitable candidate.

In addition to the leading silverback, there can also be other, non-dominant silverbacks in a group. However, they will try to challenge him for leadership when they see the time come. Male gorillas usually leave their family of origin at the age of eleven, but sometimes they stay in the group and take over the family of their father if he is forced to relinquish the lead due to his age.

When the leader dies - whether through illness, accident or a fatal confrontation with poachers - his family usually falls apart and she looks for another dominant male to offer her the necessary protection. Among the mountain gorillas of the Virunga volcanoes , a silverback only leads its family for an average of 4.7 years before it dies or is ousted by a rival. As a result of this rivalry, adult males often live loners for a long time before they fight for leadership of a group or after they have to give it up.

Mating behavior

Silverbacks live in polygyny and gather a harem of as many females as possible around them. As a rule, only the dominant silverback has the right to reproduce, but there are exceptions. Females sometimes mate with lower-ranking males without the knowledge and consent of the leader - possibly a strategy to prevent the killing of their children if one of these males takes over the group. But the granting of “permission” on the part of an (aging) leader has already been observed several times: By granting a (younger) rival sexual rights, he ensures his cooperation in protecting the group and thus prevents the risk of leading the group to have to hand over to him. DNA analyzes in mountain gorillas have shown that around 15% of the offspring were not sired by the dominant silverback.

The initiative for mating almost always comes from the females, who are only ready to conceive within three days of their monthly cycle. They signal their readiness through approach, posture and long-term eye contact with the male. In the case of mutual agreement, several pairings usually take place every few hours to ensure conception.

If a group is taken over by a new leader, the latter sometimes kills the babies of his predecessor (see infanticide ) in order to be able to successfully mate with the newly conceivable mothers. In the meantime (2004) this behavior has also been observed in the eastern lowland gorillas , in addition to the mountain gorillas , where it seems to be relatively common .

In purely male, d. H. Bachelors groups have also occasionally seen homosexual pairings. The “passive” gorillas were always younger than their “active” partners. Research explains these sexual interactions with the unavailability of females combined with the males' excess sexual energy.

social behaviour

Silverbacks often behave indifferently towards their young , and occasionally they put them in their place. However, if their mother has died, they allow the half-orphans to be closer and more affectionate than usual. B. by sharing their sleeping nests with them and using their body heat to ensure the necessary protection against the cold at night.

In the event of a threat, they take a stand between the attacker and their family and try to drive him away with a sequence of threatening gestures. These include the display of their physical strength (showing themselves to the potential attacker from the side), the baring of their teeth, the staring gaze, loud screams and drumming on the chest, the breaking off and tossing of branches and finally - mostly pretended - Attack. In addition, with the help of glands in their armpits, they create a particularly intense odor that signals arousal and readiness for aggression. However, if this intimidation strategy fails, real fighting occasionally occurs with rival silverbacks, and it can be fatal.

Definition of terms

Sexually mature male gorillas up to the age of about twelve are called black-backed because their fur does not yet have the characteristic color of a silver-backed. Nevertheless, they contribute to the protection of their family by supporting their head in his duties.

The term "gray back" is occasionally used, but the correct name for adult males is silverback. This may be confused with the “gray gorilla” (Gorilla beringei graueri), the eastern lowland gorilla .

media

The mountain gorilla Titus (1974–2009) has been constantly observed since its birth - including by Dian Fossey  - and is one of those wild gorillas that have been scientifically studied the most in depth. The BBC dedicated the documentary Titus: The Gorilla King to him in 2008 .

Well-known silverback

Mountain gorillas (in the wild)

Lowland gorillas (in captivity)

gallery

  • Lowland gorilla

  • Mountain gorilla

Web links

Wiktionary: Silverback  - explanations of meanings, word origins, synonyms, translations

literature

  • Camilla de la Bédoyère: Letters from Africa. Dian Fossey - my life with the gorillas. Collection Rolf Heyne, Munich 2005, ISBN 3-89910-277-0 .
  • Dian Fossey : Gorillas in the Fog. My life with the gentle giants. Droemer Knaur, Munich 1999, ISBN 3-426-61315-8 (original title: Gorillas in the Mist. ).
  • Angela Meder: Gorillas. Ecology and behavior. Springer, Berlin et al. 1993, ISBN 3-540-56666-X .

References and comments

  1. ↑ zooatlanta.org/animal-personality/ozoum-ozzie
  2. ↑ Oldest gorilla in the world died: Colo was the coolest! In: Spiegel Online . January 18, 2017, accessed June 9, 2018 .
  3. ↑ Martha M. Robbins: A Demographic Analysis of Male Life History and Social Structure of Mountain Gorillas. In: Behavior. Vol. 132, No. 1/2, 1995, pp. 21-47, doi : 10.1163 / 156853995X00261 .
  4. ↑ Mountain gorillas embrace coalition politics to survive.
  5. ↑ gorillafund.org ( Memento of the original from January 15, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / gorillafund.org
  6. ↑ The Mountain Gorillas of Bwindi (manuscript) SWR2
  7. ^ First Observations of Infanticides by a Silverback in Kahuzi-Biega. ( Memento of February 2, 2007 in the Internet Archive ) In: Gorilla Journal. December 29, 2004.
  8. ↑ Juichi Yamagiwa: Intra- and Inter-group Interactions of an All-male Group of Virunga Mountain Gorillas (Gorilla gorilla beringei). In: Primates. Vol. 28, No. 1, January 1987, pp. 1-30, doi : 10.1007 / BF02382180 .
  9. ^ Dian Fossey: Gorillas in the mist. Houghton Mifflin, Boston MA 1983, ISBN 0-395-28217-9 .
  10. ^ Richard Despard Estes: The Behavior Guide to African Mammals. Including hoofed mammals, carnivores, primates. 1st paperback print. University of California Press, Berkeley CA et al. 1992, ISBN 0-520-08085-8 .