Social status, not size, determines reproductive success for female
mountain gorillas
High-ranking females breed more often, but their social dominance is not influenced by body size

Date:
June 3, 2020
Source:
PLOS
Summary:
Dominance rank among female mountain gorillas is not related to
body size but does increase their reproductive output according
to new research.



FULL STORY ========================================================================== Dominance rank among female mountain gorillas is not related to body
size but does increase their reproductive output according to research publishing June 3, 2020 in the open-access journal PLOS ONE, led by
Edward Wright from the Max Planck Institute for Evolutionary Anthropology, Germany, and colleagues.


========================================================================== Mountain gorillas are the largest living primate and display extreme
size differences between the sexes, with males weighing around 200kg --
twice as much as females. Body size is an important factor determining
fighting ability in many animals and previous research has shown it
influences dominance rank in male mountain gorillas.

To test whether this relationship exists in females, an international
team of researchers measured the body size of 34 female mountain gorillas (Gorilla beringei beringei) monitored by the Dian Fossey Gorilla Fund International in Volcanoes National Park in Rwanda. They combined
dominance rank data from behavioural observations, which have been
conducted daily since 2000, with estimates of back breadth and body
length for each adult female, calculated non-invasively using a frame
mounted with lasers and a digital camera.

In contrast to many species of mammal, the researchers found that
dominance rank was unrelated to body size in female mountain gorillas. The results suggest that factors other than physical strength, such as age or
group tenure, are more important in determining the dominance hierarchy
of female mountain gorillas. Dominance rank still offers reproductive
benefits, even for a species with an abundant, year-round supply of food,
the authors say. High-ranking females produced offspring more frequently, perhaps as a result of preferential access to males.

The authors add: "Very few studies have examined the interrelationship
among body size, dominance rank and reproductive success together. So it
was really interesting to find that even though higher-ranking female
gorillas had significantly shorter inter-birth intervals than lower
ranking ones, which is a proxy for reproductive success, neither of
these variables significantly correlated with body size."

========================================================================== Story Source: Materials provided by PLOS. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Edward Wright, Jordi Galbany, Shannon C. McFarlin, Eric
Ndayishimiye,
Tara S. Stoinski, Martha M. Robbins. Dominance rank but
not body size influences female reproductive success in
mountain gorillas. PLOS ONE, 2020; 15 (6): e0233235 DOI:
10.1371/journal.pone.0233235 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200603144331.htm https://www.sciencedaily.com/releases/2020/06/200603144331.htm

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