z-logo
Premium
Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas ( Gorilla gorilla )
Author(s) -
Breuer Thomas,
Robbins Martha M.,
Boesch Christophe
Publication year - 2007
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.20678
Subject(s) - sexual dimorphism , gorilla , biology , zoology , sexual selection , pongidae , population , anatomy , evolutionary biology , ecology , demography , paleontology , sociology
Investigating sexual dimorphism is important for our understanding of its influence on reproductive strategies including male–male competition, mate choice, and sexual conflict. Measuring physical traits in wild animals can be logistically challenging and disruptive for the animals. Therefore body size and ornament variation in wild primates have rarely been quantified. Gorillas are amongst the most sexually dimorphic and dichromatic primates. Adult males (silverbacks) possess a prominent sagittal crest, a pad of fibrous and fatty tissue on top of the head, have red crest coloration, their saddle appears silver, and they possess a silverline along their stomach. Here we measure levels of sexual dimorphism and within‐male variation of body length, head size, and sexual dichromatism in a population of wild western gorillas using photogrammetry. Digital photogrammetry is a useful and precise method to measure sexual dimorphism in physical traits yielding sexual dimorphism indices (ISD), similar to those derived from traditional measurements of skeletal remains. Silverbacks were on an average 1.23 times longer in body length than adult females. Sexual dimorphism of head size was highest in measures of crest size (max ISD: 60.4) compared with measures of facial height (max ISD: 24.7). The most sexually dimorphic head size measures also showed the highest within‐sex variation. We found no clear sex differences in crest coloration but there was large sexual dichromatism with high within‐male variation in saddle coloration and silverline size. Further studies should examine if these sexually dimorphic traits are honest signals of competitive ability and confer an advantage in reproductive success. Am J Phys Anthropol, 2007. © 2007 Wiley‐Liss, Inc.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here