Wild Male_Masai giraffe sexual dimorphisms in body proportion

Giraffes exhibit a large sexual dimorphism in body size. Whether sexual dimorphisms also exist in body proportions of the axial and appendicular skeleton has been debated, particularly regarding giraffe’s iconic long neck. We examined the anatomical proportions of the neck, forelegs, hindlegs, and body trunk of the Masai giraffe (G. tippelskirchi) in captive and wild populations. We found that female Masai giraffes have proportionally longer necks relative to their forelegs than males in contradiction of the original necks-for-sex hypothesis that proposed that the evolution of giraffe’s long was driven by male-male competition. However, male neck width and apparent mass is proportionally larger than females supporting a modification of the necks-for-sex hypothesis. Moreover, male foreleg length is proportionally longer whereas female trunk length is proportionally longer. These sexual dimorphisms were found in both captive and wild Masai giraffes. We speculate that the initial evolution of giraffe’s long neck and legs was driven by the maternal nutritional demands of gestation and lactation through natural selection to gain a competitive advantage in browsing, and then later the neck mass was further increased as a consequence of male-male competition and sexual selection. Differences in the proportions of major body components define sex phenotypes, but several giraffes display opposite-sex phenotypes with a significantly higher level of discordancy seen in captive males. We speculate that body proportion sexual dimorphisms are maintained in the wild by natural and/or sexual selection, but in captivity selection is relaxed resulting in a higher occurrence of discordances in sexual phenotypes.

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Cavener, Douglas; Lee, Derek; Bond, Monica (2023). Wild Male_Masai giraffe sexual dimorphisms in body proportion [Data set]. Scholarsphere.

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Work Title Wild Male_Masai giraffe sexual dimorphisms in body proportion
Subtitle Male Wild body proportion images
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Open Access
Creators
  1. Douglas Cavener
  2. Derek Edward Lee
  3. Monica Bond
License CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives)
Work Type Dataset
Publication Date October 31, 2023
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Deposited October 31, 2023

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Version 2
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    • https://doi.org/10.1007/s42991-024-00424-4