Masai Giraffe Sexual Dimorphisms in Body proportions

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 to the original necks-for-sex hypothesis that proposed that the evolution of giraffe’s long neck 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 the giraffe’s long neck and legs was driven by interspecific competition and 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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Creators
  1. Douglas Cavener
Deposited October 31, 2023
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Creators
  1. Douglas Cavener
Deposited October 31, 2023
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Creators
  1. Douglas Cavener
  2. Derek Edward Lee
  3. Monica Bond
Deposited October 31, 2023
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Open Access
Creators
  1. Douglas Cavener
  2. Derek Edward Lee
  3. Monica Bond
Deposited October 31, 2023
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Open Access
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Creators
  1. Douglas Cavener
Deposited November 02, 2023
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Open Access
Creators
  1. Douglas Cavener
  2. Derek Edward Lee
  3. Monica Bond
Deposited October 31, 2023
Access
Open Access
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Creators
  1. Douglas Cavener
Deposited November 02, 2023
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Open Access

Metadata

Title Masai Giraffe Sexual Dimorphisms in Body proportions
Creator
  1. Douglas R. Cavener
  2. Monica L. Bond
  3. Lan Wu-Cavener
  4. George G. Lohay
  5. Mia W. Cavener
  6. Xiaoyi Hou
  7. David L. Pearce
  8. Derek E. Lee
Keyword
  1. Allometric growth
  2. Body size
  3. Axial skeleton
  4. Appendicular skeleton
  5. Necks for sex
  6. Mate competition
  7. Browse competition
DOI doi:10.26207/45ta-gp57
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Deposited at November 02, 2023

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