AAS ›› 2015, Vol. 46 ›› Issue (5): 673-678.doi: 10.16098/j.issn.0529-1356.2015.05.017

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Sex differences in the relative length of phalange in rhesus macaques (Macaca Mulatta) from the Taihang Mountains

ZHAO Xiao-jin* TIAN Hua-xiang HU Hai-yang HU Feng-xia   

  1. College of Fisheries, He’nan Normal University,  He’nan Xinxiang 453007, China
  • Received:2015-02-13 Revised:2015-04-17 Online:2015-10-06 Published:2015-10-06
  • Contact: ZHAO Xiao-jin E-mail:tianyuan98zr@sina.cn

Abstract:

Objective To study the sex difference for size and distribution of the length ratios of the phalanges in rhesus macaques from the Taihang Mountain. Methods The length of 100 fingers and 120 toes in the male and 250 fingers and 250 toes in the female on both sides of adult rhesus macaques was measured. Length ratios were constructed for all possible pairings of the five bones in each individual fingers and toes. Statistical data were analyzed by SPSS version 20.0. Results Firstly, for Macaca Mulatta, the absolute length of the five fingers and five toes exhibited significant differences between the sexes (P<0.001). Secondly, all the ten finger ratios had no sex determination (P>0.05). Thirdly, six in the ten toe ratios showed substantial sex difference (P<0.05 or P<0.01), and the ratios were significantly smaller in females than in males. The toe length ratios showing the largest sex difference was 1D:4D and 1D:5D in the lower order ratios. Finally, the present findings suggested the sex-differentiated digit length ratios pattern in Macaca Mulatta were different from other non-human primates. Conclusion The digit ratios in Macaca Mulatta are primarily affected by three factors, which are social behavior, levels of intra-female competition, and categories of intra-male competition after controlling for possible functional confounds such as substrate and phylogenetic effects. The pattern of sex-differentiated digit length in rhesus monkey may be associated with prenatal exposure to testosterone.

Key words: Digit ratio, Sex difference, Androgen, Social behavior, Bone measurement, Macaca Mulatta