Geladas in Smithsonian Magazine

Check out Smithsonian Magazine’s recent article about geladas.

Thank you Ray Comfort

I just got my 150th anniversary edition of Origin for free with a special introduction by Ray Comfort. I’m glad my university among the best at brainwashing young minds with the atheistic, racist, and thoroughly debunked theory of evolution by means of natural selection. Please note the sarcasm.

Badge of status in drills (Mandrillus leucophaeus)

The upcoming special issue of International Journal of Primatology includes a number of interesting articles on the function of primate coloration in species such as geladas (Theropithecus gelada) (Bergman et al., in press), drills (Mandrillus leucophaeus) (Marty et al., in press), mandrills (M. sphinx) (Setchell et al., in press), and red-fronted lemurs (Eulemur fulvus rufus) (Clough et al., in press). While most mammals are rather drab in color, some primates (especially primate males) are quite colorful. Indeed, sexual dimorphism and variation among males in coloration suggests that the bright colors of male primates may be sexually selected signals. Male coloration may be a ‘badge of status’, indicating rank or status to other males; or it may convey information to females about underlying male ‘quality’. In the latter, these color-based signals need to incur some cost to a male (usually physiological) in order to be kept honest. This keeps ‘low-quality’ males from advertising a ‘high-quality’ signal, thus maintaining a strong correlation between signal strength/intensity (bright coloration) and male quality. Females then discriminate among males based on this signal.

While many of the articles have been available online (not open-access sadly) for some time now, the drill article (Marty et al., in press)was just released yesterday. I have been waiting for this publication for some time, since drills are among my favorite primates (and dream post-doc/future research endeavor). Drills exhibit the highest degree in sexual size dimorphism among primates (males nearly 3x the size of females). Male also possess brightly colored patches of skin on the lip, groin, and rump (see picture below). Marty and colleagues (2009) revealed that male drill coloration is associated with social dominance rank and predicts sexual activity with female drills. However for males of a given rank, coloration was found to be unrelated to sexual activity and association patterns with female drills (Marty et al., in press). In other words, male drill coloration appears to indicate status or social dominance rank and is not (directly) related to female mate preference (Marty et al., in press).

Check out this male drill from Fig 1 in  (Marty et al., in press)

References

Bergman, T. J., Ho, L., & Beehner, J. C. (In press). Chest color and social status in male geladas (theropithecus gelada). International Journal of Primatology.

Clough, D., Heistermann, M., & Kappeler, P. M. (In press). Individual facial coloration in male eulemur fulvus rufus: A condition-dependent ornament? . International Journal of Primatology.

Marty, J. S., Higham, J. P., Gadsby, E. L., & Ross, C. (In press). Dominance, coloration, and social and sexual behavior in male drills mandrillus leucophaeus . International Journal of Primatology.

Setchell, J. M., Charpentier, M. J. E., Abbott, K. M., Wickings, E. J., & Knapp, L. A. (In press). Is brightest the best? Testing the hamilton-zuk hypothesis in mandrills. International Journal of Primatology.