Sexual Size Dimorphism and Growth Plasticity in Snakes: an Experiment on the Western Diamond‐Backed Rattlesnake (Crotalus atrox)

Emily N, Taylor, Arizona State University at the Tempe Campus
Dale F. Denardo, Arizona State University at the Tempe Campus

Article comments

This is the pre-peer reviewed version of the following article: Sexual Size Dimorphism and Growth Plasticity in Snakes: an Experiment on the Western Diamond‐Backed Rattlesnake (Crotalus atrox), Emily N. Taylor and Dale F. Denardo, Journal Of Experimental Zoology 303A(7), Copyright © 2005 Wiley-Blackwell, which has been published in final form at http://dx.doi.org/10.1002/jez.a.189

NOTE: At the time of publication, the author Emily Taylor was not yet affiliated with Cal Poly.

Abstract

We conducted an experiment to examine the effects of sex and food intake on growth, mass gain, and attainment of sexual maturity in Western Diamond‐backed Rattlesnakes (Crotalus atrox). We also measured testosterone levels to determine whether testosterone might be involved in the male‐biased sexual size dimorphism observed in this species. We collected neonate rattlesnakes and raised them in the laboratory for 2 years on either a high‐intake diet (fed one mouse per week) or a low‐intake diet (fed one mouse every 3 weeks). High‐intake snakes grew and gained mass more rapidly than low‐intake snakes, but males did not grow or gain mass more rapidly than females in either treatment group. High‐intake snakes attained reproductive maturity earlier than low‐intake snakes, indicating that size, not age, is the critical determinant of reproductive maturity. Males had higher levels of testosterone than females but did not grow more quickly, suggesting that testosterone may not affect growth in this species and may therefore not be the proximate determinant of sexual size dimorphism.