title: Sexual size dimorphism and growth plasticity in snakes: an experiment on the Western Diamond-backed Rattlesnake (Crotalus atrox).
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.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, Arizona 85287, USA. entaylor@asu.edu
authors.forename: Emily N
authors.initials: EN
authors.lastname: Taylor
authors.forename: Dale F
authors.initials: DF
authors.lastname: Denardo
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001130:Arizona; D049628:Body Size / Q000502:physiology*; D017839:Crotalus / Q000254:growth & development*; D005260:Female; D016014:Linear Models; D008297:Male; D011863:Radioimmunoassay; D012727:Sex Characteristics; D012741:Sexual Maturation / Q000502:physiology*; D013739:Testosterone / Q000097:blood
chemical_list: D013739:Testosterone