Winter profile of plasma sex steroid levels in free-living male western diamond-backed rattlesnakes, Crotalus atrox (Serpentes: Viperidae)

Gordon W. Schuett, Roger A. Repp, Emily N. Taylor, Dale Denardo, Ryan L. Earley, Edward A. Van Kirk, William J. Murdoch

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Recent field studies on the reproductive ecology of western diamond-backed rattlesnakes (Crotalus atrox) from populations in southern Arizona showed significant differences in the concentration of plasma sex steroids (testosterone, T; 5α-dihydrotestosterone, DHT; and 17β-estradiol, E2) throughout the active season (March-October), and peak levels were coincident with the two mating periods (late summer and early spring). There is, however, no information on levels of sex steroids during winter. Similar to most snakes, hibernating individuals of C. atrox are typically inaccessible, but in southern Arizona, where environmental conditions are typically mild during winter, adult males frequently bask at or near the entrances of communal dens. Basking activity, therefore, offers a unique logistical opportunity to assess the complete annual profile of plasma sex steroid levels in males of a temperate reptile in nature. From November to February, we measured levels of plasma T, DHT, and E2 in adult male C. atrox that were located basking at communal dens. Additionally, cloacal, core body, and ambient air temperatures were obtained to investigate potential relationships between body temperatures and levels of sex steroids. Mean levels of T, DHT, and E2 were relatively high, and the concentration hierarchy was T > DHT > E2. Mean levels of T, DHT, and E2 showed no significant variation across the four months of sampling; however, E2 levels decreased progressively. In the annul cycle, sex steroid levels during winter were not basal when compared to values obtained during the active season. Mean cloacal temperatures of basking males were significantly higher than core body temperatures of non-basking males (inside dens) from November-December, and in February, which suggests that one function of winter basking is to elevate body temperatures. Steroid levels, nonetheless, were not significantly correlated with cloacal temperatures. We suggest that future field studies of male C. atrox should: (a) investigate sex steroid levels in non-basking individuals and (b) test whether elevated levels of sex steroids during winter facilitate the large increases that occur in early spring, which are coincident with the second mating season. Our findings on the reproductive biology of C. atrox and other viperids are discussed in the context of the associated-dissociated model of reproduction.

Original languageEnglish (US)
Pages (from-to)72-80
Number of pages9
JournalGeneral and Comparative Endocrinology
Volume149
Issue number1
DOIs
StatePublished - Oct 2006

Fingerprint

Crotalus atrox
Crotalus
Viperidae
Serpentes
Diamond
Snakes
steroids
Steroids
winter
gender
Body Temperature
body temperature
Temperature
Reptiles
Dihydrotestosterone
Ecology
snakes
reptiles
testosterone
Reproduction

Keywords

  • Associated-dissociated reproduction
  • Body temperature
  • Hibernation
  • Mating season
  • Pitviper
  • Reptile
  • Snake
  • Steroid hormones

ASJC Scopus subject areas

  • Endocrinology

Cite this

Winter profile of plasma sex steroid levels in free-living male western diamond-backed rattlesnakes, Crotalus atrox (Serpentes : Viperidae). / Schuett, Gordon W.; Repp, Roger A.; Taylor, Emily N.; Denardo, Dale; Earley, Ryan L.; Van Kirk, Edward A.; Murdoch, William J.

In: General and Comparative Endocrinology, Vol. 149, No. 1, 10.2006, p. 72-80.

Research output: Contribution to journalArticle

Schuett, Gordon W. ; Repp, Roger A. ; Taylor, Emily N. ; Denardo, Dale ; Earley, Ryan L. ; Van Kirk, Edward A. ; Murdoch, William J. / Winter profile of plasma sex steroid levels in free-living male western diamond-backed rattlesnakes, Crotalus atrox (Serpentes : Viperidae). In: General and Comparative Endocrinology. 2006 ; Vol. 149, No. 1. pp. 72-80.
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