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

Abstract

Recent Weld studies on the reproductive ecology of western diamond-backed rattlesnakes (Crotalus atrox) from populations in southern Ari 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, oVers a unique logistical opportunity to assess the complete annual proWle 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 rela tively high, and the concentration hierarchy was T > DHT > E2. Mean levels of T, DHT, and E2 showed no signiWcant 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 com pared to values obtained during the active season. Mean cloacal temperatures of basking males were signiWcantly higher than core body tem peratures 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 signiWcantly correlated with cloacal temperatures. We suggest that future Weld studies of male C. atrox should: (a) investigate sex steroid levels in non-basking individuals and (b) test whether elevated levels of sex ste roids during winter facilitate the large increases that occur in early spring, which are coincident with the second mating season. Our Wndings on the reproductive biology of C. atrox and other viperids are discussed in the context of the associated-dissociated model of reproduction.

Stress Ecology of the Pacific Rattlesnakes (Crotalus Oreganus and Crotalus Helleri)

“…The magnitude of elevated baseline CORT in the treatment snakes at sample 2 falls within previously reported baseline levels of free-ranging rattlesnakes, including the sister species C. oreganus (Holding et al 2014;Schuett et al 2004;Lutterschmidt et al 2009, Lind et al 2010. Compared to acute elevation during the stress series, CORT was elevated to a much smaller degree via implants.…”

“…Sometimes, as in this study, no relationship between time-to-bleed and CORT is observed (Holding et al, 2014b;Hopkins & DuRant 2011), which is likely because samples were collected within an adequate timeframe before circulating CORT increased due to stress response to handling (Schuett et al 2004). …”

“…The magnitude of elevated baseline CORT in the treatment snakes at this sample is within normal baseline levels based on reports from several species of free-ranging rattlesnakes, including the sister species C. oreganus (Holding et al 2014a;Schuett et al 2004;Lutterschmidt et al 2009, Lind et al 2010. As baseline CORT varies within inidividuals, within a population, and across seasons in these studies, it is difficult to attribute a specific value of baseline CORT to achieve a general classification of "chronically stressed".…”

Evaluation of Seasonal Serum Level of Estradiol and Progesterone Hormones in Iranian Female Caucasian Viper

“…Many studies have investigated sex steroid hormone concentrations of species with known mating systems in an effort to correlate steroid hormone concentrations with events of the reproductive cycle [4,9,16,17,18,19,26,29]. Estradiol is produced by ovarian granulosa cells and it seems that it is the first stimulant for mating behavior (estrus period) and yolk protein synthesis along ovulation in female reptiles [8].…”

Effects of Experimentally Increased Testosterone on Movement and the Effects of Sex and Age on Relative Cortical Volumes in the Northern Pacific Rattlesnake (Crotalus O. Oreganus)

“…Due to their large body size and diverse mating systems, Crotaline snakes make an ideal model organism for studying the ecology and physiology of vertebrate reproduction (Beaupre and Duvall, 1998;Almeida-Santos et al, 2004;Schuett et al, 2006). Male…”