Unlike most vipers, female rattlesnakes (Crotalus atrox) continue to hunt and feed throughout pregnancy

Abstract

For various reasons, reduction or cessation of feeding (anorexia) can occur in either sex during periods of reproduction among vertebrates, from cichlids to elephant seals. Anorexia is commonly associated with gestation in snakes. Using radiotelemetry, we investigated the feeding and spatial ecology of a live‐bearing viperid snake, the western diamond‐backed rattlesnakes (Crotalus atrox). Specifically, from 2001 to 2010, we determined the feeding frequency and home range size of adult females (n = 27) during the active season (March–October) in a population from the Sonoran Desert of Arizona. We addressed a central hypothesis: Do hunting and feeding occur throughout pregnancy? Also, we tested a corollary hypothesis: Does pregnancy influence home range size? We documented hunting and feeding from March to October and during pregnancy (June to mid‐September). Feeding frequency was significantly greater in late pregnancy, a result that is in sharp contrast to most other large‐bodied vipers. Furthermore, home range sizes in gestating subjects did not differ from those in nonreproductive years. Births occurred from mid‐August to mid‐September and mean litter size was 3.4. Frequent feeding in C. atrox during gestation unquestionably provides energy and nutrients to the mother, which is likely important for survival, but such food consumption does not imply that nutrients are used by the fetuses. There is, however, recent evidence in other snakes, including a pitviper, that amino acids are transferred to fetuses. Feeding during pregnancy in C. atrox may be important for both income and capital mode reproduction. Hunting and feeding throughout gestation might be accomplished by having relatively small litters not burdened by a body cavity filled with fetuses. Reduction in litter size may thus be a life‐history (fecundity) trade‐off that permits females to survive and maintain pregnancy in regions where drought and high temperatures are often extreme and chronic.

Mating Systems, Reproductive Success, and Sexual Selection in Secretive Species: A Case Study of the Western Diamond-Backed Rattlesnake, Crotalus atrox

“…But recent work on C. atrox at the SMs has demonstrated that while a biennial pattern is typical for females, annual reproduction is not uncommon [22], [23]. The adult sex ratio at SMs appears to be at unity (G.W.…”

“…Portions of these spatial data for females have been presented elsewhere [23,23]. We performed three different types of spatial analyses to examine relationships between male proximity and parentage: home range size, pairwise home range overlap between all individuals that were radio-tracked for at least one full year, and geographic midpoint comparisons.…”

Ancestral state reconstructions require biological evidence to test evolutionary hypotheses: A case study examining the evolution of reproductive mode in squamate reptiles

“…Viviparous squamates are also capable of storing large energy reserves to avoid starvation as a result of the effects of locomotor impairment on foraging success, or due to the metabolic demands of carrying a litter of offspring (Bonnet et al, ; Gignac and Gregory, ). Ambush‐foraging species in particular may not suffer detrimental effects of viviparity on either predation or foraging success (Schuett et al, ). Viviparous reptiles can also cannibalize non‐viable offspring to quickly recoup energy after reproduction (Lourdais et al, ; Mocino‐Deloya et al, ; Van Dyke et al, ).…”

Mother Cottonmouths (Agkistrodon piscivorus) Alter Their Antipredator Behavior in the Presence of Neonates

“…; but see Schuett et al. ); in conjunction with the metabolic demands of gestation, anorexia can lead to post‐parturient emaciation (e.g., Madsen & Shine ). The intense protein catabolism and musculature loss that occurs during pregnancy has been shown to significantly reduce the physical performance of post‐parturient snakes (Lourdais et al.…”

“…Due to the physiological costs associated with viviparity, post-parturient females might be either less capable of engaging in or less willing to engage in energetically expensive antipredator behavior. Specifically, a large reduction in mobility and appetite suppression during pregnancy can result in anorexia during the reproductive cycle (Macartney & Gregory 1988;Bonnet et al 1998;Lourdais et al 2002;Crane & Greene 2008;Webber et al 2012; but see Schuett et al 2013); in conjunction with the metabolic demands of gestation, anorexia can lead to post-parturient emaciation (e.g., Madsen & Shine 1993). The intense protein catabolism and musculature loss that occurs during pregnancy has been shown to significantly reduce the physical performance of post-parturient snakes (Lourdais et al 2004), a consequence of which might be a reduction in antipredator behavior until a positive energy state is achieved.…”