Mechanisms and consequences of sexual conflict in garter snakes (Thamnophis sirtalis, Colubridae)

Abstract

Red-sided garter snakes (Thamnophis sirtalis parietalis) court and mate in early spring around large communal overwintering dens in central Manitoba. Emerging females are immediately covered by dozens or hundreds of vigorously-courting males, potentially imposing significant costs to the female. By manipulating numbers of courting males (both directly and by applying anticourtship pheromones), we quantified the degree to which female dispersal from the den is hindered by courtship. Courted females dispersed only about half as fast as did solitary females. Blood lactate levels were higher in mating than in courting or noncourting snakes of both sexes; the high levels of lactate in mating females support the idea that courtship is physiologically stressful to these animals, perhaps via constraints to female respiration. In arena trials, females that were exercised to exhaustion before courtship mated with smaller males than did control females. The spatial distribution of snakes around the den exhibits substantial heterogeneity, with densities often varying markedly between adjacent areas. Arena trials mimicking this heterogeneity showed that unmated females avoided parts of the enclosure containing scent cues from males. Our data support the hypothesis that courtship in T. s. parietalis confers significant costs to females, and that female behaviors have evolved to reduce those costs.

Sexual conflict over mating in red-sided garter snakes (Thamnophis sirtalis) as indicated by experimental manipulation of genitalia

“…The plug delays female remating [31], prevents female ejection of sperm from unwanted males, prevents sperm leakage and acts as a spermatophore from which sperm are liberated over the course of 2 days [32]. These features of the red-sided garter snake mating system suggest that sexual conflict over copulation duration, rather than cryptic female choice (CFC), is an important selective pressure operating during the female's first mating in the den [22]. As the female moves away from the den, the plug from her first mating dissolves and she may mate again in the smaller, less dense aggregations in small aspen groves surrounding the den where larger males are more prevalent and successful [23][24][25].…”

Reproductive compensation in broad-nosed pipefish females

“…As a result, it is common to take several attempts before any eggs are transferred, and even when successful, only a limited number of eggs are transferred in each attempt. Parental care is provided solely by the males during embryonic development in vascularized brood pouches, providing the embryos with oxygen, osmoregulation and nutrients (Quast & Howe 1980;Haresign & Shumway 1981;Berglund et al 1986b;Ripley & Foran 2009; C. Kvarnemo, K. B. Mobley, C. Patridge, A. G. Jones & I. Ahnesjö 2003-2004, for about a month. Thus, there are ample opportunities for phenotypic differences in quality of care to arise, which in turn may provide females with an incentive to adjust their reproductive allocations in relation to a mate's predicted paternal quality.…”

Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate

“…Nevertheless, there is no relationship between male size and copulation duration, indicating that larger males deposit plug material more quickly, perhaps because they have greater storage capacity and associated delivery ducts than smaller males (Friesen et al, 2013(Friesen et al, , 2014cShine et al, 2000a). Secondly, copulating males have increased blood lactate compared with courting males, which suggests that mating incurs an additional energetic cost over courtship alone (Shine et al, 2004b). Furthermore, energy allocation to plug production may differ among males based on male size and/or body condition as these factors affect male mating success in this species, with larger males being more likely to mate (Shine et al, 2001c(Shine et al, , 2000b(Shine et al, , 2006b.…”