30.5 Thursday, Jan. 5 The Energetic Cost of Courtship in Male vs. Female Red-Sided Garter Snakes (Thamnophis sirtalis parietalis) POWERS, D.R.*; FRIESEN, C.R.; MASON, R.T.; MICHAELSON, J.B.; George Fox University, Newberg, OR; Oregon State University, Corvallis, OR; Oregon State University, Corvallis, OR; George Fox University, Newberg, OR email@example.com
Courtship can require substantial energy investment particularly when extended courtship activity and male-male competition play a key role in determining fitness. Measuring the cost of courtship can be challenging because often it is difficult to segregate other activities. The scramble-mating system of red-sided garter snakes (Thamnophis sirtalis parietalis) offers a model system for studying courtship costs because the snakes fast and restricted movement during the courtship period. In this study we measured metabolic rate during courtship in male and female red-sided garter snakes. We also assessed morphological, metabolic, and behavioral characteristics of successful and unsuccessful males in an effort to identify traits important to fitness. Males attained a max courting metabolic rate (CMR) of 58 J/min (18X resting metabolic rate; RMR). Receptive females received more vigorous courting from males and 2X the energy investment compared to unreceptive females suggesting discrimination. Males that successfully copulated with females exhibited more intense courtship than unsuccessful males but this difference was not tied to metabolic performance. Female CMR did not differ from RMR and was as much as 15X lower than male CMR. Respiratory patterns in females also did not change during courtship suggesting that females minimize energy expenditure. Overall males appear to make a large but likely calculated energy investment in courtship as this is where their fitness will be determined. The minimal metabolic response of females makes it unlikely that they use active male exclusion to exercise “choice” perhaps relying more on alternative post-copulatory mechanisms.