P2.148 Thursday, Jan. 5 Energy Investment in Copulatory Plug Production by Large vs. Small Male Red-Sided Garter Snakes (Thamnophis sirtalis parietalis) COPENHAVER, P.E.*; POWERS, D.R.; FRIESEN, C.R.; MASON, R.T.; George Fox Univ, Newberg, OR; George Fox Univ, Newberg, OR; Oregon State Univ, Corvallis, OR; Oregon State Univ, Corvallis, OR email@example.com
Male red-sided garter snakes (Thamnophis sirtalis parietals) incur large energetic costs during reproduction due to prolonged courtship of females and male-male competition. When copulation occurs males deposit a copulatory plug (CP) into the female cloaca that delivers sperm, reduces female receptivity and attractivity, and passive mating guarding. Because CP material must be synthesized, plug production will constitute a portion of reproductive cost but the exact proportion is unknown. The rate of new plug synthesis might also play a role in mating frequency and reproductive success (smaller plugs/shorter mating intervals). If energetic cost or synthesis rate of CPs is size dependent, then plug production might play a role in male size-dependent reproductive success. We measured resting metabolic rate (RMR) of small (<30g) and large (>35g) recently-copulated and non-copulated but courting (control) males to see if post-copulation RMR > controls, and if any difference was size-group dependent. Small male post-copulative RMR (0.00396+0.00059 mL O2 g-1 min-1 ; 1.44xSMR) was higher than large-male post-copulative RMR (0.00355+0.00073 mL O2 g-1 min-1 ; 1.30xSMR), and post-copulative RMR in both small and large males was higher than controls. Control RMR in small males was 0.00332+0.00045 mL O2 g-1 min-1 (1.21xSMR) whereas control RMR in large males equalled SMR. CPs are composed of water (>90%) and protein and represent a meaningful energy investment of ~0.36 kJ. These data suggest that synthesis of CP material might cause elevation of post copulatory RMR and is consistent with the notion that larger males have an energetic advantage over smaller males in courtship.