EFFECTS OF REPRODUCTION ON SURVIVAL AND GROWTH OF FEMALE NORTHERN WATER SNAKES, NERODIA SIPEDON

The cornerstone of life-history theory is the expectation that current reproduction will have a detrimental effect on survival and (or) futu re reproduction. When fecundity increases with body size, the cost to future reproduction arises through decreased growth of reproductive in dividuals. We investigated the effects of reproduction on aspects of s urvival and growth in female northern water snakes (Nerodia sipedon). We did not find a decrease in survival associated with mating despite the conspicuousness of mating aggregations, and pregnancy did not impa ir locomotor ability. We found evidence of a decrease in over-winter s urvival of reproductive females related to their emaciated state follo wing parturition. Reproductive females grew less in length than nonrep roductive females, but increased similarly in mass. Following parturit ion, reproductive females weighed less than in the spring, indicating that mass gain prior to parturition was invested in the litter and tha t most foraging occurred prior to ovulation. Captive reproductive fema les given food ad libitum grew in length at a rate similar to free-liv ing reproductive females, but increased more in mass. Captive females weighed more after giving birth than in the spring, indicating that un like that of females in the wild, some of their mass increase was due to energy storage, and also that they continued to feed after ovulatio n. Consistent with the prediction that smaller females would benefit m ore than larger females from reproducing less and growing more to incr ease future fecundity, we found that smaller females participated less in mating aggregations and reproduced less often.