 2002 by the American Society of Ichthyologists and Herpetologists Copeia, 2002(2), pp. 504–510 Effects of Hydric Conditions during Incubation on Body Size and Triglyceride Reserves of Overwintering Hatchling Snapping Turtles (Chelydra serpentina) MICHAEL S. FINKLER,JUSTIN T. BOWEN,THERESA M. CHRISTMAN, AND ANGELA D. RENSHAW Many studies have suggested that incubating eggs under wet conditions may lead to increased fitness in snapping turtles immediately following emergence from the nest, but little is known of the consequences of associated elevated embryonic yolk use on the energetic reserves of the hatchlings during the first winter. In this ex- periment, we measured the size, dry mass, and triglyceride contents of the carcasses and yolk sacs of hatchlings from eggs incubated under wet (-50 kPa) and dry (-300 kPa) conditions at three time intervals: at one week posthatching (late August); at the onset of an overwintering period following 10 weeks of ad libitum feeding (early November); and at the end of overwintering (late March). Although initially smaller, dry hatchlings demonstrated greater increases in live mass during the autumn than did wet hatchlings, eliminating differences in live mass by early November. Dry carcass masses were greater in wet-treatment hatchlings at one week posthatching but not in either November or March. Dry yolk sac mass was greater in dry hatch- lings only at one week posthatching. Total triglyceride contents were higher in dry hatchlings than in wet hatchlings at all intervals. These findings suggest that possible preliminary survival advantages of hatchlings emerging from wet nests ultimately may be tempered by decreased energy reserves during the first winter. D IFFERENCES in water availability during incubation have a pronounced influence on the size and body composition of hatchling turtles that develop in flexible-shelled eggs. In- creased water availability from the nest substra- tum appears to increase the rate of metabolism of yolk by the embryo (reviewed in Packard, 1999). Larger hatchlings with greater dry car- cass masses, greater water contents, and re- duced yolk sac contents are produced from wet- ter nest environments. Hatchlings of aquatic species that emerge from relatively moist nests have certain attri- butes that may enhance their chances of surviv- al during dispersion from the nest. A number of studies have asserted this notion based largely upon laboratory observations of increased body size at hatching, increased locomotor perfor- mance, and greater body hydration (e.g., Miller et al., 1987; Finkler, 1999), with a handful of field-based observations providing some sup- port ( Janzen, 1993; Finkler et al., 2000; but see Congdon et al., 1999). However, if there are in- deed preliminary survival advantages associated with increased growth during embryonic devel- opment, these advantages may be offset in the long term by associated decreases in amounts of residual yolk and body fat that help support the hatchling during the neonatal period (Congdon and Gibbons, 1990; Bobyn and Brooks, 1994; Tucker et al., 1998). In northern regions, the hatchlings of many species of aquatic turtle (e.g., Chrysemys picta, Trachemys scripta, Kinosternon flavescens) overwinter either in the nest or terrestrial hibernacula and, there- fore, must rely solely on stored energy reserves for maintenance metabolism during this period (Congdon et al., 1983; Costanzo et al., 1995; Tucker et al., 1998). Moreover, hatchlings of northern species that do emerge from the nest before winter (e.g., Chelydra serpentina, Apalone spinifera) may have only limited opportunity to feed prior to entering hibernation (Gibbons and Nelson, 1978; Obbard, 1983). Thus, the im- pact of water availability during incubation on the amount of energy stored in the body of the hatchlings could have considerable influence on hatchling survivorship during overwintering (Nagle et al., 1998). Although a handful of re- cent studies have examined this influence in the terrestrially overwintering hatchlings of T. scrip- ta (Tucker et al., 1998; Filoramo and Janzen, 1999; Tucker and Paukstis, 1999), a similar ex- amination in species that migrate to the water prior to winter (and thus may have a limited opportunity to feed prior to entering hiberna- tion) has not been conducted. In the present study, we examined the influ- ence of nest substrate moisture during incuba- tion on body size, body composition, and total