We tested the hypothesis that large eggs of a terrestrial turtle when expos
ed to stressful hydric environments are more likely to hatch than are small
eggs of an aquatic turtle. Eggs of terrestrial Terrapene carolina were com
pared to eggs of two aquatic species; Trachemys scripta, whose eggs are sim
ilar in size to those of T carolina, and Chrysemys picta, with smaller eggs
than either of the other two species. Eggs of all three species were incub
ated on wet and dry substrates with nominal substrate water potentials of -
150 kPa and -1500 kPa, respectively. Overall, eggs of all three species on
wetter substrate gained mass during incubation, whereas eggs on the drier s
ubstrate either gained less mass (T carolina) or lost mass (T: scripta and
C. picta) during incubation. Eggs of II: carolina on the dry substrate gain
ed more mass during incubation than did eggs of either of the aquatic speci
es on wet substrate. The ability of eggs of T carolina to maintain a positi
ve water balance on a substrate with water potential less than -300 kPa is
unique among turtles that lay flexible-shelled eggs. All three species are
consistent in that hatchlings from wetter substrate tended to incubate long
er, to be heavier, and to have longer carapaces than those from drier subst
rate. The pattern of survivorship on the dry substrate did not support the
hypothesis that larger eggs are more Likely to survive to hatch than are sm
aller eggs when exposed to a stressful environment because survivorship was
equivalent between larger eggs of T carolina and smaller eggs of C. picta.
In contrast, survivorship of I: scripta eggs was reduced compared to the o
ther two species despite the relatively large egg size of I: scripta.