LAYNE, JR., Jack R.; RICE, Matt E.; Slippery Rock University, PA; Slippery Rock University, PA: Postfreeze locomotor performance in Rana sylvatica and Pseudacris crucifer.

Freeze tolerance exists among a few species of terrestrially-hibernating North American frog such as Rana sylvatica and Pseudacris crucifer. Both species emerge from hibernation very early in the spring. Breeding takes place at this time requiring considerable overland migration and possible avoidance of predators. We investigated jump distance and swim speed of these two species during postfreeze recovery because impaired performance, even if eventually reversed, could have adverse ecological consequences. Following a nonlethal freeze at -1.5 C R. sylvatica returned to the prefreeze level for both modes of locomotion sooner than did P. crucifer (54 hours vs. 11 days). Rana sylvatica took longer to recover their locomotor performance when they were frozen at lower temperatures. For example, frogs frozen at -3 C needed 54 hours recovery simply to swim and jump at the 50% of the prefreeze level. The faster recovery of locomotor performance by R. sylvatica versus P. crucifer parallels the greater level of freeze tolerance that has been reported for the former species in comparison to the latter species. Given the massive biochemical and physiological disturbances accompanying tissue freezing, the recovery dynamics of freeze tolerant frogs seem adequate to meet most of the ecological needs, including early spring breeding.