This study characterizes freeze tolerance and postfreeze recovery in t
he frog Pseudacris crucifer. We collected frogs from Pennsylvania duri
ng the autumns of 1994 and 1995. All experiments occurred in the labor
atory and employed a freezing temperature of -1.5 C. This treatment fr
oze 45% of the body water in these frogs, and they were clearly tolera
nt of internal freezing. However, their survival was inversely proport
ional to freeze duration (3 day = 85.0%, 7 day = 52.6%, and 28 day = 0
%). Cutaneous blood flow, breathing; hind-leg retraction, righting ref
lex, and jumping ability returned to surviving frogs within 24-48 h fo
llowing the conclusion of a 3-day freeze, Complex behavioral responses
(e.g., jumping) required more time to return than did basic physiolog
ical functions (e.g., cutaneous blood flow). Interestingly, rates of o
xygen consumption were not altered during the recovery period with res
pect to the prefreeze value. This study indicates that the freezing su
rvival of P. crucifer is markedly influenced by the duration of the fr
eeze episode, which may be an important ecological limitation during w
inters having few intervening thaws. Recovering frogs require 1-2 days
to fully regain complex motor responses; whereas vital functions are
restored quickly, and oxygen consumption is not measurably altered dur
ing this period.