Changes in the tonic immobility (TI) response in Anolis carolinensis were
investigated as a function of duration and condition of captivity in five experiments.
Although anoles ultimately show significant decreases in durations of
immobility with repeated elicitations of the response, there was an increase in
both the mean and variance of immobility durations of subjects tested on the third
day of captivity. It was demonstrated that this third-day captivity effect depended
neither on previous testing nor on crowding. If subjects were captured, released,
and then recaptured, however, the third-day effect was not seen. The 3-day
captivity effect was also eliminated if subjects were housed in terraria provided
with foliage. These findings are discussed in terms of the concept that captivity in
unnatural environments exerts cumulative stress on organisms over the initial
days of confinement that can be ameliorated by the use of more naturalistic
conditions of housing.