The Effect of Temperature on the Vocal Activity of Tropical Anurans: A Comparison of High and Low-elevation Species

The objective of this work was to determine whether behavioral adjustments reduce ex- posure to cold during activity in high-elevation anurans. I studied the daily patterns of vocal activity of two populations (2900 and 3500 m) of high-elevation species in the Colombian Andes (Colostethus sub- punctatus, Eleutherodactylus bogotensis, and Hyla labialis), and compared them with those of some low- elevation Panamanian congeners (C. talamancae, C. flotator, E. diastema, H. ebraccata, and H. microcephala). I did not find interpopulational differences in the patterns of vocal activity that could be interpreted as a response to cold in high-elevation species. In contrast, interspecific differences in the patterns of activity may relate to the cold and variable temperatures experienced by high-elevation frogs. In high-elevation Colostethus vocal activity and environmental temperature are positively correlated, whereas low-elevation congenerics reduce activity when environmental temperatures are highest. Eleutherodactylus bogotensis exhibits maximum vocal activity after dusk, when temperatures are not yet very cold. This pattern contrasts with the more extended nocturnal vocal activity of several lowland congeneric species. The species of Hyla exhibited similar diel activity patterns, which may relate to the moderate temperatures of the high- elevation ponds, calling habitat of Hyla labialis. High-elevation species appear to use temporal or spatial thermal niches that reduce exposure to cold during activity. In spite of these behaviors, substantial mod- ifications of the thermal physiology appear necessary to enhance the capacity for vocal activity at low

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