Accuracy of phonotaxis by the green treefrog (Hyla cinerea)

Summary

• 1. Phonotactic approaches (N=156) of 42 female green treefrogs (Hyla cinerea) were videotaped over a distance of 3.75 m in response to synthetic mating calls (0.9 kHz and 0.9, 2.7 and 3.0 kHz).

• 2. To quantify the accuracy of phonotaxis, jump anglesγ and head orientation angles α were measured (Fig. 2) when the animals were 1 m or farther from the sound source.

• 3. Phonotaxis was extremely accurate in response to the 3-component call, which is behaviorally equivalent to the male's natural mating call. The mean jump angle was$\bar \gamma = 16.1^\circ$ (Fig. 5). Head scanning occurred prior to about 25% of the jumps. The accuracy of head orientation after scanning was even greater$(\bar \alpha = 8.4^\circ )$ as were the subsequent jumps$(\bar \gamma = 11.8^\circ )$ (Fig. 6 and Table 1).

• 4. With respect to the two synthetic calls no statistically significant differences in jump accuracy were found (Table 1). Thus the high frequency components around 3 kHz, normally found in the mating call, do not enhance the accuracy of sound localization.

• 5. Our results are discussed in terms of models of sound localization in vertebrates and invertebrates, and we suggest that the treefrog's ear must act as a sound pressure gradient receiver.