Ultraviolet radiation influences perch selection by a neotropical poison-dart frog.

Lee B Kats,Barbara A Han,David E Schlais,Andrew R Blaustein,Gary M Bucciarelli

doi:10.1371/journal.pone.0051364

Lee B Kats, Barbara A Han + Show 3 more

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https://doi.org/10.1371/journal.pone.0051364

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Abstract

Ambient ultraviolet-B radiation can harm amphibian eggs, larvae and adults. However, some amphibians avoid UV-B radiation when given the opportunity. The strawberry poison dart frog, Oophaga pumilio, is diurnal and males vocalize throughout the day in light gaps under forest canopies that expose them to solar radiation. Previous studies have demonstrated that males calling from high perches are more successful at mating than those at lower perches. We investigated whether frogs at higher perches receive more ultraviolet-B than those calling from lower perches. We also investigated whether frogs on perches receiving relatively low ultraviolet-B levels maintained their positions for longer compared to individuals calling from perches receiving higher levels of ultraviolet-B. Finally, since it has been hypothesized that some animals utilize levels of UV-A as a visual cue to avoid UV-B damage, we artificially elevated ultraviolet-A levels to examine whether males exposed to artificially elevated ultraviolet-A abandoned their perches sooner compared to males exposed to visible light. We found that frogs called from perches receiving low ultraviolet-B regardless of perch height, and that frogs maintain their positions longer on perches receiving low ultraviolet-B compared to perches receiving even slightly higher ultraviolet-B levels. Exposing the frogs to artificially elevated levels of ultraviolet-A radiation caused males to move off of their perches faster than when they were exposed to a control light source. These experiments suggest that ultraviolet radiation plays an important role in frog behavior related to perch selection, even in rainforests where much of the solar radiation is shielded by the forest canopy.

Highlights

With growing emphasis on amphibian population declines and extinctions [1] scientists are increasingly focusing on environmental factors that may influence amphibian behavior, ecology and reproduction
Mean UV-B levels increased with height measured up to 250 cm, with mean UV-B levels ranging from 0.22 mW/cm2 (60.05 SE) on the ground to 0.66 mW/cm2 (60.07 SE) at 250 cm above the ground (Fig. 1)
When the light was either turned off or emitting visible light, the frogs did not jump until the light was significantly closer. These field observations and experiments support the hypothesis that UV levels influence perch selection by adult male strawberry poison dart frogs

Summary

Introduction

With growing emphasis on amphibian population declines and extinctions [1] scientists are increasingly focusing on environmental factors that may influence amphibian behavior, ecology and reproduction. Studies using satellite data have indicated that levels of one environmental factor, ultraviolet radiation, have increased in regions of Central America [3]. Given that male O. pumilio (the strawberry poison-dart frog) seem highly sensitive to low levels of UV-B [7], we wanted to further investigate how UVB might interact with perch selection. We hypothesized that if UV-B levels were an important determinant of perch quality, vocalizing male poison-dart frogs would spend longer time on a low UV-B exposed perch than on a perch with higher levels of UV-B exposure. If UV-A serves as a visual cue for UV-B we hypothesized that calling frogs would leave perches when exposed to artificially elevated levels of UV-A

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