Artificial light and sound disrupts feeding behavior of frog biting midges
Frog-biting midges (Corethrella spp.) utilize complex light and sound cues to locate their hosts. We surveyed 49 Panamanian Túngara frog (Physalaemus pustulosus) populations along an urban gradient, from Panama City (urban) to the forests of Gamboa (rural). We recorded midge and frog population size, light and sound levels, canopy cover, substrate type, and distance from forest. Túngara frogs were found in both urban and rural areas but midges were not found in areas with high artificial sound or light. We hypothesized that the anthropogenic factors of light and sound pollution interferes with midges’ ability to locate and feed on their frog hosts. To test this prediction, we employed a fully-crossed 3x3 design with nine treatments, implementing three sound treatments (frog call with no city noise, frog call with low city noise, and frog call with high city noise) and three light treatments (no artificial light, low artificial light and high artificial light). We examined midge preference among these treatments by collecting midges attracted to fan traps in the sound/light treatments. Following midge collection, we exposed a Túngara frog, housed in a mesh-covered container, to 20 frog biting midges for two hours to determine if the midges could locate the frog’s container, the frog within the container, and feed on the frog. We scan sampled and recorded the effect of the sound/light treatments on frog and midge behavior and the midges’ ability to locate and feed on the frog.
No midges were found among urban (Panama City) frog populations, and our data suggest that midges were not found in areas with high light or sound pollution. In fact, in the preference study more midges were collected in the fan traps that had less light or sound pollution. In addition, in our host-feeding experiment light and sound pollution reduced the number of midges that located the container holding the frog. No midges in any of the low or high light treatments were able to locate the host frog. Though midges in all of the no-light treatments were able to locate the frog, but there was a significant decrease in number of midges that located frogs as sound pollution increased. The no light/no sound pollution treatment was the only treatment where midges were able to successfully feed on frogs. These findings suggest that the anthropogenic influences of light and sound pollution disrupt this host-parasite interaction and might influence the distribution of frog-biting midges within their range.