Sensory Exploitation of Prey Escape Circuits

University Of Arizona, Tucson AZ

Investigators

Abstract

Sensory exploitation of prey escape circuits One of the mechanisms of natural selection that evolutionary biologists study is the "arms race" between predators and prey. Predators evolve various adaptations to capture the prey, and the prey species evolve more and more sophisticated ways to avoid being killed. Who wins this arms race? This proposal focuses on predator-prey relationship in which the predator, the Painted Redstart (Myioborus pictus), exploits properties of a simple pathway in the nervous system of its insect prey to win the race. Flies possess a specific cluster of neurons, the Giant Descending Neuron Cluster, which triggers an escape reflex when a conspicuous image of an approaching predator is expanding on the fly's retina. Such neural pathways and their properties have evolved millions of years ago, and undoubtedly before the evolution of fly-eating birds. This escape reaction is believed to be a general antipredatory adaptation against all sorts of predators. This research project will test the idea that the Painted Redstart is now exploiting the properties of this simple neural pathway in flies. Birdwatchers are well acquainted with the very conspicuous tail fanning and wing spreading employed by foraging redstarts to show off their white and black plumage pattern. The idea is that redstarts use these displays to activate the escape reflexes of flies and other insects making them easier for the birds to detect. Redstarts have specialized in capturing such escaping insects in mid-air. This research will consist of three components. First, a comparison of Painted Redstart's diet with the diets of several other insectivorous birds will show whether flies with well-developed Giant Descending Neuron Clusters are more common in the diet of redstarts than in the diet of other insect-eating birds that do not use this exploitative hunting technique. Second, electrophysiological studies of the neurons in the Giant Descending Neuron Cluster will be used to test whether these neurons are especially sensitive to the redstart's displays. Third, a field study of the foraging performance of redstarts with experimentally enlarged and reduced white patches will show whether the arrangement naturally present in redstarts is optimal for flushing their insect prey.