Substrate roughness affects ant foraging speed
Haileigh M. White and Stephen P. Yanoviak
Department of Biology, University of Louisville, Louisville, KY 40292
Cursorial, central-place foragers like ants often must navigate a variety of substrates to obtain resources. Worker ants are expected to minimize the costs of foraging by choosing pathways that minimize transit time. We tested this hypothesis in the field and laboratory by measuring running speed in foraging Camponotus pennsylvanicus ants on dowels covered with a gradient of rough substrates (i.e., different grits of sandpaper). Within species, average running speed was statistically similar between smooth and moderately rough substrates, but became significantly slower when the magnitude of roughness increased to ca. 33% of ant body length. When offered a choice of substrates, 62% of workers used the smoother of two pathways. These preliminary results suggest that ants choose smoother pathways even when rougher alternatives have no measurable effect on foraging speed. We are continuing to explore these patterns across a range of ant body sizes and in a phylogenetic context.
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