Abstract

Many species of animals employ camouflage to render them inconspicuous. Selection to precisely match cryptic color patterns to the background substrate should result in geographic variation in relation to substrate type. We tested this premise by examining color pattern variation in relation to substrate surface in Fowler's Toad (Anaxyrus fowleri), a noxious and cryptically colored amphibian that is widespread in eastern North America and frequently associated with sandy habitats. We quantified total dorsal spot area, number of spots, and size of the four largest dorsal spots among 330 specimens of Fowler's Toads (89 live, 241 preserved) in 14 samples from Canada and the United States. We found no significant difference in the extent or number of spots between males vs. females or between living vs. preserved specimens after compensating for variation in snout–vent length. However, toads from freshwater habitats with extensive areas of open sandy terrain had significantly smaller and fewer dorsal spots than toads from either seacoast localities with open sands present or toads from freshwater habitats with open sands absent. Because saltwater seaside beaches and sand dunes are generally uninhabitable by amphibians, we take this as evidence consistent with the presence of adaptive background pattern matching coloration in this species.

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