Food Partitioning in Three Sympatric Species of Map Turtle, Genus Graptemys (Testudinata, Emydidae)

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Abstract
Three species of map turtle, Graptemys geographica, G. ouachitensis and G. pseudogeographica, inhabit the Mississippi River near Stoddard, Vernon County, Wisconsin [USA]. Adult females of all spp. are of similar size and are distinctly larger than males. G. geographica has a notably wider head than the other 2. Quantitative analysis of fresh stomach contents of 113 adult females, qualitative analysis of 74 others and feeding observations confirm that the 3 spp. use different foods and feeding strategies. G. geographica is a carnivore specializing on mollusks. G. ouachitensis is an omnivore but specializes in surface feeding. G. pseudogeographica is a general omnivore, overlapping the other 2 spp. in food and feeding areas. G. geographica seems to be limited by food availability. G. ouachitensis represents 66% of the Graptemys in the study area and may be best at exploiting an apparently unlimited food resource of aquatic vegetation and insect larvae. In Arkansas [USA], G. pseudogeographica is a mollusk specialist, possibly due to lack of competition from G. geographica and competition from the ubiquitous generalist, Pseudemys scripta, and the strict vegetarian, P. concinna.

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