SREL Reprint #1956

Resource partitioning by the estuarine turtle, Malaclemys terrapin: trophic, spatial, and temporal foraging constraints

Anton D. Tucker, Nancy N. Fitzsimmons, and J. Whitfield Gibbons

Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

Abstract: We investigated the foraging ecology of the diamondback terrapin (Malaclemys terrapin) in South Carolina by examining fecal samples for evidence of resource partitioning. From 76-79% of the dietary volume was the salt marsh periwinkle (Littorina irrorata); crabs (Uca pugnax, Sesarma reticulatum, and Callinectes sapidus), barnacles (Balanus), and clams (Polynesoda caroliniana) constituted the remainder. Dietary partitioning is related to the ontogenetic niche of terrapins. Sexual dimorphism occurs in terrapins with females having larger heads and bodies than males. Terrapins with large head widths ingest significantly larger periwinkles and a wider diversity of prey than terrapins with small head widths. Dietary overlap between males and females is greatest when females are small and decreases as females develop larger enlarged heads. Sexual dimorphism in terrapin trophic structures appears to be partially driven by ecological divergence through resource partitioning.
High tides permit terrapins to forage aquatically in upper reaches of the salt marsh. Prey size and distribution are variable and changing tidal heights affect the spatiotemporal availability of prey to foraging terrapins. Divergent foraging strategies for terrapins of different head widths may result in habitat partitioning. Food accessibility rather than food abundance may be a limiting factor for terrapins in areas of high tidal variability. Terrapins are clearly prominent but unrecognized macrocodsumers in salt marsh ecosystems.

Keywords: Resource partitioning; Turtle; Malaclemys; Dimorphism; Salt marsh; Foraging ecology; Littorina; Trophic structure

SREL Reprint #1956

Tucker, A.D., N. FitzSimmons, and J.W. Gibbons. 1995. Resource partitioning by the estuarine turtle, Malaclemys terrapin: trophic, spatial, and temporal foraging constraints. Herpetologica 51:167-181.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).