Maximum Body Size of the Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis)

Gerald R. Johnston^1,*, Jeremy S. Geiger¹, Travis M. Thomas², Kevin M. Enge³, Eric Suarez⁴, and Bryant Davis⁵

¹Tangled Bank Conservation, 192 East Chestnut Street, Asheville NC 28801. ²Nature Coast Biological Station, University of Florida, Cedar Key, FL 32625. ³Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Gainesville, FL 32601. ⁴Division of Habitat and Species Conservation, Florida Fish and Wildlife Conservation Commission, West Palm Beach, FL 33412. ⁵Department of Statistics, University of Florida, Gainesville, FL 32611. *Corresponding author.

Southeastern Naturalist,Volume 22, Special Issue 12 (2023): 418–428

Abstract
The published literature does not provide a consensus regarding maximum body sizes of North America’s largest wild freshwater turtles (genus Macrochelys). The largest known wild M. suwanniensis (Suwannee Alligator Snapping Turtle) currently exists as a curated specimen measuring 713 mm straight-midline carapace length, 801 mm maximum carapace length, 619 mm maximum carapace width, and 236 mm maximum head width. The turtle was never weighed, but we used morphometric data from our studies in the Santa Fe and Suwannee rivers to estimate that it weighed ~76.4 kg (168 lbs) when captured. Our 95% prediction interval (67.6–86.3 kg [149–190 lbs]) suggests that speculative estimates and anecdotal reports of M. suwanniensis that weigh ≥90 kg (≥200 lbs) are dubiousy.

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