Diet of Phrynops geoffroanus (Schweigger 1812) (Chelidae) in an Environmental Protection Area in the Amazon Region of Maranhão State, Brazil

—The knowledge of the dietary composition of a species can identify important food resources for individuals and limiting resources for populations. We analyzed the dietary composition of Geoffroy’s Side-necked Turtle (Phrynops geoffroanus) by collecting stomach contents between May and November 2013. We calculated the modified Index of Relative Importance (IRI) to determine which food items were the most representative for each sex and size class. We analyzed the diet of 113 Phrynops geoffroanus (51 males, 49 females, and 13 juveniles) based on food items classified as plant or animal (fish, amphibian, insect, gastropod, crustacean or unidentified animal material). For males, there was no significant difference in the quantity consumed between animal and plant matter (χ2 = 1.376, df = 1, P = 0.241), and for females there was a significant difference, with a higher consumption of animal matter (χ2= 32.85, df = 1, P < 0.001). Based on the Index of Relative Importance (IRI), the food of greatest importance for juvenile categories were plants (IRI = 77.29%) and insects (IRI = 11.05%).