Summer Nesting of Turtles in Alligator Nests in Florida

We examined summer use of American alligator (Alligator mississippiensis) nests by nesting turtles, principally Florida redbelly turtles (Pseudemys nelsoni), in lakes Okeechobee, Apopka, Griffin, and Jesup during 1986-1991 and in three other wetlands in peninsular Florida for ≥3 yr. Other turtle species recorded using alligator nests were Apalone ferox, Kinosternon sp., and Sternotherus odoratus. In the seven wetlands, 26.6% of 1586 occupied (i.e., active) alligator nests contained P. nelsoni eggs. Of the four lakes sampled for 6 yr, Lake Okeechobee had the highest incidence of use of occupied nests by nesting P. nelsoni and the most turtle clutches per occupied nest. Nesting P. nelsoni used occupied nests more frequently in Lake Apopka than in Lake Jesup. Nesting P. nelsoni used vacant alligator nests (63.6%) more often than occupied nests (36.1%) at Lake Okeechobee, which suggests that attending female alligators may deter nesting turtles. Annual incidence of nest use by nesting turtles was correlated positively with June-July mean water levels in lakes Okeechobee and Jesup, where emergent marsh was the principal habitat and alternative nest sites were probably limited during high-water conditions. In the four lakes combined, turtles did not preferentially select alligator nests in a particular habitat type. Use of 1330 occupied nests by turtles in the four lakes was significantly lower in 1990 (13.5%) than in other years (21.9%-29.3%). We hypothesize that observed differences among lakes in turtle use of alligator nests resulted from differences in (1) water-level fluctuations, (2) availability of alternative nesting sites (i.e., distance to upland habitat), and (3) turtle population sizes.