Spatial and temporal use of floodplain habitats by lentic and lotic species of aquatic turtles

We investigated the use of aquatic and terrestrial floodplain habitats by l entic and lotic turtles inhabiting the Missouri River, a contemporary, regu lated large river. Specifically, we tested whether habitats were used diffe rentially by turtle species, sexes, and life stages over biologically deter mined spatial and temporal scales. We monitored female and male false map t urtles (Graptemys pseudogeographica) and slider turtles (Trachemys scripta) for 14 months, using radiotelemetry. In addition, over a 3-year period we trapped G. pseudogeographica (n=591) and T. scripta (n=129) to supplement d ata on habitat use. Movements based on radiotelemetry and recaptures were s ummarized for each individual. Both species of turtles displayed dynamic an nual activity patterns and used diverse habitats including those typically considered terrestrial. Although G. pseudogeographica and T.: scripta spent a substantial portion of the year in the Missouri River (primarily in the cool months), newly created scour habitats also appeared to attract turtles during the cool season. However, in the warm months, habitat use became mu ch more diverse, with turtles occupying all identified habitats including f looded agriculture and forest. Relative to their proportions, slough and sc our habitats appeared to be highly favored while forests older than 4 years and agricultural habitats were proportionally less favored. We found few d ifferences between species. However, males of both species were consistentl y more sedentary, used half as many habitats, and moved half as far from th e river as did females, especially during May through July. Juveniles of bo th species were captured on average farther from the river than were adults , perhaps reflecting the close proximity of both nesting areas and shallow, productive habitats free of aquatic predators. We estimate a riparian zone of 449 m that encompasses 95% of the population movements away from the ri ver and discuss the quality of habitats important to reproduction and survi val of lentic and lotic floodplain turtles. These spatial and temporal move ment patterns, in light of their potential adaptive costs and benefits to G . pseudogeographica and T. scripta, are critical to understanding the ecolo gy of long-lived vertebrates that depend on contemporary large rivers.