Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Edward O. Moll


An ecological study of the painted turtle (Chrysemys picta) was conducted at the Fox River site in Chain O' Lakes State Park in northeastern Illinois from March to September in 1987. Findings were compared to two studies in 1986 concerning the common snapping turtle (Chelydra serpentina) and Blandings turtle (Emydoidea blandingi) also present in the area. Population densities and composition were evaluated to determine the degree of interspecific competition.

Two hundred-forty five turtles were captured in 1986 and 1987. Painted turtles comprised 75 percent of the chelonian population, while Blandings turtles and snapping turtles made up 15 and 10 percent respectively. Densities of the three sympatric species were 114.1, 11.7 and 8.6 individuals per hectare. Biomass estimates show Chelydra predominating with 23.7 kg/ha followed by Chrysemys (15 kg/ha) and Emydoidea (11 kg/ha).

Intrasite differences show Chrysemys densities in the five ponds varying between 21.4 and 139.5/ha with highest densities in the most vegetated ponds. Conversely, Chelydra was relatively most abundant in relatively unproductive ponds (19.0/ha). Emydoidea utilized these ponds more in the spring and the richly vegetated ponds in the summer and fall. Biomass estimates for painted turtles ranged from 4.4kg/ha to 29.7kg/ha. Snapping turtles biomasses ranged from 14.7kg/ha to 58.9kg/ha, and Blandings turtles biomasses ranged from 10.5 to 25.5 kg/ha. Chrysemys was most dense in highly vegetated ponds and where Chelydra were least dense. Potential for food competition include a moderately high overlap in diet between the two species. Competition between the three species may be alleviated by differences in diet, feeding behavior, activity periods and spatial activity.

Chrysemys has the most generalized diet of the three species, while Emydoidea was most specialized. Painteds were closest to snappers in food utilization. Densities of the three species were inversely correlated, while movements and home ranges were positively correlated with the degree of specialization in diet. Chrysemys utilized surface mats of vegetation for the preponderance of their activity while Emydoidea foraged in the shallows; Chelydra was highly variable in their activity areas.