PARENT SESSION
Oral Session #36: Conservation of aquatic systems: Ecology and ecotoxicology. Presiding: R. Lathrop.
Tuesday, August 7, 2001. 1:00 PM to 5:15 PM. Hall of Ideas H.
Competitive behavioral interactions between the introduced Red-eared Slider (T.s. elegans) and the native Midland Painted Turtle (C.p. marginata).
McKenna, Kerry1, Tramer, Elliot1, 1
ABSTRACT- Introductions of non-indigenous species have had negative effects on native wildlife. The Red-eared Slider Turtle, Trachemys scripta elegans, a native of the southeastern US, has become more numerous in areas outside of its historic range. Researchers have suggested that the non-indigenous Red-eared Slider will have a harmful effect on other turtles. This study examined feeding behaviors and dispersal rates of the slider and the Midland Painted Turtle (Chrysemys picta marginata) when placed in direct competition. I hypothesized that the Red-eared Sliders would obtain more food resources than Painted Turtles and as a result, Painted Turtles would have a greater frequency of dispersal than the sliders. An eight-month indoor study was performed at the University of Toledo′s Lake Erie Research and Education Center (Oregon, OH) to test this notion. The study examined turtles in mixed species treatments versus those in single species treatments. Behavioral interactions, specifically the occurrence of aggressive (bites, swipes, open mouth gapes, food removal, rams) and non-aggressive (withholding, running, hiding and dispersing with the food) displays during feeding, were observed, videotaped and analyzed. Food rank was measured during feeding by recording the order that each individual reached the food. Turtle growth, as measured by weight, was recorded bimonthly. The tendency of turtles to disperse was measured using one-way trap doors that only allowed turtles to leave the enclosure. Results indicated that the female sliders are more aggressive, in regards to feeding rank (p=0.003) and behaviors (p=0.0001), than female Painted Turtles. The male sliders did not show significant differences from the male Painted Turtles. The sliders of both sexes did not exert a significant effect on the growth (weight) of the Painted Turtles. However, significantly more female Painted Turtles in mixed species enclosures dispersed than female Painted Turtles in conspecific enclosures (p=0.008). This suggests that the Red-eared Slider negatively affected the Midland Painted turtle and that the slider may similarly affect already declining species (e.g., Blanding′s Turtles Emydoidea blandingii, Spotted Turtles Clemmys guttata, Asian Turtles sp. Cuora sp.).
KEY WORDS: Trachemys scripta elegans, Invasionary species, behavioral competition, feeding competition