| Popis: |
We examined the orientation of 76 naive painted turtles (Chrysemys picta belli) and 746 snapping turtles (Chelydra serpentina) during initial dispersal from experimental nests in the Weaver Dunes area of southeastern Minnesota. We conducted 15 releases into large circular arenas in 4 natural nesting areas and 2 atypical areas. Hatchling orientation and dispersal for both species were 1) all nonrandom, 2) appeared to be based on vision (i.e., nonpolarized light), and 3) toward nearby, open, and highly illuminated horizons, regardless of whether or not they were associated with the wetlands. A first-order estimate of hatchling snapping turtle perception distance was 55–90 m. We found no evidence that suggests that specular light from the wetlands, olfaction, or humidity gradients were important in orientation. At 2 of 3 locations, substantial changes in orientation direction occurred when hatchling snapping turtles were released in morning vs. late afternoon. Changes in dispersal directions in the ... |
