Meeting Abstract

P1.168  Sunday, Jan. 4  Arboreal Habitat Structure Affects the Choice of Routes by Rat Snakes HAMILTON, R.A.*; JAYNE, B.C.; University of Cincinnati hamiltr4@email.uc.edu

Recent studies of arboreal vertebrates, including snakes, have found that the speed and difficulty of movement may be affected by: 1) the diameter and incline of individual branches, 2) the clutter and turns created by secondary branches, and 3) the gaps between different branches. Even though many snake species are arboreal, no previous study has determined whether or not they can perceive relevant structural variation of the habitat and respond by selecting a route that is most likely to enhance locomotor performance. Thus, we tested whether or not varying the gap distance and attributes of two (destination) perches on the far side of a crossable gap affected the route traveled by fifteen similar sized snakes belonging to two species of North American rat snakes (Elaphe [Fitzinger, 1833]), which are proficient climbers. For two destination perches with a 45 degree turn in a horizontal plane, snakes preferred to cross the shorter gap, but the strength of the preference for shorter gaps decreased when the difference in the gap distances decreased. The snakes were able to perceive gap distances differing by less than 7%. For perches that were within a horizontal plane, the snakes strongly preferred (93% of the time) going straight rather than crossing an equal distance (40 cm) gap with a 90 degree turn. However, decreased gap distance could override the preference for going straight. Additional factors such as the complexity of branching of the destination perches also resulted in non-random path choice. Thus, biases in the choices between alternative paths indicate both a sensory ability to perceive some subtle structural variation and an overall ability to select routes that optimize the mechanical benefits for locomotor performance.