Meeting Abstract

25.6  Monday, Jan. 4  Perch size and structure have species-dependent effects on the arboreal locomotion in rat snakes and boas HERRMANN, MH*; JAYNE, BC; University of Cincinnati; University of Cincinnati Herrmamp@mail.uc.edu

Arboreal habitats create many challenges for locomotion, such as balancing on or gripping narrow cylindrical surfaces with variable inclines and branching density. Although hundreds of phylogenetically diverse species of snakes climb trees, comparative data on arboreal locomotor performance are lacking. We studied the arboreal locomotion of similar-size juveniles (snout-vent length ~ 60 cm) of two distantly related species: the red rat snake, Pantherophis guttatus, and Boa constrictor. We determined the kinematics and performance of snakes moving horizontally and up vertical and 45° inclines on cylinders with seven diameters (1.7 – 108 mm). We added pegs to simulate more complex branching structure, and we varied the friction of surfaces. Both species were fastest on intermediate diameters and used lateral undulation on surfaces with pegs. Pegs enhanced speed and allowed climbing on surfaces that were otherwise impassable. On cylinders without pegs, rat snakes only used concertina locomotion, whereas boas used lateral undulation on small-diameter horizontal surfaces and concertina in all other circumstances. Although concertina locomotion always involved periodic stopping and gripping, the kinematics of this gait differed between species. The boas were generally faster and slipped less than the rat snakes on surfaces without pegs, whereas the rat snakes were often faster on surfaces with pegs. Boas could traverse larger diameters than the rat snakes. The unexpected ability of both species to move on very narrow cylinders included an ability to cope with rolling about the long axis of the cylinder. The use of a balancing gait rather than a gripping gait by boas was also unexpected in light of their apparently superior gripping ability.