Meeting Abstract
88.3 Thursday, Jan. 7 Predicting adhesive capabilities in Anolis and Phelsuma lizards via the frictional adhesion model and critical detachment angle HAGEY, TRAVIS*; HARMON, LUKE; AUTUMN, KELLAR; University of Idaho; University of Idaho; Lewis and Clark College, Portland, OR thagey@vandals.uidaho.edu
Geckos are capable climbing rapidly on nearly any surface using branched microscopic setae on the pads of their toes. Previously, based on results from the tokay gecko (Gekko gecko), Autumn et al (2006) proposed the frictional adhesion model. In this model, adhesion occurs only when setae are dragged along their natural curvature; the adhesive force (Fn) is anisotropic and controlled by the shear force, Fs ≥ -Fn/tan α*, where α* is the critical detachment angle of the seta. In tokays, α*=30°. Thus, to generate 1N of adhesion, a tokay gecko must produce 1N / tan30° = 1.7N of shear force. This model may allow us to predict the adhesive abilities of other seta-bearing lizards. To test the generality of the frictional adhesion model, we measured the detachment angle in two lizard genera, Phelsuma geckos that have similar setal morphology to that of tokays, and Anolis lizards, which have smaller, unbranched setae. Like tokays, Phelsuma climb well on vertical and even inverted surfaces with apparent ease. While Anolis are agile climbers on inclined and vertical surfaces, they are found only infrequently on inverted surfaces. We measured α* species averages between 27° and 35° in Phelsuma, similar to that of tokay. By contrast, α* varied from 16° to 20° between Anolis species, yielding shear:normal force ratios from 3.4:1 to 2.7:1. To adhere, some Anolis lizards must produce nearly 250% of the shear force required by particular gecko species. Our results suggest that the frictional adhesion model may apply broadly to seta-bearing animals. The low critical detachment angle in Anolis may limit their habitat choice to non-inverted surfaces. NSF-DEB-0844523 (LH). NSF-IOS-0847953 (KA), NSF-NBM-0900723 (KA).
