Mechanistic limits on climbing in arboreal lizards: Adhesion, Power output, and temperature effects

Most studies of locomotion assume that animals occupy flat, broad substrates, but for many arboreal species, such as climbing lizards, this is rarely the case.  Rather, their habitat is typically composed of surfaces that vary in both diameter and incline.  Thus, one of the central foci of our laboratory is to study how factors related to arboreal habitats (incline, surface diameter) affect locomotor performance.

Photo by D. J. Irschick

Fig. 1. A twig anole (Anolis sheplani) from Hispaniola.

Adhesion

Geckos and Anolis lizards, among other animals, possess elaborate and highly effective toepads that they use to climb smooth, even slick, surfaces.  A key goal of our lab is to understand the ecological and evolutionary roles of these amazing adaptations.  We apply a variety of techniques, including force-plate analyses, analysis of temperature, and microscopic studies of surface materials.

Acceleration and power output

One of the on-going areas of research is the study of how surface diameter affects acceleration in Anolis lizards.  The ability of animals to accelerate effectively may make the difference between a successful escape and being eaten, but studies of acceleration are few.  We are currently applying both a comparative and experimental approach to this subject by both comparing different Anolis lizards from different island systems, as well as manipulating surface diameters within a single species. 

When comparing different species of Anolis lizards, one expectation is that species that are fast sprinters will also excel at acceleration.  Thus, one might expect an evolutionary relationship between maximum speed and maximum ability to accelerate.  Within a species, one might also expect that acceleration will diminish when moving on narrow surfaces, but the degree to which acceleration will decline is unclear, and may vary according to the morphological and behavioral characteristics of the species.  These and other results from this research will be discussed on this web page later on.

3-D kinematics

In the near future, we will also be examining how 3-D kinematics are affected by movement on surfaces of varying diameters and inclines.  Recent work on the 3-D kinematics of terrestrial lizards shows that gaits can change dramatically with a number of variables, including incline, speed, and locomotor mode (bipedal vs. quadrupedal).  Another reason for completing this research is to determine the kinematic mechanisms by which some species decline in performance across different inclines, whereas other species do not.  Understanding the mechanistic and behavioral basis of this interspecific difference could provide a strong mechanistic link to the habitat use of different species of anoles.

Relevant literature:

Irschick DJ, Austin CC, Petren K, Fisher RN, Losos JB, Ellers O.  1996.  A comparative analysis of clinging ability among pad-bearing lizards.  Biological Journal of the Linnean Society  59:21-35.

Macrini, TE, Irschick DJ, Losos JB.  2003.  Ecomorphological differences in toepad characteristics between mainland and island anoles.  Journal of Herpetology.  37:52-58.

Elstrott J, Irschick DJ.  2004.  Evolutionary correlations among morphology, habitat use and clinging performance in Caribbean Anolis lizards.  Biological Journal of the Linnean Society. 83:389-398.

Vanhooydonck B, Andronescu A*, Herrel, A, and Irschick DJ.  2005. Effects of substrate structure on speed and acceleration capacity in climbing geckos.  Biological Journal of the Linnean Society.  85:385-393. 

Bloch N*, Irschick DJ.  2005.  Toe-clipping dramatically reduces clinging performance in a pad-bearing lizard (Anolis carolinensis).  Journal of Herpetology.  39:288-293.

Bergmann P, Irschick DJ.  2005.  Effects of temperature on maximum clinging ability in a diurnal gecko: Evidence for a passive clinging mechanism?  Journal of Experimental Zoology.  303A:785-791.

Bergmann P, Irschick DJ.  2006.  Effects of temperature on maximum acceleration, deceleration and power output during vertical running in geckos.  Journal of Experimental Biology.  209:1404-1412

Vanhooydonck B, Aerts P, Irschick DJ, Herrel A.  2006.  Power generation during locomotion in Anolis lizards: an ecomorphological approach.  In Biomechanics: A mechanical approach to the ecology of animals and plants.  A. Herrel, T. Speck and N. Rowe, Eds.  CRC Press, Boca Raton, Florida.  In press.

Irschick DJ, Herrel A, VanHooydonck B. 2006. Whole-organism studies of adhesion in pad-bearing lizards: Creative evolutionary solutions to functional problems. Journal of Comparative Physiology A. 192:1169-1177.

VanHooydonck B, Herrel A, Van Damme R, Irschick DJ.  2006.  The quick and the fast: the evolution of acceleration capacity in Anolis lizards.  Evolution.  60:2137–2147.

VanHooydonck B, Herrel A, Irschick DJ.  2006.  Out on a limb: the differential effect of substrate diameter on acceleration capacity in Anolis lizards.  Journal of Experimental Biology.  209: 4515-4523.

Click here for access to a rather large (~30 mb) gecko movie (running uphill with a large load on it)