Comparison of Tongue Extrusions in Representatives of Six Families of Lizards

Abstract

It has been widely noted that many species of lizards extend the tongue frequently under natural conditions. Although several reasons, including chemoreception, have been hypothesized for this behavior, sufficient quantitative data have not been collected to indicate its importance. We compared baseline rates of tongue extrusions for six different families of captive lizards and found significant differences between all six families. The range of variation in frequency was from a low of 3.4 tongue extrusions/30 minutes for the Cordylidae to a high of 299.5/30 minutes for the Teiidae. The frequency of tongue extrusions was: Cordylidae < Iguanidae < Gerrhosauridae < Scincidae < Helodermatidae < Teiidae. An increase in the frequency of tongue extrusions seemed to be correlated with increased bifurcation of the tongue. Possible uses of this tongue extrusion are explored for the six different families. The differences in frequency of tongue extrusion in different families may indicate the relative importance of the tongue-Jacobson's organ system.