Adhesion and the Toe-Pads of Treefrogs

Various hypotheses concerning the functional mechanism of the toe-pads of treefrogs are discussed. A test of the relative adhesive abilities of the tetraploid treefrog Hyla versicolor and its diploid sibling species Hyla chrysoscelis shows little difference in ability to adhere to glass despite known large differences in the sizes of the pad cells. The adhesion of the toe-pads is thus related to the area of contact and not to the size or number of pad cells. Freshly killed treefrogs are as sticky as live treefrogs. The reduction of surface tension by soap solutions or detergent reversibly diminishes adhesive ability. Surface tension is the primary means by which treefrog toe-pads adhere to glass.