By: Emily Powell, OTS PhD Student from the University of Miami
While visiting La Selva Biological Station, many visitors enjoy night hikes into the depths of the rainforest to look for frogs and nocturnal mammals, but a surprising diversity of herpetofauna can be found by simply looking around the walls and roofs of laboratory buildings. Mexican tree frogs (Smilisca baudinii) and Snouted tree frogs (Scinax sp.) sleep in nooks around rafters, and Cane Toads (Rhinella marina) hop around awkwardly between buildings, gulping at insects attracted to the lights. Little house geckos (Hemidactylus frenatus) crowd around light sources to snatch moths. But if you stay up really late past 10 or 11 o’clock, the real monsters come out.
The Turnip-tailed Gecko (Thecadactylus rapicauda) grows to about 9 inches in length and has a camouflaged pattern that allows it to blend seamlessly into its natural tree bark home. It has a long banded tail, that frequently breaks off when a predator tries to catch the gecko, and regrows in a particular turnip-like shape. We examined one of these geckos and were astounded by the tremendous power of its toe pads. These sticky pads are covered with adhesive lamellae which are comprised of tiny hairs called setae that are about 80-100 μM long. These tiny hairs allow the geckos to use Van der Waals forces to cling to flat surfaces. These huge geckos have such strong gripping ability that we actually had trouble removing their toes from our clothes. If one of these geckos leaps to avoid a predator, even a single toe pad is strong enough to catch the full weight of the gecko and help it scramble to a safer surface. When the gecko walks, it must curl its toes slowly off of surfaces at a particular angle to detach the forces of the setae. These geckos are a spectacular example of the way that evolution can act as an inventor, more powerful than all the imagination of mankind.
For more information on geckos and their amazing lamellae, see
Pianka, E. R., & Sweet, S. S. (2005). Integrative biology of sticky feet in geckos. BioEssays, 27(6), 647-652.