Infrared Reflectance in Chameleons (Chamaeleonidae) from Kenya

Abstract

The reflectance of infrared light is a phenomenon rarely reported in amphibians and never reported in reptiles in connection with background substrate matching. Five species of chameleons (Chamaeleo hohlzelii, schubotzi, graci/is, jacksoni, fischeri) were photographed in Kenya shortly after capture using Kodak infrared film. Two species (gracilis. fischeri) reflected infrared light while the others did not. Infrared reflectance may be a thermoregulatory mechanism or may allow the animal to blend in with its surroundings for both avoiding predators and capturing prey; all suggestions are speculative. CHAMELEONS (Chanaeleo sp.) ARE COMMON LIZARDS comprising about 75 species inhabiting a wide variety of habitats, primarily in Africa and Madagascar. Most are arboreal and diurnal, although some are terrestrial. During the day, the arboreal chameleons are concealed in bushes, shrubs, trees, and along hedges where they feed on insects and other small arthropods. At night, they sleep near the tips of branches at varying heights above the ground (Hebrard 1980), and most use a different sleeping perch each night. Despite their abundance, the ecology and behavior of free-living east African chameleons is poorly known, and much of what is published is based on laboratory observations (Bustard 1965, 1966; Kastle 1967). Most studies of chameleons center on systematics (as reviewed by Rand 1963, Hillenius 1959, Brygoo 1971, de Witte 1965) and the ability of the members of the family Chamaeleonidae to change color in response to temperature, light, and degree of excitation (as reviewed by Zoond and Eyre 1934). The belief that chameleons rely on both concealing and disruptive coloration, as well as immobility or at least very slow movement, to avoid predators is well established in the literature (Cott 1940, Stephenson and Stewart 1955). Cott (1940), using black and white infrared film, showed that the treefrog Hyla (-Litoria) caerulea and larva of the hawkmoth (Smnerinthus ocellatls) reflected infrared light such that a blending with the background occurred. Schwalm et al. (1977), using color infrared film, showed that several species of frogs reflect infrared light whereas others do not. No work has as yet been published concerning this phenomenon in terms of color-matching in reptiles although Porter (1967) and Norris (1967) measured IR reflectivity using spectrophotometer analysis. METHODS Five species of chameleons (Chanaeleo fischeri, gracilis, hohnzelii, jacksoni, schubotzi) were collected and returned tt) the laboratory at the National Museums of Kenya. All animals were photographed using Kodak Infrared Ektachrome film (ASA 160, F 5.6 16.0, 1 125 sec.) within 10 min of one another, and all photographs were taken in natural sunlight on the same roll of film. This film has a sensitivity to about 900 nm (Kodak Publ. N-17, 1974). By using a vellow filter, blue light is excluded resulting in a color shift such that green objects appear blue, red objects appear green, and infrared