The control of color change in the Pacific tree frog, Hyla regilla

Abstract

A number of environmental variables have been identified as affecting anuran color, but rarely have the interactions between these variables been investigated. In attempt to elucidate the function of color change, we conducted a within-subject, full factorial experiment designed to determine the simple and interactive effects of background, temperature, and light intensity on the rate of color change in the Pacific tree frog (Hyla regilla Baird and Girard, 1852). Color was investigated holistically, as well as by decomposing it into its constituent parts (hue, chroma, and lightness), using digital photography. The rate of color change was faster on the green versus the brown background, at 10 versus 25 °C, and at low versus high light intensity. There was also a significant effect of the interaction between background color and temperature on the rate of color change. We found increased rates of hue, chroma, lightness, and color change with increasing initial hue, chroma, lightness, and color distances between the Pacific tree frog and its background, respectively. In addition, initial color distance covaried with changes in environmental variables. After controlling for initial color distance, and thus the effects of background matching, background color and temperature still showed a significant interaction for their effects on rate of color change. These results suggest that crypsis (i.e., background matching) is not the only function of physiological color change in H. regilla. Physiological color change may also be used to hydro- and (or) thermo-regulate.

Malleable skin coloration in cephalopods: selective reflectance, transmission and absorbance of light by chromatophores and iridophores

“…Although most animal body patterns may not be changeable, some are highly reflective, such as those of many birds (Cuthill et al 1999;Osorio and Ham 2002;Vorobyev et al 1998) and reef fishes (Marshall 2000). In most animals with changeable body patterns, these changes generally take several seconds, hours, or even days (e.g., fish : Fujii 1993;Kasukawa et al 1987;Lythgoe and Shand 1989;lizards: Hadley and Oldman 1969;Taylor and Hadley 1970; tree frogs: Stegen et al 2004). One known exception may be the paradise whiptail (Pentapodus paradiseus), a tropical fish whose reflective changes are fast (i.e., fractions of a second; Mäthger et al 2003).…”

Body temperature, size, nuptial colouration and mating success in male Moor Frogs (Rana arvalis)

“…While it is known that some anurans become lighter at higher temperatures (e.g. King, Hauff and Phillips, 1994;Stegen, Gienger and Sun, 2004;Tattersall, Eterovick and de Andrade, 2006), a complete switch in colour, as that observed in male Moor Frogs from brown to blue, is probably affected by changes in sex-hormone levels (Hayes and Menendez, 1999). Nonetheless, colouration of individual males may to some extent depend on their ability to maintain high body temperatures (Stevenson, 1985a), even if physiological heat production is expected to be negligible in Moor Frog sized ectotherms (Stevenson, 1985b), and behavioural options are limited at night, when almost all males reside in the water and radiant heat is absent.…”

Camouflage, communication and thermoregulation: lessons from colour changing organisms

“…The resulting darkening or lightening, usually of either dorsal surfaces or the entire body, aids heat absorption and reflection, respectively, but may also increase conspicuousness (Norris 1967) by increasing colour contrast or reducing pattern matching. For example, in a laboratory setting, Pacific tree frogs Hyla regilla contrasted more against brown backgrounds at temperatures of 108C than 258C (Stegen et al 2004). In a pioneering study of the interaction between colour change and thermoregulation in 25 species of desert reptiles, Norris (1967) showed that the precision of background colour matching in the visible spectrum was dependent on temperature and the thermal ecology of the species.…”