Smilisca baudinii: Basking behavior and rapid color change

Abstract

Basking behavior has been considered important for digestion, control of external parasites, protection against bacterial infections, and the synthesis of vitamin D in amphibians and reptiles (Freed 1980. Physiol. Zool. 53:433–444). However, this behavior is uncommon in amphibians due to their typically highly permeable skin, which allows for significant water loss through evaporation (Tattersall et al. 2006. J. Exp. Biol. 209:1185–1196). Only a few species effectively utilize prolonged basking in dry environments for thermoregulation (e.g., Pearson and Bradford 1976. Copeia 1976:155–170; Carey 1978. Oecologia 35:197–219; Bradford 1984. Copeia 1984:966–976; Vences et al. 2002. Ann. Zool. 39:209–220; Tattersall et al. 2006, op. cit.). Frogs that tolerate prolonged exposure to full sunlight are typically from hot, arid regions of Africa and South America (Shoemaker et al. 1987. Physiol. Zool. 60:365–372). Furthermore, basking behavior in frogs is usually associated with remarkably low rates of evaporative water loss, and species exhibiting this behavior primarily belong to the genera Chiromantis, Phyllomedusa, and Hyperolius (Drewes et al. 1977. J. Comp. Physiol. 116:257–267; Withers et al. 1982. J. Comp. Physiol. 97:335–343). Smilisca baudinii is a hylid distributed across Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, and the USA (Loc-Barragán et al. 2024. Herpetozoa 37:25–42). In Guatemala, it is known to inhabit lowlands in central and northern tropical forests (Campbell 1998. Amphibians and Reptiles of Northern Guatemala, the Yucatan, and Belize. University of Oklahoma Press, Norman, Oklahoma. 400 pp.). The skin coloration in S. baudinii is highly variable, ranging from light green with olive green or dark brown markings to yellow or cream flanks with dark brown or black spots (Duellman 2001. The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Ithaca, New York. 1158 pp.), with a recorded case of axanthism (Vásquez-Cruz and Fuentes-Moreno 2020. Cuad. Herpetol. 34:313–320). Despite this intense color variation, an abrupt change in skin color while basking has not been described for S. baudinii.