Information about ovarian or testicular cycles is available for several Neotropical species of snakes (Marques et al., 2009). However, descriptions about courtship, mating or combative behaviours are still scarce and most information available comes from extratropical species (Sasa and Curtis, 2006). Herein we describe the rst observation of a courtship and mating in the Calico snake Oxyrhopus petola. Oxyrhopus petola is a common colubrid snake, widely distributed throughout South America and in parts of Central America (Savage and Villa, 1986; Markezich, 2002; Lynch, 2009, Palmuti, Cassimiro and Bertoluci, 2009). However, MacCulloch et al. (2009) suggest that the wide distribution of O. petola could represent more than one species. In Brazil, it is found in different habitats like Gallery forests and Brazilian Savannah (Vaz-Silva et al., 2007), Atlantic forests (Santana et al., 2008) and Amazon forests (Bernarde and Machado, 2000). Information about its reproductive biology is scarce in the scientic literature. Lynch (2009) found in Colombia, a clutch of eight near-term eggs in October, 2006 (early spring) and describes O. petola as having a markedly seasonal reproductive pattern. Test et al. (1966) presented information about a captive female Herpetology Notes, volume 3: 139-140 (2010) (published online on 13 May 2010) Observation of mating in the Calico Snake Oxyrhopus petola Linnaeus, 1758 Rogério Loesch Zacariotti 1 *; Rodrigo del Rio do Valle 2,3 1 Laboratório de Ecologia e Evolução, Instituto Butantan. Avenida Dr. Vit al Brasil, 1500, 05503-900, São Paulo, Brazil; e-mail: [email protected] 2 Faculdade de Medicina V eterinária e Zootecnia, Departa- mento de Cirurgia, Universidade de São Paulo, A v Prof. Dr. Orlando Marques de Paiva, 87, 05508-270, Sao Paulo, Brasil. 3 Wildlife Management Consultoria V eterinária Ltda. *corresponding author Abstract. Oxyrhopus petola is a common colubrid snake, widely distributed throughout South America and in parts of Central America. However, information about its reproductive biology is scarce. The present communication is the rst observation of mating in Oxyrhopus petola. Keywords. Squamata, Pseudoboini, reproduction. Figure 1. Calico snakes ( Oxyrhopus petola) mating.