Xenopholis Peters, 1869 comprises small to medium sized, terrestrial-fossorial snakes from eastern South America (Hoge and Federsoni, 1975; Loebmann, 2009; Ribeiro et al., 2011). Three species of Xenopholis are currently recognized (Uetz, 2018): Xenopholis undulatus (Jensen, 1900), Xenopholis scalaris (Wucherer, 1861) and Xenopholis werdingorum Jansen, Álvarez and Köhler, 2009. Xenopholis undulatus (Jensen, 1900) is a small opisthoglyphous snake, distributed from the central plateau of Brazil to Paraguay. This nocturnal snake has terrestrial-fossorial habits and occurs in gallery forests of the Cerrado in Central Brazil (França and Braz, 2013). Its diet is composed of amphibians and lizards (Cunha and Nascimento, 1993; França et al., 2008, Costa et al., 2013), and its reproduction is oviparous (Costa et al., 2013). Physalaemus cuvieri (Fitzinger, 1826) is widely distributed in the east-central region of South America, from northeastern Brazil to eastern Paraguay and northern Argentina (Mijares et al., 2010). Its diet is composed of invertebrates (Pinto, 2011), mainly Isoptera and Formicidae (Araújo et al., 2009). In 20 December 2017, we encountered one individual of Xenopholis undulatus in the municipality of Guapó (-16.8323°S, -49.5382°W), state of Goiás, Brazil, on top of a rock (30cm above the ground), at 10:30 pm, in a flooded area at the border of a gallery forest (Figure 1). The individual was preying upon an individual of Physalaemus cuvieri, swallowing the latter by its caudal portion and subjugating it with envenomation (Figure 2). When the snake noticed our presence, it immediately released the prey and moved to the rocks on the floor; the frog returned, still alive, to the water. Xenopholis undulatus is a common predator of amphibians, with a single observation of this species preying upon amphibians in situ (Kokobum and Maciel, 2010). Other events of predation were ex situ records, on specimens of Physalaemus cuvieri, and the lizard Hemidactylus mabouia (Costa et al., 2013). Besides being a rare field observation, we are not aware of reports of X. undulatus preying upon P. cuvieri in situ, and the documented predation attempt agrees with the assessment of Costa et al. (2013) that Herpetology Notes, volume 11: 829-830 (2018) (published online on 28 September 2018) Predation attempt of Xenopholis undulatus (Serpentes, Dipsadidae) on Physalaemus cuvieri (Amphibia, Leptodactylidae) André Teles 1 , Arthur de Sena 2,3,* , and Maurivan Vaz Ribeiro 1,4 1 Laboratório de Herpetologia e Comportamento Animal, Universidade Federal de Goiás. CEP: 74690-900, Goiânia/ GO, Brasil. 2 Departamento de Zoologia, Universidade de Brasília. CEP 70910-900, Brasília/DF, Brasil. 3 Departamento de Biologia, Universidade do Estado de Mato Grosso. CEP 78690-000, Nova Xavantina/MT, Brazil. 4 Programa de Pós-graduação em Biodiversidade Animal, Universidade Federal de Goiás. CEP: 74690-900, Goiânia /GO, Brasil. * Corresponding author. E-mail: [email protected] Figure 1. The flooded area near the gallery forest. Photo: André Teles.