The endemic species, Atelopus laetissimus Ruiz-Carranza, Ardila-Robayo & HernandezCamacho (1994), from Sierra Nevada de Santa Marta (department of Magdalena, Cuchilla de San Lorenzo, Colombia), inhabits streams and rivers in humid low montane (sub-Andean) forest (bmh–MB; Espinal and Montenegro, 1963; Tamaris-Turizo & Lopez-Salgado, 2006) between 1900 and 2880 m. This species belongs to the world’s most endangered vertebrate genus (Young et al., 2004), listed under the Critically Endangered category by RamirezPinilla (2004). Since its description in 1994 it was not seen again until 2006 (CarvajalinoFernandez, et al. 2008). After rediscovery, the species has been subject of only limited research (Granda-Rodriguez et al., 2008). Here we report new localities for A. laetissimus, which extend its lower altitudinal limit and report another life zone for the specie; with temperature data from different microhabitats used. The study area is known as “La Cascada” (11°10’02.0” N, 74°10’41.5” W, 1,560 m; Fig. 1). It is characterized by steep slopes and has an average annual rainfall of 2446 mm. The area is surrounded by forest composed mainly of Anarcadiaceae, Areaceae, Cecropiaceae, Moraceae, Piperaceae and Sapotaceae. Microhabits are characterized by rocky areas with sand and leaf litter on the banks at the river (Fig 2a). The soil in the forest is mostly covered by leaf litter and wood in decomposition process; and ferns in open fields (Fig. 2b). Sampling was by visual encounter surveys (VES; Lips et al., 2001; Crump & Scott, 1994) in an approximate area of 1000 m x 30 m along the watershed, including 10 m at each side of the riverside. Field work was conducted on November 11 and 12, 2008; January 30 and 31, 2009; March 18 and 19, 2009, during the following periods: 09:00 to 11:00 h, 12:0014:00 h, 15:00-17:00 h, 18:00-20:00 h and 21:00-23:00 h by a single person. Sampling was repeated from October 18 to 28, during the following periods: 09:00–12:00 h, 15:00–17:00 h, 19:00–21:00 h and 22:00-00:00 h by two observers. This gave a total sampling effort of 234 hours/person.