Taxonomic notes: Atelopus mittermeieri is distinguished from other species of the genus in the region by its colour patterns (Acosta-Galvis et al. 2006).

Atelopus mittermeieri is known from the western slopes of the Cordillera Oriental, quebrada Aguas Claras (6 14' N, 72 56 W, 2525 masl) vereda Río Negro, Santuario de Flora y Fauna Guanentá-Alto Río Fonce, Municipality of El Encino, Department of Santander, Colombia (Acosta-Galvis et al. 2006).

The population at the type locality appears to be stable (Acosta-Galvis et al., 2006), although densities of adults are found to be low, while tadpole densities appear to be high (A. Acosta, pers. comm. 2008).

The species inhabits montane humid forest with canopy heights not exceeding 10 m. This forest is rich in moss and lichens. Atelopus mittermeieri is a diurnal stream-associated species, where adults are found either near the margins of the Aguas Claras stream or in the stream itself. Tadpoles are also found within the stream. Breeding activity has been recorded for July, after the rainy season, although tadpoles have been found both during March and July. Calls attributed to this species have been heard during the months of May and August. One female revealed 393 cream-coloured eggs (Acosta-Galvis et al., 2006).

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The presence of Batrachochytrium dendrobatidis has been confirmed for the known extant population of Atelopus mittermeieri (A. Acosta, pers. comm. 2008; Ruiz and Rueda-Almonacid, 2008), although live specimens did not exhibit clinical symptoms of chytridiomycosis (Ruiz and Rueda-Almonacid, 2008). Other possible threat factors include predation by introduced trout, pollution and sudden fluctuations in the stream's water level (Acosta-Galvis et al., 2006).

• 8.1.1 Unspecified species
• 11.4 Storms & flooding
• 9.3.4 Type Unknown/Unrecorded
• 8.1.2 Named species

The species is being constantly monitored at the type locality, which is in a protected area. Efforts have been directed towards the captive breeding of this species, although unfortunately without positive results in producing captive-bred offspring.

Listed as Endangered because of a serious population decline, estimated to be more than 50% over the last ten years, inferred from observed reduction in population size, the confirmed presence of chytridiomycosis, and a decline in both the extent of occurrence and area of occupancy, currently estimated to be 10 km2.

• Acosta-Galvis, A.R., Rueda-Almonacid, J.V., Velásquez-Álvarez, A.A., Sánchez-Pacheco, S.J., and Peña Prieto, J.A. 2006. Descubrimiento de una nueva especie de Atelopus (Bufonidae) para Colombia: ¿una luz de esperanza o el ocaso de los sapos arlequines? Revista de la Academia Colombiana de Ciencias Exactas y Naturales 30: 279-290.
• Ruiz, A., and Rueda-Almonacid, J.V. 2008. Batrachochytrium dendrobatidis and chytridiomycosis in anuran amphibians of Colombia. EcoHealth DOI: 10.1007/s10393-008-0159-z.