Sinaloa Toad (Incilius mazatlanensis)
Sinaloa Toad, Sierra Aconchi, Sonora, MX. Photo by Jim Rorabaugh
The Sinaloa Toad is of moderate size (<86 mm SVL), and the dorsum is characterized by irregular light and dark mottling with dark, horny, tubercles and an irregular mid-dorsal light stripe. Adults have very prominent, dark-edged cranial crests; the interorbital crests are not united anteriorly. In small juveniles, these distinctive cranial crests may be much reduced and not dark-edged. The parotoid glands are small and round or vertically oval, and about as wide as the tympanum.
This is a Mexican species that barely enters our area on the Río Bambuto in the Imuris area south of Nogales, where the river, a tributary to the Río Magdalena, runs through a region in which the vegetation is at an ecotone among Sonoran desertscrub, foothills thornscrub, and semi-desert grassland. In 2016, it was also found near the Río Cocospera at Rancho El Aribabi in a mesquite-invaded semi-desert grassland (Rorabaugh and Verdugo-Figueroa in press). Throughout its range in Mexico, this is a species of arroyos, streams, rivers, agricultural ditches and canals, and impoundments, such as cattle tanks. Breeding occurs throughout the summer rainy season primarily in permanent waters, but also in rain-filled pools and ephemeral streams. The advertisement call of the male is a rattling trill, 2.5-6.6 seconds in duration, typically given from the water’s edge. Females deposit long strings of eggs, and tadpoles metamorphose in a month or less. Larger tadpoles are black on the head and back, with mottling on the face, cheeks, and snout. The tail has a barred appearance when viewed from the top, but the tail fin is mottled. The intestines are clearly visible through the abdomen. The largest tadpoles are about 20 mm total length. The diets of Sinaloa Toads from two sites in Sonora and three in Chihuahua consisted of invertebrates, and were dominated numerically by ants, beetles, and true bugs. Beetles dominated volumetrically. Hybrids between this species and the Red-spotted Toad have been reported. Most of the literature on this species is under the name Bufo mazatlanensis.
Throughout its range, the Sinaloa Toad is not known to be significantly threatened, although it has likely declined or been extirpated from some developed areas. It is listed as a species of least concern on the IUCN Red List. The Sinaloa Toad is endemic to Mexico.
Ford, P.L., and N.J. Scott. 2006. Community level analysis of opportunistically-breeding anurans in western México. Herpetological Natural History 9(2):177-182.
Oliver-Lopez, L., G.A. Woolrich-Piña, and J.A. Lemos-Espinal. 2009. La Familia Bufonidae en México. Universidad Nacional Autónoma de México, Tlalnepantla y CONABIO, México, D.F.
Lemos-Espinal, J.A. and H.M. Smith. 2007. Anfibios y Reptiles del Estado de Chihuahua, Mexico (Amphibians and Reptiles of the State of Chihuahua, Mexico). CONABIO, México, D.F.
Rorabaugh, J.C., and J.A. Lemos Espinal. 2016. A Field Guide to the Amphibians and Reptiles of Sonora, Mexico. ECO Herpetological Publishing and Distribution, Rodeo, New Mexico, USA.
Rorabaugh, J.C., and L. Verdugo-Figueroa. In press. Incilius mazatlanensis (Sinaloa Toad). Mexico: Sonora. Herpetological Review.
Smith, G.R., J.A. Lemos-Espinal, A.B. Burner, K.E. Winter, and C.B. Dayer. 2011. Diets of three species of Bufonids (Amphibia, Anura) from northern Mexico. Western North American Naturalist 71(4):563-569.
Author: Jim Rorabaugh