Mexican Treefrog, Smilisca baudinii

Mexican Treefrog, Smilisca baudinii. Photograph taken in the greater Zihuantanejo area, Guerrero, November 2019. Photograph courtesy of Ron Woheau, Zihuantanejo.

Mexican Treefrog, Smilisca baudinii. Photograph taken in the greater Alamos area, Alamos, Sonora, January 2019. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

The Mexican Treefrog, Smilisca baudinii, is a member of the Hylidae family of Tree Frogs.  The Hylidae family consists of six hundred and thirty species placed into thirty-seven genera. There are nine species in the Smilisca Genus. The Mexican Treefrog is known in Mexico as Ranas Arborícolas.

Mexican Treefrogs are chubby and stocky in stature with short legs that have a row of warts along the lower arm. Their head is broad and flat with a rounded snout that is bluntly truncated. They are small to medium in size having a snout-to-vent length of 3.8 cm (1.5 inches) to 9.0 cm (3.5 inches). Slight sexual dimorphism is displayed with the females growing larger than the males. Their dorsum is slightly roughened and tan, brown, or green in color. Some individuals have blotched or barred dorsal patterns of brown, green, and/or red. A dark stripe runs from their snout to their shoulder. Their venter is densely granular and typically cream or white in color, except for the gray vocal sacs of breeding males. The dorsal surfaces of their hind limbs are typically marked with dark bars or blotches. The amount of webbing on their feet is highly variable, and the first digit of their foot is shorter than the second. Their pupils are horizontally elliptical with gold or silver irises, and their vocal sacs are paired. They often have a dark spot or bar on their lip below their eye. Mexican Treefrogs can readily change their dorsal color according to their circumstance. They may change rapidly from a dark spotted coloration to a light unspotted coloration in response to temperature and light levels. In addition to providing camouflage, color change may also help regulate body moisture and temperature. 

Mexican Treefrogs are nocturnal and often found in arroyos or on roads at night from June through September. During dry periods, they retreat to moist places such as tree holes, the outer sheaths of banana plants, damp soil, or under loose bark. They may encase themselves in several layers of outer skin, which provides protection from desiccation. They breed during the summer rains in the shallow, temporary waters of arroyos, roadside ditches, and pools.

Treefrogs primarily feed on a variety of invertebrates, especially insects and spiders. Cannibalism has also been documented within this species. In turn, they are preyed upon by birds, snakes, and large fish. When attacked, they emit high-pitched distress calls with their mouths wide open. The advertisement call of the male is a nasal “heck” sound that is repeated 2 to 15 times, sometimes interspersed with chuckling noises. The “heck” sounds may resemble someone trying to start a car in the distance. Males will respond to one another, resulting in calling duets. Most calling occurs nocturnally and early in the summer rainy season, however, individual males can sometimes be heard throughout the summer and periodically during the day. Sexual maturity is attained at approximately 47 mm (1.9 in) snout-to-vent length for males, and approximately 56 mm (2.2 in) snout-to-vent length for females.Their mating call consists of a series of short, explosive “wonk-wonk-wonk” notes. Call groups are spaced about 15 seconds to several minutes apart. Breeding is triggered by the first substantial summer storm. Females deposit several hundred eggs at a time in a film on the surface of shallow, temporary pools. Each female may lay 2,500 to 3.500 eggs in a season. The eggs are approximately 1.3 mm in diameter (1.5 mm including the vitelline membrane) and black and cream in color. Eggs are fertilized externally by the males, and metamorphosis occurs 14 to 20 days after fertilization. The tadpoles grow to approximately 37 mm in length, and are dark dorsally with a light, creamy gray crescent near the base of their tail. Their tail musculature is dark or striped and their tail fin is flecked with brown. Tadpoles feed on suspended organic and inorganic particles within their pool. The Mexican Treefrog has a lifespan of six to ten years in the wild and up to fifteen years in captivity.  The Mexican Treefrogs are poorly studied and very little is known about their behavioral patterns. 

Mexican Treefrogs may be confused with the Lowland Burrowing Treefrog, Smilisca fodiens (lack the dark stripe from their snout to their shoulder; juveniles are similar in color but have reduced digit pads and webbing, and skin atop their head that is fused to the top and sides of their skull and  a transverse fold of skin at the rear of their head). 

The Mexican Treefrog is considered to be of Least Concern due to their wide distribution, tolerance of a broad range of habitats, and presumed large population size. No major threats have been identified for this species. The Mexican Treefrog has been listed as Threatened by the state of Texas due to their small and patchy populations, but no federal protection exists.