Baja California Treefrog (Pseudacris hypochondriaca*)

Photo by Jim Rorabaugh

Baja California Treefog, Ventura Co., CA. Photo by Jim Rorabaugh

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Description

The Baja California Treefrog is a small (< 51 mm SVL), gray, tan, or green frog with conspicuous, expanded toe pads on the digits of all feet, and a dark stripe on either side of the head that runs from the snout back through the eye to the front leg insertion point and sometimes beyond.  The dorsum may or may not have additional dark spots or stripes, and often there is a dark Y marking between the eyes.  Individual frogs can become lighter or darker, and dorsal spots may appear or disappear depending on environmental conditions.  The skin is lightly roughened and modestly glandular.   In the 100-Mile Circle, the Baja California Treefrog is only known as an introduced species.  It apparently hitchhikes on potted plants imported from plant nurseries in southern California.  It has been found in nurseries in Mesa, Apache Junction, and Tucson, and was recently (2013) found in a northwestern Tucson backyard after plants were purchased at a nearby Home Depot.  Treefrogs (likely the closely related Pseudacris regilla) have also been documented in bundles of Christmas Trees in the Phoenix area, and they are likely imported to Tucson via this mechanism as well.  The Baja California Treefrog is similar to the Arizona Treefrog (Hyla wrightorum), but the latter has smoother skin, the eye stripe always extends past the front limb insertion point – often to the groin, it is a somewhat larger frog (< 57 mm SVL), and the calls are quite different (see below and the account for the Arizona Treefrog).

Throughout its range, the Baja California Treefrog breeds in the winter and spring in a variety of permanent or ephemeral waters such as lakes, ponds, slow-moving streams and rivers, backwaters, golf course ponds, and irrigation ditches and canals.  At a Mesa nursery, tadpoles were found in an evaporative cooler.  On the Lower Colorado River, Arizona/California, frogs call from November to June.  Clutches of 400-1,250 eggs are laid in clusters of 9-80 that are typically attached to submerged vegetation, sticks, or debris.  Tadpoles, which grow to about 56 mm total length, take about two months to metamorphose.   The typical advertisement call is a “kreck-ek” repeated over and over again, a sound often heard in old Hollywood movies.  Frogs call mainly at night.  The call can be heard here: http://amphibiaweb.org/cgi-bin/amphib_query?special=call&genus=Pseudacris&species=regilla

Baja California Treefrogs feed upon a variety of invertebrate prey, including insects, isopods, spiders, and snails.  They often take invertebrates at the water’s surface or from nearby vegetation.  This frog was known as the Pacific Treefrog (Pseudacris or Hyla regilla) for well more than a century but was recently split into three species (Recuero et al. 2006), of which Pseudacris hypochondriaca is the southernmost of the trio.  The IUCN has not yet evaluated the conservation status of the Baja California Treefrog, but the closely related Pacific Treefrog is listed as a species of least concern.

Suggested Reading:

Brennan, T.C., and A.T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix, AZ.

Recuero, E., I. Martinez-Solano, G. Parra-Olea, and M. Barcia-Paris. 2006. Phylogeography of Pseudacris regilla (Anura:Hylidae) in western North America, with a proposal for a new taxonomic rearrangement.  Molecular Phylogenetics and Evolution 39:293-304.

Rorabaugh, J.C., J.M. Howland, and R.D. Babb. 2004. Distribution and habitat use of the Pacific treefrog (Pseudacris regilla) on the lower Colorado River and in Arizona.  The Southwestern Naturalist 49(1):94-99.

Rorabaugh, J.C., and M.J. Lannoo. 2005. Pseudacris regilla Baird and Girard, 1852, Pacific treefrog. Pages 478-484 in M.J. Lannoo (ed.), Amphibian Declines: The Conservation Status of United States Species.  University of California Press, Berkeley.

Author: Jim Rorabaugh

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