Barred Tiger Salamander (Ambystoma mavortium)

Photo by Jim Rorabaugh

Tiger Salamander, Huachuca Mountains, AZ. Photo by Jim Rorabaugh

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Description

Ambystoma mavortium is a comparatively large salamander found almost exclusively in ponded water such as cattle tanks and other artificial or natural impoundments, or in uplands adjacent to such waters.  Three commonly encountered life stages include terrestrial adults and juveniles (< 165 mm SVL and < 345 mm total length), gilled aquatic adults known as paedomorphs (< 385 total length), and gilled aquatic larvae, which can metamorphose into adults at a SVL as small as 45 mm, but often stay in the natal ponds as juveniles until they achieve greater size.  In the spring or winter, and more rarely during the summer monsoon, from 200 to several thousand eggs are laid singly or in small clumps attached to submerged branches or vegetation.  They hatch in two to four weeks, depending on water temperature.  Aquatic forms of the Barred Tiger Salamander can often be seen surfacing for air in cattle tanks.  The terrestrial forms are sometimes encountered on the surface, such as on roads at night, particularly during or after rain storms.

All forms of this salamander possess conspicuous, vertical grooves on the sides of the body and a rudder-like tail.  Aquatic forms are olive gray, sometimes with small dark speckling or other markings, and they possess feathery gills.  The dorsal pattern of terrestrial salamanders consists of dark spots, barring, or reticulation on a lighter background.  Three forms of this salamander occur within the 100-Mile Circle:  the Barred Tiger Salamander (Ambystoma mavortium mavortium), the Arizona Tiger Salamander (A. m. nebulosum), and the Sonora Tiger Salamander (A. m. stebbinsi). The Barred Tiger Salamander is introduced from points east in the United States and is found throughout most of the 100-Mile Circle, except for the driest portions of the desert.  The native Arizona Tiger Salamander is found typically in forested lands to the north of the Gila and Salt rivers.  The native Sonora Tiger Salamander is found only in the San Rafael Valley and adjacent portions of the Huachuca and Patagonia mountains, the Canelo Hills, and adjacent grasslands near the border in Sonora, Mexico.  The dorsal pattern of terrestrial forms of the Sonora Tiger Salamander can be spotted, barred, or reticulated.  The Barred Tiger Salamander is either barred or spotted.  The Arizona Tiger Salamander typically has fewer dark markings than the other subspecies.  On the underside of terrestrial Barred Salamanders, yellow bars cross the venter, whereas in the native A .m. stebbinsi the light marks do not extend across the venter, which is mostly dark.

The Tarahumara Salamander (Ambystoma rosaceum) is similar in appearance, but it is a species of streams and pools within stream courses, and in the 100-Mile Circle it is limited to mountain ranges in Sonora, generally to the south of the current, known range of the Barred Tiger Salamander.  The Barred Tiger Salamander is distinguished from the Tarahumara Salamander by its higher mean number of gill rakers (15-20 vs 9-15), often larger size (Tarahumara Salamanders are <163 mm total length), and the presence of prominent tubercles on the underside of the hind and front feet.  Moderate-sized Tarahumara Salamander larvae are also boldly and distinctly marked with dark spots or lines on a gold background.  The literature on the Barred Tiger Salamander in Arizona often uses the name A. tigrinum.  Shaffer and McKnight (1996) elevated A. t. mavortium to species.

The status of this species has not yet been assessed by the IUCN.  However, the native Sonora Tiger Salamander is listed as Endangered under the U.S. Endangered Species Act and is threatened by a virulent iridovirus (Ambystoma tigrinum virus or ATV), habitat alteration, and introduction of and hybridization with non-native A. m. mavortium,

Suggested Reading:

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

Lannoo, M.J., and C.A. Phillips. 2005. Ambystoma tigrinum (Green, 1825) Tiger Salamander.  Pages 636-639 in M.J. Lannoo (editor), Amphibian Declines: The Conservation Status of United States Species.  University of California Press, Berkeley.

Petranka, J.W. 1998. Salamanders of the United States and Canada.  Smithsonian Institution Press, Washington D.C.

Shaffer, H.B., and M.L. McKnight. 1996. The polytypic species revisited: differentiation and molecular phylogenetics of the Tiger Salamander Ambystoma tigrinum (Amphibia: Caudata) complex. Evolution 50:417-433.

U.S. Fish and Wildlife Service. 2002. Sonora tiger salamander (Ambystoma tigrinum stebbinsi) recovery plan.  U.S. Fish and Wildlife Service, Region 2, Albuquerque, NM.

Author:  Jim Rorabaugh

For additional information on this species, please see the following volumes and pages in the Sonoran Herpetologist: 1998 May:56; 1999 Oct:106; 2003 Feb:21; 2006 Apr:41-42.

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