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In most of North America, warm winter rains are a sure sign that ambystomatid salamanders will be on the move from their subterranean retreats towards breeding ponds. Collectively known as mole salamanders, these chunky salamanders spend most of their time underground. Many species can only be observed reliably during their annual breeding migrations or as larva in the aquatic environment. The family Ambystomatidae contains only a single genus (Ambystoma) and approximately 32 species that can be found across the U.S., into southern Canada, and a large part of Mexico. The group includes the well-known axolotl (Ambystoma mexicanum), which is common in the pet trade but critically endangered in the wild. Overall, ambystomatid salamanders are one of the most recognizable salamander groups thanks to their large size and often colorful appearance. Everyone should get the opportunity to experience an ‘Ambystoma Night’ at least once in their lives. It is truly special to see a wetland teeming with these large salamanders.
The largest member of the Ambystomatidae family is the Tiger Salamander (now split into multiple species: A. tigrinum, A. californiense, and A. mavortium). Adult Tiger Salamanders can approach lengths of 35 cm and come in a variety of color patterns. They typically have a black dorsum with various irregular yellow or brown patches over the entire body. Tiger Salamanders can be found across most of the U.S., although populations are disjunct in many places and declining in others. These salamanders have a mostly typical pond-breeding amphibian life cycle. In the eastern portion of the range, adults typically move into breeding ponds from December to February where larvae will remain until later in the spring or summer. In populations that breed in permanent water bodies, larvae may overwinter before metamorphosing at large sizes the following year. Some populations may also contain neotenic (maintaining larval characteristics) adults that remain in the breeding pond as sexually mature individuals.
Larval Tiger Salamanders are characterized by large, flat heads, large gills, and laterally compressed tails to help navigate aquatic environments. They are formidable predators in many aquatic systems that they inhabit. In some populations, a subset of larva will actually develop characteristics that allow them to become specialized predators of other, smaller Tiger Salamander larva. To do this, their heads become enlarged allowing them to swallow smaller larvae whole (Pierce et al. 1983).
Much of what we know about Tiger Salamanders comes from studies of breeding populations (usually captured with drift fences while moving to or from breeding ponds) or from studying larval salamanders. For example, Church et al. (2003) found that adult Tiger Salamanders regularly skip breeding years when conditions may be suboptimal and that adult survival is significantly lower during drought years. In the southeast, adults have been reported moving over 250m away from breeding ponds (Steen et al. 2006) and inhabiting burrows 12 cm below ground (Semlitsch 1983). Ultimately, we have much to learn about the terrestrial portion of the Tiger Salamander life cycle, and much of their ecology will likely remain hidden until technology allows us to track animals underground more consistently.
In the Georgia Coastal Plain, Tiger Salamander populations are few and far between, and many historic breeding wetlands have been lost to land conversion or severe habitat degradation. It was an exciting discovery when we found several adults in a borrow pit at the Longleaf Stewardship Center back in January 2018. Borrow pits are places where the soil has been removed for other uses, usually creating small wetlands. This population of Tiger Salamanders had gone undetected for several years, despite many herpetologists working on the property. We again observed adult salamanders at the Stewardship Center in 2023 and have now observed individuals in six consecutive years. It appears likely that this population is successfully reproducing in some years, and additional survey efforts have found salamanders in some nearby wetlands as well.
Literature Cited
Church, D. R., L. L. Bailey, H. M. Wilbur, W. L. Kendall, and J. E. Hines. 2007. Iteroparity in the variable environment of the salamander Ambystoma tigrinum. Ecology 88:891-903.
Pierce, B. A., J. B. Miton, L. Jacobson, and F. L. Rose. 1983. Head shape and size in cannibal and noncannibal larvae of the tiger salamander from West Texas. Copeia 4:1006–1012.
Semlitsch, R. D. 1983. Terrestrial movements of an eastern tiger salamander, Ambystoma tigrinum. Herpetological Review 14:112–113.
Steen, D. A., L. L. Smith, G. J. Miller, and S. C. Sterrett. 2006. Post-breeding terrestrial movements of Ambystoma tigrinum (eastern tiger salamander). Southeastern Naturalist 5:285–288.
