Species Description
The Eastern Tiger Salamander (Ambystoma tigrinum) is a large, robust terrestrial salamander that can reach body lengths of 7.5–16.0 cm and total lengths of over 30 cm. This makes them one of the largest terrestrial salamanders in the United States, surpassed only by the giant salamanders (Genus Dicamptodon) of the Pacific Northwest. They have a rather heavy-set body, and gravid females can appear particularly plump.
The coloration of Eastern Tiger Salamanders varies widely among individuals but generally consists of a black background with yellow to yellowish-brown spots or irregular “wormy” markings across the body. The number of these markings can also vary significantly, with some individuals having more than 60, while others may have fewer than 15.
During the breeding season, adults develop an extremely keeled, paddle-like tail that aids in swimming within breeding wetlands. Their toes are tipped with keratin, and they possess large, ossified skulls—both adaptations that help them dig burrows in upland habitats outside the breeding season. Their rounded heads give them a distinctive, “bug-eyed” appearance, which adds to their endearing charm.
Like most salamanders, they are capable of impressive tissue regeneration. Although tiger salamanders do not practice tail autotomy, they can still regrow both their tails and limbs if injured during a predation attempt. Eastern Tiger Salamanders also secrete a milky, toxic substance from the back of their tails and will raise them in defense if threatened. While this secretion is not lethal, it is distasteful enough to deter many predators, making the salamanders an unappealing meal.
Taxonomy
The genus name Ambystoma either comes from the Greek words amblys, which means “blunt,” and stoma, which means “mouth,” or from the Latin word anabystoma, which means “to cram into the mouth.” The specific epithet tigrinum comes from the Latin root tigrinus, which means “tiger-like.”
Up until 1997, Ambystoma tigrinum was considered one of several subspecies of tiger salamanders across North America. However, many of those subspecies were later reclassified under the Western Tiger Salamander (Ambystoma mavortium).
Distribution
Eastern Tiger Salamanders range throughout much of the midwestern and eastern U.S., but their populations can be very patchy. Their range extends from Long Island, New York, southward along the coastal plain to northern Florida, west to the beginning of the Great Plains, and northward into the Great Lakes region. They do not occur in the Appalachian Mountains, the Piedmont, or the Mississippi River floodplain.
While they are patchily distributed and have specific habitat requirements, Eastern Tiger Salamanders are almost certainly underreported. Their secretive nature and brief periods of surface activity cause them to be seldom observed, and they are likely more widespread than is currently known.
Habitat
Eastern Tiger Salamander habitat varies across their range. In the Coastal Plain, they prefer upland habitats often associated with longleaf pine or oak-dominated sandhills. Further inland, they require open pasture or prairie and, unlike most salamanders, often persist in agricultural areas.
While they spend most of their time underground in dry landscapes such as these, they also require seasonal wetlands during their breeding season. These wetlands are usually small, isolated, open, and lack woody vegetation. They typically fill between late fall and early spring, and their ephemeral nature precludes many aquatic predators, such as large fish. In the Coastal Plain, wetlands like these require regular warm-season burns to prevent woody shrubs and trees from shading out the grassy vegetation and shortening the seasonal water availability.
Movement and Home Range
As a member of the mole salamander family, Eastern Tiger Salamanders spend most of their lives underground in burrows and do not often move outside of the winter breeding season. During this time, however, they will make long-distance movements to breeding wetlands. These migrations are triggered by warm winter rains, and salamanders may move up to 500 meters to reach their ponds. Conversely, in late spring, newly metamorphosed salamanders leave the wetland after they complete their development. Eastern Tiger Salamanders are not known to be territorial and likely have very small home range sizes, as they are not very mobile while in their burrows.
Diet
Eastern Tiger Salamanders are carnivorous, primarily eating annelids, insects, and other invertebrates. Their larvae are likewise carnivorous and eat a variety of aquatic invertebrates. Larvae have also been observed cannibalizing one another if resources are scarce within the wetland.
Reproduction
Eastern Tiger Salamanders are stochastic breeders, meaning they breed once a year for a very short period of time. The timing of breeding events varies by region. At the southern extent of their range, they can start breeding as early as late November. However, further north in the midwestern states, breeding may not occur until March.
Once in the breeding wetlands, males lay packets of sperm called spermatophores on the bottom of the pond, and females then pick up these spermatophores into their cloacas, internally fertilizing their eggs. Egg masses are subsequently laid and attached to structures in the wetlands, such as fallen branches or grass. The eggs develop rapidly, and within a few weeks, salamander larvae hatch. The larvae feed on a variety of invertebrates and, eventually, on tadpoles and larval salamanders of other species. In some populations, tiger salamander larvae are highly cannibalistic, developing wider heads and an extra row of teeth specifically for consuming members of their own species.
This species has a biphasic lifestyle, meaning it typically undergoes an aquatic larval stage with external gills before metamorphosing into a terrestrial adult with internal lungs. However, when water and resources are abundant, tiger salamanders may not metamorphose into terrestrial adults but instead remain in their wetlands indefinitely. These neotenic adults retain many larval traits, such as external gills, but grow well beyond normal larval sizes and are reproductively mature.
Conservation Concerns
Eastern Tiger Salamanders are listed as a species of “Least Concern” on the IUCN Red List of Threatened Species. However, while the species as a whole may be relatively stable, certain populations have experienced declines in recent years. In particular, northeastern populations in New York, New Jersey, Maryland, and Virginia are listed as endangered.
Habitat destruction, fragmentation, wetland degradation, road mortality, pollution, and emerging diseases are likely their biggest threats. Fortunately, due to their prairie-like natural habitat in the Midwest, they can often persist in areas that have been converted to agriculture and make use of cattle ponds as breeding sites. In the Southeast, however, there is concern about the loss of upland habitat and ephemeral breeding wetlands.
Climate change and its effects on winter weather patterns could also threaten this species. Drier winter conditions could greatly reduce the tiger salamander’s window for breeding and larval development or, in some years, eliminate it altogether. By protecting upland sandhills and ephemeral wetlands, as well as properly maintaining these habitats through fire and the mechanical removal of hardwood vegetation, Eastern Tiger Salamanders may continue to persist in the Southeast.