Eastern Tiger Salamander (Ambystoma tigrinum)
by Jeff LeClere
Species of Greatest Conservation Need. A valid fishing license is required to possess this species as bait. Tiger salamanders are found throughout Iowa, although they remain underground most of the year.
This is a large Iowa salamander with specimens up to 13 inches long. Adults are black to gray in ground color with irregular yellow spots all over the body. These spots vary intensively among individuals; there may be yellow spots or the yellow pigment may take over so that the black is reduced to a network of lines. Usually, adults have a yellow lower lip and throat. They have 11 to 14 costal grooves and there are four toes on the front and five on the back feet. Larvae have bushy gills and are much paler in coloration than adults.
No subspecies of the eastern tiger salamander, Ambystoma tigrinum, are currently recognized. Western forms of the tiger salamander almost surely exist in Iowa (under current taxonomy, likely the western tiger salamander, Ambystoma mavortium, subspecies blotched tiger salamander, Ambystoma mavortium melanostictum), but until studies elucidate the uncertain taxonomy and range of the tiger salamander complex, I list only the eastern tiger salamander as occurring in Iowa.
The eastern tiger salamander is found throughout the entire state of Iowa.
Everywhere. This species is found in open fields, prairies, cultivated fields, pastures, forests, and even towns. A primary requirement is ponds, lakes, marshes or other permanent bodies of water in which to breed.
Tiger salamanders, although abundant, are one of the most secretive salamanders in our state. Nearly all of their time is spent underground in burrows of other animals or burrows they have constructed themselves. Occasionally they are found above ground on damp or humid nights. They often fall into window wells or are found in damp basements. I used to find many in window wells in Linn County. The only time they are found above ground in numbers are during heavy spring and fall rains while they migrate to and from overwintering sites.
Tiger salamanders breed in spring, often before all the ice has melted from the ponds surface. Females may lay 30 – 50 eggs in loose masses. The larvae metamorphose between June and August. The larvae grow quicker in warmer water and may be smaller upon transformation then when they were larvae. The terrestrial adults overwinter underground in burrows or other debris in October. Tiger salamanders have declined in abundance in the last twenty years; I do not see as many as I used to during fall migrations, however, Christiansen (1998) has shown an increase in this species. It is presumed that this increase reflects new localities for tiger salamanders, and not population size at a given locality. They may be declining more in some areas than others due to variable circumstances. Conserving marshes and other water bodies and adjacent open prairies will help eastern tiger salamander populations.
Both adults and larvae alike are extremely voracious feeders consuming anything that is smaller than themselves. They snap quickly and sometimes use their tongue to catch prey, but they are also very clumsy hunters. Larval tiger salamanders are aggressive feeders and thus will reduce the survivorship of larval blue-spotted, smallmouth, and Tremblay’s salamanders when sharing the same pond (Wilbur, 1972). Some larvae become cannibalistic. These have huge heads compared to other larvae and also metamorphose faster. Varying factors contribute to the development of the cannibalistic morph. Some populations of tiger salamanders are progenetic. The larvae become sexually mature without transforming into a terrestrial adult. Adults have many enemies so they secrete a milky toxin from glands on the back and tail for defense.