The Tiger Salamander (Ambystoma tigrinum) is a widespread amphibian native to North America. As a burrowing mole salamander, it plays an ecological role in its diverse habitats, adapting to various environmental conditions.
Physical Traits and Identification
The Tiger Salamander is one of the largest terrestrial salamanders in North America, with adults ranging from 6 to 13 inches (15 to 33 cm) in total length. Its body is stout, featuring a broad head and a rounded snout. The skin is smooth and moist, aiding in respiration and moisture retention.
A distinguishing characteristic of Ambystoma tigrinum is its coloration. Adults display irregular blotches or spots of yellow or olive against a dark brown, gray, or black background. Larvae typically have a yellowish-green or olive body with dark blotches, developing adult patterns as they grow.
Habitat and Geographic Range
Tiger Salamanders inhabit diverse environments across North America. Their range extends from southern Canada, throughout much of the United States, and into northern Mexico, making them the most widespread salamander species on the continent. They are found in terrestrial habitats including forests, grasslands, prairies, and some semi-desert and urban areas.
A requirement for Ambystoma tigrinum is loose soil, as they are primarily burrowing creatures. They excavate burrows over 2 feet (60 cm) deep, escaping temperature extremes and seeking humidity. While adults are largely terrestrial, they depend on aquatic environments like ponds, vernal pools, and slow-moving streams for breeding, particularly those free of predatory fish.
Life Cycle and Development
The life cycle of the Tiger Salamander begins with eggs laid in aquatic environments. Females can deposit hundreds to over a thousand eggs per breeding season. These eggs hatch into aquatic larvae within 2 to 5 weeks, depending on water temperature.
Larval salamanders possess external gills for underwater respiration and a tail fin for swimming. Over 2.5 to 5 months, these larvae undergo metamorphosis, transforming into terrestrial adults. During metamorphosis, they lose their gills, develop lungs, and their tail fin recedes, preparing them for a life on land.
Facultative neoteny is a key aspect of the Tiger Salamander’s development, where individuals retain larval characteristics, such as gills and an aquatic lifestyle, even after reaching sexual maturity. This phenomenon is common in populations inhabiting stable aquatic environments, especially those without fish predators. Neotenic individuals can reproduce while remaining entirely aquatic. If their aquatic habitat dries, neotenic salamanders may still undergo metamorphosis, though their ability to do so can decrease with age.
Behavior and Ecological Role
Tiger Salamanders are nocturnal and fossorial, spending most of their time underground. Their burrowing habits contribute to soil aeration. They are generalist predators, with their diet varying between larval and adult stages.
As larvae, they feed on small aquatic invertebrates, such as crustaceans and insect larvae. Larger larvae can also prey on tadpoles and other smaller salamander larvae. Adult Tiger Salamanders primarily consume worms, snails, slugs, and various insects found in the soil and on the surface. They occasionally prey on small vertebrates like mice, frogs, and snakes. In their ecosystem, Tiger Salamanders serve as both predators and prey. They are preyed upon by animals including badgers, snakes, bobcats, and owls, while their larvae are consumed by aquatic insects and other salamander larvae.
Conservation Status and Importance
The Tiger Salamander (Ambystoma tigrinum) is considered a species of “Least Concern” by the IUCN, indicating a stable population across its range. However, specific subspecies or isolated populations face conservation challenges and may be listed as threatened or endangered in certain regions. For example, some populations in Canada are considered endangered due to specific threats.
Threats to Tiger Salamander populations include habitat loss and fragmentation, particularly the destruction or degradation of wetlands and surrounding terrestrial areas. Pollution of breeding sites and the introduction of predatory fish can impact their populations. Diseases, such as ranaviruses and chytrid fungus, pose additional threats, with salamanders potentially acting as carriers. Tiger Salamanders serve as indicators of environmental health, reflecting the condition of both aquatic and terrestrial habitats.