The Jefferson salamander (Ambystoma jeffersonianum) is a forest-dwelling salamander native to northeastern North America. Within Canada, it is only found in Southern Ontario. They are a member of the Ambystomatidae family, also known as “mole salamanders,” because they spend much of their lives underground. In Canada, the Jefferson salamander faces a severity of threats and is declining across much of its range, and it is listed as an endangered species under the Canadian Species at Risk Act.
The Jefferson salamander is a medium-sized salamander with an adult body length (also known as snout-vent length) of 6–10 cm. Their tail is almost as long as their body and is flattened along the sides. Females reach slightly larger sizes than males. Individuals are dark grey to brownish grey with light blue-grey or silver mottling on the limbs, lower sides and tail.
The aquatic larvae have a broad head, feathery external gills, a large tail fin and four legs that develop as the larvae grow. Larvae are typically olive green, brown or grey with varying amounts of yellow mottling. Older larvae develop a pale stripe along the side of the body. Jefferson salamander larvae are 0.8–1.4 cm long when they hatch and can grow to 5.5 cm before undergoing metamorphosis.
Distribution and Habitat
In Canada, the Jefferson salamander is found only in Southwestern Ontario. Its distribution wraps around the west end of Lake Ontario and extends inland along the Niagara Escarpment and in a few other areas, with isolated populations on the north shore of Lake Erie near Long Point. This species is also found throughout the Northeastern United States, from New Hampshire south and west to Virginia, Kentucky and Indiana, as well as in isolated locations in Illinois.
Jefferson salamanders live in deciduous or mixed forests. Like most amphibians, Jefferson salamanders have moist, porous skin and can quickly dehydrate if exposed to hot, dry conditions. For this reason, they live in cool, damp environments on the forest floor. They spend most of their time in mammal burrows, root hollows, and other underground spaces, particularly during the hot, dry summer months. Jefferson salamanders also spend the winter in underground shelters where they can get below the frost line and avoid freezing temperatures. When not underground, they rely on leaf litter, woody debris (e.g., logs and stumps) and other cover on the forest floor to provide cool, damp conditions and protection from predators. Breeding occurs in shallow, fish-free pools and ponds that usually dry up during the late summer, but permanent ponds are used occasionally. Jefferson salamanders have relatively large home ranges. Individuals often migrate several hundred metres from their breeding pond each year to reach their hibernation site or summer activity area.
Did you know?
Jefferson salamanders are one of the earliest-breeding amphibians in Eastern North America. Adults emerge from hibernation and migrate to their breeding sites in the early spring as soon as the ground starts to thaw — typically in late March or early April in Canada. Individuals often travel over ice and snow and enter the frigid water as the ice cover is still receding from the pond.
Reproduction and Development
Adults migrate to their breeding sites in the early spring, typically on rainy nights with air temperatures above 5°C. After courting the female, the male deposits a spermatophore (sperm packet), which the female picks up with her cloaca (a single opening at the base of the tail for the digestive, urinary and reproductive tracts). One or two days later, the female lays between 107 and 286 eggs, which are deposited in several masses that typically contain around 30 eggs each. The eggs are dark-coloured and surrounded by three jelly layers. The egg masses are attached to sticks, vegetation or other structures in shallow water. The eggs hatch after 3–14 weeks, with northern populations at this range's lower end. The larvae are aquatic and breathe through gills. They undergo metamorphosis in 2–4 months, which typically takes place from mid-July to early September in Canada. The newly transformed juveniles, which now have lungs and breathe air, disperse into the surrounding forest. Jefferson salamanders reach maturity at 3–4 years of age. While one study indicated that adults may only live a few years, others have suggested a much longer lifespan, possibly several decades.
Diet and Predation
Adults and juveniles forage underground, under woody debris and other cover, and in leaf litter on the forest floor. They are suspected to eat a variety of invertebrates, such as earthworms and insects. Young larvae eat zooplankton, which are tiny free-floating aquatic invertebrates. Older larvae consume larger aquatic invertebrates, such as insects and their larvae, small crustaceans and snails. They also feed on other amphibian larvae, including smaller Jefferson salamander larvae.
Predators of adult and juvenile Jefferson salamanders likely include snakes, birds and mammals such as raccoons and skunks. Aquatic insects and their larvae are suspected to be the primary predators of Jefferson salamander eggs and larvae. Like most amphibians, Jefferson salamanders have poison glands that provide defence against predators. The Jefferson salamander’s poison glands are concentrated along the top of the tail. When confronted by a potential predator, salamanders will raise their tails toward the predator, often undulating or waving it to display the noxious secretions.
Jefferson salamanders live in Canada’s most heavily developed region, and much of their habitat has been destroyed and heavily fragmented. Ongoing destruction of breeding sites and surrounding forested habitats, primarily due to urban and industrial development, threatens the remaining Canadian populations. The high density of roads throughout the species’ range is also a serious threat, as large numbers of individuals are killed on busy roads as they migrate to and from their breeding sites each spring. Because their skin is permeable to chemicals in the environment, amphibians are especially sensitive to chemical pollution such as pesticides, fertilizers, industrial chemicals, road salt and heavy metals. Their proximity to urban and industrial areas puts Jefferson salamanders at high risk of exposure to environmental contamination. Additional threats include habitat acidification, other pollutants (e.g., light pollution, microplastics), climate change, and stocking ponds with predatory fish.
Status and Conservation
Globally, the Jefferson salamander is listed as least concern by the International Union for the Conservation of Nature. However, due to the severity of threats and ongoing population declines across much of its Canadian range, this species is listed as endangered under Canada’s Species at Risk Act. The Species at Risk Act and the Ontario Endangered Species Act provide an important legal framework for the protection of the species and its remaining habitat. However, public support to implement these protections amidst increasing pressure for urban and industrial growth is essential to effectively recover the Jefferson salamander in Canada.