The Jefferson salamander (Ambystoma jeffersonianum) and the blue-spotted salamander (Ambystoma laterale), by virtue of a complicated hybridization scheme, present one of the great mysteries of amphibian biology.
The Jefferson salamander is black or grey-brown with bluish white spots. Individuals up to 21 centimetres in length have been recorded. The spotted salamander (Amblystoma maculatum) and the mudpuppy are the only two Ontario salamander species known to grow larger than the Jefferson salamander.
Jefferson and blue-spotted salamanders cannot be distinguished reliably without genetic testing. Where their ranges overlap, hybridization between the two species complicates identification even further. Small-mouthed salamanders appear similar to salamanders in the Jefferson complex and hybridize with them where their ranges overlap. The eastern red-backed salamander in the leadback colour phase can be distinguished from the Jefferson complex salamanders by its much thinner body and limbs, and lack of blue spots.
Jefferson salamanders are found in a wide variety of woodland habitats (deciduous, coniferous or mixed forests), as well as swamps. Typically, these salamanders spend their lives on the forest floor, often living underground in burrows. They breed in permanent swamps or temporary ponds, marshes or even roadside ditches, and overwinter underground in the forest.
View an interactive map of the known ranges of Jefferson salamanders in Ontario.
Jefferson salamanders are nocturnal (most active at night) and are especially active on warm rainy nights. Breeding occurs in late March. Females can lay up to 200 eggs, either singly or in loose clumps, that are attached to underwater vegetation. The eggs hatch three to four weeks later, and the larvae transform into adult salamanders in late summer. Outside of the breeding season, adults are terrestrial carnivores, eating a large variety of insects and other invertebrates, including spiders and worms.
The Jefferson salamander and the blue-spotted salamander are part of one of the most bizarre and complex mysteries of amphibian biology. These two species are associated with hybrids, usually female, that have three, four or even five complete sets of chromosomes (such individuals are referred to, respectively, as triploid, tetraploid or pentaploid) in their DNA rather than the usual two sets (diploid). Under certain circumstances, when hybrid females breed with male blue-spotted or Jefferson salamanders, sperm stimulates egg development but is not incorporated into the genetic material of the egg. In such cases, the offspring are genetically identical to the mother. Sometimes one or both chromosomes of the sperm are incorporated into the egg, producing offspring with three or four sets of chromosomes (triploids or tetraploids, respectively). Further complicating the issue, hybrids that have more than two sets of chromosomes can mate with either species and produce offspring that have four or more sets of chromosomes. No matter what their ploidy level (number of sets of chromosomes), these salamanders appear nearly identical. Biologists are still trying to fully understand this complicated genetic system.
Other names: Ambystoma tremblayi, Salamandra jeffersoniana, Ambystoma platineum
Threats and Trends
Extensive agricultural development and urbanization in south-central Ontario have severely reduced and fragmented the wetlands and forest habitat available to this species. Jefferson salamanders are also killed on roads every spring during their migration to breeding ponds. Reports of road-killed salamanders can be submitted to the Ontario Reptile and Amphibian Atlas and will help researchers identify these critical migration routes. Because its range coincides with one of the most developed areas of Canada, the Jefferson salamander will probably continue to decline, and its tendency to hybridize will continue to complicate and frustrate conservation efforts.
Current Status and Protection
The Jefferson salamander is currently listed as Endangered under the Ontario Endangered Species Act, 2007 and Threatened under the federal Species at Risk Act. The species has also been designated as a Specially Protected Amphibian under the Ontario Fish and Wildlife Conservation Act. These acts offer protection to individuals and their habitat. The habitat of this species is further protected in Ontario by the Provincial Policy Statement under the Planning Act. The International Union for Conservation of Nature lists the global status of the Jefferson salamander as Least Concern. The species’ status was last confirmed in 2011. Additional detail about legal protection for species at risk in Ontario is available on our Legal Protection page.
Learn more about reptile and amphibian conservation and what you can do to help these species on our Reptile and Amphibian Stewardship page.