by Carla Church
Many species of amphibians are undergoing population decline, range reduction and extinction. Thirty percent of all amphibian species are considered threatened by the International Union for Conservation of Nature (IUCN), far exceeding declines in other vertebrate groups. Habitat loss and destruction are a major cause of these declines but other causes include disease, climate change, pollution, exploitation, and invasive species.
Salamanders play an important role in ecosystem health as both mid-level predators and as prey species. Terrestrial salamanders feed on earthworms, insects, small mice and voles, frogs and other salamanders. In turn, salamanders are prey for many species of predacious fish, invertebrates, garter snakes, and birds such as herons.
Photo: Newly hatched larval salamander
Due to their sensitivity to subtle environmental changes, salamanders are useful bio-indicators. Many salamanders require two distinct habitats: water for juvenile development and breeding and upland terrestrial habitat for foraging and overwintering. These qualities make them vulnerable to both water and soil pollution.
North American Salamanders
North and Central America have the greatest diversity of salamander species in the world. There are ten families containing approximately 400 species that are almost entirely limited to the Northern Hemisphere. Canada is home to 22 species of salamander including eight species of “mole salamanders” (large salamanders in the genus Amystomatidae).
Salamanders in Manitoba
Manitoba is home to four species of salamanders: Blue-spotted Salamander (Ambystoma laterale), Western Tiger Salamander (Ambystoma mavortium), Eastern Tiger Salamander (Ambystoma tigrinum) and the aquatic Common Mudpuppy (Necturus maculosus).
Of these, the Western is listed as Special Concern (Prairie/Boreal population) and the Eastern is listed as Endangered (Prairie population).
Eastern Tiger Salamanders
Eastern Tiger Salamanders have a dark brown to grayish black dorsal ground colour with numerous, large, irregular brown to yellow spots.
Photo: Large larval Eastern Tiger Salamander likely close to metamorphosis
Eastern Tiger Salamanders are typically found in areas where fishless semi-permanent or permanent ponds are surrounded by sandy or friable soils (i.e. soft, crumbly texture). Terrestrial adults are found primarily in in treed areas with a relatively closed canopy that also have these soil types, where salamanders can use underground blind tunnels, burrows and mammal runway systems. Such underground refuges are used both summer and winter.
Eastern Tiger salamander females lay eggs in masses on submerged twigs, weed stems and other support structures in ponds. In Manitoba, eggs are laid in mid-April and juvenile salamanders usually exit the pond in mid-August.
Photo: Eastern Tiger Salamander gelatinous egg masses
Range and Habitat
Eastern Tiger Salamanders have a large but disjointed range running throughout eastern North America. Although Canadian records are known from the extreme southern tip of Ontario, no Eastern Tiger Salamanders have been found in that area since 1915. In Manitoba, the range of the Eastern Tiger Salamander is unclear due to a lack of surveys and previous taxonomy (Eastern and Western Tiger Salamanders were formerly considered one species). Data from the Manitoba Herps Atlas and recent surveys conducted by the Manitoba Conservation Data Centre (MBCDC) show the Manitoba range to extend further northeast than previously thought, at least as far north as Hadashville.
Salamanders are vulnerable to human overexploitation such as use in the pet trade, bait for fishing and in some cases, as a luxury food item. In Manitoba, the movement of salamanders and other amphibians may increase the spread of the Chytrid Fungus Batrachochytridium dendrobatidis (Bd) and the highly infectious and lethal iridovirus Ambystoma tigrinum virus (ATV).
Photo: Carla Church with adult Eastern Tiger Salamander
Research by the University of Winnipeg in conjunction with the MBCDC will conduct focussed field studies to establish baseline population data and delineate the complete range of the species in the province. Information from this study and future inventory work will inform conservation efforts including protecting existing habitat and restoring or creating new habitat as required.