Tigers on the Prowl: Determining the Distribution and Habitat Requirements of Eastern Tiger Salamander (Ambystoma tigrinum) in Manitoba

Manitoba has the only remaining population of Eastern Tiger Salamanders (Ambystoma tigrinum) in Canada. Unfortunately, very little is known regarding its range and habitat in the province. The purpose of this study was to determine key biological and physical habitat requirements that influence the distribution of A. tigrinum in the forested areas of southeastern Manitoba. Fifty-four sites were surveyed in the Sandilands Provincial Forest and surrounding areas using a combination of visual searches and funnel-trapping methods to locate salamander breeding ponds. Much of the Sandilands provides quality habitat for A. tigrinum with little variation between ponds. They are typically sandy, shallow, clear, and most ponds do not contain fish or are unable to sustain a fish population for more than one season. The upland habitat is forested with little agriculture or mining but with some forestry activity. Overall, percent of sand ranged from 85.7% to 99.7%, indicating that the substrate in all ponds is similarly friable. The ponds were mostly small, ranging from 61.38 m2 to 2336.42 m2. All ponds are relatively shallow, ranging in depth from 23 to 300 cm; all sites where salamanders were found at least once were less than 160 cm in depth except for one outlier that is 300 cm. The slope of the bank ranged from -0.06 to -0.80 cm/cm, but salamanders were only found in sites with slopes of less than -0.54 cm/cm. There was a large range in both aquatic vegetation cover (0 to 100% submerged vegetation; 0 to 50% emergent vegetation) and proximity of terrestrial vegetation (minimum distance to forest 0 to 23 m, maximum distance to forest 0 to 312 m; % of shoreline vegetated (0 to 100%), although both ponds with and without salamanders had similar ranges for these vegetation variables (above). Even with the relative homogeneity of the landscape in Sandilands, salamander larvae are not found in all ponds. The results of the analysis identified two key environmental variables: salamanders were more likely to be found in ponds with no fish and with low TDS. Of the 54 total sites, 13 sites had fish present, and of those 13 sites, zero had salamanders present in more than one year. The concentration of TDS in the ponds (the critical value for the split was 207 ppm TDS) also impacted salamander presence. In ponds with high concentrations of TDS (n = 13), approximately nine sites did not have salamanders, while zero sites had salamanders in only one year and four sites had salamanders in more than one year. Ponds with lower TDS concentrations (n = 28) had the opposite pattern of salamander presence; five sites did not have salamanders, four had salamanders in only one year while 19 sites had salamanders in more than one year. With global amphibian decline and the increased risk of climate change, knowledge of local populations of salamanders is important for the conservation of the species, informing policy and recovery strategies.

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