A research report by Kyle Welsh.
This project was funded in part by the Friends of Elk Island Society.
The Western Tiger Salamander reaches the northern extent of its continent-wide distribution in central Alberta. Here, like elsewhere, this salamander breeds in semi-permanent to permanent fish-less wetlands and develops as a gilled larva for several months before metamorphosing and returning to the terrestrial environment where it will spend the majority of its life, only returning to wetlands to breed. Because of this biphasic lifestyle that characterizes most pond-breeding amphibians, tiger salamander populations require both suitable aquatic habitat and adjacent terrestrial foraging and overwintering habitat. This aspect of their life cycle makes them particularly sensitive to habitat loss and degradation. Recent concern of global amphibian declines, regional urban development, and increasing occurrences of disease have led to western tiger salamanders (Ambystoma mavortium) becoming a species of special concern in the prairie provinces and endangered in British Columbia. To effectively assess and maintain the well-being of this species in Alberta, we need to know what they need to thrive. We know what their aquatic needs are, however, relatively little is know of their terrestrial requirements. This is largely due to their secretive nature that makes them difficult to encounter with regularity outside of above ground migration events during rainy nights and the occasional discovery in a compost pile or gopher trap.
My question is: What is their terrestrial habitat? In a region with lots of options to choose from, do they prefer grassland habitats over forested ones? Do they even have a preference?
In 2013, I sampled wetlands in the Beaver Hills for salamander presence and abundance. I sought them in their aquatic habitat because they are much easier to locate with regularity. I then analyzed the terrestrial habitat surrounding these wetlands to determine if salamander presence at a given site is related to the surrounding habitat. I specifically examined the proportion of forested versus grassland and grazing land available to the salamanders.
My results suggest that given suitable aquatic habitat for breeding and larval development, tiger salamanders do not exhibit a preference for forested or grassland habitat. This is surprising given that western tiger salamanders (not to be confused with their eastern counterpart, A. tigrinum) typically inhabit grassland ecosystems. Therefore one could presume that they would prefer similar open habitat types in the parkland regions where they occur but this does not appear to be the case. However, there appears to be a potential relationship between tiger salamander abundance on a landscape and the abundance of small mammal burrows, specifically northern pocket gophers. This is not surprising as these “mole” salamanders are known for their fossorial lifestyle and are occasionally found in mammal retreats. They use these tunnel networks to avoid desiccation during the warm, dry summers, and to escape the frost in the winter. In 2014, I plan to examine the potential relationship between mammal burrows and tiger salamander density as a mechanism of providing overwintering habitat. I will also examine the effect of agricultural development on salamander density and distribution.
Photos:Salamander habitat after the 2005 fireAssorted shots of a tiger salamander during sampling.