2015-16 Project Results Summary

For those who are interested in knowing what we have learned so far about toad winter hibernation, below is a summary of the results from our 2015 report.

Executive Summary from 2015-16 Report

Western Toads (Anaxyrus boreas) are listed federally and in British Columbia (BC) as Special Concern (S3/S4). On the south coast of BC, where rural and urban development has been extensive Western Toad breeding populations are relatively rare and patchily distributed and they are believed to be in decline. The BC Western Toad Provincial Working Group prepared a Draft Provincial Management Plan for this species, citing urban development and transportation corridors as medium and high threats for the species respectively and identified hibernation sites as a knowledge gap needed to assess population viability and improve best management practices. The overall goal of this multi-year project is to identify important terrestrial habitats on eastern Vancouver Island in order to contribute towards habitat protection and improved connectivity. The objectives of the study for 2015-16 were to locate and describe Western Toad hibernation sites, determine whether hibernacula are communal, and determine the distance between important habitat features such as hibernation and breeding sites.

Our study site is located in the Cowichan River Valley west of Duncan, on Vancouver Island within a mosaic of land uses (forestry, housing developments, agricultural land, etc.). We captured toads via two main methods—volunteers telling us when they had a toad on their property and by conducting night road surveys. We fit adult toads with BD-2 radio transmitters, some of which had temperature sensors. Toads were re-located every 4 to 7 days throughout the fall and winter. In fall 2015, we set remote cameras at three hibernation sites from 2014-15 to see if the sites would be re-used. We also set cameras at 11 hibernation sites in winter 2016 to capture toad emergence and to determine if the sites were communal. Lastly, we set microclimate data loggers at hibernation sites to record air temperature and relative humidity and we measured habitat variables at three spatial scales at 16 hibernation sites and 48 random sites.

Of the 23 toads fitted with transmitters in fall 2015, we tracked 13 toads to 12 confirmed hibernation sites. Toads moved extensive distances in the fall, and many moved in the direction of / closer to their breeding site for hibernation. As a result of these extensive movements, toads crossed at least one public road during their migrations. Most of the toads (62%) utilized the area around their hibernation structure prior to hibernation or post emergence for many weeks (within 25 m). All of the toads hibernated in some type of edge habitat, of which a component included trees. More than half (54%) of the toads we tracked in 2015-16 hibernated in a 10-15 year-old clearcut that contained a mosaic of old logging roads, small wetlands, and tree patches. The majority of toads (75%) utilized wood structures (relatively large logs and stumps) for hibernation, while others used banks or mounds that appeared to have a woody component. The toads went subsurface for approximately 7 to 15 weeks from late Oct. to late Jan. Underground temperatures at toads fitted with temperature-sensor transmitters were on average 3°C warmer than surface air temperatures recorded during daytime re-locations, except during the mid-point of the hibernation period (mid-Dec to early Jan). Wildlife camera data confirmed that at least one of the 2015-16 hibernation sites was used by at least four toads, most hibernacula were used by other amphibian and mammal species, and one site was also used by a reptile species.

The improved and continued success of this toad habitat project is due to the attention we have given to increased public awareness (media coverage, blog, public presentation, mail out fliers), improving and expanding our techniques (e.g., capturing toads earlier in the season, including habitat data collection, increased awareness around the timing of toad activities), and vigilant monitoring.