4.1 Roads and 4.2 Utility and Service Lines Impact Score: Low.

Scope: The exposure of T. elegans to roads, and thus potential for roadkill, is variable across their broad range (e.g., Lower Mainland vs. inland BC). Wide distribution dilutes this threat.

Severity: T. elegans cover large distances over the active season, and many encounter roads. Colubrid snakes move hundreds of meters to kilometers away from dens sites (Macartney et al. 1988). The species is commonly observed alive and dead on roads (approximately 21% of the 1780 T. elegans observations in iNaturalist for BC were of snakes on roads; Wind, pers. obs.), but no studies have determined road mortality rates for the species. No road studies for T. elegans specifically, however roads alter T. sirtalis movement patterns and make it more difficult for males to find mates (Shine et al. 2004). Fewer T. sirtalis were captured at sites with higher road densities in ON (Gigeroff 2022). T. sirtalis may be attracted to edge habitat near roads (Wagner et al. 2021), but not in all landscapes (Patrick and Gibbs 2009). T. elegans will use underpasses when available (Pagnucco et al. 2011), but underpasses may not be effective where road crossing locations are occur over a broad area (i.e., are not localized; Wagner et al. 2021). Negative effects are likely greatest where roads occur near critical habitat, such as overwintering dens. Blasting of a rocky outcrop in ID for road construction, the latter of which was used by T. elegans for overwintering, resulted in direct mortalities and no further observations of the species in the area (Andrews et al. 2006). Thamnophis spp. use of rocky outcrops along roadways in BC as hibernaculum (Van Damme 2009), however entire populations are likely not lost.

11.1 Habitat Shifts and Alterations: Impact Score: Low.

Across BC is experiencing regular heat waves and droughts, which is affecting hydrology and aquatic habitats. Severity: Climate change is expected to affect wetlands in the southern interior as a result of climate change (Bunnell et al. 2011), and these are important foraging areas for T. elegans. From 1992 ? 2012, the total number and surface water area of ponds across south-central BC decreased by 63% and 54% respectively due to decreased snow pack and increased temperature/evaporation (Coelho 2015). There is a complex interaction between snowpack, precipitation in spring and summer, air temperature affecting water temperature in shallow ponds, and hydroperiod.

11.2 Droughts. Impact Score: Low.

Throughout this species? range in BC, there are increasing periods of drought. The impact has not been studied in B.C., however elsewhere the amount of precipitation received in spring in California affected the immune response of T. sirtalis and T. elegans (e.g., dry periods may reduce their resistance to disease and parasites); thus they may reflect a greater vulnerability to repeat drought events (Combrick et al. 2021). However, the population im