Road mortality and climate change (e.g., shifting habitats, and droughts and temperature extremes that affect the prey base) were identified as the largest threats for this species. The species' range overlaps with the geographic area of the province that has extensive land use for agriculture and forestry, a variety of non-native vertebrate predators in aquatic habitats, and experiences relatively high development pressure. However, it is a generalist that occurs in and exploits a variety of habitat types and elevations and is adaptable to habitat change. Pollutants may affect the species (e.g., bioaccumulate toxins via their prey), but the extent of impacts are unknown.

Below are the comments that were included in the original calculator (2023) comment fields

4.1 Roads and Railways: Impact score is Low. The exposure of this species to roads, and thus potential for roadkill, is variable across their broad range (e.g., high in the Lower Mainland vs. low in parts of inland BC). The wide distribution dilutes (range extent) this threat. Individuals cover large distances over the active season and are likely to encounter roads. Average distance between summer and winter range for this species in eastern BC was 1.5 km, with a maximum of 2.7 km with cumulative distance moved over active season estimated to be between 3.5 and 15 km (McAllister 2018). 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 14% of the 3,082 of the observations for this species in iNaturalist for BC were of snakes on roads; Wind, pers. obs.), but no studies have determined road mortality rates for the species. Fewer T. sirtalis captured at sites with higher road densities in ON (Gigeroff 2022). Roads alter movement patterns for this species and make it more difficult for males to find mates (Shine et al. 2004). They may be attracted to edge habitat near roads (Wagner et al. 2021), but not in all landscapes (Patrick and Gibbs 2009). The species will use underpasses when available (Dillon et al. 2020; Boyle et al. 2021), but underpasses are not effective where road crossing locations 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 Idaho 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). Garter snake use of rocky outcrops along roadways in BC as hibernaculum (Van Damme 2009), however it is unlikely that entire populations are lost.

9.3 Agricultural and Forestry Effluents: Impact Score is Unknown. Herbicides and pesticides. Scope: The range of this species overlaps with extensive agricultural and forestry development across BC, however the large range likely dilutes effects. Numerous chemicals are associated with these industries (e.g., the herbicide glyphosate; Govindarajulu 2008). A review found only one study with this species and herbicides used in forestry (from Ontario) - no obvious negative effects from herbicide treatment were documented (possibly positive effects; Lautenschlager and Sullivan 2002). Reduction in amphibian populations, which are their primary prey base may negatively affect this gartersnake?s populations. Snakes bioaccumulate pollutants such as pesticides and PCBs (Quoc Hoang et al. 2021) but the impact on populations of this species in BC are not known.

Under 11. Climate Change four threats each scored low.

They are:

11.1 Habitat Shifts and Alterations: Throughout this species? range,