Sensitive Snake Species and Hibernacula Range Science Support Document Government of Alberta Wildlife Sensitivity Feature Layer

Sensitive Snake Species and Hibernacula Range Science support document Government of Alberta wildlife sensitivity feature layer

Background

Alberta has seven species of snakes. The majority of the species are found in the south eastern portion of the province. However, snakes are found throughout the province. The prairie rattlesnake (Crotalus viridius), bull snake (Pituophis catenifer), western hog-nosed snake (Heterodon nasicus) and eastern yellow-bellied racer (Coluber constrictor) are only found in the south eastern portion. The wandering garter snake (Thamnophis elegans) and plains garter snake (Thamnophis radix) are found throughout the south and central parts of the province. The red-sided garter snake (Thamnophis sirtalis) is primarily found in the parkland and boreal regions.

Snakes spend the cold months (October-April) underground in dens called hibernacula. Hibernacula are critical features that protect the snakes from freezing and predators during hibernation. In Alberta, hibernacula have been found in stable slump blocks, meander scarps and fissures, sinkholes, rocky outcrops, and mammal burrows (Didiuk 1999; Waye and Shewchuk 2002; Kissner and Nicholson 2003, Kendall 2020). These habitat features are usually associated with coulee habitat and major river valleys (Kissner and Nicholson 2003). Over- wintering sites are often located on south- and southeast-facing slopes to provide snakes with the maximum amount of sunshine and warmth for thermoregulation. The rookery sites (where gravid females and young aggregate) of the prairie rattlesnake have been found within 500 metres of the hibernaculum (Jorgensen 2009). Habitat where snake hibernacula occur have been subject to significant urban, agricultural and industrial disturbance that threatens the persistence of snakes in Alberta. Several historical dens are considered to be extirpated due to human land use activities (Robertson pers comm.).

Snakes are generally active, i.e., migrating, mating and foraging, between April and September. Alberta’s snake species can travel significant distances from the hibernacula during this period. The prairie rattlesnake has been detected migrating 25 km from the den to forage and find mates (Didiuk 1999), but typically this species travels between 10 - 15 km from the den (ESRD 2012). Bull snakes travel up to 12 km from the hibernacula (COSEWIC 2017).

Prairie rattlesnakes and bull snakes are economically important because their prey is primarly rodents. Rodents cause significant damage to buildings, range land, and agricultural crops; their populations need to be controlled. Ranchers and farmers in Alberta have been known to relocate snakes to areas of high ground squirrel and pocket gopher activity as a means of pest control (Kissner and Nicholson 2003).

Desired outcomes These guidelines serve three primary purposes: 1. Prevent destruction of snake hibernacula and rookeries by human activities. 2. Maintain habitat and function, and opportunity for use of hibernaculum* and rookery* sites. 3. Prevent human-caused and road mortality, and persecution of snake species.

Digital layers available A. Sensitive Snake Hibernacula Range Methods The Sensitive Snake Hibernacula Range dataset replaces the former “Sensitive Snake Species Range” dataset. The original range was created by modeling from GVI, however, due to the inprecise nature of spatial data layers important habitat was not included. The dataset was revised based on data in FWMIS, imagery and Habitat Suitability Indices. Species experts reviewed maps and provided additional insight.

B. Snake Hibernacula Methods The snake hibernacula deteset is based on recent (2016-2020) provincial surveys and FWMIS records. Hibernacula confirmed active are included with the required 500 m buffer.

C. Snake Habitat Methods The Snake Habitat layer includes Townships where snake (prairie rattlesnake, bull snake, and garter snake) activity is known to occur.

Insufficient survey work has been conducted to know the precise extent of movement. Observations were compiled from the Government of Alberta’s Fisheries and Wildlife Management Information System (FWMIS) which includes data from provincial surveys conducted by regional wildlife biologists and independent researchers.

Figure 1: The Sensitive Snake Species and Hibernacula Ranges and known hibernacula buffered in Alberta. Rationale The provincial designation of the prairie rattlesnake is Special Concern, western hog-nosed snake (Heterodon nasicus) is May Be At Risk, and bull snake is Sensitive; as well, these species are non-game species in the Alberta Wildlife Act. Prior to 2015-16, the garter snake species (wandering, plains, red-sided) were designated as non-licenced species and not afforded protections. Recently, their classification was amended in the Wildlife Act to non-game and they were designated Sensitive; as a result, affording protections. In 2017, the eastern yellow- bellied racer was added to Alberta’s Wildlife Act as non-game and designated Sensitive. Federally, the prairie rattlesnake and bull snake are designated Special Concern, and the eastern yellow-bellied racer is designated Threatened by COSEWIC.

Hibernacula are vital to snake survival and considered limited in availability, and snakes exhibit high site fidelity; in Alberta, snakes are known to overwinter in the same den year after year (AESRD 2012, Jorgensen 2009, Martinson 2009). In southern Alberta, multiple snake species will den together in the same hiberncalum. Rookeries of prairie rattlesnake can be used by numerous females (Jorgenson 2006) as well as other individuals

to provide refuge as the snakes move away from the over-wintering den. Several female bull snakes may lay their eggs in the same rookery, a single nesting site may have several chambers with eggs from different females.

Land use activities have a high potential to result in the death of individual snakes and destruction of their habitat. Between April and September, when snakes are away from their hibernaculum they have limited capibilities to flee from vehicles, equipment or machinery during contruction/project activities. Snakes often fall into excavations (pipelines, etc.) and pass through or may occupy active construction areas seeking cover in/under equipment. Additionally, snakes are rarely detected during wildlife sweeps or surveys; therefore these methods cannot be relied on to guide mitigation. Mortality from vehicles on paved roads, gravel roads, and trails is the greatest threat to snake populations in Alberta and elsewhere in the world (AESRD 2012, COSEWIC 2015, COSEWIC 2017, Martinson 2009, Fortney et. al. 2012, AEP 2016). Construction activities that occur during the active season, in areas where snakes are known to be present must consider snakes and avoid incidental mortality. Land use guidelines that consider the sensitive nature of these species’ and include restricted areas, restricted timing, setback conditions, and mitigations will assist with the recovery of the prairie rattlesnake and decrease the risk of up-listing the other species of snakes. Snake populations are inferred to have significantly declined in Alberta (AEP 2016, COSEWIC 2015, COSEWIC 2017).

Species specific standards and conditions Standards or conditions that apply within Sensitive Snake Hibernacula Range, Provincial Hibernacula Buffer and Sensitive Snake Habitat can be found in the Master Schedule of Standards and Conditions.

Relevant legislation/policy Currently, under the Alberta Wildlife Act prairie rattlesnake, bull snake, western hog-nosed snake, eastern yellow- bellied racer, wandering garter snake, plains garter snake, and red-sided garter snake are afforded protection against killing/hunting; and their hibernacula and rookeries are protected from disruption or destruction year round. However, effective management of hibernacula also requires protection of the surrounding area. Maintenance of over-wintering sites and the associated habitats for hunting, basking and birthing is critical for the survival of Alberta’s snake species.

Snake hibernacula protection is embedded in the following legislation and regulations:

 Alberta Wildlife Act, 1997: Section 36(1) o Wildlife Regulations: Section 96, Schedule 6 (Part 1, Sub-Part 1)

The above conditions align with the current Master Schedule of Standards and Conditions, which outlines standards for a 500 metre setback from snake hibernacula and 200 metre setback from snake rookeries in the Sensitive Snake Species Range.

Additionally, AEP has a Conservation Management Plan developed for the prairie rattlesnake that outlines measures to protect rattlesnakes from land use activities.

Frequency of maintenance, reviews and updates Updates to this layer will be made based on the availability of new field observations. These Wildlife Sensitivity Layers will undergo a broader review and update every five years in alignment with hibernacula surveys. It is vital to maintain hibernacula and prevent mortality to avoid extirpation of snake species from Alberta.

References Alberta Environment and Parks. 2016. Prairie Rattlesnake Conservation Management Plan 2016- 2021. Alberta Environment and Parks. Species at Risk Conservation Management Plan No.12. Edmonton, AB. 10 pp.

Alberta Environment and Sustainable Resource Development and Alberta Conservation Association (AESRD and ACA). 2012. Status of the Prairie Rattlesnake (Crotalus viridis) in Alberta: Update 2012. Alberta Wildlife Status Report No. 6 (update 2012). Alberta Environment and Sustainable Resource Development, Edmonton, AB. 49 pp.

COSEWIC. 2015. COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. x + 69 pp.

COSEWIC. 2017. COSEWIC assessment and status report on the Bullsnake Pituophis catenifer sayi in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 34 pp.

Didiuk, A. 1999. Reptile and amphibian component report. Canadian Forces Base Suffield National Wildlife Area Wildlife Inventory. Unpub. Rep., Canadian Wildlife Service. Edmonton, Alberta. 70pp.

Fortney, A.N., R.G. Poulin, J.A. Martino, D.L. Parker, and C.M. Somers. 2012. Proximity to hibernacula and road type influence potential road mortality of snakes in southwestern Saskatchewan. Canadian Field- Naturalist 126:194–203.

Jorgensen, D. 2009. Annual movement patterns of female prairie rattlesnakes in Alberta, Canada. M.Sc. Thesis, Faculty of Environmental Design, Univ. of Calgary, Calgary, AB.

Kendell, K. 2020. Garter snake (Thamnophis spp.) surveys at historical den sites in Alberta, 2017–2019. Data Report, produced by Alberta Conservation Association, Sherwood Park, Alberta, Canada. 17 pp + App

Kissner, K.J., and J. Nicholson. 2003. Bullsnakes (Pituophis catenifer sayi) in Alberta: literature review and data compilation. Species at Risk Report No. 62, Alberta Sustainable Resource Development, Fish and Wildlife Division, Edmonton, Alberta.

Martinson, A. 2009. Modeling road mortality of prairie rattlesnakes and bullsnakes in Alberta. M.Sc thesis, University of Calgary. Calgary, Alberta.

Watson, S.M and A.P. Russell. 1997. Status of the Prairie Rattlesnake (Crotalus viridis viridis) in Alberta. Alberta Environmental Protection, Wildlife Management Division, Wildlife Status Report No. 6. Edmonton, AB. 26pp.