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BC Conservation Data Centre: Conservation Status Report

Coluber constrictor
North American Racer

 
Scientific Name: Coluber constrictor
Scientific Name Synonyms: Coluber constrictor mormon
English Name: North American Racer
English Name Synonyms: Racer
Western Yellow-bellied Racer
   
Provincial Status Summary
Status: S2S3
Date Status Assigned: March 30, 2018
Date Last Reviewed: March 30, 2018
Reasons: North American Racer is restricted to the dry grasslands of the southern interior of the province where they are faced with significant threats, including road mortality along with habitat loss and fragmentation.
 
Range
Range Extent: F = 20,000-200,000 square km
Range Extent Estimate (km2): 48,493
Range Extent Comments: Racers are restricted to the dry southern interior grasslands of the southern Columbia, Okanagan/Similkameen, Kettle, Thompson, Nicola and the middle Fraser drainages (Shewchuck and Waye 1995; Matsuda et al. 2006i). COSEWIC (2015i) calculated the estimated extent of occurrence to be 48,493 square kilometres.
Area of Occupancy (km2): F = 126-500
Area of Occupancy Estimate (km2): 1148
Area of Occupancy Comments: COSEWIC (2015i) calculated the index of area of occupancy ( IAO) to be less than 1,000 km², based on known and suspected communal overwintering den sites. The actual IAO may be larger, as an unknown proportion of racers may hibernate singly away from these sites. In 2017, the B.C. CDC calculated the area of occupancy to be 1,148 km2 (284 2x2 km grid cells), based on mapped occurrences.
 
Occurrences & Population
Number of Occurrences: D = 81 - 300
Comments: As of December 2017, the B.C. Conservation Data Centre has 98 element occurrences mapped.
Number of Occurrences with Good Viability / Ecological Integrity: U = Unknown
Number of Occurrences Appropriately Protected & Managed: CD = 4 - 40
Comments: There are a several protected areas with suitable habitat for Racers; however these are mostly small and disconnected from each other and few contain both the summer and winter habitats that are required. Suitable habitat within protected areas include Okanagan Mountain Provincial Park, Beaver Creek Provincial Park, Throne Ecological Reserve, White Lake Grasslands Protected Area, South Okanagan Grasslands Provincial Park, Churn Creek Protected Area, other areas managed by Nature Trust of BC, and other Ecological Reserves. Overall, in the Okanagan-Similkameen region about 10% of the remaining grassland is protected and about 7% in the Thompson region (COSEWIC 2004r). In 2006, this species was listed as Identified Wildlife under the Forest and Range Practices Act. Several Wildlife Habitat Areas (WHA's) have been established to protect Rattlesnake and Gopher Snake den sites, some which are known to host Racers. In the Thompson region, there are 16 Rattlesnake and two Gopher Snake WHA's and in the Okanagan region, there are 10 Gopher Snake, two Rattlesnake and one Racer WHA (Racer Management Team Working Group 2013).
Population Size: E = 2,500 - 10,000 individuals
Comments: There has been no extensive inventory of Racers in British Columbia. However, an estimate of 5,000 to 10,000 mature individuals is reasonable given the estimates for the more widely studied Western Rattlesnake and Gophersnake which have similar distribution, common usage of hibernacula, and frequency of sightings (COSEWIC 2004r; 2015i).
 
Threats (to population, occurrences, or area affected)
Degree of Threat: B = High
Comments: From COSEWIC 2015i: Western Yellow-bellied Racers are vulnerable to habitat loss and fragmentation. These snakes exhibit a high degree of fidelity to specific hibernacula, nesting sites, and summer foraging areas, and appear not to tolerate significant disturbance to these habitats. Racers are limited by the availability of suitable den sites and are unlikely to be able to relocate to other areas if dens are destroyed. Large geographic distances or habitat-barriers isolate small subpopulations, further decreasing the probability of individuals dispersing between sites. Both subspecies of Racer (Eastern and Western) are regularly killed on roads, but the threat of road mortality varies greatly across their ranges, being considerably greater for the western subspecies. The overall threat impact was assessed as ?high? for the Western Yellow-bellied Racer.
 
Trend (in population, range, area occupied, and/or condition of occurrences)
Short-Term Trend: E = Decline of 30-50%
Comments: 2018: COSEWIC (2015i) suggests an Inferred and suspected decline of >30% based on threats (past and projected) and habitat loss (COSEWIC2015i)

2012: There are no data; however, habitat is declining in area and quality. Loss of native grassland varies from 11-45% in the Okanagan-Similkameen region to 10-20% in the Thompson region. Racers have likely been extirpated on urban and intensely cultivated lands so declines of 10-45% could be estimated based on grassland data. In the Okanagan Valley local declines have occurred as orchards in and near the valley bottoms and ranching on adjacent slopes have expanded as well as housing developments on south-facing slopes that snakes use for hibernating sites (COSEWIC 2004r).
Long-Term Trend: E = Decline of 30-50%
Comments: 2018: Western Yellow-bellied Racers were probably never widespread or abundant, as the southern regions of B.C. are the northern extremes of their geographic distribution (COSEWIC 2015i). Although historical data is not available, the number of Racers in B.C. has likely declined due to loss of habitat. Native grassland cover within the southern interior of B.C. has decreased up to 52%. Because Racers will not persist without this habitat, declines up to 45% are likely to have occurred (COSEWIC 2004r, 2015i; Racer Management Team Working Group 2013). 

2012: The long-term trend for Racer populations is continued declines. This is largely due to accelerating urbanization throughout most of their range. This includes new developments and infilling of rural areas, in addition to increased number of roads and traffic volumes. The resident population in the Thompson-Okanagan doubled between 1971 and 2001, and is expected to increase 40% by the year 2031 (Hobson and Associates 2006).
 
Other Factors
Intrinsic Vulnerability: A=Highly vulnerable
Comments: "Relatively low reproductive rate (small clutch size and often biennial reproductive cycle of females, and a late age at maturity) results in a slow rate of recovery from perturbations." (COSEWIC 2015i)
Environmental Specificity: B=Narrow. Specialist or community with key requirements common.
Comments: Restricted to dry grassland habitat. Racer populations are naturally limited by the fact that individuals are highly reliant on hibernation sites located in very specific areas (eg. deep enough to prevent freezing during winter) and by their limited ability to disperse. Subpopulations are geographically isolated, which coupled with their small size, could increase the risk of extirpation. Potential for recolonization from other areas is low as dens are often great distances from one another with unsuitable habitat in between them, leaving no corridors for movement (COSEWIC 2004r; COSEWIC 2015i).
Other Rank Considerations:
 
Information Gaps
Research Needs: Racers have been poorly studied in B.C. The most needed knowledge is whether their populations are viable and what habitat attributes are important to their life requisites.
Inventory Needs: There needs to be information obtained about population trends - this may be achieved by monitoring individual populations over long time periods. Occurrences in marginal habitat at the edge of their ranges should be investigated to see if their range is expanding or contracting.
 
Stewardship
Protection:
Management: Much of the habitat for Racers in B.C. is on grazed grasslands - research into the effect of varying grazing regimes on reproductive success or population density would be very useful. Determination of hibernaculum, nesting and dispersal requirements is needed to adequately manage for this species.
 
Version
Author: L. Ramsay and S. Cannings (1998); L. Westereng and M. Sarell (2008); L. Gelling (2012, 2018)
Date: March 30, 2018
 
References
Campbell, C.A., and D.W. Perrin. 1991. Status report on the Racer, Coluber constrictor, in Canada. Unpubl. rep. submitted to the Comm. on the Status of Endangered Wildl. in Can., Ottawa, ON. 34pp.
Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
Corn, P.S., and R.B. Bury. 1986. Morphological variation and zoogeography of racers (Coluber constrictor) in the Central Rocky Mountains. Herpetologica 42:258-264.
COSEWIC. 2004r. COSEWIC assessment and update status report on the Eastern and Western Yellow- bellied Racers, Coluber constrictor flaviventris and Coluber constrictor mormon in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 35 pp. (www.sararegistry.gc.ca/status/status_e.cfm)
COSEWIC. 2015i. COSEWIC assessment and status report on the Eastern Yellow-bellied Racer Coluber constrictor flaviventris and Western Yellow-bellied Racer Coluber constrictor mormon in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xvii + 64 pp.
Dulisse, J. 2007. Western yellow-bellied Racer (Coluber constrictor mormon) Inventory in Southeastern British Columbia 2006. Prepared for Columbia Basin Fish and Wildlife Compensation Program, Nelson, BC
Environment Canada. 2015t. Management Plan for the Western Yellow-bellied Racer (Coluber constrictor mormon) in Canada. Species at Risk Act Management Plan Series. Environment Canada, Ottawa. 3 pp. + Annex
Fitch, H.S., W.S. Brown, and W.S. Parker. 1981. Coluber mormon, a species distinct from C. constrictor. Trans. Kansas Acad. Sci. 84:196-203.
Greene, H.W. 1984. Taxonomic status of the western racer, COLUBER CONSTRICTOR MORMON. Journal of Herpetology 18:210-211.
Gregory, L.A., and P.T. Gregory. 1999. The Reptiles of British Columbia, A taxonomic catalogue. B.C. Minist. Environ., Lands and Parks, Victoria. Wildl. Bull. B-88. 28pp.
Hammerson, G.A. 1982. Amphibians and reptiles in Colorado. Colorado Div. Wildl., Denver. vii+131pp.
Hobson & Associates. 2006. Environmental issues and options for the South Okanagan Regional Growth Strategy. Prepared for the Environmental Advisory Committee, Regional District of Okanagan-Similkameen.
Matsuda, B.M., D.M. Green and P.T. Gregory. 2006. Royal BC Museum handbook amphibians and reptiles of British Columbia. Royal B.C. Mus., Victoria, BC. 266pp.
Nussbaum, R.A., E.D. Brodie Jr., and R.M. Storm. 1983. Amphibians and Reptiles of the Pacific Northwest. Univ. Press of Idaho. 332pp.
Sarell, M.J. 1993. Snake hibernacula in the South Okanagan. Unpubl. rep. submitted to Wildl. Program, B.C. Environ., Penticton. 19pp. + appendix.
Shewchuk, C.H., and H.L. Waye. 1995b. Status of the western yellow-bellied racer in British Columbia. Unpubl. rep. B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria. 16pp.
Smith, H. M. and E. D. Brodie, Jr. 1982. Reptiles of North America. Golden Press, New York. 240 pp.
Stebbins, R.C. 1985. A field guide to western reptiles and amphibians. Second ed. Houghton Mifflin Co., Boston, MA. xiv+336pp.
Wilson, L. D. 1978. Coluber constrictor. Cat. Am. Amph. Rep. 218.1-218.4.
 

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Suggested Citation:

B.C. Conservation Data Centre. 2018. Conservation Status Report: Coluber constrictor. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Dec 8, 2024).