title: A population model of the impact of a rodenticide containing strychnine on Great Basin Gophersnakes (Pituophis catenifer deserticola).
abstract: Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burrows to suppress pocket gopher (Thomomys talpoides) populations in range and crop land in western North America. The population level impact was modelled of the use of strychnine-based rodenticides on a non-target snake species, the Great Basin Gophersnake (Pituophis catenifer deserticola), which is a predator of pocket gopher and a Species at Risk in Canada. Using information on population density, demographics, and movement and habitat suitability for the Gophersnake living in an agricultural valley in BC, Canada, we estimated the impact of the poisoning of adult snakes on the long-term population size. To determine the area where Gophersnakes could be exposed to strychnine, we used vendor records of a rodenticide, and quantified the landcover areas of orchards and vineyards where the compound was most commonly applied. GIS analysis determined the areas of overlap between those agricultural lands and suitable habitats used by Gophersnakes. Stage-based population matrix models revealed that in a low density (0.1/ha) population scenario, a diet of one pocket gopher per year wherein 10 % of them carried enough strychnine to kill an adult snake could cause the loss of 2 females annually from the population and this would reduce the population by 35.3 % in 25 years. Under the same dietary exposure, up to 35 females could die per year in a high density (0.4/ha) population which would result in a loss of 50 % of adults in 25 years.
authors.affiliation: Environment and Climate Change Canada, Science and Technology Branch, 5421 Robertson Road, Delta, BC, V4K3N2, Canada. cab.bishop@canada.ca.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Bishop
authors.affiliation: Van Hees Environmental, 206 Glover Street, Twisp, WA, 98856, USA.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Williams
authors.affiliation: Aquila Conservation & Environment Consulting, 75 Albert Street, Suite 300, Ottawa, ON, K1P 5E7, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Kirk
authors.affiliation: Parks Canada, Office of the Chief Ecosystem Scientist, 30 Victoria St., 3rd Floor, PC-03-D, Gatineau, QC, J8X 0B3, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Nantel
authors.affiliation: Environment and Climate Change Canada, Canadian Wildlife Service, 5019- 52 Street, Yellowknife, NT, X1A 2P7, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Reed
authors.affiliation: Environment and Climate Change Canada, Science and Technology Branch, 5421 Robertson Road, Delta, BC, V4K3N2, Canada.
authors.forename: John E
authors.initials: JE
authors.lastname: Elliott
mesh_terms: D000383:Agriculture; D000818:Animals; D002170:Canada; D003710:Demography; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants / Q000633:toxicity*; D008962:Models, Theoretical; D012378:Rodenticides / Q000633:toxicity*; D012911:Snakes / Q000502:physiology*; D013331:Strychnine / Q000633:toxicity*
chemical_list: D004785:Environmental Pollutants; D012378:Rodenticides; D013331:Strychnine
keywords: Gopher; Population impact; Reptiles; Rodenticide; Snakes; Stage-based population matrix models; Strychnine