Snake mortality and cover board effectiveness along exclusion fencing in British Columbia, Canada

Published source details Eye D.M., Maida J.R., McKibbin O.M., Larsen K.W. & Bishop C.A. (2018) Snake mortality and cover board effectiveness along exclusion fencing in British Columbia, Canada. Canadian Field-Naturalist, 132, 30-35.
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This study is summarised as evidence for the following.

	Action	Category
	Provide artificial shade for individuals Action Link
	Install barriers along roads/railways Action Link

Provide artificial shade for individuals

A study in 2007–2017 in shrub-steppe desert in the Okanagan Valley, Canada (2) found that coverboards provided as artificial shade after the installation of an exclusion fence were used by northern pacific rattlesnakes Crotaus oreganus oreganus in the year after the fence was installed, but there was no evidence that they were used 10 years later. Coverboards to provide shade during high temperatures were used by nine northern pacific rattlesnakes in the year they were installed. Nine to 10 years later, no snakes were found under the coverboards although 116 live snakes (northern pacific rattlesnake, great basin gophersnake Pituophis catenifer deserticola, and western yellow-bellied racer Coluber constrictor mormon) were captured along an adjacent exclusion fence over the same time period. In 2007, wooden coverboards (70 x 70 x 7 cm, 7 cm off the ground with 15–20 cm of sand excavated from underneath) were placed at 12 locations spaced at 30 m intervals along (360 m of) a 4 km long wire mesh snake exclusion fence (installed in 2006) to mitigate snake mortality due to heat exposure. At each interval, two coverboards were placed either side of the fence and one was placed 10–15 m away from the fence in natural habitat. Coverboard use was initially monitored in July 2007, and then monitoring was continued by mark-recapture surveys 5–6 days/week and walking the fence line 2–3 times/week in May–October 2016–2017.

(Summarised by: Katie Sainsbury)
Install barriers along roads/railways

A study in 2006–2017 in shrub-steppe desert in British Columbia, Canada (Eye et al. 2018) found that building an exclusion fence to prevent snakes entering high human areas activity and associated roads did not prevent road related snake mortality. In the first year after the exclusion fence was installed, seven snake mortalities were observed near the fence. Ten to 11 years after the fence was installed, 22 of 45 (49%) snake deaths were road kill, and a further 15 (33%) dead snakes were found next to the fence. Six of the 15 dead snakes near the fence were found next to a section that had been rerouted the previous year. Western yellow-bellied racer Coluber constrictor mormon were disproportionately represented among dead snakes. In total 341 live snakes (northern pacific rattlesnake Crotalus oreganus oreganus, great basin gopher snake Pituophis catenifer deserticola, and western yellow-bellied racer) were captured around the fence in the tenth and eleventh year after it was installed. In 2006, approximately 4 km of exclusion fencing (60 cm high with 0.6 cm mesh) was built. The fence was upgraded and 200 m rerouted in 2015. Snake mortality was monitored in May–October 2016–2017 by walking the fence line 2–3 times/week and live snakes were monitored using mark-recapture methods 5–6 days/week.

(Summarised by: Katie Sainsbury)