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Relevance of Life-History Parameter Estimation to Conservation Listing: Case of the Sharp-tailed Snake (Contia tenuis)

Abstract Optimizing conservation efforts requires distinguishing between rare and potentially endangered species (few extant individuals, functionally rare) and species that are difficult to find (operationally rare). Certain suites of life-history parameters such as slow growth, late maturity, low fecundity, and long interbreeding intervals are thought to be associated with functional rarity and with intrinsic vulnerability to population declines. We estimated life-history parameters by using capture-recapture data of one such elusive species, the Sharp-tailed Snake (Contia tenuis), from 1997 to 2005 in northern portions of its range in British Columbia, Canada. Body size ranged from 84 mm (smallest juvenile) to 323 mm (largest female). Mean snout–vent lengths were 212 ± 14 mm (mean ± SD) for adult males and 251 ± 28 mm for females. They were slow growing (adult growth rate, 4.3 ± 3.8 mm/yr), had extended time-to-sexual maturity (5–6 yr), and had small clutch size (3.6 ± 1.1 eggs). Estimated adult survival was 0.71 (95% confidence interval [CI]  =  0.59–0.81). Estimated population growth rate for one population over the 8-yr study period was 0.89 (95% CI  =  0.79–1.1). Compared with populations farther south and other similarly sized colubrid snakes, Sharp-tailed Snakes at our study site exhibited many “slow” life-history traits that could increase their vulnerability to population declines. Our analysis validated Sharp-tailed Snakes as a species of conservation concern in British Columbia with traits that could lead to functional rarity and highlighted research into mortality, migration, and recruitment patterns as key needs for conservation planning.