HEADSTARTING AS A MANAGEMENT TOOL: A CASE STUDY OF THE PLAINS GARTERSNAKE

Abstract

The use of headstarting and related techniques as management tools for threatened and endangered species remains controversial, due in part to a lack of empirical data on their effectiveness. Here, we present data on pre-natal mortality, growth, and survival during headstarting as well as growth, survival, and reproduction following release for an unprotected population of plains gartersnakes. We combine these data with data on growth and survival of comparably sized wild-caught snakes to provide an overall evaluation of the potential effectiveness of headstarting. Depending on rearing conditions, proportions of live births varied from 0.79 (‘worst-case’) to 0.94 (‘best-case’), survival during headstarting ranged from 0.74 (‘worst-case’) to 0.88 (‘best-case’), and second-year survival following release ranged from 0.11 (‘worst-case’) to 0.40 (‘best-case’). In comparison, survival of free-ranging snakes was 0.16 in their first year and 0.40 in their second year. Assuming the proportion of live births in nature is close to 1, expected survival to reproductive maturity among free-ranging snakes is 0.06, whereas that for headstarted snakes ranges from 0.07 (‘worst-case’) to 0.33 (‘best-case’). The growth rate of headstarted snakes following release was similar to that of similar-sized free-ranging snakes, and headstarted snakes were successful at reproduction. Together, these results suggest that, if carefully implemented, headstarting may be an effective management tool for endangered plains gartersnake populations in Ohio and for other natricine snakes with similar demographic characteristics.