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Open Access Publications from the University of California

Strychnine for the Control of Richardson’s Ground Squirrels: Efficiency and Selectivity Issues

  • Author(s): Proulx, Gilbert
  • MacKenzie, Neil
  • MacKenzie, Keith
  • Walsh, Kara
  • Proulx, Benjamin
  • Stang, Kim
  • et al.

Strychnine has recently been made available in Canada under an emergency registration program for the control of Richardson’s ground squirrels. From 2007 to 2009, we tested the control efficacy of this poison using >1-year-old and newly produced strychnine on hulless oats, canary seed, and alfalfa pellets. Newly produced 2% liquid strychnine, mixed with hulless oats to formulate 0.4% strychnine freshly mixed baits, controlled ≥70% of adult and juvenile ground squirrels in spring and summer. Other types of strychnine baits were not as reliable from one season to the other. At 0.2% concentration, strychnine-treated oats were relatively inefficient. When >1 year old, the control efficacy of strychnine baits dropped significantly. Independent of the age of the product, strychnine killed non-target animals. This paper recommends a series of measures to ensure quality control and greater selectivity.

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