Efficacy of aluminum phosphide tablets to control Richardson’s ground squirrel (Spermophilus richardsonii) populations in southern Saskatchewan, Canada

The objective of this study was to assess, using a capture-recapture program, the effectiveness of aluminum phosphide tablets for control of Richardson’s ground squirrels (Spermophilus richardsonii) in southern Saskatchewan grasslands, from April to July 2007–2009. Aluminum phosphide tablets were tested in study plots in moist or dry soil conditions, where burrow openings had either been marked with a flag (to ensure that all openings would be found and treated) before treatment or left unmarked. In five study plots with moist soil conditions and flagged burrow openings, the mean control level was 80.9 (SD = 6.3) %. In two study plots with dry soil conditions and flagged burrow openings, and one study with moist soil conditions and unflagged burrow openings, control levels were < 60%. It is recommended that aluminum phosphide tablets be used to control Richardson’s ground squirrels in relatively small areas (i.e., < 5 ha) with moist soil conditions and flagged burrow openings, or in specific sites where there are still high concentrations of ground squirrels after an initial treatment with poison food baits.

► Aluminum phosphide pellets were tested to control Richardson’s ground squirrels.
► In fields with moist soils and flagged burrow openings, control exceeded 70%.
► Control was lower than 70% when soils were dry or burrow openings were unmarked.
► Aluminum phosphide tablets should be used in relatively small areas.