Current (1994) Ground Squirrel Control Practices in California

Current control practices are discussed for the California ground squirrel (Spermophilus beecheyi) which is considered a major rodent pest to agriculture. The primary control options are poison baits, burrow fumigation and trapping. The effectiveness of baits and fumigants is linked closely with the squirrel's annual life cycle, hence knowledge of their cycle is essential. The elements of the squirrel's life cycle importance to management are given in detail. Habitat modification and other methods useful in select instances are provided, along with control strategies within the context of integrated pest management. Proc. 16th Vertebr. Pest Conf. (W.S. Halverson& A.C. Crabb, Eds.) Published at Univ. of Calif., Davis. 1994. INTRODUCTION The California ground squirrel (Spermophilus beecheyi) is considered to be the most serious rangeland vertebrate pest in California because of its forage competition with livestock, ranking, along with pocket gophers (Thomomys spp.), as a major pest of crops. Squirrels feed on the vegetative parts of some plants and on the fruit or seed of others. Bark gnawing of shrubs and trees occurs, but is much less common. Ground squirrels cause damage to a wide variety of field and orchard crops. Almonds, walnuts, and pistachios suffer some of the most serious damage of the nut crops. Citrus, apricots, strawberries, beans, sugar beets, and alfalfa are subject to damage—and the list goes on. The California ground squirrel naturally inhabits burrow systems in grasslands and oak-savannah type habitats. They are, however, very adaptable and live in and around crop land and man-made facilities. The squirrels tend to disappear from land which is under complete and frequent cultivation, but remain along fence lines, road right-of-ways and in other suitable uncultivated areas. They may travel 100 yards or more to feed in adjacent crops. Ground squirrels often live in colonies or are concentrated in localized areas.