Effects of the insecticide Bacillus thuringiensis on Sorex cinereus (masked shrew) populations, diet, and prey selection in a jack pine plantation in northern Ontario

Abstract

A simulated operational spray with Bacillus thuringiensis in a jack pine (Pinus banksiana) plantation near Gogama, Ontario, showed effects of the insecticide on the population structure, diet, and prey selection of the masked shrew, Sorex cinereus. During the pretreatment period, the abundance and population structure of S. cinereus were similar in the control and experimental areas. Although the total abundance of shrews was also similar after spraying, there were fewer adult males and more juveniles in the treated area than in the control. The emigration of adult males was apparently increased after spraying. Lepidopteran larvae and Araneae were the most abundant items in the diet. After spraying, more lepidopteran larvae were eaten on the control than on the treated area. Juveniles and adult females but not adult males shifted from lepidoptran larvae to alternative prey in the treated area. Generalist insectivores such as S. cinereus are more likely to control the abundance of arthropods and less likely to be impacted negatively by selective insecticides such as B. thuringiensis.