Use of predator odors as repellents to reduce feeding damage by herbivores : IV. Northern pocket gophers (Thomomys talpoides).

This study investigated the influence of the major anal-gland compounds from the stoat (Mustela erminea) and ferret (M. putorius) in generating an avoidance response by northern pocket gophers (Thomomys talpoides) in tree fruit orchards in the Okanagan Valley of British Columbia, Canada. A secondary objective assessed the impact of additional predator odors on gopher avoidance behavior in laboratory bioassays. In field bioassays, a 1: 1 mixture of 2-propylthietane and 3-propyl-1,2-dithiolane, as well as 3,3-dimethyl-1,2-dithiolane, placed in gopher burrows did not reduce the number of gophers colonizing treatment versus control grids in orchard blocks. However, these predator gophers did dramatically alter the distribution of gophers. Significantly more gophers were captured at perimeter than nonperimeter trap stations on treatment versus control grids in two of three orchards. In all orchards, significantly more gophers were captured at perimeter stations after the predator odors had been placed in burrows than prior to the start of the experiment. Gophers clearly avoided 2,5-dihydro-2,4,5-trimethylthiazoline, a component of fox (Vulpes vulpes) feces, but did not avoid 2,2-dimethylthietane from the mink (M. vison) or 3-methyl-3-butenyl methyl sulfide from fox urine in laboratory bioassays. Poor avoidance was also recorded for 3,3-dimethyl-1,2-dithiolane, although this may be due to the state of polymerization of this compound. An improved formulation is required to dispense these semiochemicals in controlled-release devices within orchards and other forest-agricultural areas.