title: Capsicum oleoresin: development of an in-soil repellent for pocket gophers.
abstract: A pre- and post-monitoring study was conducted of the potential use of capsicum oleoresin as an in-soil repellent for northern pocket gophers (Thomomys talpoides). Pocket gophers were captured in irrigated alfalfa (Medicago sativa L), affixed with radio transmitters, and monitored daily for location. Six plots (4.87 x 4.87 m) each were randomly assigned to capsicum oleoresin and soybean oil treatments; these were set up based upon the centers of initial core areas of gophers. Mean (+/-SD) volumes of capsicum oleoresin and water and soybean oil and water mixtures (10 + 90 by volume) dispensed onto plots equaled 178.5 (+/-4.7) and 175.7 (+/-14.0) liters, respectively. Movements (m) of the radio-transmitted gophers from plot centers were computed for four daily readings (i.e., 0801-1000, 1101-1300, 1501-1700 and 1801-2000 h). Spectrophotometric analysis of soil samples from capsicum oleoresin plots validated the presence of capsicum on plots and the absence of capsicum on placebo- and off-plot locations. Analysis of variance for movement distances of gophers yielded a Date main effect [F(11, 103) = 2.08, P < or = 0.03] and a Date x Reading (time) interaction [F(32, 299) = 3.21, P < or = 0.01]. Results showed that gophers were located farther from plot centers for the 0801-1000 and 1501-1700 h telemetry readings for < or =3 days post-chemical application-a probable 'disturbance' effect rather than a chemical-induced avoidance. In a prior laboratory study, capsicum oleoresin and soil treatments of 1.5% w/w capsicum caused nearly a 50% decrease in soil contact time by gophers relative to placebo-exposed control animals. This implies that procedural variables warrant revision before abandoning this approach. The potential for soil insertion of repellents as a technique for expelling pocket gophers from territories and some methodological changes for future research of the technique are discussed.
authors.affiliation: USDA, APHIS, Wildlife Services, National Wildlife Research Center, 4101 LaPorte Avenue, Fort Collins, CO 80521-2154, USA. ray.t.sterner@aphis.usda.gov
authors.forename: Ray T
authors.initials: RT
authors.lastname: Sterner
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Shumake
authors.forename: Stanley E
authors.initials: SE
authors.lastname: Gaddis
authors.forename: Jean B
authors.initials: JB
authors.lastname: Bourassa
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002211:Capsaicin; D002212:Capsicum; D046348:Gophers; D010936:Plant Extracts; D012375:Rodent Control / Q000379:methods*; D013053:Spectrophotometry; D013686:Telemetry
chemical_list: D010936:Plant Extracts; C018620:oleoresins; D002211:Capsaicin