Repellents to reduce cable gnawing by northern pocket gophers

There is a continuing need to develop improved repellent formulations to protect buried cable installations from damage by problem wildlife. We evaluated 2.0% mass/mass levels of capsaicin and denatonium benzoate in a polybutene carrier material (Indopol®) and an aboveground, rodent-deer plastic mesh barrier (Vexar®) for reducing gnawing by northern pocket gophers (Thomomys talpoides) on communications cable (RG-8U). When treatments were applied as surface coatings, neither capsaicin nor denatonium samples were lower (P > 0.05) in measures of cable damage compared to control (Indopol® alone) or samples treated with Vexar® plastic mesh. When the test was repeated with a new group of 24 gophers (n = 6/group in each of 4 groups) but with the 2.0% capsaicin, 2.0% denatonium benzoate, and Indopol® enclosed with electrical shrink tubing, there was less damage for the capsaicin samples (P < 0.05) on mass, depth of cut, width, and volume of cable chewed when compared to samples treated with the Vexar® and Indopol®. Denatonium benzoate treatment also produced repellent effects (P < 0.05) on the width measure when compared to Vexar® samples. In addition, the denatonium benzoate samples were damaged less than Indopol® samples, although not significantly, as measured by mass loss and depth of gnawing. Therefore, we concluded that although capsaicin and denatoneum benzoate appeared to be completely ineffective when applied as a surface coating to cable, the same agents became effective cable gnawing repellents when encased in electrical shrink tubing. This encasing procedure demonstrated quite clearly that the means for applying the repellent agent are an all important aspect of developing effective products to control gnawing damage by northern pocket gophers.