Is pressurized exhaust an effective tool against burrowing rodents?

Burrow fumigants are lethal tools for mitigating rodent damage, but until recently, only gas cartridges and aluminum phosphide were registered for use in California, USA. In 2012, pressurized exhaust machines that emit carbon monoxide were legalized for use, although their efficacy was unknown. From 2014 through 2015, we assessed the efficacy of the Pressurized Exhaust Rodent Controller (PERC) for managing California ground squirrels ( Otospermophilus spp.) and pocket gophers ( Thomomys bottae ) across various localities in California. The PERC machine proved effective for California ground squirrels (efficacy = 83%), although results were variable across the 2 study areas (efficacy = 66–100%), potentially due to differences in soil moisture or injection time across study sites. The PERC machine was moderately effective at controlling pocket gophers (efficacy = 68%), but performed better than in previous studies. Pressurized exhaust machines show promise as a tool for managing burrowing rodents.