Acetaminophen as an oral toxicant for invasive California kingsnakes (Lampropeltis californiae) on Gran Canaria, Canary Islands, Spain

Invasive species are threatening biodiversity and ecosystem stability globally. The introduction of the California kingsnake (Lampropeltis californiae) on Gran Canaria, Canary Islands. Spain represents an emerging invasion that is already threatening endemic island species. Dead neonatal mice treated with 80-mg acetaminophen tablets are approved as a registered pesticide for control of invasive brown treesnakes (Boiga irregularis) in Guam and could potentially be used as an oral toxicant to control invasive California kingsnake populations. We sought to evaluate oral toxicity of acetaminophen and to determine the dosage necessary for lethal control of invasive California kingsnake populations. Dead mice inserted with a known acetaminophen dose (0 mg, 40 mg. 60 mg, and 80 mg) were fed to California kingsnakes from Gran Canaria. Each dose was tested in 20 male and 20 female snakes representing the size range found in Gran Canaria. After snakes ate their dead mouse, they were monitored for mortality, regurgitation, and time of death and regurgitation. Treatments of 60 mg and 80 mg had 100% mortality, while 40 mg had 87.5% mortality. No control snakes died. Time to death occurred on average 38.6 hours after consuming the dead mouse. The top two time to death models accounted for 97% of model weights and included variables dosage (mg/kg). sex, and dosage * sex or those terms plus body condition index. Out of the 116 snakes that died, 97 regurgitated the mouse that contained the acetaminophen capsule, and time to regurgitation was highly correlated with time to death. Acetaminophen is a highly effective oral toxicant for California kingsnakes. Dead mouse baits treated with acetaminophen have potential as a control method on Gran Canaria but should not solely be expected to protect native species or eradicate California kingsnakes on Gran Canaria. Future efforts should focus on preventing California kingsnakes from invading other Canary Islands.