Assuring that 1080 toxicosis in the red fox (Vulpes vulpes) is humane: fluoroacetic acid (1080) and drug combinations

Abstract

Fluoroacetic acid (1080) is frequently used to poison the introduced red fox (Vulpes vulpes) in Australia. The symptoms of 1080 poisoning in dogs appear extremely distressing to observers as manic running, yelping and convulsing are readily interpreted as being indicative of pain and distress. Assessment of pain perceived by animals poisoned by 1080 is difficult, as severe CNS disruptions alter behaviour and EEG patterns that may otherwise be useful in such assessments. This study compared three drug agents combined with 1080 to address the possibility of pain and distress that may be experienced by foxes during 1080 toxicosis. A mixed-sex group of 15 foxes was used in the trial of each of the three drugs: an analgesic (carprofen; 10 mg kg–1), an anxiolytic/sedative (diazepam; 10 mg kg–1) or an analgesic/sedative (clonidine; 0.75 mg kg–1). Each group of 15 foxes was randomly allocated between three treatments of either 0.5 mg kg–1 of 1080, 0.5 mg kg–1 of 1080 and a dose of the trial drug, and a dose of the trial drug alone. A telemetry collar was used on each fox to monitor the duration and intensity of activity, and behaviour from dosage to death was recorded using daylight/infra-red video cameras. In foxes dosed with 1080 alone, a mean of 4.05 (0.86, P < 0.05) h was observed from dosage to symptoms and 1.57 (0.46, P < 0.05) h from symptoms to death. Diazepam reduced the overall intensity of activity from dosage to death (P < 0.002) and from first symptoms to death (P < 0.05). Diazepam also extended the time until death (P < 0.01) and time taken from dosage to first symptoms (P < 0.01). In the dosages used, clonidine was not as effective as diazepam in reducing activity associated with symptoms of poisoning, although it prolonged the time taken from dosing to first symptoms (P < 0.05). Carprofen did not significantly alter the progression of 1080 toxicosis or the intensity of activity of foxes compared with the group that received 1080 alone. The initial symptoms of 1080 toxicosis include retching and manic running and foxes may be more capable of suffering at this stage than after collapse, where behaviour is likely to be associated with CNS disruption. Diazepam may be effective in minimising any anxiety experienced by foxes especially during the first symptoms of 1080 toxicosis.