The oral and dermal toxicity of selected chemicals to brown tree snakes (Boiga irregularis)

We evaluated the oral and dermal toxicity of 18 chemicals to brown tree snakes (Boiga irregularis). Chemicals that produced mortality when dosed orally were rotenone, propoxur, natural pyrethrins, allethrin, resmethrin, diphacinone, warfarin, and aspirin. The lowest oral doses that gave 100% mortality were: rotenone, 2.5 mg kg(-1); pyrethrins, 40 mg kg(-1); propoxur, 40 mg kg(-1); diphacinone, 80 mg kg(-1); and aspirin, 1280 mg kg(-1). Allethrin, resmethrin, and warfarin produced 80% mortality at 40 mg kg(-1), the highest dose tested. Materials given orally that produced little mortality were permethrin, fenvalerate, and carbaryl; those giving no mortality were phenothrin, tetramethrin, piperonyl butoxide, propylene glycol, and cholecalciferol. Chemicals that produced mortality when applied dermally at doses of 40 mg kg(-1) were rotenone, nicotine, propoxur, natural pyrethrins, allethrin, and resmethrin; those that gave no mortality were permethrin, fenvalerate, phenothrin, tetramethrin, piperonyl butoxide, and diphacinone. Rotenone, at 10 mg kg(-1), and nicotine, at 40 mg kg(-1), were the most toxic dermally, killing all tested snakes. Piperonyl butoxide enhanced the oral toxicity of allethrin and resmethrin and the dermal activity of resmethrin; it did not enhance the activity of natural pyrethrins either orally or dermally.