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Context. Invasive species are a growing global problem. Biological invasions can result in numerous harmful impacts on local ecologies, and non-native herpetofauna are frequently ignored. Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus, recently reassessed as Python bivittatus bivittatus), have become established in southern Florida. Both are large, semi-aquatic predators that pose serious threats to a variety of threatened and endangered species, as well as to the unique ecology of the area.


Aims. Acetaminophen (CAS#103-90-2), a lethal oral toxicant for the invasive brown treesnake (Boiga irregularis) on Guam, was investigated as a possible toxicant in juvenile Burmese pythons and Nile monitors.


Methods. Dead neonatal mouse (DNM) baits containing 0, 10, 20, or 40 mg acetaminophen were force-fed to Nile monitors, whereas DNM containing doses of 0, 20, 40, or 80 mg were freely consumed by Burmese pythons. Subjects were frequently observed post-treatment for general condition and position, with special attention paid to activity (if any), behaviour, respiration, bleeding, emesis, ataxia, and mortality.


Key results. In Nile monitors, acetaminophen doses of 10, 20, or 40 mg resulted in 0, 50 and 100% mortality, respectively. In Burmese pythons, doses of 20, 40, or 80 mg resulted in 14.3, 85.7 and 100% mortality, respectively. No mortality was observed in control individuals of either species. A negative correlation between dosage (mg kg–1) and time-to-death was observed in both species. Dosages ranging from 522 to 2438 mg kg–1 and 263 to 703 mg kg–1 were uniformly lethal to monitors and pythons, respectively. Neither species exhibited signs of pain or discomfort following acetaminophen treatment.


Conclusions. Acetaminophen is an effective toxicant in juvenile Nile monitors and Burmese pythons. Further investigation into acetaminophen toxicity in adults of these species is merited.


Implications. Although further investigation into adult lethal dosages and strategies to optimise bait deployment while minimising secondary hazards is required, acetaminophen may have a role to play in the control of these invasive species in Florida.

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.

Public and governmental concerns about the health, safety, and environmental impacts of pesticides have led to increased regulatory requirements to determine the hazards and risks associated with their manufacture, distribution, and use. Vertebrate pesticides are regulated by the U.S. Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), as amended. Much of the data required for registration of these pesticides will be generated by commercial testing laboratories under contract to the product registrants or sponsors. In this paper, we address aspects of the contract research process including: 1) an overview of FIFRA requirements, 2) the nature of the contract research process, 3) guidelines for setting up and administering a contract for this type of work, and 4) several case studies to illustrate some of the "pitfalls" that may be encountered. The information presented is based on the collective experience of the authors' involvement with 49 contracted studies over a three-year period.