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Evaluation of Bait Matrices and Chemical Lure Attractants for Brown Tree Snakes

  • Author(s): Savarie, Peter J.
  • Clark, Larry
  • et al.
Abstract

Brown tree snake introduction to the snake-free island of Guam has severely impacted its native terrestrial vertebrates and economy. These nocturnal predators have extirpated forest birds, caused drastic reductions of lizards, and there is a major concern that snakes could be dispersed to other areas through Guam’s cargo transportation systems. Techniques to deter the spread of snakes include cargo inspection with detector dogs and live trapping using live mice as lures to reduce snake densities in cargo handling areas. Maintaining mice in traps is expensive, and an inanimate lure would be highly desirable. Oral baiting with dead neonatal mice (DNM) treated with acetaminophen is another technique being implemented for reducing snake populations. An objection to DNM is that they decompose and become putrid after 3-4 days. Consumption of 21 candidate bait matrices was compared to DNM in free-choice tests in individually caged snakes under laboratory conditions. Consumption of dead quail chicks and geckos was equivalent to DNM. Processed canned meat products, stew beef, and chicken were 30-50% as effective as DNM. Baits not consumed included dog blood, beef liver, and quail eggs. Under field conditions with live trapped snakes, consumption of 7 bait matrices was compared to DNM in 1-choice tests. DNM were preferred (55% consumption) over all other baits. Consumption of plastic lizards, chicken fat, and mealworms was 33%, 14%, and 13%, respectively. Odoriferous chemicals (n = 23), characteristic of decomposing animal flesh, were evaluated for their ability to attract snakes in the field. Chemicals were individually evaluated by placing them on tofu baits in PVC tubes (bait stations). Snake activity around the bait stations was monitored with infrared videography. Some of the 23 chemicals (i.e., L-methionine, 3-methyl-1-butanethiol) appeared to attract snakes to the tubes. However, no tofu baits treated with chemicals were consumed, whereas 100% of the snakes that visited tubes baited with DNM consumed the dead mice. These results, along with analysis of videos, indicate that chemicals may act as long distance lures but are insufficient for stimulating and initiating consumptive or appetitive search behaviors at close range.

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