Dead neonatal mice (DNM) are the bait substrate for delivery of acetaminophen to brown treesnakes (Boiga irregularis, BTS) on Guam. Acetaminophen is a registered oral toxicant for BTS. DNM serve as a lure attractant and are well accepted by snakes; however, for logistic and economic reasons, it is necessary to develop an effective bait substrate to replace DNM. The objective of this project was to evaluate extracts from aged DNM that, when applied to non-prey baits, will enhance the bait take (consumption) by BTS.
Decomposition products from DNM carcasses aged for 48 hours in an environmental chamber and in headspace volatiles from DNM aged for 24 hours and 48 hours were fractionated and chemicals in the fractions were characterized by gas chromatography/mass spectrometry. Beef and Pup-Peroni®, a commercial dog food snack (used as surrogates for non-prey food items), were treated with formulations of these chemical extracts and decomposition products from 48 hour aged DNM. These substrates were then evaluated as bait enhancers for BTS under field conditions on Guam. Solvent extracts from DNM carcasses aged for 48 hours applied to beef baits also were evaluated as bait take enhancers.
In this study, 29 chemicals were identified from the decomposition products of DNM carcasses aged for 48 hours. Three chemical extract formulations and decomposition products from these 48 hour aged DNM were evaluated as bait enhancers for BTS. Each of the three extracts tested contained three to seven chemicals that represented fatty acids and volatile organic chemicals. None of the beef baits treated with the three chemical extract formulations from 48 hour aged DNM enhanced consumption of treated beef baits. In addition, volatile chemical recipes from 24 hour and 48 hour aged DNM were not effective bait enhancers. Beef and the commercial dog food snack were treated with decomposition products from 48 hour aged DNM. Treated beef consumption was enhanced, but not the treated dog food snack. Diethyl ether, pentane, and water extracts from decomposition products of DNM aged for 48 hour enhanced bait consumption, but chemicals in these extracts have not been identified. Finally, acetone and ethanol extracts did not enhance bait consumption.
The data from this study indicate the importance of the whole odiferous complement from aged dead neonatal mice to promote bait consumption by brown treesnakes and that bait consumption may be substrate specific. The high bait take efficacy with the diethyl ether, pentane, and water extracts indicate that bait enhancer chemicals could be identified and evaluated in future research. The odiferous plume from dead mice probably consists of several chemical signatures that change over time, and the attractiveness of these temporal chemical fingerprints probably also change. Although the preceding results are important findings, they also indicate that the path to developing a cost-efficient chemical signature enhancement for non-DNM bait will be difficult and success is not certain.