Comparison of the efficiency and ethical implications of pitfall and Tomahawk traps on Virginia opposums (Didelphis virginiana)

The choice of methods for trapping animals can greatly affect the studies and their results, despite that there are relatively few studies on the matter. Thus, the purpose of this study is to compare two common methods of live trapping (Tomahawk traps and pitfall traps), their efficiency and ethical implications for trapping Virginia opossums (Didelphis virginiana). Traps were located in a paired design, the trapped animals were checked for sex, injuries caused by the trap and stress level, then marked and released in the same spot. At the same time, costs of both trap types were compared. Tomahawk traps were 60 % more efficient to trap opossums but the pitfall traps had better results in all the other categories: were more cost-effective, did not injure the animals as often and were less stressful. Neither type of trap presented bias in sex proportion or number of recaptured animals. In general, both types of traps resulted to be effective, the pitfall trap was the better option in almost all of the categories but has the disadvantage that in the infrequent event of two males being caught on in the same trap, they are likely to fight.