Covering funnel traps in fauna surveys is important

Using uncovered funnel traps to catch vertebrate fauna during the warmer months significantly increases the risk of killing animals (Thompson and Thompson 2009). Some environmental consultants do not use funnel traps in hot conditions (Biota Environmental Sciences 2008) on the belief that it will result in the unnecessary death of animals. Other consultants don’t cover the funnel traps at all.

Our paper (Thompson and Thompson 2009) reports on surface temperature in shaded and unshaded funnel traps. The figure below has been extracted from the data in the paper to show the surface temperature in funnel traps without a cover, with one and two shade covers relative to ground temperature and ambient temperature on a day in Perth where the maximum temperature was 41.8°C. It is very apparent that shade covers reduce the surface temperature in funnel traps during the hottest part of the day by about 5°C, and two covers are about 1o°C better than no covers. The ground temperature on this occasion peaked and started to decline in response to a slight westerly breeze.

We would strongly recommend that a single cover is used whenever funnel traps are deployed, and two covers are used in hot conditions. The surface temperature in a covered funnel trap during the middle of the day can be less than the surface temperature in the bottom of a 20L bucket used as a pit-trap.

Plate 1. Funnel traps with a double shade cloth cover and extra bucket lid during summer in the goldfields	Plate 2. Temperature comparisons between covers and no covers for funnel traps

References

Biota Environmental Sciences. 2008. Marandoo Mine Phase 2 Seasonal Fauna Survey. Perth.

Thompson, G. G. and S. A. Thompson. 2009. Comparative temperature in funnel and pit traps. Australian Journal of Zoology 57:311-316.