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Brown County, WI
February 2000
Michael Draney

snow pitfall trap in the woods.

Snow Pitfall Traps

If you've been skiing or walking the arboretum you may have wondered what the pink flags were out in the woods. They are part of a winter pitfall research project being conducted by Dr. Michael Draney in collaboration with a researcher at University of Alberta, Edmonton, and with the help of UWGB students Joan Berkopec and Steve Price. Pitfall traps are a very effective way to capture and study the ground-dwelling invertebrates that teem in almost every terrestrial habitat. Pitfall traps are very simple devices consisting of a cup buried with the lip flush to the ground surface, and filled with a fluid to trap and then preserve any small animals that fall into the cup while wandering about on the ground surface. Usually a plywood roof is placed over the trap to keep out rain. Sometimes wire mesh is used to cover the traps to prevent mammals from disturbing them.

Ground-dwelling invertebrates, including insects and spiders are usually sampled between April and October, when abundance is highest and during which time most species reproduce. However, studies have shown that many invertebrate species are active and even reproduce during the winter months, usually living in the space between the ground surface and the snow layer. Temperatures under the snow rarely fall much below freezing, protecting these animals from winter temperature extremes. Dr. Draney and his colleagues have designed, tested, and modified special pitfall traps to capture invertebrates that remain active under the snow. These traps do not disturb the layer of snow that is critical to these winter animals' survival.

These traps operate in five habitats on the Cofrin Arboretum: Deciduous woods, cedar woods, an old field, a seep-fed wetland, and the Keith White Prairie. Besides snow flies and snow fleas, we have also found slugs, woodlice, millipedes, centipedes, flies, caddisflies, and several species of mites and spiders that are active under the snow.

Contributed by Dr. Michael Draney

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Last updated on August 20, 2014