Wire Funnel Traps

Please Note:  Information in this section is based on Darby et al. 2001, Valentine-Darby et al. 2008, and discussions with PhilDarby (University of West Florida).

What they are:

• Wire funnel traps are a modified version of a commercially available crayfish trap. 
• An individual trap, shown below, consists of three parts:  the funnel base, the stack (or chimney), and the lid.  The trap base has three conical funnel entrances that taper from 20 cm at the outside entrance to 5 cm inside.

  
                           
                              Drawing published in Darby et al. (2001).
  



• Trap specifications (i.e., mesh size & funnel openings) result in captured snails 20-50 mm in size. 
• Snails get captured in funnel traps as they move around the marsh.  No bait is required.

What the method is used for:

• Collecting snails (can also be used for density estimation, see Mark-Recapture). 
• Their use significantly decreases collection time and effort.  For example, in one location, the time required to collect ~100 snails was around 6 hours (of actual field work), compared to 40 hours with a throw trap and dip net.
• Funnel traps can easily be used in a variety of wetland habitat types and across a range of plant densities (including very dense vegetation, see pictures below). 

         

• Other wetland animals (e.g., fish, snakes, turtles, frogs, and amphiumas) may also be captured.

         

  

How they are used:

• No bait is needed.
• Traps are used in water depths of 15 to 75-80 cm (depending on trap height; see picture below).

  

• Set trap by inserting a nylon cable tie through the stack wire and around a 2.5-cm-diameter PVC pole driven into the substrate.

  

• Place traps 2 to 5 meters apart, as close to the substrate as possible.
• Use of these traps does not require vegetation removal, but some vegetation and substrate compaction does result from repeated visits to check traps.
• Check traps every 3 to 5 days.  However, if other animals (e.g., snakes turtles, or amphiumas) are common, trap checks should be made more often (e.g., 1-2 days) to avoid injuries or mortalities.

  

• One person can set-up 100 funnel traps in 2.5-3 hours, and check them in 1-1.5 hours.
• Expect to capture ~ 2-10 snails for every 10 traps deployed (based on captures in areas with snail densities of 0.1 to 0.3 snails m²). 
• See Darby et al. (2001) for more detail.

Their limitations:

• Ineffective in deep water where snails are found near the surface in vegetation. 
• Snail movements (and therefore capture rates) vary due to temperature, water levels, and/or mating activity.  
• Can not be used to estimate density, unless used in a mark-recapture framework.
• May capture non-target species, which may be injured (e.g., snakes, amphiumas).  To minimize injuries, trap checks may need to be made daily.
• When not in use, a large storage space is required.

Literature Cited:

• Darby, P.C., P.L. Valentine-Darby, H. F. Percival, and W.M. Kitchens.  2001.  Collecting Florida applesnails (Pomacea paludosa) from wetland habitats using funnel traps.  Wetlands 21(2): 308-311.

• Valentine-Darby, P.L., P.C. Darby, R.E. Bennetts, W.M. Kitchens, and H.F. Percival.  2008.  The use of mark-recapture to estimate Florida apple snail (Pomacea paludosa SAY) density in wetland habitats.  Florida Scientist 71(2):115-127.