Drop Net Trap Designs

A drop net consists of a large net, which is often hung from poles, and suspended over a baited target area.  The trap must be monitored and when the target animal is under the net, it is either manually or remotely triggered, and drops on the animal.  Drop nets were first used to capture game birds and are now widely used by wildlife biologists to catch deer and other ungulates.  They have also been used to try and capture extremely trap-shy lost or stray dogs.

Here is a video of a drop net available from Wildlife Capture.com. Their drop net uses a radio-controlled electromagnetic trigger, and a 25′ x 25′ drop net costs $3,950.  They do also offer rentals, but prices are not provided.

Commercial drop net costs are prohibitive to most pet detectives, rescue workers, and owners who might need one to capture a trap-shy lost or stray dog.  However, I was able to find several drop net trap designs in scientific research journals that are relatively inexpensive and might not be that hard to build.

Manual Trigger Drop Net Designs

Deer drop nets where originally built with an explosive tripping mechanism (Ramsey 1968), and some more recent drop nets use radio-controlled release of electromagnets.  However, I wanted to start by looking at some simple manually triggered drop nets, which might be easier to build for the average person.  Honestly, I found most of the instructions at least somewhat confusing, and I may attempt to contact the researchers for more detailed instructions.  However, these instructions should at least provide useful brainstorming ideas for designing your own drop net.

Here’s a comparison of three manually triggered drop net designs.

Lopez, R.R., N.J. Silvy, J.D. Sebesta, S.D. Higgs, M.W. Salazar.  1998.  A Portable Drop Net for Capturing Urban Deer.  Proceedings Annual Conference of Southeastern Association of Fish and Wildlife Agencies 52: 206-209.

Lopez et al.’s (1998) drop net design is the least expensive and easiest to set up.  The trap frame is portable and constructed of chain link fence top rail tubing with welded corner posts.  The net is 5.2 m x 5.2 m, which is held up by tension using a perimeter rope and washers.  The trigger mechanism is a piece of bailing twine tied to a pull-pin and washer mechanism.  For construction directions, see Lopez et al.’s (1998) Methods.

D’Eon, R. G., G. Pavan, and P. Lindgren.  2003. A Small Drop-Net versus Clover Trap for Capturing Mule Deer in Southeastern British Columbia.  Northwest Science 77(2): 178-181.

D’Eon et al.’s (2003) design has the advantage that it can be constructed and set up by a single person.  The trap is meant to be suspended 1-2 m from the ground between two large trees.  The net is 6.1 m x 6.1 m with four sections of galvanized pipe attached to either end for weight.   A 60 m release cord is used to trigger the net by pivoting two additional sections of galvanized pipe.  For design instructions, see D’Eon et al.’s (2003) Methods.

D’Eon et al.’s (2003) success rate (75%) was considerably lower than the other two designs.  However, they only attempted to catch four deer, and the first one escaped when they suspended the net 2 m above the ground.  When they moved the net to 1 m above the ground, they caught three additional deer in two trapping attempts.

Jedrzejewski, W. and J.F. Kamler.  2004.  From the Field: modified drop-net for capturing ungulates.  Wildlife Society Bulletin 32(4): 1305-1308.

Jedrzejewski and Kamler’s (2004) drop net design is more labor intensive to set up and costs significantly more than the other designs (though even this net is far cheaper than the commercially available ones).  However, this net is also three to four times the size of the other nets since it was being used to capture the much larger red deer.  Modifications of the net set up and trigger mechanism could probably be used on a much smaller net though the success rate would most likely decrease.

This drop net was built on a semi-permanent frame constructed of wooden poles sunk into the ground and braced with metal cables to support the weight of the net.  A pulley was attached to the cable at the top of each wooden pole.  Nylon ropes were then attached to the net near each pole, and the ropes were run through the nearest pulley.  All the ropes were tied to a single metal ring at the trigger mechanism with ropes on the far end coming across the top of the net.  The trigger mechanism is simply a hook through a metal ring, which releases when another rope is pulled.  This might sound complicated, but it will make a lot more sense when you look at the diagrams.  For complete instructions, see Jedrzejewski and Kamler’s (2004) Trap description and construction. 

Remote Trigger Drop Net Designs

For the more tech savvy people out there, a remote controlled drop net is another option.  Lockowandt (1993) wrote a paper on how to build “An Electromagnetic Trigger for Drop-Nets.” Unfortunately, I haven’t been able to find a copy of this paper available on the internet, but you could get a copy from your local University (like I did). Lockowandt (1993) estimated that the electromagnetic trigger system cost $980 and it took three days to build. Missing Pet Partnership was able to get instructions on building an electromagnetic drop net from their local Fish & Wildlife Agency.  See their case on Catching Sophie.

A somewhat different remote net trap was designed by Dematteis et al. (2010). This net trap is also activated by remote radio-controlled electromagnets, but it is an up-net rather than a drop net. With an up-net, the sides of the net enclosure lie on the ground, and when the net is triggered, the sides of the net are raised up creating an enclosure trap. Dematteis et al. (2010) reports that the up-net had a 96.2% (50/52) success rate when used to capture chamois (a goat-antelope species native to mountains in Europe) in their study. The estimated cost of their up-net enclosure trap was $4,617, making it cost prohibitive to duplicate. However, modifications of their design could be used to create a smaller, less expensive net trap.

If anyone has already built a small portable drop net that might be used to help capture skittish lost dogs, I would love to hear about it, especially if you are willing to share you designs with others.

Literature Researched

D’Eon, R. G., G. Pavan, and P. Lindgren.  2003. A Small Drop-Net versus Clover Trap for Capturing Mule Deer in Southeastern British Columbia.  Northwest Science 77(2): 178-181.

Dematteis, A., M. Giovo, F. Rostagno, O. Giordano, D. Finn, A. Menzano, P. Tizzani, G. Ficetto, L. Rossi, and P.G. Menguz.  2010.  Radio-controlled up-net enclosure to capture free-ranging Alpine chamois Rupicapra rupicapra.  European Journal of Wildlife Research 56: 535-539.

Jedrzejewski, W. and J.F. Kamler.  2004.  From the Field: modified drop-net for capturing ungulates.  Wildlife Society Bulletin 32(4): 1305-1308.

Lockowandt, S.P.E.  1993.  An Electromagnetic Trigger for Drop-Nets.  Wildlife Society Bulletin 21: 140-142.

Lopez, R.R., N.J. Silvy, J.D. Sebesta, S.D. Higgs, M.W. Salazar.  1998.  A Portable Drop Net for Capturing Urban Deer.  Proceedings Annual Conference of Southeastern Association of Fish and Wildlife Agencies 52: 206-209.

Ramsey, C. W.  1968.  A Drop-Net Deer Trap.  Journal of Wildlife Management 32(1): 187-190.