How did we determine the best capture technique for prairie dogs?
- Because we are wildlife biologists we care about the health and well-being of all living creatures. If those creatures must be captured for any reason, it must be done in the most respectful and humane way possible.
- Because we are private small business owners, we believe in capitalism and want to make money as efficiently as possible. So, we obviously have chosen to utilize the most cost-effective technique available.
The result? Live-trapping is the only way to meet our objectives
How did we get there? We will show you below so you can see for yourself.
Cage-type live-traps are placed near the burrow entrance and are baited to
encourage the prairie dogs to enter the trap. The biggest advantages to this method are: 1) if animals are checked regularly there is low stress on the animals trapped; and 2) one can avoid harming non-target wildlife. If non-target animals are trapped, they can be released onsite unharmed. There is a great deal of data available on this method which indicate that if conducted correctly, live-trapping has an extremely low rate (if any) of mortality and a high rate of effectiveness and efficiency.
Water flushing entails using a water truck or other such tank and pump system to fill burrows with water, usually with some sort of household detergent
added, and waiting until the prairie dog emerges at which time they are noosed or caught by hand. Although eluded to in the scientific literature, the only written reference to the exact amount of water required per capture was, “[a]n average of 518 liters (136.8 gallons) of water and 946 grams (33 ounces) of detergent were required per capture; half the flooded burrows provided a capture.” In our search through the scientific literature, we found many biologists believe that water/burrow flushing drowns many prairie dogs and other wildlife in their burrows and may cause death due to hypothermia.
Traditional water flushing has been controversial and often touted as “quicker and more effective” than live-trapping, which is why it is often used despite the fact that it is much less humane than live-trapping. In fact, claims have been made that 30+ acre sites could be cleared in a matter of days. So, we sought to determine if this was accurate or instead “false advertising.”
In addition, although water flushing usually uses a “soapy water” mixture, current techniques produce only light bubbles and very little foam. While the purpose of the soap suds is reportedly to cause the prairie dogs eyes to sting, making them want to exit the burrow, in reality, the prairie dogs travel up the burrow system within or just slightly ahead of the soap suds. Because of the nature of the soap used, and the method by which the soapy water is injected into the burrow system, the soap suds are created after they enter the burrow system and as such just sit on the surface of the water – like they would in a kitchen sink. As a result, prairie dogs and other wildlife do not in fact exit the complete burrow until they are forced out by the water. Because of this, traditional water flushing has been criticized as causing a hazard of drowning by prairie dogs and other wildlife species. Therefore, we sought to find a piece of equipment and methodology that would instead produce a higher quantity and density of foam to reduce, if not eliminate, any drowning danger.
Equipment / Methodology
In order to try to improve upon current methodology and properly test flow rates and foam concentrations, we had to find or develop a piece of equipment which would produce whatever flow rate and foam consistency we desired. Because there are no commercially available “prairie dog foamers,” we worked with a private company to develop a custom piece of equipment that would allow us to manipulate water/soap/foam mixes to our specified needs. A large amount of time was spent manipulating the equipment to produce appropriate and consistent flow rates and testable concentrations of foam appropriate for humane application into a burrow system.
Preliminary Results
- There is a very fine line between too much foam and what seems to be “just right.” Too high of a foam:water ratio (as low as 75% foam:25% water) results in the foam backing up in the entrance of the burrow system and not penetrating the burrow system sufficiently enough to encourage prairie dogs to leave the burrow. In fact, depending on the nature and arrangement of the burrow entrance, foam may only penetrate as little as two (2) to three (3) feet down a burrow in some cases. Therefore, based on our preliminary results, >25% of the mixture must be water.
- Burrow length/depth may be critical. We found that the longer/deeper the burrow, the less likely prairie dogs would emerge. In addition, we only foamed burrows we were able to confirm as being occupied (by watching the prairie dog(s) run into the burrow). Of these burrows, only one out of every approximately 10 to 15 would result in a successful “extraction.” We have not yet calculated the volume of foam (or water if using traditional flushing) but we estimate 20-30 gallons per burrow, which means that for every prairie dog, 200-450 gallons are being used.
Conclusion
The results suggest that flushing utilizes a very large amount of water per prairie dog extracted, extraction efficiency is no greater than live-trapping and arguably much less, and it is unknown what happened to the prairie dogs that were verified entering a burrow, but were not extracted. There appear to be no advantages - from either a cost-effectiveness or humane-treatment standpoint - to flushing/foaming over live-trapping for prairie dog capture.
Based on everything presented here, we believe anyone with an ounce of common sense could answer YES!
In an email on 11 October 2003, a local prairie dog activist can be quoted as stating the following regarding flushing:
If you have a job where you have even a couple of months before construction starts, it would be common to try
trapping. As the deadline approaches, flushing is used as it is considered a faster way to catch a larger number
of dogs. (you hope, sometimes it is really slow and you only get a few dogs.) But, it is a more risky process, no
matter what. There are pds that don't survive and other animals that don't. Everyone is always especially
concerned about any baby animal. Of course, it is likely they won't survive flushing, though many have. I once
felt something truly gross and slimy feeling and almost didn't want to pull my hand out of the hole to see what I
was holding. We got several tiny baby rabbits out and took them to a rabbit rehabilitator. Any time any animal is
caught, it is carefully watched to see if it needs extra care. Fortunately, relocators become pretty good at helping
animals recover when they are overwhelmed by the flushing. By the way, there is never a minute that you hope
the hole you just stuck your unprotected hand down doesn't have a scared and angry rattlesnake living in it. It is
a very difficult balance to know you are using a process that not all animals will survive. You know you may be in
cause of death for an animal. But, you are at least saving many that would never had a chance of surviving the
construction process. It is a horrible feeling to feel that you may have just killed an animal you were trying to
save. You try really hard to save everyone. You don't.
Further, a procedure actually exists which uses foam and water to kill ground squirrels...
According to the website for Exit Concentrate Rodenticide:
- EXIT is a [non-toxic] "Rodenticide" sold as a liquid concentrate in 4 litre containers. Each container is then mixed with 96 litres of water to produce 100 litres of field solution.
- EXIT is applied into the ground squirrel burrows through a pump and hose assemble.
- The EXIT foam completely fills the ground squirrel burrow. The ground squirrel breathes in the EXIT
foam and becomes unconscious within 2 minutes. In most cases, ground squirrels in the burrow are
asphyxiated in approximately 3 minutes from the time of application.
- The testing required during the registration process showed that EXIT is 95 - 100% effective when applied correctly. Our experience has shown that when active burrows are identified and treated, the majority of the ground squirrels in the burrows die. There may be cases where a treated ground squirrel escapes the burrow. Usually they will enter another burrow where they can be re-treated.
- Will EXIT harm other species? Yes, it may harm other species if they are present in a burrow being treated. Burrows must be inspected prior to treatment to ensure that they are inhabited by only Richardson's ground squirrels and no other species.
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