By C.J. Winand
Deer Contraceptives (Part II)
In Part I of this series we discussed ways in which biologists can prevent whitetails from becoming pregnant and the methods used to administer contraceptive drugs. We also discussed the use of Porcine Zona Pellucida (PZP), a well known immunocontraception vaccine which causes the doe's egg to reject any sperm cells, thus preventing pregnancy. In Part II we will take a closer look at this controversial method of population control and the feasibility of using PZP to control an urban deer herd using a computer simulated model.
Computerized Immunocontraception Study:
Recently, Marrett Grund and Jay McAninch published a paper entitled "Simulating the Use of Immunocontraception to Control an Urban Deer Population". The purpose of their research was to use a standard deer population modeling approach to a burgeoning urban deer project in Minnetonka (suburb of Minneapolis), Minnesota. Although I'm not too keen on computer models when it comes to population dynamics, I must admit, they did a really good job with the assumptions they made. In fact, if they biased anything it was in the favor of proving that this controversial method would work.
After the authors ran the model their results estimated a cost of $359 per treated antlerless deer. It should be pointed out that this figure assumed that all deer were darted only once. This is important, because presently there is no one-shot contraceptive currently available. They also assumed all the female deer would be effectively treated with PZP, even though misses, poor hits or malfunctioning darts would certainly occur. Additionally, they incorporated the cost of shooting button bucks which would surely increase the total cost.
The authors state, "The results of our work clearly indicate that fertility control can only be expected to stabilize deer populations if applied in an extremely ambitious effort. Until many of the logistical considerations...have been adequately addressed, immunocontraception as a deer population management method for controlling deer in urban communities, will likely only be practical when simulated on a computer."
Before this study was conducted a subcommittee on Wildlife Contraception was formed within the International Association of Fish and Wildlife Agencies. There findings indicated that, "Currently, no species specific, orally deliverable immunocontraceptive technology exists. No registration of a wildlife contraceptive vaccine either as a pesticide (U.S. Environmental Protection Agency) or a vaccine (U.S. Department of Agriculture or U.S. Food and Drug Administration) has been applied for or approved. It currently appears that this technology may have application on some limited, isolated or confined populations where hunting is not feasible. However, its eventual use on wild, free-ranging populations appears in question."
Anti-Hunters start the spin machine
Although this information sounds fairly absolute, the Humane Society of the United States which is an anti-hunting group says immunocontraceptives are "safe, humane and fully reversible form of fertility control..." In fact, the First International Convention on Contraception in Wildlife was held in 1987. Back then, I remember reading the anti-hunting news releases referring to the conference as "The Revolution without Guns" and "We have a Better Solution". Once again, either the leaders in this group are naive or they are hiding there real objective of eliminating all forms of hunting.
Bred to death...
Research utilizing immunocontraceptives has already been conducted and documented with foxes, skunks, beavers and horses with less than impressive results! In one case with wild horses the stallions were actually given vasectomies. This caused serious behavioral and social side effects which resulted in greater mortality of dominant stallions. What basically happened was since the mares were not impregnated, they kept cycling. Thus, the stallions were literally breeding themselves to death (Whoa, what a way to go!). Some other may say that when we compare horses to deer we are comparing apples to oranges, but are we?
Most biologists believe the same scenario would happen with deer. Since bucks already lose as much as 25 percent of their body weight during the rut, extending the rut six or more months would certainly reduce a buck's vigor/nutritional level and lower his resistance to illness. From an energetics stand point, dominant bucks would continue to chase subordinate bucks away in order to protect their "territory", thus reducing any stored energy they need to make it through the winter months. Simply put, chances are these bucks will not survive. Thus, survival of the fittest bucks would no occur because of the secondary side effects of contraceptives.
What will the abnormal length of the rut have on people? As you know, deer/vehicle collisions always increase during the rutting times. Obviously, bucks in the area will be rutting and bucks from surrounding areas will surely become involved during the prolonged breeding season. How many human deaths will it take to convince the public that this option may not be everything the anti-hunting groups claim?
Many hunters may be wondering why any respectable wildlife biologist would be endorsing a technique that is publicized by anti-hunting groups to eliminate sport hunting? And what about the cost issue, who's going to pay for it? At this point in time, it is my opinion that the cost benefit ratios would make contraception technology impractical for free-ranging populations. The actual contraceptive drugs are rather inexpensive, but the time and operating expenses associated with administrating a program would void any attempt.
Nevertheless, there are some municipalities where hunting is out of the question and the money factor is simply moot. In these specific cases, some biologists believe they have a professional responsibility to control deer population utilizing non-lethal methods. Since most wildlife agencies are largely funded through the sales of hunting licenses I have a hard time trying to justify hunter dollars being spent funding such an endeavor. However, if state or local government monies fund the program, then and only then, should state wildlife biologists become involved.
What about the Bigger Picture?
Other questions concerning, "What impacts do immunocontraceptives have on an ecological scale?" Dr. Bob Warren states, "Wildlife population control with contraception technology must be evaluated within its complete ecological context including effects on non-target species, including humans". Biologists Mark Ellingwood and Suzanne Caturano point out that questions regarding the potential negative impacts of fertility control agents on deer energetics and genetics remain largely unresolved. Even if this technology was perfected and allowed to be administered by all governmental agencies most believe it would take at least 20 years before all legal, bio-political and public review would be settled. As of this date, there are many unanswered ecological questions that need to be addressed.
In my opinion, the prospect that immunocontraceptives will work in a free-ranging population is simply a fallacy and should not be publicized as the new revolution in deer management as many of the anti-hunting groups claim. Until someone proves that immunocontraception is a viable alternative from a biological, physiological and social viewpoint I will advise against any attempt to utilize this technology.
Basically, immunos fail in five critical areas
1) they only last for one to two reproductive season
2) you must inject the same animal from year to year, which is basically impractical
3) trapping/handling operations are cost prohibited for most citizens and free-ranging population
4) even if we endorse such a program, who is going to pay to implement an immunocontraception project?
5) what are the secondary ecological effects to nontarget critters and humans?
Additionally, I do not know of any laws or regulations which govern wildlife contraception. As far as I know, no one has surveyed the general public, via a public notice about how they feel about changing a wild animal's basic reproductive biology? Who's liable if nontarget species or humans are infected with something unknown? One thing for sure, if I have learned anything in the wildlife management field, 99 percent of the time whenever we mess with Mother Nature - we loose.
After reading both parts of the deer contraception story the question that begs to be answered is, "Are you willing to take a chance with this unproven method of immunocontraception?" As for me, I'll need a lot more research and stick with the cost efficient, time proven wildlife population control method called...HUNTING!
If you have any questions on Deer Biology, feel free to visit our Q&A Section hosted by C.J. in our Knowledge Base
C.J. Winand is a whitetail biologist from Randallstown, MD. He is a staff writer for Bowhunter as well as Deer and Deer Hunting Magazine. This article was originally published in the October Issue of BuckMasters Magazine.