When I first learned that serious scientific research has been conducted for decades on wildlife fertility control, I questioned the underlying premise. To an extent, I still do. The need for wildlife contraception stems from the belief that many species are overabundant, and without human intervention in the form of population control, the animals will wreak havoc on plant life, other species, on our limited natural resources and on the ecosystems the animals live within. With 40 years of lethal animal population control, it appears that certain wild animals are continuously thought of as too numerous.
The early contraception studies of the 1960's focused on birds with the goal of finding a chemical to inhibit egg hatching. Interestingly, one of the bird species these early studies tried to control was the red-winged blackbird; the same species the USDA Wildlife Service still targets today as overabundant with just under a million killed by the USDA in 2009 (see prior blog post "Taxpayers Footing the Bill to Kill Wildlife" 2/15/11). Avian contraception was soon joined by mammal research emphasizing population control for deer, horses, dogs, coyotes, elephants and bears. But much of the research today is devoted to finding fertility control specifically for deer and wild horses. (Wildlife Fertility Control Technical Review 02-2, The Wildlife Society, 2002). Deer are a focus due to the widespread interest in suburban deer culls and wild horses are a focus due to their population numbers in the western United States.
The goal of current contraception research is perfection of an immunocontraceptive vaccine. The vaccine most widely used is the porcine zona pellucida (PZP) vaccine. The PZP vaccine is derived from proteins naturally occurring in pig ovaries although research to find a synthetic substitute is ongoing. The PZP vaccine works by causing the animal to produce antibodies that prevents the egg from being fertilized by sperm thus blocking pregnancy and reproduction. The vaccine has been thoroughly tested and is available for use however; some practical and regulatory considerations remain (Science and Conservation Center website, www.zoomontana.org/science-and-conservation-center/).
While proven successful in zoos and game parks in South Africa, delivery of the vaccine to free roaming animals such as deer and wild horses can be problematic. The vaccine must be injected into the animals muscle tissue at its rump or hip area to be effective. This requires personnel to be relatively close to the animal for accuracy. As an alternative, the animal can be captured and restrained however, since the animal's natural fight or flight response could be triggered, tranquilizing would also be needed.
Since remote darting is the preferred delivery method, focus has been on perfecting a dart gun that properly delivers the vaccine to the animal from a reasonable distance without causing injury. In addition, the environmental issue of spent darts was a concern but studies have shown the darts are easy to see when left on the forest floor and are typically retrieved. Delivering contraception orally through the use of food plots has been rejected due to the high risk of consumption by non-target animals ("Wildlife Contraception" by Douglas Fox, Conservation Magazine, Oct/Dec 2007).
Another practical consideration involving delivery of the vaccine is the need for multiple injections. Currently, the PZP vaccine requires two shots (and perhaps, subsequent boosters). This raises the issue of identifying the animal that was originally inoculated and finding it at the appropriate time to properly deliver the subsequent shots. Methods have been developed that permit a harmless identifying color spot to be created on the animal at the vaccination site. A time release pellet would be helpful and is being researched. The current cost of a dose of PZP is minimal however labor costs, for the reasons outlined above, can be meaningful ("Immunocontraceptive Reproductive Control Using Porcine Zona Pellucida (PZP) in Federal Wild Horse Populations" (Third Edition), by Jay Kirkpatrick, 2010).
Because PZP is primarily protein it is not in the flesh, the saliva or the feces of an animal and does not contaminate the meat of the animal. If the animal is subsequently consumed by humans, other animal predators or scavengers, it will not cause illness.
The complete sterilization of an animal by surgically removing its ovaries has also been widely researched. Again, the resources needed to capture, tranquilize, operate and release free roaming wild animals probably makes this option of less practical use.
The regulatory framework for wildlife contraception is somewhat complex. Overall authority currently rests with the EPA under the curious category of "pesticide" (authority was previously held by the FDA but transferred recently to the EPA). PZP has been officially registered with the EPA however; other governmental agencies must also approve usage of the drug including state wildlife agencies regarding deer and the Bureau of Land Management for wild horses. And this is where much of the politics begins.
The push to bring wildlife contraception products to market has been fueled by a number of interests, many of which have roots in hunting. Recognizing that public acceptance of lethal animal control may be waning, and not wanting to miss the bandwagon on continuing their control of wildlife, state wildlife agencies, the USDA Wildlife Services, the Bureau of Land Management, the National Park Service and the natural resource departments of various public universities, have all funded research and conducted studies on wildlife fertility control.
The Humane Society of the United States has spearheaded multiple fertility studies seeking nonlethal means to control both deer and wild horse populations. HSUS conducted a well known and successful deer study on Fire Island, New York in partnership with the National Park Service (www.nps.gov/fiis/naturescience/deer.htm) and continues to be actively involved in the push for nonlethal control of wild horses.
But the literature on the development of wildlife contraception acknowledges the various conflicts of interest that have stymied bringing product to market. "Wildlife agencies and biologists have been reluctant to acknowledge the potential applicability of fertility control for managing wildlife populations, in part because the techniques available have been publicized as a replacement for sport hunting....[however,] agencies recognize that people representing a variety of views are legitimate stakeholders in management, and the public is demanding to have their concerns addressed-one of which is that managers seek nonlethal means for the management of wildlife" (Wildlife Fertility Control, Technical Review 02-2, The Wildlife Society, 2002).
With so many agendas, it is not surprising that the road to market for wildlife contraception has been a long one. But there may be other considerations as well. While current research has concluded wildlife contraception does not negatively affect the health of the animal, what impact does it have on their social order? How is the social hierarchy impacted when females in a herd reach an age where they would otherwise naturally mate and reproduce but are not? In addition, what species specific traits are being interfered with by tampering with the natural selection process? These are difficult questions to answer and perhaps should be more seriously considered when evaluating how necessary it is to contracept our wildlife.
Taking a quick look at the complicated situation regarding wild horses in the western states, one can see the quandary of management. The Bureau of Land Management (BLM) is responsible for managing certain public lands and for managing the wild horses that live there. According to BLM's website, there are approximately 38,000 wild horses and burros on these lands. This, according to BLM, is about 12,000 too many animals for the health of the land therefore, annual removals are necessary (sometimes via helicopter round ups). Before there was a strong public outcry against it, the horses were killed. Now the animals are kept in holding stalls for sale and/or adoption. BLM reports that holding costs for these animals amounts to a little over half their annual $64 million horse and burro budget (a budget suggested to reach $75 million for 2011)(www.blm.gov/wo/st/en.html).
The BLM (an agency within the Department of the Interior) and USDA Wildlife Services (an agency within the Department of Agriculture), have similarities. The agencies kill or remove wild animals in the name of ecosystem health (while BLM is asking for $75 million this year, USDA spends about $121 million). BLM says "[w]ild horses and burros have virtually no natural predators and their herd size can double about every four years. As a result, the agency must remove thousands of animals from the range each year to control herd sizes." (Interestingly, almost the same claim is made by state wildlife agencies explaining why deer culls are necessary). It is notable that the herd size has remained relatively constant for the last 14 years. According to the BLM website, there were approximately 42,000 wild horses and burros in 1996 (the earliest date available on their website) and there are approximately 38,000 today.
The thought of letting nature take its course appears ignorant and abhorrent to wildlife agencies. BLM makes the somewhat odd assertion on its website that "[t]here is absolutely no scientific evidence to support the idea that wild horses will automatically limit their own population...if left unchecked, Mother Nature would regulate the wild horse and burro population through the classic boom-and-bust cycle, where the population increases dramatically, food becomes scarce, and the population crashes through starvation."
If nature has a built in population cycle, why would decades of killing, capturing and now possibly contracepting wildlife, necessarily be better? It is unclear whether our governmental agencies will ever implement large scale wildlife fertility programs or in fact, whether they should. Perhaps if it comes to a point where they can no longer shoot or capture the animals, they may turn to contraception...then they can at least ensure their line item in the national budget.
Prior Blog Posts:
The Structure of our State Wildlife Agency System
9/25/09
Teaching Children to Kill
10/02/09
The Supreme Court and the Culpability of a Child
11/18/09
The Federal Gun Tax
12/09/09
Lead Ammunition
1/14/10
Connecting the Dots of Violence
2/01/10
Man as "Super-Predator"
3/17/10
U.S. v Stevens: What interests are being protected?
4/27/10
Predation Control: to what end?
9/14/10
The Paradox of Killing Wildlife as Population Control
10/24/10
Who Does Wildlife Belong to? (The Public Trust Doctrine)
11/22/10
Lyme Disease: Ticks Without Deer
1/20/11
Taxpayers Footing the Bill to Kill Wildlife
2/15/11
