BILLINGS, RENO, WHITEHORSEImmunocontraceptives for dogs, cats, and deer are still not quite here yet, but widespread applications and planned deployments involving bears, elephants, wolves, and wild horses indicate that immunocontraception of wildlife may at last be close to losing the qualifying adjective "experimental" at least in the species that are easiest to inject and keep track of.
New Jersey Department of Environ-mental Protection commissioner Bradley Campbell announced in November 2002 that his agency hopes to test immunocontraceptives to control bears this spring. The New Jersey bear population has increased from an estimated 100 in 1970, when the state last opened a bear hunting season, to as many as 2,500 according to much disputed official figures. An attempt to resume bear hunting in 2000 was quashed by adverse public opinion.
Immunocontraceptive injections given to 25 bears at the Bear country USA safari park in South Dakota in 2001 totally halted reproduction in 2002, University of California School of Veterinary Medicine professor Irwin Liu told Patty Paugh of the Newark Star-Ledger.
Hunters in the U.S. have vocally opposed wildlife contraception experiments for more than 30 years, arguing that reducing wild animal populations should be left exclusively to them. Hunting lobby pressure has even obtained short-lived bans on wildlife contraception in some states, and banning wildlife contraception is often a provision of so-called "hunters' rights" bills when introduced, though so far this has not been part of any such statutes as enacted.
In British Columbia and the Yukon, however, hunters are funding wolf sterilization this winter in hopes of rebuilding populations of moose, bighorn sheep, and caribou that were shot down to less than stable levels, and purportedly now cannot withstand even normal natural predation.
As in Alaska, where the state has sterilized wolves to limit predation since 1999, most of the Canadian wolf sterilizations are done by conventional surgery. The Canadian wolf sterilization programs reportedly also involve lethal culling, as packs are diminished to just the alpha pair. However, Yukon territorial government biologist Michele Oakley disclosed in November 2002 that immunosterilants had been injected into some wolves who were caught in the vicinity of the Fortymile herd, which ranges into Alaska. Oakley said that the immunosterilant approach would be quicker to use and less disruptive to the wolves than conventional surgery, if it proves to be as effective.
Calling immunocontraceptive applications "experimental" remains convenient for wildlife agencies inching toward acceptance of the technology, but with many species the greater part of the experiment now involves public relations.
Along with hunters, wild horse advocates, philosophical and religious opponents of any form of intervention in natural life cycles, and even some strict vegans object to immunocontraception, the latter because the standard immunocontraceptive, porcine zona pellicida (PZP), is produced from the ovaries of pigs who have been slaughtered for meat.
There is also considerable resistance to immunocontraception ingrained in the culture of wildlife agencies, including some of the agencies now giving it a try.
At Kruger National Park in South Africa, for instance, elephant specialist Ian Whyte told Agence France-Presse in October 2002 that immunocontraception experiments with elephants had worked, but that immunocontraception would not be as practical as either hunting, culling, or relocation in stabilizing or reducing the Kruger population of about 10,500 elephants. Whyte estimated, reasonably enough, that about 4,000 elephant cows would have to be innoculated each year, after receiving three PZP doses to start the process, but he also postulated that each elephant would have to be radio-collared to keep track of which elephants had already been dosed, which could be avoided by use of small colored ear tags or fluorescent tattoos, and spoke as South Africa was preparing to seek permission from the Convention on International Trade in Endangered Species triennial meeting in Santiago, Chile, to raise funds for wildlife conservation by auctioning stockpiled ivory from culled elephants.
Wildlife management, evolving out of gamekeeping, has historically focused on creating an abundance of hunted species. The newer task of conserving and propagating endangered species was accepted relatively easily, since it also had the goal of creating abundance, typically achieved by protecting habitat and preventing poaching and predation.
Now wildlife agencies are being asked to limit the numbers of animals of species that they worked long and hard to make abundant in the mistaken belief that growing numbers of hunters would suffice to prevent overpopulation.
Instead, while the populations of deer, elk, black bears, and other hunted species soared to their recorded highs in recent years, the U.S. hunter population plummeted from 21 million in 1981 to 13 million or fewer today, while the average age of hunters rose from 36 to 46a clear sign that recruitment of young hunters is running far behind attrition among older hunters who are quitting or dying.
Suddenly hunting license revenue is no longer the only important revenue stream for many agencies, which are having to com
pete for money from general funds even to fulfill their traditional roles in wildlife law enforcement. The agencies are having to learn to cater to nonhunting taxpayers, who do not want hunters in their back yards, or parks, and increasingly often object to use of lethal solutions to deal with problematic wildlife, especially if nonlethal solutions exist.
Except for predator control, which typically involves killing animals who are few relative to their prey, wildlife agencies rarely tried until recent years to reduce wildlife populations by any means other than hunting.
The one major exception in the U.S. may be the Bureau of Land Management wild horse and burro program, which since 1972 has removed equines from BLM property, offering them for public adoption.
The BLM wild horse program is very small compared to most U.S. wildlife agencies, and is staffed mainly by people with backgrounds involving hooved livestock. As the horses and burros are considered an invasive alien species by the National Park Service, Fish and Wildlife Service, Forest Service, and most state wildlife departments, the BLM wild horse program is something of a wildlife management pariah.
In 1996 the BLM wild horse program stepped even farther beyond the confines of the wildlife management old boys' club by becoming the first U.S. wildlife agency to accept immunocontraception as an approved-and-available tool, ready for use wherever it might be deemed appropriate.
Immunocontraception pioneer Jay F. Kirkpatrick, the longtime director of conservation at ZooMontana in Billings, began testing experimental versions of PZP on wild horses in 1975.
Field-testing among wild and free-roaming horse herds was initially done at Assateague Island, off coastal Maryland and Virginia. In 1995 the technology was approved for mainland use. Experiments with western wild horse herds began a year later but the Bureau of Land Management has proceeded slowly, in part due to opposition from wild horse advocates who view either horse removals or immunocontraception as unjustly favoring cattle over horses.
"We believe that immunocontraception is far more humane than conducting roundups on a routine basis, which break up social structures," Fund for Animals coordinator for the Rocky Mountain region Andrea Lococo recently told Mike Stark of the Billings Gazette Wyoming Bureau.
"We don't believe immunocontraception is a silver bullet," Lococo continued. "The BLM needs to examine all of its options. There are a lot more than just fertility control," including allowing horses to return to management zones from which they have been eliminated, and increasing the share of forage allocated to horses rather than cattle.
In fall 2002 the BLM tested PZP on 15 mares from the Pryor Mountain herd in rural Wyoming. The mares "were shot with a dart containing PZP, which blocks fertility for one breeding season," explained Stark. "The fertility control program targets young and old mares," he continued. "Giving the contraceptive to a 2-year-old mare, BLM officials say, gives the horse an extra year to grow and mature before getting pregnant. The result should be a healthy foal and mare. For older mares the yearly breeding cycle can be difficult," with adverse effects on the foals. Thus if older mares do not conceive every year, the foals they do have are also expected to be healthier.
The BLM is reportedly now considering a test of PZP among the 300-horse McCullough Peaks herd in Wyoming. The McCullough herd is struggling due to a summer drought that left little fodder beneath the snow. The cost of using PZP has dropped during the past decade from about $2,000 per horse to as little as $20 per horse, but the range managers are still reluctant to spend the money, BLM wild horse specialist Trish Hatle told Associated Press in late December.
Immunocontraception may nonetheless be the longterm answer to the perennial squeeze the BLM occupies between ranchers who want to be rid of competition from horses for grass and water, especially during drought years, and activists who want the cattle to go. The adoption market for wild horses is glutted, easing adoption requirements increases the risk that horses will be "adopted" only to be sold to slaughter as soon as the BLM turns over title to the adoptors (supposed to be one year from the date of adoption), keeping large numbers of wild horses in holding pens has long strained the BLM wild horse program budget, the BLM has no budget for establishing more permanent sanctuaries for wild horses, and the two most discussed alternatives at present are also problematic.
The first alternative, raised by vegetable grower, auto racer, and lifelong horse enthusiast Slick Gardner of Buellton, California, would be to persuade Congress to allow ranchers with BLM leases to convert cattle and sheep grazing allowances into horse grazing allowances. This would make possible a mutually beneficial trade-off.
Currently, ranchers pay the BLM a specified grazing fee per month per head of cattle or sheep allowed to occupy the leased land. The BLM meanwhile removes wild horses deemed to be in excess of what the land can support, and buys hay to feed them.
Gardner reasons that a more cost-efficient alternative would be to compensate ranchers for accepting more horses in exchange for grazing fewer cattle or sheep. For example, if a rancher starts out with 10,000 cattle on land with 100 wild horses, the grazing fee for 1,000 of the cattle might be waived as an incentive to remove 1,000 cattle to make room for an additional 1,000 horses. Then the land would support 9,000 cattle and 1,100 horses. Instead of the rancher paying the BLM to graze 10,000 cattle while the BLM paid to buy hay for 1,000 horses, the rancher would pay the BLM to graze 8,000 cattle.
If a rancher who now grazes 10,000 cattle on BLM land took 5,000 wild horses, the cattle would in effect graze freebut the rancher would still be obligated to do all the maintenance of fences, wells, fire breaks, and other land improvements that ranchers do now, with only half the income from selling cattle. Gardner believes this would nonetheless make ranching more profitable while saving the BLM money.
If the rancher took 10,000 wild horses and grazed no cattle, the grazing fees for the horses would be paid to the rancher, amounting to a salary for becoming, in effect, a wild horse sanctuarian.
The exact value of cattle grazing fees relative to horse grazing fees could be negotiated.
Gardner believes that any reasonable conversion allowance would be sufficient to persuade many struggling cattle ranchers to get out of the cattle industry entirely and instead establish a wild horse range on contiguous properties, with immense value as a tourist draw. A vast wild horse range with few if any domestic cattle or sheep, Gardner points out, could also tolerate a strong population of wild horse predators such as pumas, wolves, and grizzly bearsand scavengers, such as the recently reintroduced California condor. Implementing the entire plan, Gardner argues, would be better for all the animals and people involved, and would cost much less than maintaining the status quo.
Immunocontraception might never be needed under the Gardner scenario, but would be available to use if natural predation on a horse range such as he envisions could not keep the horse population in check.
The other most discussed alternative to the wild horse management status quo, advanced by Merle Edsall of Avon, Montana, would be to relocate up to 10,000 horses to the northern Sonora desert in Mexico, southeast of the Sonora Biosphere Reserve. The very dry region, which already has a small wild horse population, is heavily traveled by would-be illegal immigrants to the U.S. and the "people-smugglers" who help them cross the border.
Partners in the horses-to-Mexico scheme include retired McDonnell-Douglas vice president Philip Edsall, Sonora rancher Humberto Hoyhos, and Johannes von Trapp, one of the younger members of the family whose story was told in the 1963 film The Sound of Music, who went on to build the Stowe ski resort in northern Vermont.
National Wild Horse and Burro Program group manager John Fend advised in August 2002 that the relocation to Mexico would remove the horses from the protection of the 1971 Wild and Free Ranging Horse and Burro Act, and would therefore require Congressional action to implement. Fend pointed out that the requirement of an authorizing Act of Congress forestalled further development of a 1989 proposal to send wild horses to Mexico.
"Although Mr. Edsall's plan seems like a benign solution to rancher/mustang conflicts on the surface, the likely outcome is much grimmer," opined the Humane Society of the U.S. "In 2001, 626,000 horses were slaughtered in Mexico."
Added Christopher J. Heyde of the Society for Animal Protection Legislation, the lobbying arm of the Animal Welfare Institute, "Mexico has neither the laws nor the needed law enforcement to ensure the protection of such a huge influx of wild horses. We have been in contact with several of our Mexican colleagues, and they share our concerns."
"Our position," Fund for Animals president Mike Markarian told ANIMAL PEOPLE, "is that if the BLM cannot even prevent horses in the U.S. from [illegally] going to slaughter, how on earth are they going to protect horses who are no longer in our jurisdiction?"
The big money in selling wild horses to slaughter, Slick Gardner observes, involves selling the foals of mares who are adopted while pregnant. Gardner believes this is about half of all the mares who are removed from the wild each winter. Since the foals are not branded, they can be sold without risk of being identified as ex-BLM horses. Gardner estimates that 10,000 wild horses relocated to the Sonora desert might produce a sustainable saleable yield of about 2,000 foals per year. That could happen on the privately managed horse range he envisions in the U.S., too, but in the U.S. the fate of foals could be better monitoredand the use of immunocontraception could prevent the births of any horses beyond those needed for normal herd replacements.
The Holy Grail sought by immunocontraceptive researchers ever since investigation of the idea began is finding a safe and effective method of preventing births of deer and elk.
This is potentially the most lucrative use for immunocontraception, since it involves protecting the lives, property, and sensibilities of affluent suburbanites who like to see deer and mostly disapprove of recreational hunting, but do not like to share their rose bushes with deer, hit deer on the road, or get Lyme disease from deer ticks that they associate by name with deer, even though the ticks are carried mainly by mice.
The administrators of suburbs, parks, and university campuses where hunting and sharpshooting are unpopular and unsafe are believed to be willing to pay a premium price to use any deer control method that does not offend the majority of voters and taxpayers. Therefore immunocontraceptive developers have concentrated most of their research-and-development budget over the past decade on experiments involving deer and elk, even though deer and elk have turned out to be among the hardest species to use immunocontraception with.
Earlier, deer defeated attempts to limit their numbers by using hormonal and chemical contraceptives. In one of the first such experiments, at Angel Island in San Francisco Bay, California, some hormonal contraceptives for deer actually appeared to stimulate their fecundity.
Deer appear to be less able to defeat immunocontraceptives by adjusting their body chemistry, but finding safe and effective delivery methods remains an elusive goal.
Jay F. Kirkpatrick, physiology professor John W. Turner of the Medical College of Ohio at Toledo, and Alan Rutberg of Tufts University have been field-testing immunocontraceptives for deer and elk since 1993 without achieving unequivocally positive results.
Critics of immunocontraception recite failures, ambiguous findings, and program cancellations, mostly associated with complications of delivery, at Fire Island, New York, 1993-present; Amherst, New York, 1996, where the planned trial never got underway due to opposition from hunting lobbyists; the Frelignhuysen Arbortem in Morris Township, New Jersey, 1997; and Irondequoit, New York, near Rochester, 1997-1999.
At Irondequoit the technology worked, but took an average of 46 volunteer hours per deer to administer and monitor, according to State University of New York College of Environmental Science and Forestry professor William F. Porter, who headed the on-site research team.
The Fire Island experiment has now achieved a 40% reduction of the deer population, says Kirkpatrick, but it came close to cancellation several times when residents were unable to see quick results.
Despite the setbacks and expense, however, the need to produce a cost-effective, foolproof birth control method for use in deer and elk has escalated in urgency throughout the U.S. during the past year, due to the detection of chronic wasting disease among both wild and captive deer and elk herds. Closely related to mad cow disease and also believed capable of killing humans who consume infected brain or nerve tissue, CWD is now known to occur in most states north of the snow line. Although state wildlife agencies eased restrictions on doe hunting, raised bag limits, and urged hunters to kill deer whether or not they planned to keep the meat, hunting participation reportedly dropped during late 2002 because many hunters were unwilling to spend the money and time necessary to hunt without at least the pretext of getting meat.
If CWD can be stopped, observers increasingly believe, the effort will require completely eliminating the deer and elk populations of the afflicted areas. All reproduction must be halted until the disease is gone and the means by which it passes among deer and elk is fully understood.
PZP trials are now underway at the Western North Carolina Nature Center in Asheville and are under consideration by public officials in Princeton Township, New Jersey, and Beverly Shores, Indiana.
Other methods, however, are getting another look.
The National Park Service and Colorado Division of Wildlife began testing a new hormonal contraceptive called leuprolide at Rocky Mountains National Park in mid-2002. Manufactured by Atrix Laboratories of Fort Collins, leuprolide has been tested at the C-DoW research station in Fort Collins since 1999. Biologist Dan Baker reported that leuprolide met the requirements of being reversible, working 90% of the time, not harming the meat of animals who might be hunted, and not changing what Denver Post environment writer Theo Stein described as "the breeding behavior that brings busloads of tourists to the park each fall."
Highland Park, Illinois, in January 2002 teamed with the University of Wisconsin at Madison and the Milwaukee County Zoo to test surgical sterilization of deer. Nineteen does were given tubal ligations during the next four months. The results are now being monitored. Previous experiments with surgically sterilizing deer have failed, outside of zoos, because capturing, anesthetizing, and operating on the does tends to put them under life-threatening stress, because the procedures are expensive, and because other deer immigrate into under-occupied suitable habitat.
Immunocontraception remains the technology of most promise in the wildlife contraception field.
Extensive zoo and laboratory trials of PZP on species ranging from dogs and cats to the pygmy hippos at the Amsterdam Zoo in The Netherlands demonstrate that wherever doses can easily be given and the outcome can be observed, PZP injections are safer and more reliable than the older hormonal and chemosterilant animal birth control methods.
Immunocontraceptives such as PZP work by tricking
the immune system of a female animal into attacking the sperm cells of a male of her species with her own natural antibodies, as if the sperm were an invading infection. The process involves less alteration of body chemistry than the hormonal approach used in birth control pills for humans, and in the oral contraceptives thus far available for animals, which trick the female body into responding to sperm as if already pregnant.
Immunocontraceptives are also believed to be gentler than the chemosterilant methods used in the current generation of injectible contraceptives for male animals, which are gentle enough that one such product, Neutrosol, has also been deployed recently in increasingly ambitious field trials hosted and sponsored by humane organizationsamong them the Arizona Humane Society, Humane Society of Missouri, Humane Society International division of the Humane Society of the U.S., and the North Shore Animal League America.
Because immunocontraceptives are designed to be species-specific, they tend to be safer for use in the wild than any substance which might affect a range of species.
Hormonal contraceptives and chemosterilants are not currently known to have second-hand effects, but with immunocontraceptives there is believed to be little way that second-hand effects could occur even by fluke.
In addition, immunocontraceptives offer some hope that the dosage might eventually be embedded in edible bait-balls designed to attract only the target species and gender. This would be slightly more difficult than administering species-specific oral rabies vaccination, now done successfully in Europe for more than 20 years and in the U.S. for more than 10 years. As male and female animals often have different scent preferences and tastes in food, producing a gender-specific bait is theoretically possible.
For now, however, delivering an immunocontraceptive dose still depends upon either darting the animals or tranquilizing them for conventional injection.
This in turn is one of the obstacles to producing immunocontraceptives for dogs and cats. The smaller the animal, the riskier either darting or tranquilization tends to be. Many of the street dogs common to much of the world could be caught and injected with relative ease, but injecting an immunocontraceptive dose into a frantic feral cat might only be possible with use of a squeeze-cage, and then only with difficulty. Further, once a cat is held securely enough to innoculate safely, a high-speed spay surgeon using gas anesthesia could do a conventional spay in just a few more minutes.
There are enough advantages to surgical sterilization, in terms of producing permanent results and modifying problematic behavior, and the cost difference between immunocontraception and surgical sterilization would be low enough if an animal was already captured, that going ahead with the surgery might remain the preferred choice for dealing with any animal who might be socialized for adoption or be released anywhere that she could disturb meighbors.
Surgical sterilization produces a very slightly higher risk of post-operative infection than administering an injection, all other factors being equal, but many high-speed clinics that emphasize a sanitary surgical environment already count post-operative infection cases in numbers per thousand or even 10,000 animals handleda rapid advance from the standards of barely a decade ago, when post-operative infection cases were counted in numbers per 100.
Street dog and feral cat rescuers, especially in underdeveloped parts of the world, are often still working in environments where trying to achieve sanitary conditions is nearly impossible, and post-operative infection remains routine. However, as Jeff Young, DVM, recently pointed out in a conversation with ANIMAL PEOPLE about his experience in teaching sterilization technique abroad for the Spay/USA division of the North Shore Animal League America, a veterinarian who cannot perform clean surgeries probably cannot perform consistently clean injections either. The answer therefore is to do a better job of impressing upon vets the need to maintain sterile operating facilities.
Great savings are unlikely to be realized through replacing surgical sterilization with immunocontraception until species-specific and gender-specific oral delivery systems are perfected. Until then, what savings there might be would probably be more significant in a wealthy nation whose veterinarians command high wages than in a poor nation whereas in Indiathe typical cost of sterilization surgery on a dog or cat ranges from $5.00 to $10.00, plus the cost of several days of post-operative care to avoid the complications of infection which in the U.S. are rarely a worry. M.C.