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2001 Fertility Control in Animals Jay F. Kirkpatrick University of California - Davis

Allen T. Rutberg Tufts nU iversity

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Recommended Citation Kirkpatrick, J.F., & Rutberg, A.T. (2001). Fertility control in animals. In D.J. Salem & A.N. Rowan (Eds.), The ts ate of the animals 2001 (pp.183-198). Washington, DC: Humane Society Press.

This Book Chapter is brought to you for free and open access by the Humane Society Institute for Science and Policy. It has been accepted for inclusion by an authorized administrator of the Animal Studies Repository. For more information, please contact [email protected]. Fertility Control in Animals 12CHAPTER

Jay F. Kirkpatrick and Allen T. Rutberg

From Mortality Control to Fertility Control or most of the twentieth centu- license sales and Pittman-Robertson severe conflicts arise in loca- ry, government agencies charged grants), volunteer labor, and a dedi- tions that are effectively unhuntable, Fby law with managing wildlife were cated political constituency. such as parks, research campuses, and dedicated to building the size and At the beginning of the twenty-first suburban neighborhoods. Killing of productivity of populations of game century, this neat system is unravel- some species, such as wild horses, is species. Under a utilitarian philoso- ing. Demographic changes are pro- simply unacceptable to the public. phy of wildlife conservation, this ded- ducing a shrinking and aging popula- The public’s tolerance of invasions of ication made sense and, in its time, tion of hunters and trappers (hunters, their parks and backyards by armed was arguably a highly progressive for example, now represent only 7 strangers is declining just as its sym- view of wildlife (Dunlap 1988). percent of the total U.S. population) pathy for wild animals and its interest In the United States, state game (U.S. Fish and Wildlife Service 1997); in nonlethal solutions to wildlife prob- management went far to reverse the a growing public appreciation of lems are rising. wildlife catastrophe of the nineteenth “nongame” species that have been While the public is searching for century. In the 1800s hunting and neglected, and even harmed, by new, humane approaches to solving trapping for commercial markets management of game species; and conflicts with wildlife, state wildlife drove Carolina parakeets and passen- changes in public values, from utili- agencies persist in recommending ger pigeons extinct and nearly extir- tarian views to moral views of wildlife hunting and its variations. Wildlife pated bison, , deer, beavers, egrets, (Kellert 1985; Dunlap 1988). The agencies in some states, such as New waterfowl, songbirds, and any other biggest challenge to the system may York, are required by law to promote furred or feathered creature that could arise from the failure of state agen- recreational hunting (Marion 1987). make a meal or adorn a hat (Tober cies to respond effectively to the But, more pervasively, most state 1981). Predatory birds and mammals problems associated with dense popu- agency personnel have strong cultur- were shot on sight because of the lations of deer, geese, and other al and political links to the hunting threat they posed to domestic live- species, especially in urban and sub- and trapping community. This com- stock and poultry and because they urban communities. munity is (somewhat irrationally) hos- were believed by some to be genuine- How could a system founded on tile to the concept of nonlethal man- ly evil (Dunlap 1988).1 hunting and trapping—killing—find agement of wildlife (Kirkpatrick and Through an aggressive program of itself unable to control wildlife popu- Turner 1995; Hagood 1997). Wildlife reintroduction, habitat management, lations and solve problems associated agencies’ advocacy of hunting and and restrictions on killing, state wild- with abundant wildlife? There are sev- trapping is coupled with a reluctance life agencies succeeded in restoring eral reasons. Reflecting cultural atti- to pursue or encourage research into populations of deer, elk, beavers, tudes—and regulations—that discour- other approaches. As a result, the pub- otters, waterfowl, and other game and age the killing of females, public lic is turning elsewhere for solutions. fur-bearing species (Gilbert and Dodds hunting has focused on removing There are, effectively, only two 1992). The linchpin of this effort was male deer and other big-game ani- choices for actively managing the size recreational hunting and trapping, mals, leaving populations streamlined of animal populations: reducing the which furnished funding (through for reproduction. Many of the most birth rate and increasing the death

183 rate. (Local population size may also proaches and, more specifically, the passed the rigorous regulatory re- be controlled by movement of individ- nature of the chemicals, hormones, quirements of today’s FDA or Envi- uals in and out; but when the size and other compounds that have been ronmental Protection Agency (EPA). of animal populations concerns us, applied to various species. Chronolog- Some nonhormonal compounds movement of individuals merely relo- ically, these approaches can be classi- were derived from plant products and cates the concerns. We are not fied as (1) nonhormonal chemicals, based on historical evidence that absolved of our responsibility for ani- (2) steroid hormones, (3) non- Native Americans used certain plants mals simply because they go some- steroidal hormones, (4) barrier meth- for contraceptive purposes. A comp- where else.) Killing certainly can ods, and (5) immunocontraceptives. rehensive review (Farnsworth and reduce and even destroy wildlife pop- This oversimplification is com- Waller 1982) listed fifty plant families ulations if enough animals of the pounded by the various permutations with documented antifertility effects right description are removed from of chemical agent, delivery system, in males and females. Despite some the population. Until the last decade and specific species. For example, a controlled tests with laboratory ani- of the twentieth century, however, fer- contraceptive can be delivered (1) mals (Cranston 1945; Barfnect and tility control for wildlife was not seen orally, (2) by surgically placed im- Peng 1968) and a few wild species of as a feasible option. plant, (3) by hand-injection, or (4) by rodents (Berger et al. 1977) and re- Everything changed between 1988 remotely delivered dart.2 The histori- ports of occasional interference with and 1989. The successful use of a cal development of wildlife contracep- fertility in humans (Shao 1987), few remotely deliverable immunocontra- tives had to take into account whe- investigators have attempted to ex- ceptive on free-ranging wild horses at ther the animal was (1) small and ploit these naturally occurring sub- Assateague Island National Seashore, easily live-trapped, (2) usually wary stances to control reproduction in in Maryland, opened a new universe of and unapproachable, (3) living in a wildlife. This area remains a fertile possibilities for the humane, non- captive setting, (4) capable of being subject for interested scientists. lethal control of wildlife populations. induced to take baits, or (5) classified as a food animal by the U.S. Food and Steroid Hormones Drug Administration (FDA). Research into the use of steroid hor- The History of mones for wildlife fertility control be- Nonhormonal came common in the 1960s and ’70s Wildlife Fertility Compounds and was based on the research origi- Nonhormonal compounds have been nally directed at human fertility con- Control trol (Pincus et al. 1958). In general, The history of wildlife fertility control used most extensively in birds. Some steroid hormones work as contracep- and its application to the manage- of the compounds used were classi- tives by feeding back upon the hypo- ment of free-roaming and captive fied as fungicides and seed disinfec- thalamus and/or pituitary glands and wildlife populations is relatively short, tants (Arasan®, DuPont Co.) (Elder depressing gonadotropic hormones, perhaps no more than fifty years. 1964), others as anticholesterol thereby reducing or eliminating ovu- Until the late 1980s, wildlife contra- agents (22,25-diacholesterol dihy- lation or spermatogenesis, or by ception was a “boutique” subject drochloride, later marketed as Orni- changing the speed with which the among scientists and wildlife man- trol®, G. D. Searle and Co.) (Wofford ovum moves through the oviducts. agers. This lack of interest is a bit sur- and Elder 1967). In both cases, fertil- Diethylstilbestrol (DES, a synthetic prising, because the technology devel- ity was inhibited but toxic effects estrogen) was introduced into bait oped for contraception in humans has made the compounds unacceptable. and fed to foxes (Vulpes vulpes) (Lin- been impressive and its application to Most of the other compounds used hart and Enders 1964; Cheatum wildlife is fundamentally sound, at for birds (thiotepta and triethylene 1967; Oleyar and McGinnes 1974; least in a pharmacological context. melamine) had similar shortcomings Allen 1982), (Canis latrans) Various compounds developed for use (Davis 1959, 1962). In general, non- (Balser 1964; Brushman et al. 1967), in humans were first tested in animal hormonal compounds were aban- whitetailed deer (Odocoileus virgini- models. The resistance to new ap- doned because of their accompanying anus) (Harder 1971; Harder and proaches in wildlife management, toxic effects. While some degree of Peterle 1974), and black-tailed which played a significant role in the contraception, and in a few cases ster- prairie (Cynomys ludovicianus) slow pace of development and interest ilization, could be achieved, the ad- (Garrott and Franklin 1983) with sig- in wildlife contraception, stem not ministered dose had to be very pre- nificant contraceptive effects. Anoth- from science but from a variety of so- cise. This was not possible with oral er steroid, mestranol, which is closely cial, cultural, and economic factors. delivery in wildlife. In addition, the related to DES, was fed to red foxes That said, the history of wildlife mechanisms of action were poorly (Storm and Sanderson 1969), small contraception can be traced broadly understood, and it is unlikely that any rodents (voles, rats, and mice) (Marsh by examining the technological ap- of these compounds could have

184 The State of the Animals: 2001 and Howard 1969; Howard and Marsh (Buergelt and Kollias 1987). These of wildlife contraception exist (Kirk- 1969; Storm and Sanderson 1970), molecules were also shown to have patrick and Turner, 1985, 1991). and (Burke 1977) with some profound effects upon the behavior contraceptive success, but bait accep- of treated animals, something that tance decreased quickly. At about the would be undesirable in valued wild- More recently, immunocontraception, same time, oral medroxyprogesterone life species. or vaccine-based fertility control, be- ® acetate (MPA) was tested in red foxes Norplant implants containing lev- came a reality for use in wildlife. Im- (Storm and Sanderson 1969). Shortly onorgestrol were effective in striped munocontraception is based on the thereafter, other investigators ex- skunks (Mephitis mephitis) (Bickle et same principles as is disease preven- plored the use of oral progestins for al. 1991), and raccoons (Procyon lotor) tion through vaccination. Humans controlling fertility in domestic can- (Kirkpatrick, unpublished data), which and other animals are vaccinated ids. Oral melengestrol acetate (MGA) could be easily captured in live traps in against diseases by injections of dead was highly effective in inhibiting fer- urban settings, but these two species or attenuated disease bacteria or vi- tility in dogs (Sokolowski and Van were clearly an exception to the practi- ruses or of molecules that are harm- Ravenswaay 1976) and a related com- cal application of injectable or implant less but similar to toxins the disease pound, megestrol acetate (MA), was steroids to larger species. organisms produce. The stimulated approved for commercial use in dogs immune systems then produce anti- ® (Ovaban , Schering Corporation) Nonsteroidal bodies against some essential event or (Wildt and Seager 1977). Hormones structure in the reproductive process. The use of these and similar oral A variety of immunocontraceptive steroid hormones in wildlife was re- Wildlife contraceptive research with nonsteroidal hormones has been large- vaccines are under development, in- stricted by problems with bait accep- cluding vaccines against brain repro- tance and dosage and by environmen- ly confined to agonists and antagonists of gonadotropin releasing hormone ductive hormones such as GnRH tal concerns, especially effects on (Hassan et al. 1985; Ladd et al. 1988, nontarget species (all these steroids (GnRH) (Becker and Katz 1997). Nor- mally GnRH signals the pituitary to se- 1989; Bell et al. 1997) and LH (Al- pass through the food chain). These Kafawi et al. 1974) and vaccines problems changed the focus of wild- crete the gonadotropin luteinizing hormone (LH) or follicle stimulating against sperm (Primikoff et al. 1988; life contraceptive research to more Herr et al. 1989) and egg (Florman narrowly targeted delivery systems. hormone (FSH), both necessary for normal function in the ovaries and and Wassarman 1985), which prevent Steroid hormones were administered fertilization. One of the first immuno- via injection or surgicallyplaced im- testes. The agonists and antagonists of GnRH block the effects of GnRH on logical approaches was a vaccine plants in wapiti (Cervus elaphus) against the zona pellucida of the (Greer et al. 1968), large exotic spe- the pituitary by one of several mecha- nisms. These compounds have been mammalian egg, which was patented cies of cats (Seal et al. 1976), deer as an antifertility agent in 1976 by R. (Bell and Peterle 1975; Levenson used successfully to inhibit fertility in dogs (Vickery et al. 1984, 1985; Inaba B. L. Gwatkin for Merck and Compa- 1984), and wild horses (Equus cabal- ny (Skinner et al. 1996). In 1988 this lus) (Kirkpatrick et al. 1982; Plotka et al. 1996), monkeys (Macaca spp.) (Fraser et al. 1987), and a variety of vaccine was applied to wild horses and Vevea 1990). Significant contra- with great success. Success with the ceptive effects were achieved in these other species. To date, however, these compounds have been short-lived in porcine zona pellucida vaccine (PZP) species, but several new problems has opened the door to a practical arose. Application of these steroids to their effects and require large doses for extended effectiveness. approach to wildlife fertility control; free-roaming wildlife required rela- since then other experiments with anti- tively large doses of the compounds, sperm vaccines have been initiated. negating the use of remote delivery Barrier Methods The biology of the PZP vaccine, via darts. This meant that each animal Mechanical devices have which is derived from pig eggs, is had to be captured before it could be been tested in white-tailed deer (un- both simple and complex. An extra- hand-injected or given a surgical im- successfully), horses (successfully), cellular matrix known as the zona pel- plant. This was impractical with most and a variety of zoo animals (mixed lucida (ZP) surrounds all mammalian species, because of the stresses associ- results), but the logistics of applica- eggs. The ZP consists of three major ated with capture, the frequency with tion to free-roaming wildlife are pro- glycoprotein families, one of which, which the steroid had to be adminis- hibitory in most species. These meth- ZP3, is thought to be the principal tered, and the large doses that had to ods have included IUD-like barriers sperm receptor in most species (Pra- be administered. Unknown at the time for the deer (Matschke 1980) and sad et al. 2000). When the vaccine is but evident in later years were various horses (Daels and Hughes 1995) and injected into the muscle of the target pathologies that resulted from long- silastic vas deferens plugs in the zoo female animal, it stimulates her im- term use of these steroids, particularly animals (Porton et al. 1990). More mune system to produce antibodies among (but not restricted to) felids comprehensive reviews of the history

Fertility Control in Animals 185 against the vaccine. These antibodies to develop a single-dose form of the of capture-related stress. In other sit- attach themselves to the sperm re- vaccine that would provide at least uations, such as with wild horses in ceptors on the ZP of the target’s eggs one, and perhaps several, years of the West, hundreds of animals at a and distort their shape, thereby block- contraception from one application. time are rounded up for entry into ing fertilization (Florman and Wassar- (The use of the raw, native form of the adoption programs, and it is relative- man 1985). PZP vaccine requires two inoculations ly easy to hand-inject animals as they the first year, which can be very diffi- pass through a chute. cult with wary species like deer.) The For most species of wildlife, the only The Art challenge of elephant contraception, delivery option is by dart. It has ad- where doses of vaccine must be ten vantages and disadvantages. The most and Science times larger than standard wild-horse obvious advantage is that it eliminates or deer doses, raised the need for the the need for stressful capture of ani- of Wildlife development of a synthetic form of mals. The small volume of vaccine ne- the vaccine. The process of producing cessary to immunize an animal (1.0 Immunocon- the native PZP vaccine is laborious, cc) permits the use of very small and and the number of doses that can be light darts. This increases the effective traception produced in a year is limited at this range of darting and decreases the In the late 1980s, the failure to time by the production process. A chances of injury to the target animal. achieve practical results and the dan- synthetic form of the vaccine would The disadvantages include the need to gers associated with steroid hor- expand the application of wildlife con- approach the animal to within fifty mones had led to a reexamination of traception beyond present logistical meters, the need to separate the ani- the problems associated with wildlife restrictions and eliminate some of mals that have been inoculated from contraception. Research had been the regulatory concerns raised by the those that haven’t, and the labor-in- proceeding without an idealized stan- use of natural products. tensive nature of the endeavor. dard by which to evaluate each new The mere availability of a good phy- Despite the fact that inoculation of approach. Kirkpatrick and Turner siological immunocontraceptive does free-roaming wildlife with a contra- (1991) created such a standard, not insure its effective application to ceptive vaccine is at best difficult, a which included the following goals: wildlife. The first step in the develop- significant degree of success has been 1. Contraceptive effectiveness of at ment of a wildlife contraceptive is to achieved under field conditions. least 90 percent test its efficacy in captive animals or 2. The capacity for remote delivery domestic counterparts, but once this with no (or minimal) handling of ani- Wild Horses has been done and physiological effi- mals Liu et al. (1989) first discovered that cacy has been determined, strategies 3. Reversibility of contraceptive the PZP vaccine would inhibit fertility for application to free-roaming spe- effects (more important for some spe- in domestic mares. Soon after, wild cies must be developed. It is a large cies than for others) horses were treated with the PZP vac- leap from inoculating a deer in a pen 4. Safety for use in pregnant animals cine on Assateague Island National to inoculating a wild free-roaming 5. Absence of significant health Seashore, in Maryland; studies have deer; it’s yet another leap from ad- side effects, short or long term continued for twelve years. The vac- ministering the vaccine in the field to 6. No passage of the contraceptive cine was delivered remotely, with controlling a wildlife population. agent through the food chain small darts. Contraceptive efficacy Actual application to free-roaming 7. Minimal effects upon individual was greater than 95 percent (Kirk- species requires a variety of delivery and social behaviors patrick et al. 1990). The vaccine was and access strategies. Immunocon- 8. Low cost safe to administer to pregnant ani- traceptives can currently be delivered While some of these goals are more mals and did not interfere either with by intramuscular injection: an animal or less arbitrary, they at least provid- pregnancies in progress or the health must be given the vaccine either by ed reasonable guidelines for discus- of the foals born to inoculated moth- hand injection or by a dart. Two deliv- sion and planning. They were built ers. A single annual booster inocula- ery systems require at least two exclusively around wild-horse contra- tion was sufficient to maintain the access strategies. Hand injection re- ception and did not address all prob- contraceptive effects (Kirkpatrick et quires physical capture of the target lems associated with diverse species al. 1991), and contraception was animal; it increases the stress for the and settings. reversible after three and four years of target animal, danger to the per- In the development of the PZP vac- treatment (Kirkpatrick et al. 1992, son(s) doing the work, and expense. cine for certain species, some of these 1995a, 1996a). No changes occurred Although in some settings, such as problems became clear. The chal- in the social organization or behav- zoos, access is not so great a problem, lenge of deer contraception, for ex- iors of the treated animals. In 1994 it is not always possible to hand-inject ample, even in urban areas, was and is the National Park Service began the animals without causing some degree

186 The State of the Animals: 2001 management of the Assateague wild deer. Effects on captive deer resem- tion had risen to approximately 250, horses via the PZP vaccine and, after bled those in wild horses; the two- and it peaked at approximately 300 in only three years, the herd reached shot vaccine protocol was highly ef- autumn 1997 (Thiele 1999). By au- zero population growth (Kirkpatrick fective, the vaccine could be delivered tumn 1998, however, more than 90 1995; Kirkpatrick et al. 1997). This remotely, its effects were reversible percent of the NIST females were re- approach as of 2000 was being ap- after at least two years of treatment, ceiving PZP treatments, and the popu- plied to large wild-horse herds in Ne- and no health side effects were appar- lation had declined about 20 percent vada (Turner et al. 1996a), and trials ent (Turner et al. 1992, 1996c, 1997; below peak levels by spring 2000 with feral donkeys (E. asinus) in Vir- Kirkpatrick et al. 1997; see also (HSUS, unpublished data). Good ac- gin Islands National Park have been Miller et al. 1999). A subsequent trial cess to deer for treatment, high pop- successful (Turner et al. 1996b). with semi–free-roaming deer at the ulation mortality (the majority due to Smithsonian Institution’s Conserva- vehicle collisions), and relatively low White-Tailed and tion and Research Center, in Front reproductive rate all contributed to Royal, Virginia, provided evidence success in controlling this population. Black-Tailed Deer that the vaccine could be delivered re- Populations of white-tailed deer and, motely under field conditions; al- Zoo Animals to a lesser extent, black-tailed deer though there was evidence that PZP (O. hemionus) exploded in North A third application of the concept of treatments extended the mating sea- wildlife immunocontraception is the America during the last two to three son, treated females gained more decades of the twentieth century. The control of the production of “surplus” weight than untreated females, pre- animals in zoos. Despite often-heard causes of the population explosion sumably because they were spared the are undoubtedly complex. It is gener- discussions of the challenges of energetic costs of pregnancy and lac- breeding endangered species in cap- ally attributed to the use of high-yield tation (McShea et al. 1997). A study crops; the spread of deer-friendly sub- tivity, most zoo species breed quite begun in 1993 at Fire Island National successfully, and the production— urbs, which offer a diverse menu of Seashore, New York, launched a series heavily fertilized ornamental shrubs and disposition—of surplus animals is of field studies that explored the ef- perhaps the largest single problem and grasses intermingled with dis- fectiveness and costs of different field turbed “natural areas” such as small facing zoos worldwide. Beginning in techniques, vaccination schedules, 1990 the PZP vaccine was applied to parks and woodlots; increasingly mild and vaccine preparations, as well as winters; the absence of natural preda- various exotic species in zoos, begin- investigated effects of PZP on behav- ning with Przewalski’s horses (E. tors; and recreational hunting prac- ior and survival (Kirkpatrick et al. tices ill-suited to controlling deer przewalskii) and banteng (Bos jav- 1997; Thiele 1999; Walter 2000; anicus) at the Cologne Zoo (Kirk- populations in suburbs. Rudolf et al. 2000). The Fire Island With burgeoning deer populations patrick et al. 1995b), and five species study was the first to show that bio- of deer at the Bronx Zoo (now the and suburban sprawl has come a rapid logically significant numbers of fe- rise in conflicts between deer and Wildlife Conservation Center) (Kirk- males could be efficiently and effec- patrick et al. 1996b). The PZP vac- people. These have centered on an tively treated in the field; approx- increase in deer-vehicle collisions, cine has been tested in more than imately 200 females a year were under ninety species in more than seventy damage to crops and ornamental treatment by 1996. However, vaccine plants, undesirable impacts on some zoos worldwide (Frisbie and Kirk- effectiveness in this study was lower patrick 1998). Today it is reducing forest ecosystems, and tick-borne than in previous deer studies, espe- zoonotic diseases, particularly Lyme zoo births and providing some relief cially in the first year following treat- to the problem of surplus animals. disease (Conover 1997; Rutberg ment, probably due to incomplete 1997). There is now enormous inter- or misdelivered initial vaccinations African Elephants est in finding new tools that will allow (Kirkpatrick et al. 1997; Thiele 1999, people and deer to coexist, and much HSUS unpublished data). A fourth major application is under public attention has focused on im- The first demonstration that im- way in Africa. Devastated by the lucra- munocontraception. In autumn 1997 munocontraception reduced an un- tive trade in elephant ivory, popula- alone, for example, The Humane Soci- confined deer population was accom- tions of African elephants (Loxodonta ety of the United States (HSUS) re- plished at the National Institute of africana) were reduced to dangerous- ceived requests for information on Standards and Technology (NIST). ly low numbers during the 1970s and deer immunocontraception from peo- NIST, a 574-acre federal research facil- 1980s. Elephants basically retreated ple in more than sixty communities ity within the city of Gaithersburg, to the sanctuary of national parks. In across the United States. Maryland, supported a deer popula- the meantime, much former elephant The 1988–89 field demonstration tion of approximately 180 animals in habitat outside of these parks has on wild horses at Assateague spurred 1993. By the time PZP treatments come under intensive agricultural preliminary testing of PZP on captive began in autumn 1996, the popula- use. In a sense Africa’s elephant popu-

Fertility Control in Animals 187 lations are now trapped in the nation- tem of the treated animals (uteri and ner mark the animal as well as inocu- al parks. As poaching has diminished, ovaries) remained normal. late it, so that it could be distin- their numbers are increasing by as guished from untreated animals. The much as 5 percent per year. Ironically Other Species ZP antigen itself would be readily in some areas elephants are now In May 1997 ZooMontana, under con- available in large and inexpensive threatening both the ecosystems of tract to the U.S. Navy, began treating quantities,which suggests the need national parks and their own health. thirty water buffalo (Bubalis bubalis) for genetically-engineered or synthet- In recent years this problem has been on the island of Guam with the PZP ic forms. Current research addressing managed through “,” a eu- vaccine. Preliminary results indicate these goals is described below. phemism for shooting. Four African that the experiment significantly nations currently kill elephants in ord- reduced pregnancies in these ani- A One-Inoculation er to keep populations within the car- mals. These results have led to a new, rying capacity of their parks. (Kruger Vaccine five-year project by the U.S. Navy and The current vaccine requires animals National Park, in South Africa, killed the U.S. Fish and Wildlife Service 300 to 700 elephants annually for to be treated twice before full effec- using PZP to control water buffalo on tiveness is achieved, with the second thirty years but suspended culling in the U.S. naval base at Guam. This pro- 1995.) This is tragic, particularly for a vaccination being administered a few ject will set the important precedent weeks before the onset of the breed- species that is believed to understand of nonlethal control of wildlife by the the concept of death. ing season. However, it is quite diffi- Department of Defense. cult to treat individual wild animals In 1995 preliminary experiments On Point Reyes National Seashore provided evidence that the PZP vac- twice, and the time just prior to the in California, Tule elk (C. elaphus breeding season is not always the cine would work in elephants. Several nannodes) are being treated with PZP zoo elephants were treated with the most practical time for administering as part of a series of tests to deter- treatments. Consequently, research is vaccine and, while these were not mine whether the herd can be man- breeding animals, we determined focusing on the development and aged with contraception. Preliminary testing of a longer-acting one-inocula- that they produced antibodies against evidence shows that elk can be suc- the vaccine. In October 1996 twenty- tion vaccine. cessfully contracepted with PZP The first approach to a one-inocula- one elephants in Kruger National (Kirkpatrick et al. 1996b; Heilmann Park were captured, radio-collared, tion vaccine used microspheres et al. 1998; Shideler, personal com- formed from a lactide-glycolide poly- and treated with the PZP vaccine in munication). order to determine its contraceptive mer that is biodegradable after injec- efficacy. In November 1996 and again tion and nontoxic as it breaks down in June 1997, each treated elephant (Kreeger 1997; Turner et al. 1997). was given a single booster inoculation Research These microspheres can be engi- by means of a dart fired by a shooter in Progress neered to release the incorporated in a helicopter. None of the animals vaccine at varying rates by means of The PZP vaccine appears to come altering the size of the spheres and was captured for these booster inocu- close to the optimum contraceptive lations, proving that elephants need the ratio of lactide to glycolide agent when measured against the (Eldridge et al. 1989). In the first not be captured to be vaccinated “ideal” wildlife contraceptive. So far, (Fayrer-Hosken et al. 1997). In this experiment with these microspheres, at least, its physiological actions in wild horses in Nevada, a single inoc- trial pregnancy rates in elephants appear to be sound and safe; it does were reduced from 90 percent in un- ulation achieved the same degree of not appear to pass through the food contraception as two inoculations of treated control animals to approxi- chain; and it is not associated with mately 37.5 percent in treated ani- the raw vaccine. However, the spheres immune responses to somatic tissues clogged syringes, needles, and darts, mals. Based on the successful pre- (Turner et al. 1997; Barber and Fayr- liminary results, there may be a non- and delivery was impractical (Turner er-Hosken 2000). However, the ideal et al. 2001). This led to experiments lethal solution to the wise manage- wildlife contraceptive vaccine would ment of park elephants. Additional with small pellets, made of the same require only a single inoculation in material but shaped to fit into the studies designed to increase the effi- order to achieve several years of con- cacy of the vaccine in elephants were needle of a dart. When the pellets are traception. It would use adjuvants injected into the muscle of the ani- carried out in 1998. In this latest that have already been federally round of trials, fertility was reduced mal, along with a bolus of raw vaccine licensed for use in food animals, and adjuvant, they begin to erode, by 75 percent. There were no changes instead of the experimental or nonap- in behavior among the treated ani- releasing the vaccine at one and three proved adjuvants currently in use, or months. In an initial study with the mals, the contraceptive effects were use no adjuvants at all. The remote reversible, and the reproductive sys- pellets, antibody titers in domestic delivery system would in some man- mares remained at contraceptive lev-

188 The State of the Animals: 2001 els for close to a year, and in a small cine, and success may lead to more- there is a significant need to produce pilot study with wild mares, signifi- relaxed regulation of the vaccine by a synthetic form of the vaccine. cant contraception was achieved (Liu the FDA. A number of investigators have suc- and Turner, personal communica- Different adjuvants may target dif- cessfully cloned the protein backbone tion). Additional research is being car- ferent immune pathways, which has of the ZP molecules of several species ried out in an attempt to develop pel- important implications for both the (Harris et al. 1994; Prasad et al. lets that will release at nine months, mechanism and duration of action 2000). Thus far, however, they have thereby permitting two years of con- (Weeratna et al. 2000). PZP has been been unsuccessful at producing a traception from a single inoculation. assumed to work through short-term recombinant ZP with contraceptive A second approach involves the activation of the humoral immune sys- effects, probably because of difficul- packaging of the PZP vaccine in lipo- tem. However, some adjuvants appear ties in glycosylating this backbone. somes, which are formed from phos- to activate the cellular immune sys- This step is essential in order to pholipids and cholesterol in saline tem, which could lead to the destruc- impart adequate antigenicity to the (Brown et al. 1997a). This prepara- tion of target tissues, such as the antigen. Even several large pharma- tion, which is being tested under the ovaries. Preliminary experiments sug- ceutical companies have failed in name SpayVac™ (NuTech, Halifax, gest that conjugation of PZP to other their attempts to produce a geneti- Canada), has shown especially immunogenic molecules, such as key- cally engineered form of the vaccine. promising results for gray seals (Hali- hole limpet hemocyanin (KLH) or Work on this project continues in sev- choerus grypus), some of which tetanus toxoid, may also activate the eral foreign companies and a number remained infertile for at least six cellular immune system. of research groups; among the most years after a single dose (Brown et al. Activation of the cellular immune promising approaches is conjugating 1996, 1997b). Published data con- system against the ZP protein could short sequences of the ZP antigen to cerning the effects of SpayVac in lead to irreversible sterilants, as well tetanus toxin or other nonspecific other species are limited at this time, as more effective contraceptives. The immune-system booster (Patterson et but there is considerable interest in ability to cause sterilization rather al. 1999; but see Kaul et al. 1996). further testing, which is under way. than temporary contraception may represent a huge advantage with Marking Darts, Oral PZP, Adjuvants, and some species in some situations, such as white-tailed deer or compan- Delivery, and the Immune System ion animals. Transmissible Vectors The PZP vaccine works in most mam- The ability to treat free-roaming malian species because the ZP mole- Genetically wildlife remotely with darts and know cule is similar, but not identical, Engineered which animals have been treated is among many species. The drawback essential in the course of most appli- to this similarity across species is that or Synthetic cations in wildlife management. To PZP is not very good at causing anti- ZP Vaccines this end, a dart has been developed by bodies to be formed. Thus, it must be Pneu-dart® that inoculates the animal given with a general immunostimu- Currently the PZP vaccine must be made as a natural product; the actual with vaccine and leaves a small paint lant known as an adjuvant. The adju- or dye mark on the animal at the vant, when given with a specific vac- glycoprotein antigen is extracted from the zona pellucida of pig eggs. same time. While this would not allow cine, causes the body to make greater long-term individual recognition, it concentrations of antibodies against Production of the vaccine is very labor intensive and must rely on an ade- would allow darters to discriminate the vaccine, which results in better between treated and untreated ani- contraception. The most effective quate supply of pig ovaries from slaughterhouses. It is unlikely that mals, which is all that is needed when available adjuvant, and the one em- success is measured by impact on the ployed in most previous PZP tests, is any given small laboratory operation can produce more than fifteen thou- population. At the present time, this known as Freund’s Complete Adju- dart works in a fairly reliable manner vant (FCA). In many species, however, sand 65 µg doses per year. That level of production can probably meet but only at relatively short ranges; FCA also causes localized inflamma- improvements are being pursued. The tion and tissue damage and may trig- demands for wild horses, zoo animals, and deer, but use in elephants (which various dyes tested thus far have also ger false-positive tuberculosis tests fallen short of the mark. Deer in par- after injection (Hanly et al. 1997). currently requires three 600 µg doses) and companion animals (which num- ticular have a tendency to lick the dye Thus, the FDA and other regulators, off the injection site. More perma- as well as those concerned with ani- ber in the hundreds of thousands or millions) will far exceed the ability to nent, nontoxic dyes must be found mal welfare, discourage its wide- that will survive attention by the tar- spread use. Several new adjuvants are produce the native PZP (see also the discussion of ethics, below). Thus, get animal and persist over at least a under study for use with the PZP vac- three-to-four-week period. Fertility Control in Animals 189 Delivering contraceptives to wildlife Abortifacients feral populations). Ideally, such a orally, in baits, would be easier and At least two research groups are seek- sterilant should also mimic the be- more cost effective than darting. ing to administer compounds that havioral and health effects of surgical However, for safety and ethical rea- will cause abortion in recipient ani- sterilization, including reduced ag- sons, both the public and regulatory mals. This has already been shown to gression in males and reduced inci- agencies are likely to demand that any be feasible in deer, with prostaglandin dence of ovarian cancer in females. oral contraceptive must be species F2 delivered remotely via biobullet As noted above, a number of hor- specific. This will be extremely diffi- (DeNicola et al. 1997). By its nature, monal methods have been used suc- cult and expensive to accomplish, and however, this method will require an- cessfully for contraception of dogs and little progress thus far has been nual application, and a multi-year cats (see “History of Wildlife Fertility made. A second problem is that the Control”). Some, including megestrol treatment will not be possible. More- ® PZP vaccine (or any ZP vaccine) is over, the social objections that will acetate (Ovaban ) and Mibolerone protein in nature and easily destroyed attend this method of wildlife control (the synthetic androgen “Cheque”), by the digestive process of most ani- make it an unlikely solution to large- are licensed for use as oral contracep- mals. Needed is a delivery system that scale management efforts, especially tives on dogs and/or cats. However, permits the undigested protein of the if a safe and effective contraceptive is behavioral and health side effects are antigen to pass into the lymph of the available. common, and they are of no use to target animal’s gastrointestinal sys- animal shelters or for control of stray tem. Several strategies to accomplish and feral populations, since effective- this are available. One is to insert a ness ends soon after treatment stops. ZP vaccine into a nontransmissible Immuno- Thus, immunological approaches bacterial or viral vector; this is the sterilization may prove more fruitful, and research approach used for the oral rabies vac- efforts in these fields have been accel- cine, which is incorporated into a for Companion erating. In an attempt to immunize Vaccinia (smallpox) vaccine (Bradley dogs against their own LH, injections et al. 1997; Linhart et al. 1997; Miller Animals of human chorionic gonadotropin 1997). Another method would be to The invention of an immunosterilant (hCG) were administered (Al-Kafawi incorporate the ZP vaccine into a for companion animals would be an et al. 1974). This experiment failed microcapsule designed to be ab- extraordinary gift to the millions of because canine LH did not crossreact sorbed through the lymphoid tissue dogs and cats worldwide who suffer with anti-hCG antibodies. An immun- (or other route) in the digestive tract and die each year for want of compas- ological approach to fertility control (Miller 1997). Until the species-speci- sionate care and loving homes. In the was also attempted in cats (Chan et ficity issue is resolved, however, solv- United States alone, an estimated 6 al. 1981). Feline ovaries were homog- ing the technical problems of oral to 8 million unwanted dogs and cats enized and used to raise rabbit anti- delivery will not move the idea far are euthanized in shelters each year, bodies against the protein fractions. toward management application. and countless other stray, feral, and The antibodies, when administered to Researchers working with the Aus- abandoned animals live and die under pregnant cats, caused some fetal re- tralian government are seeking to en- the harshest conditions imaginable. sorption, but the results were dis- gineer the genes for PZP and similar Elsewhere the situation for cats and couraging. As in dogs, nonspecificity contraceptive molecules into trans- dogs is far, far, worse. There are many of the antibody appeared to be the missible, nonpathogenic viruses for useful and important approaches to cause of failure. use in controlling populations of the problems faced by dogs and cats— In a different immunological ap- introduced wildlife species such as most notably, educational outreach by proach, male dogs were immunized European rabbits (Oryctolagus cun- animal shelters (in those communi- against their own GnRH (gonadotro- iculus) (Holland et al. 1997; Robinson ties that even have animal shelters). pin releasing hormone) with GnRH et al. 1997). These viruses would be However, only effective population conjugated to human serum globulin introduced into the wild populations, control will allow such problems to be or tetanus toxoid (Hassan et al. 1985; then transmitted from animal to ani- solved through these efforts. Ladd et al. 1994). Plasma testos- mal without further human interven- To be truly useful to animal shelters terone, LH, and sperm counts were all tion. While the approach is scientifi- and others trying to control stray and depressed; however, the effect was re- cally feasible, controlling the spread feral populations, the ideal immuno- versed when antibody levels dropped. of the vaccine would be a serious sterilant would require only one shot, A GnRH vaccine would have several problem, and such a vaccine would be free of harmful or unpleasant side important advantages. First, it should raise serious safety and environmen- effects, and cause permanent sterility work on both sexes. Second, it could tal concerns in the United States and (although a multi-year, one-shot con- convey the same benefits as surgical around the world (see the discussion traceptive vaccine might be some- sterilization, including loss of libido of ethics below). what helpful for controlling stray and and estrus, reduction of aggressive

190 The State of the Animals: 2001 behavior, and reduced incidence of re- archery manufacturers, the trapping hunting industry regularly feature productive tract cancers. and fur industries, and the other com- articles on how immunocontracep- Another promising approach to mercial interests that profit directly tion can’t work—it is too cumber- contraception/sterilization is immun- or indirectly from the killing of some and/or expensive, it is failing in ization with the PZP vaccine (Mahi- wildlife (Gill and Miller 1997; Hagood this way or that, and of course, it is Brown et al. 1985, 1988). Small and 1997). In this paradigm wildlife has inferior to hunting in every way. One infrequent doses of the PZP vaccine no value or significance apart from its more extreme hunting newsletter fea- appeared to cause cellular-mediated use. This is evident in the jargon of the tured a letter that drew parallels immune responses in bitches and led culture: deer are the “deer resource”; between our research and that of the to a longer-term infertility. Long-term beavers and otters are “fur bearers”; Nazis. In community deer meetings, studies were not carried out, but in wildlife is divided into “game” and angry hunters stand up one after an- the short term this cellular immune “nongame” species; ending an ani- other to denounce immunocontracep- response was associated with histo- mal’s life is “harvesting.” tion as a fraud, as a threat to wildlife logic alterations of the ovaries. Con- In a culture of use, contraception of management and a traditional way of cerns about potential pathologies “game” animals is illogical: why pre- life, as “playing God,” and as an anti- would have to be resolved before this vent animal births when you can in- hunting plot (Kirkpatrick and Turner approach could be considered safe stead stimulate births and “harvest” a 1997). A national bowhunting advoca- (Mahi-Brown et al. 1988). Some of surplus for human use? A choice to cy group recently began issuing action these concerns might be resolved by contracept rather than kill also intro- alerts notifying its members of our use of a more highly purified PZP duces into wildlife management a new public speaking engagements. preparation than was used in these moral dimension disconcerting to In the United States the culture of studies. As mentioned above, careful those who think in terms of exploita- wildlife use is waning, especially in the selection of recombinant ZP peptides tion: that each individual animal has a cities and suburbs, where most people should allow a more targeted immune claim on the world and on us, a claim now live (Kellert 1985, 1993). Interest response and help resolve these con- to its own life. Recognizing this claim in and support for wildlife immuno- cerns (Paterson et al. 1999; Prasad et collapses the jargon of “harvest” and contraception on the part of the pub- al. 2000). “resource” and undermines the para- lic, the media, and some state legisla- digm of use that it supports. tures suggests that this obstacle will The moral challenge that wildlife be overcome. Culture, immunocontraception poses to the In much of the world, however, the culture of use is, in our view, the only culture of wildlife use remains domi- Regulations, possible explanation for the extraordi- nant and is reflected in the multi-bil- nary antipathy wildlife immunocon- lion-dollar worldwide trade in wildlife and Politics traception has generated in state and wildlife parts (Freese 1998). Immunocontraception faces a variety wildlife agencies and the hunting Among people struggling to support of technical, cultural, regulatory, and community. It is certainly not the their families and maintain human life political obstacles before it will be threat that the technology itself and dignity, such attitudes are under- used as a tool for management of poses to hunting; immunocontracep- standable, if tragic. But no such free-ranging wildlife. The technical is- tion, at least the dart-delivered kind, “necessity defense” can be construct- sues have already been discussed: is not and will not be an effective ed for the profiteers, the entrepre- what is needed is a safe, effective, management tool in the environ- neurs from wealthy nations who make one-shot, multi-year vaccine that can ments in which most recreational fortunes trading in wild-caught birds, be delivered remotely to wildlife un- hunting occurs (Kirkpatrick and bear gall bladders, and rhinoceros der field conditions. In some ways, Turner 1995). horn. Although the international com- however, the technical obstacles are But the antipathy is unmistakable. munity frowns on smuggling, the the least significant. Almost every attempt to get a state entire premise of treaties such as the In our view, the single most formi- permit to conduct an immunocontra- Convention on International Trade in dable barrier to the adoption of im- ception field study on deer has ex- Endangered Species of Fauna and munocontraception as a wildlife man- ploded into a titanic political battle, Flora (CITES) is that wildlife use is agement tool is the entrenched with the state agencies often leading good so long as it is “sustainable.” culture of wildlife use. In the United (or goading) the opposition. One pro- Wildlife contraception makes little States, this culture is most evident in posed study, in Amherst, New York, sense in that context. Why contracept the wildlife management establish- was blocked by a lawsuit by Safari elephants when you could shoot them, ment, which includes the state wild- Club International. Another was near- eat the meat, and sell the hides and life management agencies, much of ly blocked by the personal interven- tusks for great profit? The answers to the U.S. Fish and Wildlife Service, the tion of several pro-hunting members that question are not simple. They ul- hunting community, the arms and of Congress. The publications of the timately rest on the morality of shoot-

Fertility Control in Animals 191 ing elephants and the long-term eco- ly; it extends to manufacturing, stor- repeatedly and loudly voice their ob- nomic, social, and spiritual advan- age, packaging, means and schedule jections to having their license fees tages of treating these and other wild of delivery, animals targeted, and spent on contraception. State legisla- creatures with respect and compas- labeling of the vaccine or drug. These tures have become accustomed to sion. But the question will have to be will be high hurdles for PZP or any state wildlife agencies generating answered, and answered convincingly, contraceptive vaccine (especially a their own funds and depending on before immunocontraception can be recombinant form) or drug to over- hunters to conduct management widely applied to elephants and other come. But it can be done, and even- activities. They are extremely reluc- locally overabundant wildlife through- tually it will be done for a safe, ef- tant to start diverting general rev- out the world. fective wildlife contraceptive. enues to these otherwise self-support- Since management of wildlife in ing agencies. Although some im- the United States is carried out under munocontraception studies have re- Regulatory and state authority (with some exceptions ceived state funding and support (no- on federal land), applying immuno- tably in New York and Connecticut), Practical Issues contraceptives to free-ranging wildlife the prospects for state wildlife agen- Several specific regulatory and practi- will generally require permits from cies getting any money to conduct cal issues will have to be addressed state wildlife agencies (Messmer et al. immunocontraception management and resolved before PZP or other im- 1997). Many will yield such permits programs in the field are very limited. munocontraceptives become main- only slowly and grudgingly. However, If state agencies do not fund and stream management tools. as the novelty of the technique wears conduct these programs, who will? Within the United States, the most off, as its limitations and successes We believe the answers are already be- important regulatory barrier is ap- are demonstrated in field studies, as a ginning to emerge. Generally, HSUS proval by the Center for Veterinary safety record is accumulated, and as immunocontraception studies have Medicine of the U.S. Food and Drug FDA concerns are met, state agencies been funded at least in part by land Administration (FDA). The FDA has will become more comfortable with owners, land management agencies, little experience with animal vac- immunocontraception techniques. and communities in which the studies cines. Most animal vaccines are regu- Some progress has already been occur. The wild-horse contraception lated by the U.S. Department of Agri- made, at least in the agencies’ rhe- projects at Assateague Island and culture (USDA), but the USDA’s toric. While in the early 1990s the Cape Lookout National Seashores are authorizing legislation only permits it response of state agencies to deer being funded and carried out by the to regulate vaccines for disease pre- contraception was “no, not now, not National Park Service, which is also vention. Since pregnancy is not con- ever,” by the close of the decade many involved in supporting and carrying sidered a disease, regulatory authori- state agency personnel were conced- out the deer project at Fire Island Na- ty reverts to the FDA. Unfortunately, ing that PZP does at least stop deer tional Seashore and the Tule elk pro- most of the FDA regulations and stan- from breeding, and they began to ject at Point Reyes National Seashore. dards that apply to immunocontra- speak of contraception as an impor- Wild-horse contraception studies on ception are tailored to approval of tant tool for future management ef- western public lands have been coop- drugs, which are generally more strin- forts. Given the scope and serious- erative efforts of The HSUS, the re- gently regulated and require more ri- ness of public concerns over deer and search team, and the Bureau of Land gorous testing than do vaccines. other wildlife, it is inconceivable that Management; over time, the BLM is As of mid-2000, research on PZP is state agencies could resist indefinite- increasing its responsibility for carry- being carried out under the authority ly public demands for a humane, non- ing out these programs. NIST, part of of Investigational New Animal Drug lethal tool that could help solve at the U.S. Department of Commerce, is (INAD) files established with the FDA. least some conflicts with deer. jointly undertaking a deer contracep- (In our case, the INAD is held by The The practical issues include deter- tion study with The HSUS on the HSUS.) The INAD file is the heart of a mining who will pay for wildlife con- NIST campus in Maryland. The U.S. process designed to control develop- traception and who will carry it out. Navy is implementing fertility control ment and testing of new animal drugs State agencies are uniquely unsuited of water buffalo on Guam. Local agen- and vaccines and guide acceptable to pay for or conduct wildlife man- cies, such as Columbus-Franklin Coun- products toward eventual FDA ap- agement through immunocontracep- ty Metro Parks, in Ohio, and Morris proval for marketing and commercial tion. They have neither the money County Parks, in New Jersey, have also distribution. Fundamentally, the FDA nor the personnel (a situation that taken lead roles in conducting deer asks this question when considering a certainly aggravates agency worries immunocontraception studies on product for approval: Is the specific over the potential spread of immun- their own properties. At Fire Island product safe and effective for its ocontraception as a management and in Groton, Connecticut, funding intended purpose if used as directed? tool). The resources they do have are has been provided by local communi- The question is asked comprehensive- generated principally by hunters, who ties and residents.

192 The State of the Animals: 2001 Deer management, in particular, is low must be added the implicit ques- asserting that humans are hunters by increasingly being carried out at the tion, “compared to what?” (Oojges nature and that hunting fulfills some local level. Confronted with increas- 1997; Singer 1997). biological imperative.) To this role ing numbers of deer-human conflicts, Is it right to manipulate a wild ani- they contrast immunocontraception, town councils, county governments, mal’s reproductive system, and poten- which they dub “unnatural” and park commissions, and other munici- tially its behavior, for human purpos- “playing God.” pal bodies have developed deer-man- es? All other things being equal, our A strong case can be made that agement plans and employed city ethical and esthetic preference would sport hunting is not natural. The use police, animal control officers, volun- be simply to leave wildlife alone. We of all-terrain vehicles, laser sights, teer hunters, and private contractors recognize the intrinsic right of all GPS units, and other twenty-first-cen- to carry them out. This localization wild creatures to live out their lives tury gadgets and gizmos is not natur- has been formally recognized in Mary- unmanipulated by humans, and we al, nor are the pervasive population, land, where the state deer-manage- personally take great pleasure in ob- behavioral, even genetic effects of ment plan emphasizes local needs serving and participating in the con- American sport hunting: the focus on and preferences, and in New Jersey, tinuing and ever-surprising story of trophy animals, the likely disruption where recently approved legislation life on earth. But the lives of many of normal social organization, the dis- establishes community-based deer wild creatures—especially those close tortion of normal population age and management plans. These plans to human habitation—are already sex structures. Sport hunter (or would be developed locally by county subject to human manipulation, predator) populations are not regu- and municipal governments, submit- much of it deliberately or incidentally lated by game (or prey) populations, ted to the state divisions of fish, destructive. We shape the terms of as they would be in nature. Although game, and wildlife for review and ap- animal existence by our settlement the population, behavioral, and genet- proval, and carried out by either gov- patterns; engineering of land and ic effects of immunocontraception are ernment personnel or private con- water; discharging of the byproducts not yet fully known, they are unlikely tractors. While the emphasis of these of human life into the rivers, oceans, ever to achieve the profound and plans clearly now rests on killing, fer- and atmosphere; and invasion of al- unnatural impacts of sport hunting. tility control is explicitly recognized most every corner of the planet. Is it right to kill pigs (to make PZP) in the New Jersey legislation as a local And as a practical matter, leaving to save deer and horses? No. PZP is management alternative. them alone is not always a choice we produced from the ovaries of pigs pur- We envision that immunocontra- have. The public demands that action chased from slaughterhouses. If we ception projects (indeed, all urban be taken when public health, safety, or believed that more pigs were dying wildlife management) eventually will subsistence are threatened by wildlife. because we were making PZP, we be funded locally, carried out by local Not only is this view ethically defen- would stop. More than 100 million government personnel or private sible, but (more to the point) it is also pigs are killed in slaughterhouses contractors, and regulated by the widespread, and we do not see this each year, and we cannot believe that states, which will establish policies, consensus changing in our lifetimes. PZP research has any impact on that issue permits, oversee research, and The action taken need not be manipu- total. Nevertheless, this consideration certify private contractors and other lation of wildlife populations; but at adds urgency to the search for a syn- practitioners. very high population densities, “pas- thetic form of the vaccine, especially sive” management techniques (e.g., if a form of ZP should ever prove ap- exclusion and traffic manipulation) plicable to companion animals. In The Ethics may be insufficient to resolve public that case, the commercial production concerns. Alternatives typically con- of millions of doses per year might of Immuno- sidered include some form of public actually affect the market for dead hunting, sharpshooting, capture and pigs, and extraction of PZP from pigs contraception relocation or slaughter, or other on that scale would be ethically unac- Ethical questions concerning the ap- actions that are lethal, cruel, or both. ceptable to us. plication of immunocontraception to In comparison to those alternatives, Would it ever be appropriate to use wildlife have been raised by people immunocontraception appears to be a oral contraceptives or transmissible expressing a wide spectrum of view- fairly gentle population manipulation. contraceptives on free-ranging wild- points, from sport hunters to hard- Isn’t immunocontraception unnat- life? Oral contraceptives for wildlife, line animal rights advocates. We ural? Many sport hunters feel that packaged in attractive baits, would choose to take a pragmatic approach. they fill the ecological niche vacated certainly make vaccine delivery easier When immunocontraception is con- by the natural predators that have and cheaper. Consequently, they sidered, it will be considered as one of been eliminated from the landscape would broaden the range of potential several management alternatives, and and that hunting is therefore a natur- applications. This could be good or so to each of the questions posed be- al activity. (Some take this further, bad. We would consider it desirable if

Fertility Control in Animals 193 contraceptives could replace noxious conditions) the ongoing research into roaming animals at greater ranges; thus, dart- delivered drugs were not an early priority for sci- lethal controls with minimal behav- transmissible immunocontraceptives entists looking into this field. ioral and ecological effects. Like poi- (Oojges 1997). But because the risks son baits and pesticides, however, oral of releasing such agents would extend contraceptives offer many opportuni- beyond Australia, a clash between Aus- ties for abuse. Rather than the careful tralians and the rest of the world Literature Cited Al-Kafawi, A.A., M.L. Hopwood, M.H. and limited application that dart de- might be anticipated, even among ani- Pineda, and L.C. Faulkner. 1974. livery forces on our current use of mal protectionists. Immunization of dogs against immunocontraceptives, oral contra- human chorionic gonadotropin. ceptives could be scattered incau- American Journal of Veterinary tiously and indiscriminately, leading Conclusion Research 35: 261–64. to unpredictable biological effects on In spite of the frustrations and obsta- Allen, S.H. 1982. Bait consumption a large scale. These risks are amplified cles—personal, political, and bureau- and diethylstilbestrol influence on if the immunocontraceptives are not cratic—we remain optimistic about North Dakota red fox reproductive species specific. the future of wildlife contraception. It performance. Wildlife Society Bul- The subject of transmissible contra- may be that we are simply optimistic letin 10: 370–74. ceptives is even more complex. In his people, but our optimism draws sup- Balser, D.C. 1964. Management of 1985 novel Galapagos, Kurt Vonnegut port from our experience. One of us predator populations with antifer- describes a world in which the human (JFK) has been working on wildlife tility agents. Journal of Wildlife population is driven nearly to extinc- fertility control for almost thirty years Management 28: 352–58. tion by a virus that sweeps across the and the other (ATR), for just under a Barber, M.R., and R.A. Fayrer-Hosken. planet rendering its human hosts decade; we have seen progress. Oper- 2000. Evaluation of somatic and infertile (except for a small group iso- ationally, we’ve progressed in thirty reproductive immunotoxic effects lated on the Galapagos Islands, where years from capture, field surgery, and of the porcine zona pellucida vacci- the plot then unfolds). This is the implantation with gobs of physiologi- nation. Journal of Experimental deepest fear engendered by the con- cally and environmentally suspect Zoology 286: 641–46. cept of transmissible contraceptives— steroids to darting animals in the Barfnect, C.F., and H.C. Peng. 1968. that once released, such an agent field at a distance of twenty-five to Antifertility factors from plants. I. could not be controlled and its unan- fifty yards with one-fifth of a teaspoon Preliminary extraction and screen- ticipated effects could be catastroph- of biodegradable vaccine. In the pub- ing. Journal of Pharmaceutical Sci- ic for the target species, for nontarget lic’s eyes, wildlife contraception has ences 57: 1607–08. species, and even for our own species. gone from a joke to a pretty darned Becker, S.E., and L.S. Katz. 1997. We believe that there would be abso- good idea, “if you can make it work.” Gonadatropin-releasing hormone lutely no support in the United States Even in the deer meetings we’ve sur- (GnRH) analogs or active immu- for release of such an agent: no vived (Kirkpatrick and Turner 1997; nization against GnRH to control wildlife overabundance problem with Rutberg 1997), after all the shouting, fertility in wildlife. Pp. 11–19 in which we are presently coping could blustering, posturing, and accusing is Contraception in wildlife manage- justify even considering assuming that over, there’s usually someone who ment, ed. T. J. Kreeger. USDA/ level of risk. takes us aside and says, “You know, APHIS Technical Bulletin No. 1853. In Australia, where much of the these animals really are a problem, Bell, R.L., and T.J. Peterle. 1975. Hor- research on transmissible immuno- but it’s not right to kill them, so if mone implants control reproduc- contraceptives is being conducted, a you could find another way to control tion in white–tailed deer. Wildlife different story line is unfolding. The them it would make people really, Society Bulletin 3: 152–56. introduction and phenomenal pros- really, happy.” Bell, M., C. A. Daley, S. L. Berry, and perity of European rabbits, red foxes, For the animals—the old mares on T. E. Adams. 1997. Pregnancy sta- domestic cats, and house mice has Assateague, the old does on Fire Is- tus and feedlot performance of beef devastated dozens of native marsupial land, and the rest—and for those peo- heifers actively immunized against species in a true ecological catastro- ple in the back of the room, we should gonadatropin-releasing hormone. phe. Australia’s response has been to all be working to find that other way. Journal of Animal Science 75: kill these once-welcomed invaders by 1185–89. the millions with poison, traps, guns, Notes Berger, P.J., E.H. Sanders, P.D. Gard- blasting, gas, disease, and every other ner, and N.C. Negus. 1977. Pheno- cruel, destructive device imaginable. 1These attitudes still linger, and many of these lic plant compounds functioning as That animal welfare catastrophe, in species, such as gray wolves and grizzly bears, still confront them in their path to recovery. reproductive inhibitors in Microtus conjunction with the ecological cata- 2 Dart delivery systems have changed dramati- montanus. Science 195: 575–77. strophe, has led animal protection cally in the past twenty-five years and have groups in Australia to support (with improved significantly the ability to treat free-

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