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1 This article was downloaded by: [Dr Kenneth Shapiro] On: 08 June 2015, At: 08:24 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Journal of Applied Animal Welfare Science Publication details, including instructions for authors and subscription information: Preliminary Evaluation of Porcine Zona Pellucida (PZP) Immunocontraception for Behavioral Effects in Feral Horses (Equus caballus) David M. Powell Published online: 04 Jun To cite this article: David M. Powell (1999) Preliminary Evaluation of Porcine Zona Pellucida (PZP) Immunocontraception for Behavioral Effects in Feral Horses (Equus caballus), Journal of Applied Animal Welfare Science, 2:4, , DOI: /s jaws0204_6 To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities

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3 JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, 2(4), Copyright , Lawrence Erlbaum Associates, Inc. Downloaded by [Dr Kenneth Shapiro] at 08:24 08 June 2015 Preliminary Evaluation of Porcine Zona Pellucida (PZP) Immunocontraception for Behavioral Effects in Feral Horses (Equus caballus) David M. Powell Department of Zoologrcal Research National Zoological Park and Department of Biology University of Maryland Successful management of captive populations of wild animals requires effective control of reproduction. Contraception is one tool for controlling reproduction of animals in zoos; however, the options available to the animal manager are limited. Contraceptives vary in efficacy, reversibility, and side effects, and thus may not be suitable for widespread use. One consideration when selecting a contraceptive is its potential for side effects on behavior, especially given the fact that reproduction plays such a prominent role in the biology of any species. To date, there have been few evaluations of contraceptives for behavioral effects, and those that have been conducted have focused on hormone-based contraceptives. This study sought to evaluate a novel method of population control, imrnunocontraception, for behavioral effects in apopulation of feral horses. Porcine zona pellucida (PZP) imrnunocon~ception prevents fertilization of ova and does not alter nonnal hormone secretion patterns. It therefore should leave the animal behaviorally intact in terms of reproductive behavior. The study examined the behavior of 43 sexually mature mares on Assateague Island during the 1997 breeding season and, with help from Earthwatch volunteers, collected observations over a 3-month period. The study found no significant differences between treated and untreated mares in general activity budget, aggression given or received, and spatial relationships relative to the stallion. These preliminary findings indicate that PZP contraception seems to have no acute behavioral effects on the behavior of individuals. The study findings also suggest that PZP could be a desirable Requests for reprints should be sent to David M. Powell, Department of Zoological Research, National Zoological Park, Washington, DC dpowell@nzp.si.edu

4 and effective management tool for captive species in which social behavior plays an integral role in group dynamics. Analyses of group level effects and population level effects are continuing. Downloaded by [Dr Kenneth Shapiro] at 08:24 08 June 2015 One of the many challenges facing zoological parks and aquaria is the management and maintenance of genetically viable populations of endangered species. In theory, these populations will eventually serve as reservoirs ofgenetic diversity forthe reinforcement or reestablishment of "wild''populations of nonhuman animals. To meet this goal, animal populations must be managed efficiently and effectively, given the constraints of space and resources. Breeding must be managed to maximize the production of genetically valuable individuals and to minimize the numbers of either overrepresented or genetically inferior individuals. In cooperation with the American Zoo and Aquarium Association, zoos and aquaria have developed a variety of tools to facilitate the development and execution of successfil breeding programs. These tools include studbooks, population management plans, and species survival plans (SSPs) that, in one way or another, contribute to making recommendations about allocation of captive space and pairing of individuals for reproduction. Coordination of breeding programs often involves many animals distributed over many institutions. In general, the institutions participating in a breeding program agree on the means by which to achieve the program's objectives; however, unplanned pregnancies do occur, and variation in litter or clutch sizes produces surplus individuals. In most cases, the number of offspring required from an individual to maintain a genetically healthy captive population is significantly lower than the potential number of offspring it could produce. Thus, by their very design, programs like SSPs require animal managers to have a variety of tools available to allow for compliance with breeding recommendations (Asa, Porton, Baker, & Plotka, 1996). These tools often must be applied to nonendangered species as well, because they occupy valuable space or consume resources that may be needed for endangered species programs. Two methods by which breeding can be managed are separation of the sexes and establishment of same-sex groups of individuals. Separating the sexes may lead to negative effects on animal health and behavior (Conway, 1976). The practice of establishing same-sex groups is in its infancy in zoological parks, though some groups have been established and maintained with success (T. Stoinski, personal communication, May 1,1997). Given the current limitations ofthese methods, contraception seems to be the best tool available for effective management of reproduction. NEED FOR RESEARCH AND SHARED INFORMATION Research involving various contraceptive methods has traditionally been aimed at humans, companion animals, and wildlife. Much less is known about the effi-

5 PRELIMINARY EVALUATION OF PZP 323 Downloaded by [Dr Kenneth Shapiro] at 08:24 08 June 2015 cacy and safety of contraceptives in captive exotic species (Knowles, 1986). In 1989, the American Zoo and Aquarium Association (AZA), responding to this lack of knowledge, formed a contraception task force, later formalized as the AZA Contraception Advisory Group (CAG). Its goals include (a) the collection and dissemination of data on the efficacy and safety of contraceptives and (b) the coordination and recommendation of research on contraceptive use in captive exotic species (Wemmer, 1989). The CAG has conducted surveys of zoos to assess the extent of use, efficacy, and effects of various contraceptives in primates, carnivores, and ungulates. These surveys are ongoing and updated as new data come in on an annual basis. A database has been created to find taxon-specific recommendations about which contraceptives should be used (Porton, Asa, & Baker, 1990; Porton & Hornbeck, 1993). Despite the number of different contraceptives available, a captive manager's available options for a given species remain limited because of the inherent characteristics of the contraceptive, its mode of action, and the unique biology of the species. A tremendous need remains for both contraceptive research in exotic animals and data sharing on contraceptive use among institutions (Asa et a]., 1996). Full Understanding of Potential Effects One aspect of contraceptives about which we know comparatively little is how they affect the behavior of the contracepted individual and the conspecifics with which it interacts. By comparison, our knowledge of how contraceptives affect the physiology of the reproductive process is much greater. Clearly, for recommendations to be made about contraception, we must have a complete understanding of all its potential effects. In general, we know more about how hormone-based contraceptives affect behavior because of the history of research on behavioral endocrinology. However, research in this area is restricted to relatively few taxa and has rarely focused on exotic species. In addition, we know virtually nothing about the potential effects that non-hormone-based contraceptives (e.g., immunocontraception) may have on behavior. I provide a brief discussion of some studies that have examined the effects of contraception on the behavior of captive exotic wildlife. For a more general discussion of contraception in exotic species, see Asa et al. (1996). Hormone-Based Contraception and Behavior of Captive Exotic Animals Portugal and Asa (1995) assessed the effects of melengestrol acetate (MGA) implants on behavior in Hamadryas baboons (Papio hamadryzs). Hayes, Feistner,

6 and Halliwell (1996) assessed the implants' behavioral effects on Rodrigues fruit bats (Pteropus rodricensis). Portugal and Asa's first experiment compared the behavior of female baboons immediately before and following implant insertion. They documented significant decreases in open-mouth grin (an aggressive behavior) and time spent foraging during MGA treatment. In addition, they reported nonsignificant trends toward decreased locomotion and increased time spent immobile during treatment. Portugal and Asa also noted that perineal tumescence did not recede entirely in treated females. In their second experiment, they compared the behavior of female baboons after long-term (2 years) treatment with their behavior after implant removal. They found a significant increase in affiliative behavior received by the females following treatment and a trend toward increased affiliative behavior initiated by the females. All females had gained weight during the treatment period (ranging from a 17.3% to 47.6% increase over starting weights). They also found that perineal swellings never fully subsided, indicating that some tissue hypertrophy may have been permanent. In a study of stumptail macaques (Macaca arctoides), Lim and Steklis (1990) found that during treatment with depo-medroxyprogesterone (Depo- Provera), another synthetic progestin, there was a decrease in rates of affiliation and a tendency for higher rates of aggression. Hayes et al. (1996) observed the behavior of control and MGA-implanted Rodrigues fruit bats during a preimplantation period, 1 month postimplantation, and 6 months postimplantation. During the preimplantation period, there wereno differences in activity budget between control and treated bats. At 1 month postimplantation, they found that implanted bats moved significantly more than control bats. At 6 months postimplantation, this trend had reversed; however, both groups showed decreased movement compared to 1 month postimplantation. In addition, Hayes et al. noted within-group changes during these study periods. In an analysis of spatial relationships, they found that at 1 month postimplantation, treated bats spent significantly more time with a nearest neighbor than control bats who tended to roost apart from others. Hayes et al. found no effects of treatment on the age-sex structure of neighbors or in the number of displacements given or received. They saw no effect of treatment on the rate of copulation. The authors suggested that the changes in activity budget between groups were most likely due to changes that occurred within groups and not to implants. They found that implanted females had gained weight (more than 8% of body weight), and 7 of 9 treated bats showed poor regrowth of hair and some scarring over the implant insertion site. Porcine Zona Pellucida (PZP) lmmunocontraception Irnmunocontraception relies on the body's production of antibodies that interfere with some critical event in reproduction. Immunocontraceptive vaccines have so far been developed against neuropeptides, gonadotropins (Moudgal et al., 1986),

7 steroid hormones (Al-Kawafi, Hopwood, Pineda, & Faulkner, 1974), sperm (Primikoff, Lathrop, Woolman, Cowan, & Myles, 1988), and ova (Sacco, 1987). To date, the most promising of these vaccines are those directed against the zona pellucida (ZP; Aitken, Richardson, & Hulme, 1984; Sacco & Yurewicz, 1989). The ZP is a noncellular layer surrounding all mammalian oocytes. The ZP contains two glycoproteins (designated ZP3 and ZP4) that are thought to serve as sperm receptor molecules (Florman & Wassarman, 1985; Hasagawa, Koyama, Inoue, Takemura, & Isojima, 1992). These glycoproteins are so highly conserved in structure across mammals that the ZP of pigs has been used to block fertilization in various nonhuman primates (Sacco, 1987), rabbits (Wood, Liu, & Dunbar, 198 l), dogs (Mahi-Brown, Yanagimachi, Hofhan, & Huang, 1985), and humans (Sacco, Pierce, Subrarnanian, Yurewicz, & Dukelow, 1987). The basic mechanism of action for these ZP vaccines depends on this structural similarity across taxa. When injected, ZP fiom pig ova causes the host's immune system to produce antibodies to the ZP. These antibodies bind to the PZP as well as to the ZP on the host's oocytes, effectively blocking sperm binding and fertilization. Emphasizing Variability To date, PZP has had variable effects on health and reproductive function, depending on the taxon (AZA Contraception Advisory Group, 1995; Kirkpatrick, Naugle, Liu, Bemoco, & Turner, 1995). Among feral horses, PZP contraception appears to be completely reversible and to have no ill effects on ovarian function when animals are contracepted for fewer than 3 consecutive years (Kirkpatrick, 1995; krkpatrick, Liu, Turner, Naugle, & Keiper, 1992). After 3 years of contraception with PZP, effects on ovarian function were noted. Treated mares showed lower ovulation rates and depressed estrogen levels (Kirkpatrick et al., 1992). In order for this contraception to be reversed, antibody titers have to decrease to levels that permit successful ovulation and fertilization. Mares treated for 3 consecutive years and then taken off contraception for breeding have at least a 2-year latency to reproduction (Unpublished U.S. National Park Service data). Seven consecutive years of contraception with PZP severely alters ovarian function and endocrine production (Kirkpatrick et al., 1995). It should be emphasized that immune response is variable across individuals and species, and this variability may be manifested in magnitude or duration of response (Fraser, 1980). Further research on immunocontraceptive techniques should include assessments of factors affecting immune response to vaccines. McShea, Monfort, and Munson (1997) evaluated the efficacy of PZP immunocontraception and its impact on behavior of white-tailed deer (Odocoileus virginianus). Does were divided into one control group and two treatment groups. The two treatment groups differed in the total dose of PZP. Treatment with the

8 smaller of two doses in this study did not prevent parturition, but it significantly delayed parturition dates in treated does. As in the MGA studies discussed previously, treated does showed significantly more weight gain than control does during the study period. McShea et al. found that males exhibited longer breeding seasons during the first year of their study; in the second year, they noted that the breeding season was not longer but had started over 2 weeks earlier. Among does, contracepted females were more active (exhibited more running or walking) than untreated does, though this difference was only evident during estrus and may have been due to the treated does undergoing one to two nonconceptive cycles before getting pregnant. Treated does also exhibited estrous periods later in the season than control does (McShea et at., 1997). Heilmann, Garrott, Cadwell, and Tiller (1998) analyzed behavioral responses of free-ranging elk to PZP irnmunocontraception. They found that sexual interaction rates of treated and untreated cows were similar during the normal breeding season for this species but that rates of sexual interaction remained at breeding season levels for treated cows after the end of the normal breeding period. They also found no differences in proportion of time spent feeding, idling, or moving between contracepted and uncontracepted cows. Hypotheses Tested I generated a series of hypotheses about how contracepted and uncontracepted mares might differ in their behavior. I first hypothesized that, if contraception was having a severe impact on behavior, I would expect to find differences in the overall activity budgets of contracepted and uncontracepted mares. My second hypothesis predicted differences in spatial relationships between contracepted and uncontracepted mares relative to the stallion in the harem band. One could imagine that contracepted mares either might (a) be close to the stallion more often because they are continuously cycling during the breeding season and hence would show repeated periods of estrous behavior or (b) be far from the stallion and on the periphery of the group because the stallion might find them unsuitable as mates. Finally, I hypothesized that contracepted and uncontracepted mares would differ in social rank and the amount of aggression they gave and received. METHODS Study Animals With the assistance of Earthwatch volunteers, I conducted behavioral observations on a population of feral horses (Equus caballus) living on Assateague Is-

9 land National Seashore, a 33-mile long banier island running along the coasts of Maryland and Virginia. Observations were restricted to the Maryland herd, which contains approximately 173 individuals and is essentially unmanaged, except for population control. Though equid social organization appears closely tied to ecology (Rubenstein, 198 l), the typical social group in feral horses is the harem band, which contains one breeding male, several reproductive mares, and their dependent offspring. Harem bands on Assateague occupy overlapping home ranges and are not characterized by territoriality. A dominance hierarchy exists within each harem band, and the stallion may not be the alpha animal (Houpt & Keiper, 1982). Among mares, rank correlates most highly with tenure (Seligsohn, 1987) but also very highly with age (Keiper & Sambraus, 1986; Rutberg & Greenberg, 1990). Female hierarchies tend to be stable with few reversals (Berger, 1986; Keiper & Sarnbraus, 1986). In 1997, nine bands of horses were observed from June 1 to September 5. These bands contained 43 sexually mature mares. National Park Service personnel and outside researchers had documented significant impacts by the horses on the island's vegetation during the 1980s. Concern over the size of the herd led to the development of a plan to reduce the population using the immunocontraceptive, PZP. Widespread inoculation of the herd began in 1994, though some mares had been treated previously as part of research on PZP's reversibility. Of the 43 mares observed in this study, 24 were contracepted and 19 were uncontracepted during the breeding season of 1997, though all mares in the study had been contracepted for some period in the past. Contracepted mares had been on contraception for an average of 2.54 consecutive breeding seasons (range = 1 to 5). Eighteen of the 19 uncontracepted mares had been on contraception for the previous 3 breeding seasons ( ) and were taken off treatment either to decrease potential side effects of longer term treatment or to allow for breeding. Behavioral Observations Observations were conducted from 7 a.m. until 7 p.m. and were approximately balanced across time of day. Each band was observed twice per week on average. Observers received an average of 2.5 days of training in behavioral observation techniques specific to this project. Observers were left to work on their own only after they had achieved a criterion of 85% reliability with the principal investigator. At least two observers were assigned to observe a band during an observation period. Focal animal observations (Altmann, 1974) were conducted with scan sampling of each sexually mature mare in the bandaefined as 2 years old and beyond (Keiper, 1985). Mares were observed in random order. Every 5 min, the identities

10 of the nearest neighbor to the focal mare and the stallion were recorded. The nearest and most distant adult mare to or from the stallion was also recorded on the 5-min mark. Every 10 min the activity of every group member was recorded. Some of the behavioral categories used in these observations were grazing, standing, resting, locomotion, grooming, and social. Social included any behavior in which the focal animal was interacting with any other animal (including sexual behavior, aggression, mutual grooming, and nursing). In addition, on the 10-min mark, the identities of the most distant animal and most distant sexually mature mare in the group were recorded. Determining which individual had the greatest distance between him or herself and his or her nearest neighbor (who could be any age or sex) scored this. In cases where distances between horses appeared equal, we tried to determine which individual was most distant from the core of the group. Core was defined as the subgroup containing the most individuals. All occurrences of sexual, aggressive, and affiliative behaviors were recorded. Data on aggressive encounters and their outcomes were used to rank individuals in a hierarchy according to the method of Schein and Fohrman (1 955). A dominance index was then calculated for each mare that would allow for comparison of mares across differently sized bands (Clutton-Brock, Guinness, & Albon, 1982). Each band, except for 1 band of 3 uncontracepted mares, contained both contracepted and uncontracepted mares. There was no relation between age and contraception status (Mann-Whitney U = 233,p =.5 144) nor between group size and proportion of mares in the group that were contracepted (r, =.1952, n = 8, p =,643). For these reasons, data for contracepted and uncontracepted mares were pooled across bands. Nonparametric statistical tests were used, and significance was assessed when p <.05. RESULTS Contracepted and uncontracepted mares had virtually identical activity budgets for most behaviors scored. There was a trend for contracepted mares to be engaged in more social behavior than uncontracepted mares; however, there were no statistically significant differences for any of the behavior categories scored (Table 1). A mean percentage of scans in which a female was the nearest mare to the stallion and the most distant female from the stallion was calculated for each mare. These were then scaled by group size. There were no significant differences for either measure between contracepted and uncontracepted mares (stallion's nearest female: U = 1 16, p =.I 66 1 ; most distant female from stallion: U = 144,p =.6 105; Figure I). Mean dominance index was compared between contracepted and uncontracepted mares. Each of three mares who switched bands during the study was

11 TABLE 1 Activity Budgets of Contracepted and Uncontracepted Mares Percent Time Behavior Uncontracepted Contracepted P" Downloaded by [Dr Kenneth Shapiro] at 08:24 08 June 2015 Graze Rest Stand Locomote Groom Social 'Mann-Whitney U Test. SDF FIGURE 1 Mean percentage of scans in which a mare was the stallion's nearest mare (SNF) and most distant mare (SDF), scaled by group size. treated as two separate data points because her social rank could potentially change on entering a new group (Seligsohn, 1987). There was no significant difference in mean dominance index between treated and untreated mares (U= 253,p = 3339). There also was no significant difference in aggression received (U = 206.5, p =.7338) or aggression given (U = 179,p =.3016) between contracepted and uncontracepted mares (Figure 2). SNF DISCUSSION Previous studies of MGA contraception and one study of PZP contraception have found differences in activity budgets between contracepted and uncontracepted animals (Hayes et al., 1996; McShea et al., 1997; Portugal & Asa, 1995). I found no differences between treated and untreated feral horse mares in this study. There was a nonsignificant trend for treated mares to spend more time en-

12 ,-, 5 J w $ ::;;.k :::: 1, 0.02 ' ' lo--- I 0.01 / 0 I- Received Gkn Contracepted FIGURE 2 Comparison of rates of aggression between contracepted and uncontracepted mares. gaged in social behavior. This finding might be expected, given that treated mares undergo repeated nonconceptive cycles and thus demonstrate estrous behavior at regular intervals. Heilmann et al. (1998) demonstrated that PZP-treated elk cows showed higher rates of sexual interaction outside the normal breeding season, though their rates were similar to those of untreated cows during the breeding season. Their findings of no significant impact on overall activity budget are in agreement with the results of this study, although fewer categories were scored. Studies of horse behavior on Assateague before implementation of the contraception program indicated that the horses spent an average of 50% of their time foraging (Keiper, 1985). Studies of other populations of feral equids have found that the percentage of time spent grazing ranges from roughly 35% to 70% during the summer months (June, July, August), depending on the habitat (Berger, 1977; Rubenstein, 1981). The results of these studies indicate that both the contracepted and uncontracepted mares in this study have activity patterns that are similar, at least in terms of grazing, to feral horses that have never been exposed to contraception. Spatial Relationships Unaffected PZP immunocontraception did not appear to affect spatial relationships between mares and stallions in this study. Contracepted and uncontracepted mares were equally as likely to be the closest or most distant mare from the stallion in the harem band. This may indicate that the contraception status of a mare is not discernable to other individuals in the group. PZP treatment did not appear to affect social rank or rates of aggression given or received in this study. Rutberg and Greenberg (1990) reported aggression rates ranging from.6 to 1.9 aggressive acts per sampling hour in this population before contraception. During the 1997 breeding season, I observed an average of 1.94 aggressive acts per sampling hour.

13 As mentioned earlier, current data for this population of horses indicate that a mare who has been on PZP for 3 years probably requires 2 years to become fertile again. To date, all mares who have been on PZP for 3 consecutive years and then taken off have become pregnant within 3 years post-treatment. Kirkpatrick (1995) reported that antibody titers only remained high enough to provide contraception for 1 year; thus an annual booster must be given to ensure continued contraception. All but one of the uncontracepted mares in this study had been off PZP only a little more than 1 year. If antibody titers were still high, however, these mares may still have been behaviorally contracepted. Currently, it is unclear how high titers must be to suppress reproduction without affecting behavior. Although much is known about how behavior affects the immune system, there is a paucity of information on how the immune system might affect behavior. Most studies addressing this topic have focused on the effects of exposure toxins rather than non-infectious proteins, and these studies have used neonates of selectively bred individuals as test subjects (Granger, Hood, Ikeda, Reed, & Block, 1996). A control group of untreated (unexposed) mares was not available for this study. At the beginning of observations, virtually every mare on the island was either on PZP or had been exposed to the vaccine previously. On Assateague, young females are treated in either October of their first year or March of their second year to prevent conception during their second summer. Observations of these females before treatment would not serve as a proper control because they would not have been sexually mature. For most of the behavioral variables reported here, similar values have been reported either for this population before contraception or for other populations of feral horses. However for more complex analyses, valid comparisons probably cannot be made. This underlines the need to conduct baseline studies before interventions of any kind are taken with populations of animals either in the wild or in captivity. A baseline study that addresses behavior and, in many cases, ecology is necessary to identifl unambiguously the effects of intervention later. National parks and rehges typically do not have the resources in terms of staff and time to conduct these kinds of studies, which require many hours of observation. Therefore, it is imperative that they solicit local universities, zoos, and other research institutions for assistance so that correctly controlled studies can be done. Duration of Breeding Behavior Extended These data should not be taken to mean that PZP contraception has absolutely no effects on the behavior of feral horses. By default, this contraceptive very likely extends the duration of breeding behavior. Normally, mares would get pregnant during a foal heat or in one to two cycles; however, PZP-treated mares continually undergo nonconceptive cycles and thus demonstrate estrous behav-

14 ior throughout the season. Similarly, stallions continue to tend and mate with mares until they cease to cycle in the fall. Whether this extension of the breeding season has negative effects on behavior remains to be seen. For Hamadryas baboons, it has been suggested that contraceptive methods that allow for continued, nonconceptive cycles should be avoided (Portugal & Asa, 1995). The veterinary literature has also documented the negative effects of repeated exposure to a female's own endogenous hormone cycles associated with ovulation. Imrnunocontraceptives that do not affect hormone levels (e.g., PZP) and allow for normal ovulatory cycles should be used with caution. Effects on Sociosexual Behavior Contraceptives may also have more complex effects on sociosexual behavior. Females who fail to become pregnant afterrepeated ovulations may seekout new mates (e.g., subordinate males), thus disrupting group stability and order. In situations where only a portion ofthe females in a group are contracepted, a contraceptive that suppresses estrous behavior may intensify male-male competition forthose females who show normal sexual behavior (Asaet al., 1996). Contracepted femalesmay also be aggressive toward other females and their infants. This is a preliminary evaluation of this contraceptive. Data are currently being analyzed to determine if activity budgets differ between treated and untreated mares during the estrous period. Longitudinal fecal samples were collected from a sample of mares to assess ovarian function and reversibility. Behavioral data will be matched with hormonal data to determine if contracepted and uncontracepted mares exhibit similar patterns of sexual behavior. Data are also being analyzed to assess group stability. Membership in feral horse bands tends to be stable; however, females do change bands occasionally. These membership changes may be temporary or permanent. The National Park Service has conducted a monthly census of the herd for the past 9 years. During the census, membership in each band is recorded. I am currently trying to determine if contracepted mares are more likely than uncontracepted mares to change bands. One could envision a scenario in which a mare leaves a band because she repeatedly fails to get pregnant by a certain stallion. Similarly, a stallion might expel a seemingly barren mare from the harem. Finally, data from the 1997 and 1998 breeding seasons are being analyzed to determine if there are within-individual differences in behavior that are attributable to contraception. Research Participation and Information Exchange We clearly need more studies of contraception in wild and captive exotic animals. Many of the methods currently used are still considered experimental-

15 PRELIMINARY EVALUATION OF PZP 333 Downloaded by [Dr Kenneth Shapiro] at 08:24 08 June 2015 even for humans. The current data strongly indicate that there is considerable individual and species variability in contraceptive dose, efficacy, and safety (Asa et al., 1996). A contraceptive that effectively halts reproduction while disrupting social behavior may not be desirable to animal managers or humane to the treated animals. For this reason, it is also important for behavioral effects to be included in assessments of contraceptives. If we are to improve and validate our recommendations for the use of contraceptives in exotic wildlife, there must be greater participation in research trials coordinated by the Contraception Advisory Group, and there must be more exchange of information among zoos, wildlife agencies, and university researchers. ACKNOWLEDGMENTS These results were presented as part of a poster presentation at the 7th World Conference on Breeding Endangered Species in May Cincinnati, OH. Funding for this project was provided by Earthwatch Institute, Biology of Small Populations Training Grant BIR at the University of Maryland, the National Zoological Park of the Smithsonian Institution, and the Chesapeake Bay Foundation. The National Park Service also provided logistical and technical support, as well as housing for the researchers and volunteers. I thank Dr. Devra Kleiman (National Zoo), Dr. Cheryl Asa (St. Louis Zoo), and Dr. Jay Kirkpatrick (Zoo Montana) for their comments on this research, as well as National Park Service personnel Carl Zimmerman, Jack Kumer, and Allison Turner for access to historical records on the Assateague horses. REFERENCES Aitken, R. J., Richardson, D. W., & Hulme, M. (1984). Immunological interference with the properties of the zona pellucida. In D. B. Crighton (Ed.), Immunologicalaspects of reproduction in mammals (pp ). London: Bunenvorths. Al-Kawafi, A. A., Hopwood, M. L., Pineda, M. H., & Faulker, L. C. (1974). Immunization of dogs against human chorionic gonadotropin. American Journal of Veterinan; Research, Altmann, J. (1974). Observational study of behavior: Sampling methods. Behaviour, 49, Asa, C. S., Porton, I., Baker, A. M., & Plotka, E. D. (1996). Contraception as a management tool for controlling s~lrplusanimals. InD. C;. Kleiman, M. E. Allen, K. V. Thompson, & S. Lumpkin (Eds.), Wild mammals in captrvi&: Principles and techniques (pp ). Chicago: University of Chicago Press. AU contraception advisory group recommendations. (1995). Silver Spr~ng. MD: American Zoo & Aquarium Association. Berger, J. (1977). Organizational systems and dominance in feral horses in the Grand Canyon. Behavioral Ecology and Sociobiology, 2, Berger, J. (1986). Wild horses of the Great Basin. Chicago: University of Chicago Press.

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