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1 ~ Vampire Bat Control in Latin Arnenca To find an effective control agent that affects only the species of concern normally requires knowledge of the life history of the target species. The current control of vampire bats in Latin America rests on the following aspects of the biology of the bats: they are much more susceptible than cattle to the action of anticoagulants, they roost extremely close to each other, they groom each other, their rate of reproduction is low, they do not migrate, and they forage only in the absence of moonlight. These pieces of information were acquired in a search for control methods, and they yielded methods that are effective and that have minimal or no effect on nontarget species. The approach in this case was to find and use weak links in the life history of the animal in question. It also reflects an attempt to save money by comparing the cost and availabilities of various chem- icals. 151
Case Stucly G. CLAY MITCHELL, Denver Wildlife Research Center, Denver, Colorado INTRODUCTION When the Conquistadors arrived in Mexico in 1527, their horses were immediately attacked by the common vampire bat, Desmodus rotundas (Molina Solis, 18961. Over four centuries later, Bernardo Villa (1969) made the following statement after reviewing the vampire bat problem in Brazil: "No notable success has been achieved in controlling bats of the family Desmodontidae, particularly the species Desmodus rotundus, in any of the countries of tropical America." Of the three species of vampire bats, only the common vampire, the subject of this review, is economically damaging. The others, Diphylla ecaudata and Diaemus youngii, have specialized feeding habits, preferring to feed on the blood of birds (Uieda, 1982; Villa, 19661. Vampire bats range from tropical Mexico to northern Argentina and northern Chile, and they cost the Latin American livestock industry $350 million a year: $100 million in direct losses to rabies and $250 million in secondary losses, such as reduction in milk production and secondary infections (Kverno and Mitchell, 1976~. In addition, several humans die each year of rabies transmitted by vampire bats (Beer, 1975; Irons et al., 1957; Venters et al., 1954). Previous attempts to reduce vampire bat populations in Latin America have been ineffective, dangerous, destructive, impractical, too localized, or too expensive. Methods tried included the use of flame throwers in Trinidad (Greenhall, 1970), the dynamiting of several thousand caves in the State of Grande do Sul, Brazil (Villa, 1969), the placement of a strychnine-syrup mixture at old bite sites (Greenhall, 1963), the gassing of thousands of caves in Latin America (Arteche, 1969), the use of Jap- anese mist nets (Dalquest, 1954; Greenhall, 1963), and the placement of traps at the entrances of caves (Constantine, 19691. Bats have also been killed with clubs or firearms in stables and dwellings where they attack their prey (Constantine, 19701. In 1967, under the authority of the Foreign Assistance Act, the U.S. Agency for International Development (AID) asked the U.S. Department of the Interior's Fish and Wildlife Service to conduct research on vertebrate pests (rodents, pest birds, and vampire bats) in developing countries. In 152
VAMPIRE BAT CONTROL IN LATIN AMERICA 153 June 1968, the Service's Denver Wildlife Research Center (DWRC) ini- tiated a program of research on the vampire bat problem under the auspices of AID. The program consisted of two phases: (1) research conducted by a laboratory team at DWRC and a field team at the Instituto Nacional de Investigaciones Pecuarias in Palo Alto, Mexico; and (2) a utilization and training phase, developed after species-specific control methods were available. THE ENVIRONMENTAL PROBLEMS The main objective of the program was to increase livestock production in Latin America by reducing vampire bat populations. The main envi- ronmental problems were how to accomplish this objective without de- stroying habitat, contaminating the environment with pesticides, destroying desirable species, and adversely affecting an endangered species, the white- winged vampire (Diaemus youngii). It was most important to develop species-specific control methods that were effective, inexpensive, and safe and required little training to apply. APPROACHES TO CONTROLLING VAMPIRE BATS When this project began, the morphology, physiology, and distribution of vampires (primarily Desmodus) were reasonably well known, but little was known of their social structure, behavior, movement, population dynamics, and interspecific relationships, and no techniques were avail- able for determining their relative or absolute abundance (Linhart, 1975~. Hence, the proposed initial research was aimed at acquiring some knowl- edge of the behavior and ecology of vampires. The following studies were undertaken during the research phase from 1969 to 1973: · Pharmacological evaluation of chemical agents, such as toxicants and substances that alter physiology or behavior, for controlling vampire bats. O Laboratory evaluation of techniques for applying control agents, in- cluding feeding and grooming behavior of captive vampires, carrier com- pounds or liquid vehicles for application of control agents to livestock, and the application of control agents directly to livestock. o Field evaluation of techniques for applying control, including devices for applying carrier agents and their persistence on livestock, feeding behavior of free-ranging vampires, and treatment of cattle with control agents.
154 SELECTED CASE STUDIES · Estimation of actual numbers and repopulation or recovery rates of natural populations of vampire bats. Additional studies focused on vampire bat movements, sensory mech- anisms associated with locating prey, and pharmacological hazards as- sociated with the application of control agents to livestock. Ecology of Vampire Bats Research identified two potential weak links in vampires. First, Des- moclus produce only one or possibly two young each year (Burns, 1970), although each has a potential longevity of 13-14 years (Linhart, 1973; Trapido, 19461. Therefore, population recovery after reduction by control is slow. Second, vampire populations are concentrated near herds of live- stock to which they fly nightly (Constantine, 19701. Vampires do not migrate, although they can move locally during the breeding season (Burns and Flores Crespo, 19751. They forage every night, except when there is a full moon, but only during the darkest part of the night, either before the moon rises or after it sets (Flores Crespo et al., 19721. Finally, vampire bats form mobile communities that use multiple roosts; the number of vampires in a colony might remain the same, but there can be nightly exchange of individuals among roosts (Mitchell et al., 19731. The most practical time to capture bats in mist nets set around corralled cattle is during the week after a full moon, when the period of complete darkness is still short. Development of Control Methods Two species-specific control methods for reducing vampire bat popu- lations were developed in this project: the systemic method, in which cattle are treated with a chemical; and the topical method, in which cap- tured vampire bats are treated with the same chemical. Systemic Method. The idea of treating cattle with systemic toxicants originated at a Communicable Disease Center (CDC) laboratory working on bats and rabies in Las Cruces, New Mexico. Denny G. Constantine, a CDC veterinarian, was told that a Bayer systemic insecticide, Neguvon, would kill vampire bats. He treated cattle with Neguvon, but no vampires that fed on the treated cattle died. Although Neguvon did not kill vampires in Constantine's experiments, other systemic insecticides recommended by the U.S. Department of Agriculture (USDA) Livestock Insects Inves- tigations Laboratory were tested. The recommendations on agents and
VAMPIRE BAT CONTROL IN LATIN AMERICA 155 dosages were based on margins of safety for cattle. These compounds were tested in Mexico, and one of them, Famophos, gave positive results. In the laboratory, cattle were treated with a 13.2% pour-on formulation of Famophos recommended for the control of screwworm larvae and sucking flies. All vampire bats that fed on these treated cattle died (Mitchell et al., 1970, 197 11. However, research with Famophos was discontinued, because it was not available in Latin America and it was prohibitively expensive. When it was shown that vampires could be killed with a systemic insecticide, DWRC scientists began looking at other substances that could be administered to cattle, especially anticoagulants. Because they bind to blood proteins, anticoagulants are excreted by the cow very slowly and are available longer than most other chemicals for the bat to ingest with a blood meal. Bats ingest about 50% of their body weight in blood at each feeding and concentrate it by excreting water (Breidenstein, 1982), so finding a dose of anticoagulant lethal to the bat but not harmful to cattle appeared feasible. Treating cattle with the anticoagulant actually selected, diphenadione, at a concentration of 1.0 mg/kg gave a wide margin of safety for the cattle and killed all the vampires that fed on blood taken from the treated cattle up to 72 hours after treatment. Diphenadione was not retained in the liver of treated animals, as was another effective anticoagulant, chlorophaci- none (Bullard et al., 1970, 19711. In 1971, diphenadione was administered with a balling gun to cattle in Mexico. Results were good at Rancho Huichi (90.2% reduction in fresh bites) and poor at Rancho Don Tomas (20% reduction in fresh bites) (Mitchell et al., 19711. The poor results at Rancho Don Tomas were attributed to weather that reduced the normal foraging activities of the bats. In 1972, diphenadione was again field-tested in Mexico, but was administered intraruminally with a syringe; this test reduced biting by 93% (Thompson et al., 19721. Topical Method. The idea of topical treatment was based on the like- lihood that bats would ingest a toxicant while grooming. Similar behavior is a basis of common methods of rat control. Greenhall (1965) reported that vampires are thorough groomers and spend a considerable amount of time in this activity. Captive vampires were observed to spend some 2 hours per day grooming (Flores Crespo et al., 1971a) enough time for a control compound on the fur to be ingested. To determine whether there would be sufficient contact between the vampire and its prey for the vampire to receive the chemical from a cow's skin and whether the vampire has a preferred biting area, 49 feedings
156 SELECTED CASE STUDIES were observed in a bat-proof corral under laboratory conditions. Of the 49 bites, 27 were made in the hoof region while the cattle were standing, and 22 on various parts of the body while they were lying down; moreover, each feeding entailed minimal contact between the vampire and its prey (Flores Crespo et al., 1971b). As a followup to the laboratory study, vampires were observed with Starlight night-vision telescopes, which elec- tronically magnify available light, while they fed under natural conditions. Vampires were observed while feeding under normal conditions on three races of cattle Brahma, Charolais, and Holstein. Approximately one- third of the bats landed on the Brahma before biting and feeding, and 31% on the Charolais, but 85% landed directly on the Holstein. Only on the Holstein was there a preferred area for biting: 74.5~o of the bites were on the neck (Flores Crespo et al., 19741. Almost all cattle in the geographical range of vampire bats are Brahma. Because the Brahma are on open range and because only 21% of the vampires that fed on Brahma cattle fed on their necks, the idea of applying a control compound to an appropriate area of the prey animal was discarded as impractical. An alternative topical method would be to apply the toxicant to the bat itself. While writing a manuscript on grooming, DWRC biologist Samuel B. Linhart recognized that vampires are extensive groomers and roost in compact groups separate from beneficial bats in the same cave. Hence, a substance placed on the fur of a captured bat might be passed to other bats in the colony once the treated bat returned to the roost. These ideas led Linhart to develop the topical method now in use. On the basis of the recommendations of DWRC specialists, four chem- icals were tested for toxicity to vampire bats. Chlorophacinone, an anti- coagulant, was the most toxic. Ten carriers were evaluated by mixing them with a dye and applying them to the dorsal surface of vampire bats. Bats were checked several times a day to determine the persistence of the carriers. Three carriers were selected for additional study: a saturated solution of acetone and an acrylic polyester fluorescent paint pigment; petroleum jelly; and a mixture of abalyn (a resin), mineral oil, and poly- ethylene (Epoline- 101. For each candidate carrier, one vampire was treated with a mixture of carrier and a dye and then introduced into a simulated roost containing 19 other vampires. The roost was checked several times a day to determine the degree of transfer among colony members by grooming. Petroleum jelly was superior to the other carriers. In the final test with the simulated roost, 50 mg of chlorophacinone was mixed with 1.5 ml of petroleum jelly and applied to the dorsal surface of one vampire. This vampire was put into the roost with 19 other bats. The carrier bat was found dead on the morning after reintroduction into
VAMPIRE BAT CONTROL IN LATIN AMERICA 157 the roost, and 18 of the 19 other bats died 5-19 days after reintroduction (Linhart, 19701. Several field tests confirmed these results. Vampire bats captured in two caves were treated with a mixture of 50 mg of chlorophacinone and 1.5 ml of petroleum jelly. Six vampires captured in one cave were treated and released; later, 94 dead vampires were found a ratio of 15-16 vam- pires killed to each one treated. After 2 weeks, the caves contained only one live vampire (Linhart et al., 1972~. In another test, bats were captured in mist nets as they flew in to feed on corralled cattle on two ranches, were treated with the control mixture, and were released. Two weeks later, vampire bites on the same cattle had decreased by 95% (Linhart et al., 19721. At first, all vampires captured were treated with the chlorophacinone- petroleum jelly mixture. Later, it was determined that one treated bat would kill 19 others in the roost. There is a high correlation between the number of fresh bites on members of a herd and the number of vampires feeding on the herd. If a herd had 100 fresh bites, the vampire population was estimated to be 100 and only five bats were treated. There were two reasons for changing the control chemical from chloro- phacinone to diphenadione. First, other anticoagulants were as effective as chlorophacinone in controlling vampire bat populations with the topical method. Second, diphenadione was available for manufacture, because the patent had e.~nir~rl The aloe natent is held bv the U.S. Government. which gives per ~A~J~- ~ A4~ In_ r~_~ Rev .,_ -_ ~ ~.~ . ~ ~ . . _ i_ mission to anyone to use the chemical as a vampiricidal agent. Although the topical method is more difficult to use than the systemic method, because it requires night work and the proper identification and treatment of only vampires, it is sometimes the preferred method. Injection of the anticoagulant into the rumen is the easiest way to administer it; but, of the animals commonly attacked by vampires, only cattle have a rumen and can be treated this way. If other livestock or humans are being attacked, the topical method is recommended. Another control method, application of anticoagulants to roost walls, was evaluated in a pilot study in Mexico. Diphenadione in petroleum jelly was placed at vampire roost sites in a tunnel and in a mine (Mitchell et al., 1971, 19721. In both cases, all the vampires were killed. Four non- hematophagous bats also died in the tunnel. In view of these results, control of vampire bats by treating roosts was not recommended. Control Techniques Systemic Treatment of Cattle with Diphenadione. Diphenadione is injected into cattle intraruminally at l.O mg/kg of body weight. The drug
158 SELECTED CASE STUDIES is absorbed and circulates in the blood. Any vampire bat that feeds on a properly treated animal within 72 hours after treatment receives a lethal dose of the drug. Treating all cattle in a herd reduces biting by 90-95% (Thompson et al., 19721. Topical Treatment of Vampire Bats with Diphenadione. Vampire bats are captured with mist nets that are set around corralled cattle or at cave entrances. Approximately l.S ml of a diphenadione-petroleum jelly mix- ture is placed on the dorsal surface of each captured bat, and the bat is released. The bats return to their roost, and, because they live in compact colonies, pass the chemical from one to another. The bats die after in- gesting the chemical during grooming (Linhart et al., 19721. For every treated bat, approximately 20 vampires die at the roost. Vaccines Although topical or systemic use of anticoagulants can reduce the num- ber of bites by up to 96%, and thus reduce secondary losses by a similar amount, rabies can still occur among unvaccinated cattle even when the bat population is reduced. Therefore, both cattle vaccination and bat pop- ulation control are recommended if the aim is to eliminate the disease, rather than only to reduce cattle losses to an acceptable point (Lord, 19801. Piccinini (1977) used both vaccines and anticoagulants in a 500 km2 area in the State of Pernambuco, Brazil. In the 2 years before control, 17,870 cattle were in the study area, 2,342 were not protected by vaccines, and 140 died of rabies. After application of both control methods, the vampire population was reduced by 96.1%. In the 2 years after control, 17,431 cattle were in the area, 4,848 were not vaccinated, and only 2 died of rabies. This shows that reduction of the vampire population gives cattle some protection from rabies without the use of vaccines. It should be noted that the treatments in Piccinini's study were made by scientists; the results might be less impressive under normal operational field con- ditions. KINDS OF ECOLOGICAL KNOWLEDGE USED Ecological Facts Ecological and physiological facts were obtained from published lit- erature and from the observations of experienced people in the field. Experiments were done in simulated and natural situations and yielded
VAMPIRE BAT CONTROL IN LATIN AMERICA 159 much knowledge of the life history and behavior of vampire bats. The ecological observations provided the basis of the control programs. Pilot Studies The studies of topical anticoagulants in simulated roosts constitute an example of the successful use of analog studies, and the pilot tests of both systemic and topical anticoagulants were important in the development of practical control programs. The studies did not all lead directly to such cessful control, but the ones that "failed" enabled workers to avoid ex- pensive and ineffective methods. Project as Experiment Experience gained in the utilization phase led to improvements in the procedures. During that phase, one problem was encountered in Nicara- gua, where 9 of 14 calves died after treatment with diphenadione (1.0 ma/ kg). These calves were less than 3 months old and lacked a fully functional rumen. Further tests showed that calves without a functioning rumen should not be treated (Elias et al., 19784. UTILIZATION AND TRAINING From 1974 to 1978, AID funded DWRC biologists to develop a utili- z.ation or training phase for vampire bat control. It wanted DWRC to take the control methods to Latin American cattlemen and to continue adaptive research to answer questions that could arise. Initially, DWRC biologists conducted training seminars in Latin America, often involving teams of veterinarians organized to vaccinate cattle. The basic training tool was a pamphlet, Chemical Control of Vampire Bats, published in Spanish, Eng- lish, and Portuguese (Mitchell and Burns, 1973a,b, 19781. Later, the Peace Corps in Belize (Mitchell et al., 1975, 1976) and the Pan American Health Organization in Venezuela. Trinidad, and Surinam (Mitchell et al., 1974) became involved. In-country training also occurred. For example, 125 veterinarians from 19 states were trained in Brazil (Mitchell et al., 19764. In 1976, Rodrigo Gonzales presented results of the campaign in Nicaragua at an international conference (Gonzales and Mitchell, 1976), and the Nicaraguan government hosted a seminar on vampire bat control, attended by 46 people from 11 countries (Mitchell et al., 19761.
160 SELECTED CASE STUDIES EFFECTIVENESS OF THE PROGRAM After the publication of our control methods, new questions arose. The possibility of hazards to other bats from use of the topical method was suggested (Turner, 19751. Killing of nonhematophagous bats where vam- pires have been controlled topically has not been reported, and none was killed in the many field tests conducted. Brazilian workers controlled vampires in 3,062 caves and never found a nonhematophagous bat killed by the topical method (Mitchell et al., 19761. The topical method was field-tested in every Latin American country exposed to vampire predation. Results were consistent: 90-95% reduction in the vampire population. The systemic method of treating cattle with diphenadione is even more specific in that it kills only the vampires that are attacking cattle. If cattle are treated with the recommended dosage, 1.0 mg/kg, no chemical is passed in the milk, and residues in tissue are negligible (Bullard and Thompson, 1977; Bullard et al., 1976, 19771. With sound management and husbandry practices in Ecuador, the killing of vampire bats had no effect on milk production. In Nicaragua, under more tropical conditions, mink production increased by 16% (Thompson et al., 19771. These methods of vampire bat control are very effective even when applied by nonprofessionals. For example, in Nicaragua, 20 high-school graduates were trained to apply the control methods over 4 years. They examined 270,825 cattle on 2,124 ranches and found 123,376 fresh vam- pire bites. They treated 148,142 of the cattle and 2,696 vampires and reduced fresh bites by 90% to about 12,000. The annual benefit to farmers from the vampire bat control program in Nicaragua was US$2,414,158, and annual costs, $129,750, for a very favorable benefit-to-cost ratio of about 18.6:1 (Badger and Schmidt, 19791. ACKNOWLEDGMENTS Although I prepared this case study, the solution to the problem is based on an accumulation of many scientific experiments conducted by a host of scientists. Much of the work was done by DWRC scientists in an array of disciplines, including wildlife biology, pharmacology, animal psy- chology, statistics, physiology, electronics, chemistry, nutrition, and ecol- ogy. Undoubtedly, this multidisciplinary approach was influential in solving the problem. Thanks go to Bernardo Villa, Master Zoologist at the University of Mexico, for sharing his vast knowledge of bats. I also wish to give special thanks to Charles Ladenheim (AID retired),
VAMPIRE BAT CONTROL IN LATIN AMERICA 161 who had the insight to support the transition from a research project to an operational program. Research cannot be considered accomplished or successful until its results are made known and implemented in this case, by the small producers of livestock in Latin America. Funds for this research were provided to DWRC by AID under Partic- ipating Agency Service Agreements RA (ID) 01-67 and ID-TAB-000-10- 76. Reference to trade names in this review does not imply U.S. government endorsement. REFERENCES Arteche, E. 1969. Rabia en Rio Grande do Sul, Brazil. Zoonosis 11:34-35. Badger, D. D., and K. M. Schmidt. 1979. Evaluation of the Vampire Bat Control Program. Department of Agricultural Economics, Oklahoma State University, Stillwater, Okla. Available from U.S. Agency for International Development, Washington, D.C. Baer, G. M. 1975. Rabies in nonhematophagous bats. Pp. 79-98 in G. M. Baer, ed. The Natural History of Rabies. Vol. 2. Academic Press, New York. Breidenstein, C. P. 1982. Digestion and assimilation of bovine blood by a vampire bat (Desmodus rotundas). J. Mammal. 63:482-484. Bullard, R. W., and R. D. Thompson. 1977. Efficacy and safety of the systemic method of vampire bat control. Interciencia 2:149-152. Bullard, R. W., S. R. Kilburn, and G. Holguin. 1970. Effectiveness of chlorophacinone (DRC-3776) as a livestock systemic for control of vampire bats. Pp. 33-34 in 1970 Annual Report, Denver Wildlife Research Center, Denver, Colo. Bullard, R. W., S. R. Kilburn, and G. Holguin. 1971. Livestock systemic technique for control of vampire bats (Desmodus rotundas). Pp. 36-41 in 1971 Annual Report, Denver Wildlife Research Center, Denver, Colo. Bullard, R. W., R. D. Thompson, and G. Holguin. 1976. Diphenadione residues in tissues of cattle. J. Agric. Food Chem. 24:261-263. Bullard, R. W., R. D. Thompson, and S. R. Kilburn. 1977. Diphenadione residues in milk of cattle. J. Agric. Food Chem. 25:79-81. Burns, R. J. 1970. Twin vampire bats born in captivity. J. Mammal. 51:391-392. Burns, R. J., and R. Flores Crespo. 1975. Local movement and reproduction of common vampire bats in Colima, Mexico. Southwest. Nat. 19:446-449. Constantine, D. G. 1969. Trampa portatil pare vampires usada en programas de campana antirrabica. Boll Of. Sanit. Panam. 67:39-42. Constantine, D. G. 1970. Bats in relation to health, welfare, and economy of man. Pp. 319-449 in W. A. Wimsatt, ed. Biology of Bats. Vol. 2. Academic Press, New York. Dalquest, W. W. 1954. Netting bats in tropical Mexico. Trans. Kans. Acad. Sci. 57:1- 10. Elias, D. J., R. D. Thompson, and P. J. Savarie. 1978. Effects of the anticoagulant diphenadione on suckling calves. Bull. Environ. Contam. Toxicol. 20:71-78. Flores Crespo, R., S. B. Linhart, and R. J. Burns. 1971a. Comportamiento del vampire (Desmodus rotundas) en cautiverio. Southwest. Nat. 17:139-143. Flores Crespo, R., R. J. Burns, and S. B. Linhart. 1971b. Comportamiento del vampire (Desmodus rotundas) durante su alimentacion en ganado bovine en cautiverio. Tecnica Pecuaria en Mexico 18:40-44.
162 SELECTED CASE STUDIES Flores Crespo, R., S. B. Linhart, R. J. Burns, and G. C. Mitchell. 1972. Foraging behavior of the common vampire bat related to moonlight. J. Mammal. 53:366-368. Flores Crespo, R., SO Said Fernandez, R. J. Burns, and G. C. Mitchell. 1974. Observaciones sobre el comportamiento del vampire comun (Desmodus rotumlus) al alimentarse en condiciones naturales. Tecnica Pecuaria en Mexico 27:39-45. Gonzales, R., and G. C. Mitchell. 1976. Vampire bat control programs in Latin America. Proc. Vertebr. Pest Control Conf. 7:254-257. Greenhall, A. M. 1963. Use of mist nets and strychnine for vampire bat control in Trinidad. J. Mammal. 44:396-399. Greenhall, A. M. 1965. Notes on behavior of captive vampire bats. Mammalia 29:441- 451. Greenhall, A. M. 1970. Vampire bat control: A review and proposed research programme for Latin America. Proc. Vertebr. Pest Control Conf. 4:41-54. Irons, G. V., R. B. Eads, J. E. Grimes, and A. Conklin. 1957. The public health importance of bats. Tex. Rep. Biol. Med. 15:292-298. Kverno, N. B ., and G. C. Mitchell. 1976. Vampire bats and their effect on cattle production in Latin America. World Anim. Rev. 17:1-7. Linhart, S. B. 1970. Work Unit DF-101.1: Basic Research in Mammal and Bird Damage Control: Chemicals. 1970 Annual Progress Report, Denver Wildlife Research Center, Denver, Colo. Linhart, S. B. 1973. Age determination and occurrence of incremental growth lines in the dental cementum of the common vampire bat (Desmodus rotundas). J. Mammal. 54:493- 496. Linhart, S. B. 1975. The biology and control of vampire bats. Pp. 221-241 in G. M. Baer, ed. The Natural History of Rabies. Vol. 2. Academic Press, New York. Linhart, S. B., R. Flores Crespo, and G. C. Mitchell. 1972. Control of vampire bats by topical application of an anticoagulant, chlorophacinone. Boll Of. Sanit. Panam. 6:31- 38. Lord, R. D. 1980. An ecological strategy for controlling bovine rabies through elimination of vampire bats. Proc. Vertebr. Pest Control Conf. 9:170-175. Mitchell, G. C., and R. J. Burns. 1973a. Combate Quimico de los Murcielagos Vampiros. Regional Technical Assistance Center, U.S. Embassy, Mexico City, Mex. Mitchell, G. C., and R. J. Burns. 1973b. Chemical Control of Vampire Bats. Denver Wildlife Research Center, Denver, Colo. (mimeo) Mitchell, G. C., and R. J. Burns. 1978. Combate Quimico aos Morcegos Hematofagos. Ministry of Agriculture, EMBRAPA, Coronel Pacheco, Braz. Mitchell, G. C., R. Flores Crespo, R. J. Burns, S. Said Fernandez, and S. B. Linhart. 1970. Vampire Bats: Rabies Transmission and Livestock Production in Latin America. 1970 Annual Report of the Denver Wildlife Research Center's Mexican Field Station, Palo Alto, Mex. Mitchell, G. C., R. Flores Crespo, R. J. Burns, and S. Said Fen~andez. 1971. Vampire Bats: Rabies Transmission and Livestock Production in Latin America. 1971 Annual Report of the Denver Wildlife Research Center's Mexican Field Station, Palo Alto, Mex. Mitchell, G. C., R. Flores Crespo, R. J. Burns, and S. Said Pernandez. 1972. Vampire Bats: Rabies Transmission and Livestock Production in Latin America. 1972 Annual Report of the Denver Wildlife Research Center's Mexican Field Station, Palo Alto, Mex. Mitchell, G. C., R. J. Burns, and A. L. Kolz. 1973. Rastreo del comportamiento nocturno de los murcielagos vampiros por radio-telemetria. Tecnica Pecuaria en Mexico 24:47- 56. Mitchell, G. C., R. J. Burns, J. W. De Grazio, and D. J. Elias. 1974. Vampire Bats:
VAMPIRE BAT CONTROL IN LATIN AMERICA 163 Rabies Transmission and Livestock Production in Latin America. 1974 Annual Report. Denver Wildlife Research Center, Denver, Colo. Mitchell, G. C., R. D. Thompson, D. J. Elias, C. E. Shuart, R. W. Bullard, P. J. Savage, and R. J. Burns. 1975. Vampire Bats: Rabies Transmission and Livestock Production in Latin America. 1975 Annual Report. Denver Wildlife Research Center, Denver, Colo. Mitchell, G. C., R. D. Thompson, D. J. Elias, C. E. Shuart, and R. W. Bullard. 1976. Vampire Bats: Rabies Transmission and Livestock Production in Latin America. 1976 Annual Report. Denver Wildlife Research Center, Denver, Colo. Molina Solis, J. F. 1896. History del Descubrtmiento y Conquista de Yucatan, con una Resena de la History Antigua de la Peninsula. R. Caballero, Mer~da, Mex. Piccinini, R. S. 1977. The Use of Diphenadione (2-Diphenylacetyl-1,3 indandione) for Vampire Bat Control in Endemic Rabies Areas, Northeastern Brazil. Master's thesis, University of California, Davis. Thompson, R. D., G. C. Mitchell, and R. J. Burns. 1972. Vampire bat control by systemic treatment of livestock with an anticoagulant. Science 177:806-808. Thompson, R. D., D. J. Elias, and G. C. Mitchell. 1977. Effects of vampire bat control on bovine milk production. J. Wildl. Manage. 41:736-739. Trapido, H. 1946. Observations on the vampire bat with special reference to longevity in captivity. J. Mammal. 27:217-219. Turner, D. C. 1975. The Vampire Bat. John Hopkins University Press, Baltimore. Uieda, W. 1982. Aspectos do Comportamento Alimentar das Tres Especies do Morcegos Hematofagos (Chiroptera, Phyllostomidae). Master's thesis, Instituto de Biologia da Universidade Estadual de Campinas, Braz. Venters, H. D., W. R. Hoffert, J. E. Scatterday, and A. V. Hardy. 1954. Rabies in bats in Florida. Am. J. Public Health 44: 182- 185. Villa, R. B. 1966. Los Murcielagos de Mexico. Institute of Biology, National Autonomous University, Mexico City, Mex. Villa, R. B. 1969. The ecology and biology of vampire bats and their relationship to paralytic rabies. Report to the Government of Brazil. Rep. No. TA 2656. U.N. Devel- opment Programme/Food and Agriculture Organization. Rome. Committee Comment The control of pests is a common theme in humans' attempts to live in a world populated with animals and plants, and that theme is reflected in several of the cases discussed in this report (Chapters 14, 15, and 244. Many serious pests are controlled only poorly, despite great expense; those controlled successfully usually have idiosyncrasies of life history that make them vulnerable, and successful control depends on detailed knowledge of those idiosyncrasies. Early attempts to control vampires did not rely on knowledge of the animals' natural history; they were ineffective and destructive. The re- sulting careful and thorough research into the natural history of vampires by the Denver Wildlife Research Center (DWRC) exemplifies an approach
164 SELECTED CASE STUDIES that is usually needed for pest control; the idiosyncrasies discovered rep- resent a certain amount of the luck that so often seems to accompany successful cases. DWRC biologists studied the behavior, dispersal, physiology, and ecol- ogy of vampires, using field and laboratory experiments and observations. These studies and literature review revealed important aspects of vampires' natural history that made them susceptible to control. Two of these aspects commonly help in pest control: the bats have a low reproductive rate, which meant that less powerful control would be needed to keep their numbers down, and they do not migrate. Successful control also depended on several idiosyncrasies. The bats, because of their diet of blood, are much more susceptible to anticoagulants than cattle are. They forage only on dark nights, so when the moon rises shortly after sunset or sets shortly before sunrise, their activity is confined to short periods, and that makes them easier to trap. They roost extremely close to each other and they groom each other both characteristics that favor transfer of vampiricides between individuals and that make it un- necessary to treat more than a few members of each roost. Thus, successful control in this case depended on thorough research into the pests' natural history, which is nearly always needed, and on the vulnerabilities that the research revealed. The vulnerable points might not exist, but in the absence of thorough research they will almost surely not be found.