VAMPIRE BAT CONTROL IN THE AMERICAS: A REVIEW AND PROPOSED PROGRAM FOR ACTION’ Arthur M. Greenhall, B.A., M.S., F.L.S.* Vampire bats, which transmit paralytic rabies, pose a major obstacle to livestock raising in areas extending from Mexico to Argentina. More widespread use of available bat control meas- ures could stop large-scale animal losses and should be con- tinued. However, it is important that the innocuity and safety of recently developed anticoagulant techniques be amply dem- onstrated before the latter become widely used. Introduction stock seems to have offered a more accessible, more plentiful, and perhaps more desirable The Vampire Bat Problem source of blood than has the native fauna. In any case, Desmodus has increased its numbers Restricted to the Western Hemisphere, vam- and distribution wherever livestock raising has pire bats pose a unique veterinary public health been introduced. Also, manmade structures problem. These bats feed exclusively on the have provided supplemental roosts for this blood of vertebrates, including man, and so in- adaptable mammal. Th& result is that Desmodus fected vampires are apt to transmit paralytic and rabies now range together over most of the rabies and other pathogenic diseases in the significant livestock-raising areas from northern course of normal feeding. Aside from this, how- Mexico to central Argentina. ever, the victims’ loss of blood alone may repre- Besides spreading disease, nightly attacks by, sent a serious problem. vampire bats can debilitate livestock and poul- Vampire bats belo’ng to .the subfamily try, often exsanguinating the latter. The milk Desmodontinae of the Neti World Leaf-Nosed yield of severely bitten cows drops markedly, Bats, the Phyllostomatidae. There are three and sows bitten on their teats are often unable known species: Desmodus rotundus, the com- to nurse their young. Since a single bat may mon vampire bat; Diaemus youngi, the white- consume a daily average of 20 ml of blood, winged vampire bat; and Diphylla ecaudata, the equivalent to 15 pints per year, and since sev- hairy-legged vampire bat. All are subject to in- eral hundred Desmodus may occupy a single fection with rabies, but Desmodus is the most roost, predation can be intense. important transmitter of the disease. Moreover, open wounds caused by bat bites Ever since Latin America was first settled by and aggravated by anticoagulants in the bats’ Europeans, the presence of European-type live- saliva will continue to ooze blood for many hours and may attract blood-feeding arthro- lAn abridged and updated version of the article pods. Other pathogenic organisms such as published in Spanish in Boletin de la Oficina Sanitaria Panamericana, Volume LXXI, No. 3, September 1971, trypanosomes may thus enter the prey’s blood- pp. 231-246. stream after the bats have finished their work ZFormerly Bat Ecologist, Food and Agriculture Organization, Research ProJect on Paralytic Rabies (FAO MEX 16/UNDP 242), National Institute of Live- stock Research, Palo Alto, Mexico, D.F., Mexico. Pres- Control Other Bat Species ently Research Associate! National Museum of Natural of History, The Smithsoman Institution, Washington, D.C. 20560, U.S.A. The subject of vampire bat control is closely 30 Greenhall . VAMPIRE BAT CONTROL IN THE AMERICAS 31 linked to control of various non-vampire bat tion. The latter, after all, cannot prevent bats species (2). While these other bats do not attack from biting cattle. To facilitate control where man and livestock directly, any bat can become vampires are a serious threat to peasant farm- diseased, and certain types have become more ing, livestock owners can cooperate with numerous by adapting their feeding and roost- national agricultural authorities in carrying out ing habits to human settlement. Some have the control measures desired. even abandoned caves and hollow trees for structures occupied by man or domestic ani- mals, thus increasing the possibility of disease Methods of Limited Usefulness transmission. In particular, nine non-vampire species fre- Dynamite and poison gas. The use of dyna- quently found infected with rabies should re- mite and poison gas has been discontinued in ceive close ecological and epidemiologic surveil- several countries because these methods tend to lance (3). These bats share certain attributes be ineffective, nonselective, and dangerous to with vampires: they may be found in the same man. Brazilian authorities have reported that roost; they are widely distributed throughout the gas “Rhodiatrox” (a phosphorous-base the tropics; they sometimes occupy buildings compound) has destroyed bats in caves when frequented by domestic animals and people; used alone or together with dynamite (4). How- they live in groups or colonies; they have sharp ever, the number of vampires killed was not teeth capable of breaking human skin; they can mentioned. fly considerable distances; they frequently Argentine authorities have reported using change their roosts; they do not hibernate; and cyanide gas to kill vampires (5), and were it not they are beneficial as insect-eaters, plant pol- for the danger to man this gas might be con- linators, and seed dispersers. The species in sidered useful when Desmodus is found in colo- question are as follows: Noctilio leporinus, the nies not associated with other bat species. fisheating bat; Phyllostomus hastatus, the However, the gas clearly poses too great a greater spear-nosed bat; Glossophaga soricina, threat for its users. In July 1972 vampire bat the long-tongued bat; Carollia perspicillata, the control experiments were being conducted as short-tailed fruit bat; Artibeus jamaicensis, the part of a collaborative control effort by Argen- Jamaica fruit bat; Artibeus lituratus, the Trini- tina’s Ministry of Agriculture and the Pan Ame- dad fruit bat; Tadarida brasiliensis, the Brazil rican Zoonoses Center. The Argentine mam- free-tailed or guano bat; Molossus ater, the large malogist in charge of the program was inspect- free-tailed house bat; and Molossus molossus, ing the results of fumigating a bat-infested well the small free-tailed house bat (2, 6). when his gas mask failed and he died. Rescue efforts were hampered by cyanide gas remain- Techniques of Vampire Bat Control ing in the well (27). Smoke and fire: This method must be used General Considerations cautiously when exterminating bats in hollow trees. If the inside of the tree should ignite, the Cost should not be the primary factor upon roost will be completely ruined as a natural which a policy of vampire control is based. trap. However, any estimation of cost should include Artificial illumination: Some ranchers in personnel salaries and per diem ,payments, as Mexico and elsewhere have frustrated vampire well as expenditures on transportation, mate- attacks by providing flood-lighting or other rials, and equipment. bright illumination for cattle corrals and swine In seeking to protect the cattle of a rabies- enclosures. Other livestock owners, however, prone area, vampire bat control may be a valu- have abandoned this practice. Despite these able and necessary adjunct to rabies vaccina- mixed results, it is clear that the weak light of 32 PAHO BULLETIN . Vol. VIII, No. I, 1974 . candles, kerosene lamps, and many ordinary Protective Screening: Metal or plastic screen- bulbs have little or no deterrent effect. ing with openings no larger than 22 mm will effectively prevent vampires and most other bats from entering livestock enclosures or Other Established Methods houses, provided the screening is carefully in- stalled and maintained. In Yucatan, Mexico, the Electrocution: An elaborate network for practice of using screens to cover natural wells electrocuting cave bats has been established in (cenotes) to prevent the bats from using them Sao Paulo, Brazil. Unfortunately, besides killing as roosts has been widely adopted with good vampires it has also killed large numbers of results. other bats (9). Firearms: Shooting vampire bats inside caves Seine and trammel nets: Simple seine and or hollow trees and shooting fruit bats out of trammel nets with half-inch mesh and soft lay tall palm trees are practical extermination fiber have been used successfully to trap vam- methods that are used frequently in Trinidad pires at entrances to hollow trees. They have and Tobago. Appropriate weapons include .22 also been effectively deployed across the open- caliber pistols, revolvers, and rifles; shotguns ings of caves, tunnels, mine shafts, culverts, and using scatter-shot cartridges; and .410 shotguns wells by using some sort of makeshift frame to using the smallest possible shot sizes (shot brace the netting (6). numbers 8-l 2). Mist nets: Japanese nylon mist nets will ef- Strychnine: This method exploits the vam- fectively enmesh vampires if set along suspected pires’ habit of returning to feed at fresh wounds flyways and around livestock corrals, huts, made the previous night. If a drop of sugar dwellings, or shelters in which animals or syrup supersaturated with strychnine sulphate humans have been attacked by vampire bats. is properly applied to such a wound, it will kill They were first used in Trinidad and Tobago as the vampire within seconds after its tongue a control method and have superseded almost touches the treated bite. This technique, de- all other methods in that country (II). A de- veloped in Trinidad (11), has been used suc- tailed description of mist net rigging, operation, cessfully in Mexico and Brazil on types of live- and maintenance, as well as selection of net stock capable of being touched or handled sites, is provided in the publication Bats and without difficulty. While the method is safe Bat Banding (6). enough for use with animals and poultry, ex- The mist-net method of vampire control has treme care must be taken to make sure this been evaluated at two sites in Mexico: at a dangerous poison is kept away from un- government cattle ranch in the State of Puebla authorized persons, children, and pets.