The Successful Hand Rearing of Two Orphaned Vampire Bats
Susan M. Barnard, Assistant Curator
Department of Herpetology
Zoo Atlanta, Atlanta, GA
Nancy Sachs, Atlanta, GA
Vampire bats give birth throughout the year, having no well-defined mating season (Turner, 1975). The gestation period is approximately five (Wimsatt and Trapido, 1952) to seven months (Schmidt and Manske, 1973). At birth, vampires are well-developed, with open and functional eyes (Schmidt, 1978). Birth weight ranges from 5 to 7 grams (Schmidt, 1988; Barnard and Sachs, unpublished data). Young vampire bats develop slowly compared to other microchiropterans, and weaning does not take place before nine to ten months of age (Schmidt and Manske, 1973; Schmidt, et al., 1980).
|On 9 July 1990, 30 Vampire bats were received at the residence of the first author in Morrow, GA. They were immediately divided into two arbitrary groups of 15 members each. The bats were housed in specially-designed, low-maintenance cages (FIG. 1) measuring 91.4cm (36 in.) high by 63.5cm (25 in.) wide by 50.8cm (20 in.) deep. The cages were constructed from laminated plastic, and the walls and cage top were lined with 1/4-inch polyethylene mesh. The bats were fed either citrated porcine or bovine blood, served in ice cube trays at room temperature.|
|Fig. 1. Cage used to house vampire bats|
The bats remained in Georgia for four months, and during this time, six pups were born. Dickson and Green (1970) also reported births soon after arrival of their bats, but all of their neonates died a few hours after parturition. Of the six born, three were recovered for handraising, two were raised to adulthood by their natural mothers, and a two-month-old pup was adopted by a lactating female. The adoption was surprising because the young bat's mother was still in the colony. Unfortunately, the pup was killed at approximately six months of age. The authors presumed its death was a result of nursing attempts on other members of the group, which included adults of both sexes. Wimsatt and Guerriere (1961) observed that adults occasionally killed mobile young attempting to suckle.
The first pup, a female with placenta still attached, was retrieved from the cage floor, but died of peritonitis ten days later. The second pup, a five-week old female, was raised to maturity after she was retrieved from the side of the cage suffering from hypothermia and bite wounds. Because one bat repeatedly flew out of the cage when the door was opened, it became necessary to confine her to another cage. Unfortunately, she may have been the dam of the second pup. The third pup, a five-day old female, was also hand-raised successfully after accidental separation from her dam during loading of the shipping crates for the bats' transport to another facility.
Although many inquiries were made by the authors concerning hand-raising vampire bats, it remains unconfirmed whether anyone has done so. Therefore, it was not possible to determine if vampire bat neonates are lactose-intolerant. Taking a conservative approach, and with the assistance of staff members at Pet-Ag., Inc., the authors selected a lactose-free formula comprising 10g of Multi-Milk® powder (Pet-Ag, Inc.), 2g of dextrose powder, 75ml of tap water, 2 drops of Avitron® multivitamins (Lambert Kay) and 4 drops of Avimin® multiminerals (Lambert Kay). These ingredients yielded approximately 14.0% solids (7.5% fat, 4.1% protein and 2.3% carbohydrate). The amount of water was reduced from 75ml to 60ml when each pup reached the age of six weeks. They consumed slightly different quantities of formula. TABLE 1 lists the mean daily intake for the two bats.
Feeding Regimes for Hand Raising
Desmodus pups apparently digest their food relatively slowly compared to other microchiropterans. When attempts were made to feed them every two hours, their abdomens began to swell and the pups became lethargic. Feedings were quickly altered to three and four-hour intervals. The problem of abdominal swelling is discussed in more detail below. Like other microchiropterans, however, feeding commenced at 0600 hours and ended at 2400 hours. Before feeding the pups, the formula was warmed in a hot water bath, and the desired temperature was checked by placing a drop or two of the formula on the inside of the wrist.
The first author has observed gastric distress in insectivorous bat pups that were allowed to suck, rather than lap, formula from the end of a syringe. To avoid similar problems with the vampires, the young were encouraged to lap formula delivered to them from a tuberculin syringe (FIG. 2). Even so, abdominal swelling became increasingly pronounced, and between the fifth and tenth days, the swelling in both bats became life threatening. Shepherd (pers. comm.) suggested administering metoclopramide hydrochloride syrup to increase the rate of food passage. One drop of syrup was mixed with 4 drops of water. Two drops of this mixture was added to 1ml of milk replacer at every meal for four to six days, by which time the abdominal swelling was reduced. At about this time however, both bats began refusing food. Although Schmidt (in litt.). had suggested regularly offering infant vampire bats a few drops of blood he did not specify at what age to begin such supplements. When one part blood was added to ten parts milk replacer, both bats ate ravenously.
|Fig. 2. Two-week-old vampire bat lapping blood from the end of a tuberculin syringe. (Photo courtesy of Dany Nieves).||Fig. 3. Three and one-half-month old vampire bat learning self-feeding skills by lapping blood from a small culture dish. (Photo courtesy of Dany Nieves).|
Not feeding the pups until their previous meal had been completely digested, also helped to avoid gastric distress. Digestion was determined visually. For example, after pups had been fed, the milk replacer could be seen in their stomachs through the skin. The pups were not fed again until the food was no longer visible.
Food sharing among vampire bats is well-documented (Rasweiler, 1979; Schmidt et al., 1980; Wilkinson, 1984, 1988). When females regurgitate blood to their young, such behavior not only serves to supplement them while they are learning hunting skills, but also serves to innoculate their digestive systems early in life with symbiotic bacteria (Muller, Pinus and Schmidt as cited in Wilkinson, 1988). As it was not possible to feed our bats regurgitated blood, it was suggested that feces from adult bats be added to the milk replacer (Wilkinson, pers. comm.; Schmidt, in litt..). The amount of feces added to the formula was determined subjectively based on color. The mixture finally used comprised one FRESH fecal pellet mixed with 0.4ml of tap water. Of this mixture, 0.1ml was added to the formula and fed to the pups for one feeding, twice weekly, when they were between the ages of one and three months. When the bats were between three and five months of age, 0.2ml of this mixture was added to the formula for one feeding each week. Because dietary comparisons with other hand-raised vampire bats could not be made, it also could not be determined if feces had any effect on the pups' development.
The pups were weaned by decreasing their intake of milk replacer, while increasing the volume of blood (for approximate ages of pups, and the ratio of blood to milk replacer, see TABLE 2). It was also necessary to prepare them to feed themselves. When each pup reached the approximate age of thirteen weeks, it was introduced to a 1˝-inch glass culture dish (FIG. 3) in which the normal ration of blood-formula mixture was placed. In the event a pup refused food from the dish, additional food was held in reserve, to be fed later by syringe. Although the pups were initially reluctant to accept the unfamiliar object, they quickly adjusted and syringe feeding was discontinued.
Between eighteen and twenty-one weeks of age, the food was divided into two dishes; one dish contained the blood-milk mixture and the other pure blood. The dish of pure blood was left in each pups' cage during the evening hours (approx. six to eight hours). Until the pups learned to take food on their own (between one and two weeks), they were hand-fed from the dish containing the milk-blood mixture. Unfortunately, to the authors' frustration, blood clots in milk, usually within ten minutes or less. If the pups failed to consume their food before clotting occurred, a fresh mixture had to be offered to make up the amount that had not been consumed.
Considering the relatively long time that wild vampire pups suckle, and the observations made by Joermann (1988) on milk dependence of captive juvenile Desmodus, the authors did not remove milk from the diet until the animals reached twenty-four weeks of age.
|The vampire pups selected tight places in which to roost, and therefore they were housed in the same manner as described by Barnard (1991) for captive crevice-dwelling species. Two styrofoam coolers were used (FIG. 4), a small one (containing the bat) that measured 40.6cm (16 in.) long by 27.9cm (11 in.) deep by 33cm (13 in.) wide and a large one (to hold the small cooler) that measured 53.3cm (21 in.) long by 33cm (13 in.) deep by 38.1cm (15 in.) high. The small cooler was ventilated by punching holes in it with a ball-point pen from the inside to the outside.|
When the pups reached between two and three months of age, they became too agile for the limited space in the styrofoam cooler. Each was transferred to a cage like the one depicted in FIGURE 1. Because one bat had to be transferred during cold weather, and because the cage was relatively large (see measurements given above), it was not possible to keep the bat warm enough without the use of a heating pad. The pad (set on low) was leaned flat against the back wall of the cage. Cork bark, with a sheepskin drape, was leaned against the pad. In this manner the bat was able to select its own temperature gradient.
FIGURE 5 compares the growth rates of one mother-reared vampire pup (Jenness and Studier, 1976) with the authors' two hand-raised bats. Factors contributing to the initial slow growth of the hand-raised bats probably included stress from losing their dams, the adjustment to substitute teats, and the rapid change in diet. At approximately fifteen weeks of age, however, the hand-reared bats not only caught up with the mother-reared pup, but surpassed it in weight. It is not known whether the quantity and/or nutritional content of the milk replacer resulted in the rapid growth rate of the hand-raised bats. Wilkinson (pers. comm.) proposed that the difference in growth curves between the two groups suggests that the long period it takes wild bats to reach adult body weight could be a result of low milk flow by females, rather than a predetermined slow growth rate.
The pups' neonatal tractability diminished rapidly. FIGURE 2 shows a two-week-old pup adopting an unrestrained feeding posture, which the authors quickly learned to respect. Pups are capable of inflicting painful bites early in life, although they generally hesitate to do so.
Both bats have been introduced into a captive colony comprising thirteen individuals. The hand-raised bats were not marked, so the possibility of future behavioral observations has been lost. It is known, however, that the younger and slightly smaller bat integrated with the group on the first day of introduction. Prior to this, the animal had not been exposed to the colony. The other bat, however, had been exposed to the group previously for approximately one month. Regardless, it roosted alone for seventeen days. It is not known if its isolation was by choice, or if it had received aggression from members of the group.
The authors thank Dr. Gerald Wilkinson, Dr. Uwe
Schmidt, Dr. Mimi Shepherd and members of the staff at Pet-Ag., Inc. for their
time and assistance. We also thank Dr. Debra Forthman, Dr. Dietrich Schaaf, Mr.
John Fowler, Mr. Sam Winslow and Mr. Reg Hoyt for their helpful comments in
reviewing this manuscript.
Products Mentioned in the Text
Avimin® multiminerals - UPCO, P.O. Box 969, St. Joseph, MO 64502. Tel. (816) 233-8800.
Avitron® multivitamins - see Avimin® above.
Culture dishes - Carolina Biological Supply Co., Burlington, NC 27215, Tel. (800) 632-1231 (NC); outside NC (800) 334-5551; Gladstone, OR 97027, Tel. (503) 656-1641 (OR); outside OR (800) 547-1733.
Dextrose powder - Humco Laboratory, Texarkana, TX 75501; UPCO (see Avimin® above); also available in pharmacies.
Metoclopramide hydrochloride - A.H. Robbins Company Pharmaceutical Division, 1407 Cummings Dr., Richmond, VA 23220; also available in pharmacies.
Multi-Milk® Powder - Pet-Ag, Inc., 30W432 Rt. 20,
Elgin, IL 60120, Tel. (800) 323-0877; in IL (708) 741-3131.
Barnard, S.M. 1991. The Maintenance of Bats in Captivity. Zoo Atlanta, Atlanta, GA.
Dickson, J.M. and Green, D.G. 1970. The vampire bat (Desmodus rotundus): Improved methods of laboratory care and handling. Lab. Anim., 4:37-44.
Greenhall, A.M. 1988. Feeding behavior. In: Greenhall, A.M. and Schmidt, U. (Eds.) Natural History of Vampire Bats. CRC Press, Inc., Boca Raton, FL. pp. 111-131.
Jenness, R. and Studier, E.H. 1976. Lactation and milk. In: Baker, R.J., Jones, J.K, Jr. and Carter, D.C. (Eds.), Biology of Bats of the New World Family Phyllostomatidae, Part I. Texas Tech University, Lubbock, TX. pp. 201-218.
Joermann, G. 1988. Care of vampire bats in captivity. In: Greenhall, A.M. and Schmidt, U., (Eds.), Natural History of Vampire Bats. CRC Press, Inc. , Boca Raton, FL. pp. 227-232.
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Schmidt, U. 1990. Personal correspondence. University of Bonn, Germany.
Schmidt, U. and Manske, U. 1973. Die Jugendentwicklung der Vampirfledermause (Desmodus rotundus). Z. f. Saugetierkunde, 36:360-370.
Schmidt, C., Schmidt, U., and Manske, U. 1980. Observations of the behavior of orphaned juveniles in the common vampire bat (Desmodus rotundus). Proc. 5th Intl. Bat. Res. Conf., Texas Tech Press, Lubbock, TX.
Shepherd, M. 1990. Personal communication, For Pet's Sake Veterinary Clinic, Decatur, GA.
Turner, D.C. 1975. The Vampire Bat: A Field Study in Behavior and Ecology. The Johns Hopkins University Press, Baltimore, MD.
Wilkinson, G.S. 1984. Reciprocal food sharing in vampire bats. Nature, London, 308:181-184.
Wilkinson, G.S. 1988. Social organization and behavior. In: Greenhall, A.M. and Schmidt, U. (Eds.), Natural History of Vampire Bats. CRC Press, Inc., Boca Raton, FL. pp. 85-97.
Wilkinson, G.S. 1990. Personal communication. University of Maryland, College Park, MD.
Wimsatt, W.A- and Trapido, H. 1952. Reproduction and the female reproductive cycle in the tropical American vampire bat, Desmodus rotundus rotundus.. Am. J. Anat., 91:415-45.
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*Article originally published in Animal Keeper's Forum, Vol. 19, No. 8, 1992.
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