Chapter Seven

FEEDING NEWLY TRANSPORTED BATS

Insectivorous Species
Bats from the wild or from captivity will be stressed from the trauma of transport and sudden changes in environment. On arrival at a new facility, bats should be isolated (quarantined) in a quiet area, and at the appropriate temperature and humidity ranges for the species. A bat scheduled for rehabilitation must be identified by genus and species as quickly as possible, and the animal's normal weight determined by researching the literature, in order to estimate the amount of food it will require. For information about native bat identification and approximate weights and sizes, refer to Barbour and Davis (1969), Burt and Grossenheider (1964) and Tuttle (1988).

Wild bats can be taught to feed themselves from a dish (FIG. 47) in a relatively short period of time. The speed at which different species achieve this skill differs. I can usually train big brown bats (Eptesicus fuscus) to eat mealworms from a dish in a few minutes. Hoary bats (Lasiurus cinereus), on the other hand, may take up to a week or more; consequently, the methods vary slightly as follows:

Figure 47.  Insectivorous bats should be fed and watered in shallow, accessible containers such as Petri dishes or culture dishes.  Glass dishes are preferable to plastic because mealworms can climb out of plastic ones when the plastic dishes become scratched (photo courtesy of C.J. Marris, Atlanta, GA).

1) Big brown bats - set a Petri dish containing an evening's ration of food on a table or other surface. With the bat resting in a cloth with its head exposed, offer it a decapitated mealworm from the end of a pair of forceps (FIG. 48) as it bares its teeth. Not all wild bats display this defensive behavior, and it may become necessary to smear the larva's viscera over the animal's lips. Allow the bat to consume the mealworm, then rapidly place the next one in its mouth with the head intact. As the bat is eating it, place the animal's head in close proximity to the larvae in the dish (FIG. 49). While the bat scans the larvae, raise one of the worms slightly above the others and hold it there until the bat takes it. This step may have to be repeated once or twice more before the bat picks up one of the larvae on its own. While the bat remains preoccupied with the dish of larvae, set both into its cage with as little disturbance as possible.

Figure 48.  The proper procedure for hand-feeding insects to bats (photo courtesy of Gregory C. Greer, Marietta, GA).

Figure 49.  The proper handling technique to teach bats to self-feed (photo courtesy of Wild Birds Unlimited, Inc., Colorado Springs, CO).

2) Hoary bats - if the big brown bat technique fails, I use a technique similar to that described by Nellis (1969): place the bat in a container such as an uncovered, 21-cup Rubbermaid® canister with the day's ration. It is likely that the bat will become so agitated by the larvae crawling over it, that it will snap at them and begin eating. I usually try to get the bat to accept decapitated worms during this time.

Regardless of the method used, or the degree of difficulty one has in training bats to eat, it is necessary to insure that the animal has a Petri dish of mealworms in its cage throughout its nightly active period. Wilson (1988) emphasized the importance of maintaining the same feeding routine during the training process. He wrote, "Everything should be done exactly the same way, with the same daily routine, so that bats become conditioned to meal time. Quiet surroundings with a minimum of disturbance will increase the chance of successful feeding."

Not all insectivorous bats will accept food from the flooring of cages. Racey (1987) reported that bats which hang free, such as horseshoe bats (rhinolophids) and Old World leaf-nosed bats (hipposiderids), will not descend to a dish on the cage floor. Some, however, will eat from elevated dishes. I use coop cups (FIG. 50) for this purpose.

Figure 50. Some bats (e.g. rhinolophids, hipposiderids, mormoopids) refuse to feed from the floor of their cage.  This problem is solved by using coop cups, typically used to feed and water birds.  Cups can be hooked on the mesh sides of bat cages and are available in a variety of sizes.

Never hand-feed a bat that is willing to eat on its own; further, any bat that eats from a dish will probably drink water from one. Until a bat does master self-feeding, offer it water from an eye-dropper or syringe.

Bats that self-feed often refuse food when shipped from one facility to another. This problem is easily overcome by holding it in a soft cloth over a dish of mealworms (FIG. 49). Slowly stroke the animal to assure it that you mean it no harm, and hand-feed it 2 or 3 mealworms. Carefully remove your hands from the cloth, close the cage door, and leave the animal alone to focus on the dish of mealworms. Repeat this procedure until the bat feeds on its own, usually within a day or two after arrival.

Frugivorous Species
Rarely will fruit bats refuse to eat after being transferred from another facility, or even directly from the wild. They accept small chunks of fruit, especially of the varieties they are normally accustomed to eating. If there are no distractions in the area, they will cautiously approach food that has been left in their cage. Small species of wild fruit bats may feed from dishes (e.g., coop cups hooked over the cage mesh; FIG. 50) when confined to small cages during the initial acclimation. Small cages increase the encounters bats will have with their food. If it becomes necessary to hand-feed a small fruit bat, place liquified food from a blender in its mouth with an eyedropper or syringe for at least one night. Allow it an opportunity to feed on its own the next evening. If it does not, repeat the liquified diet procedure once again. Do not, however, routinely liquify diets for fruit bats. When possible, food and water should be presented to bats high off the floor. Place food on shelves (FIG. 51) or in baskets suspended from the cage top (FIG. 52).

Figure 51.  Instead of using coop cups (Figure 50) to feed bats that do not feed from cage flooring, food dishes can be placed on a shelf;  for example, when a room is being converted to a flight area for species such as rhinolophids, hipposiderids and mormoopids (photo courtesy of Willard Wilson, Rochester NY.)	Figure 52.  Because their toilet habits can contaminate food with urine and feces, flying foxes should never be fed from the floors of cages.  Instead, hang woven baskets (A) to the cage top.  The baskets serve as holders for food and water bowls (B and C), and they provide the bats with hours of play as they swing on them.

Sanguivorous Species
Feeding problems have not been reported in common vampire bats, Desmodus rotundus. They accept food readily from Petri dishes or ice cube trays. Feed them late in the day or early evening.

ROUTINE FEEDING OF INSECTIVOROUS BATS
Insectivorous bats eat a variety of insects from night to night and season to season. Nevertheless, over the longterm, I have maintained successfully a wide variety of insectivorous bat species in captivity on an exclusive diet of fortified mealworms (Tenebrio molitor). This is achieved by maintaining the mealworms in an enriched medium (see MAINTENANCE OF INSECT COLONIES, Chapter 14), and by supplementing the bats' drinking water with appropriate vitamins and minerals (TABLE 2).

Table 2 VITAMIN/MINERAL MIXTURE FOR DRINKING WATER MIX FRESH DAILY Tap or distilled water . . . . . . . . . . . . . . . . . . . . . 25 ml Avitron® multivitamins (FIG. 57) . . . . . . . . 1 drop (0.05 ml) Avimin® multiminerals (FIG. 58) . . . . . . . 2 drops (0.10 ml) Fig. 57.  Avitron® is an excellent multivitamin for supplementing bat diets.  Use in combination with Avimin®. Fig. 58.  Avimin® MUST be used in combination with Avitron® to supplement a bat's diet with minerals.

Ladisch et al. (1967) reported that mealworm beetles contain toxic quinones, and therefore should not be fed to bats. Additionally, these quinones are absorbed into the medium upon which the larvae feed and may be transferred to the bats when they eat them. The problem is solved easily by refrigerating the larvae, thereby arresting their development. This procedure is discussed further in Chapter 14.

The diet of insectivorous bats also can be varied during warm months by feeding them net-sweepings. Insects captured may include greenbottle and house flies, young grasshoppers, cicadas and June beetles. Also, moths and beetles can be attracted at night to a light. Many insects serve as intermediate hosts for parasites, making it necessary to perform fecal examinations on the bats about every 6 months. Also, wild-caught insects may contain residues of toxins used in weed and pest control. Sublethal levels of toxic residues may be ingested by the insects and concentrate in a bat's tissues. Finally, do not allow cockroaches, ants, or other undesirable pests to gain access to a bat's enclosure. I know of several instances in which bats died after ants gained access to caging.

Insectivorous bats are predators, not carrion-feeders. Frozen mealworms and other insects have not proven satisfactory foods (Wilson, 1988; pers. obs.). If a bat does not eat the defrosted mealworms soon after being placed in its cage, the decaying insects not only emit a foul order, but may lose essential nutrients.

Captive insectivorous bats have been fed a variety of artificial diets known as "bat glop". These are essentially mixtures of equal parts of a dairy product (such as cottage cheese or sour cream), egg yolk, banana and meat, such as strained baby beef, or canned dog or cat food. This diet effectively relieves the handler from the inconvenience and expense of purchasing or maintaining insect colonies. Unfortunately, such diets fed over long periods can cause hair loss, gastrointestinal disorders, and may ultimately result in death (Barnard, 1991; Constantine, 1986b; Wilson, 1988).

There is no definite rule as to the number of insects a bat should consume nightly. Variables include the size of the insects as well as the size of the bat, time of year, ambient temperature and the amount of nightly activity a bat receives. It is normal for temperate-zone species to increase in weight during the fall and winter in preparation for hibernation, and to lose this excess weight in spring and summer. For example, in the months of March through August, a captive big brown bat (Eptesicus fuscus) must consume about 20 to 30 medium-sized insects nightly in order to maintain a weight of 17 to 20 grams. During the months of September through February, the number of insects consumed have to be reduced to approximately 4 to 10 to prevent obesity. I weigh all incoming bats. If the animal appears to be emaciated, the bat is allowed to gain 1 to 3 grams, depending on the species, and is held at that weight by increasing or decreasing the number of mealworms. Bats should be weighed every week to 10

days. A triple-beam balance (FIG. 53), subdivided by 1/10th grams, is best; however, a postal scale will do (28.35 g = 1 oz.). A bat may be weighed safely by placing it in a small, lightweight container or a sock. The weight of the container or sock is subtracted from the total weight to obtain the weight of the bat.

Figure 53.  Triple-beam balances work well for weighing bats.  Because insectivorous bats can fluctuate drastically in weight, they should be weighed weekly.

Use shallow containers to feed and water insectivorous bats, Petri dishes (FIG. 54a) are excellent for this purpose. I use glass 100 X 20 mm Petri dishes for mealworms, and for water, either plastic or glass 60 X 15 mm Petri dishes, or 1½-in. culture dishes (FIG 54b). Avoid using plastic Petri dishes for mealworms. These scratch easily, and they provide footholds for the mealworms to climb out.

Figure 54.  Glass Petri dishes (A) provide ideal containers for feeding insectivorous bats, and either small Petri or culture dishes (B), work well for water.

In addition to the vitamins and minerals used to fortify mealworms, bats require additional supplements in their water. Dosages of vitamins and minerals listed in TABLE 2 were calculated specifically for mixing with a bat's drinking water. To prevent overdosing bats on dietary supplements, neither inject the supplements into insects prior to feeding them to bats, nor place them directly into the bat's mouth.

Feed bats at dusk or as close to that time as possible, as this is their natural feeding period. The following morning, discard the water and uneaten mealworms, which are contaminated routinely with feces and urine.

Torpid bats have difficulty feeding and digesting insects they consume. It is well known among herpetologists that failure to provide reptiles with an appropriate thermal environment results in reduced feeding and limited growth. Given that temperate-zone chiropterans are heterothermic, it seems reasonable that the same principle would apply to these animals. For example, Stones (1965) reported that the little brown bat (Myotis lucifugus) required 3 times as much food at 75 F (24 C) as it did at a thermoneutral temperature of 91 F (33 C); however, I do not advise maintaining bats at such a high ambient temperature. For appropriate environmental parameters, see Chapter 5, ENVIRONMENT AND HOUSING FOR ADULT BATS.

Occasionally, insectivorous bats stop feeding for no apparent reason. This problem appears to be more prevalent in spring and fall than in the summer and winter months. If a bat has not eaten in two or three evenings, the problem may be reversed by injecting the animal once with lactated Ringer's solution (see TABLE 13 (Chapter 9) for dosages). Also hand-feed the animal 1 or 2 mealworms. A word of caution: avoid hand-feeding a bat routinely or it may not eat again on its own.

ROUTINE FEEDING OF FRUGIVOROUS AND NECTARIVOROUS BATS

Frugivorous Species
Bats that eat fruit ingest primarily the juice and digestible portion of the pulp. They manipulate carefully the fruit to remove undigestible components such as fiber and seeds.

Frugivorous bats require the same nutrients for growth as do other animals: what is not known are the amounts. To meet their protein requirements, some fruit bats, such as the New World leaf-nosed bats (phyllostomatids), supplement their diet with insects. Because flying foxes lack echolocation abilities to catch insects to meet their protein requirement, depending on the species, they must eat enormous amounts of fruit (Horst and Skutt, 1994), consume pollen, or passively ingest insects along with fruit, blossoms and leaves. Captive fruit bats, unfortunately, are usually fed excessively high amounts of dietary protein which can result in renal disease.

Because bats are not known to synthesize vitamin C (Birney and Jenness, 1978; Jacobsen and du Plessis, 1976), it must be obtained from their diet. Fruits provide sufficient amounts of this nutrient; additional supplementation may cause renal oxalosis from ascorbic acid metabolism. Although citrus fruits provide high levels of vitamin C, they should not be fed to fruit bats because the acid may cause (unspecified) mouth problems (Luckhoff, pers. comm.; George, 1990); probably for this reason, they are not partial to these fruits.

It is not known how fruit- and nectar-eating bats acquire vitamin B₁₂ in nature, as plants do not contain this nutrient. It is possible that they obtain B₁₂ from ingesting insects, either actively or passively, and/or from drinking stagnant water which contains B₁₂-producing microfauna (Robbins et al., 1975; Tuttle, 1974).

In addition to proper nutrition, diets should be palatable and offer behavioral stimulation. In the United States, nearly all diets formulated for fruit bats contain commercially prepared dry foods such as primate diet. Although it is much more convenient to mix such products in fruit bat diets, they are not natural diet components, provide no psychological stimulation and are formulated specifically for omnivorous animals. The diet presented in TABLE 3 lacks such products, and has over a 7-year period, provided nutrition adequate to maintain healthy pregnant and lactating female giant Indian fruit bats (Pteropus giganteus), and to support the growth of their offspring. The diet also has been used successfully to feed short-tailed fruit bats (Carollia perspcillata), Jamaican fruit bats (Artibeus jamaicensis) and Egyptian fruit bats (Rousettus aegyptiacus).

Table 3 FRUIT BAT DIET MIX FRESH DAILY (PER 1000 g OF DIET)   10-30 g dried fruits, 1 or 2 types (e.g., apricots, dates, figs, prunes, raisins, etc.)   1-2 ripe bananas, peeled   1/2-1 apple   2-3 other fruits (e.g., apricots, blueberries, canteloupes, cherimoyas, grapes, guanabanas*, guavas*, honeydew, kiwis, mangos*, nectarines, papayas*, peaches, pears, plums, star fruits, raspberries, scuppernongs, strawberries, tomatoes, etc.)   30-50 g chopped fresh leafy greens and herbs, 1 or 2 types, WITHOUT stalks (e.g., basil, cabbage, cilantro, collard, mint, mustard, parsley, spinach, turnip, watercress, etc.)   5-10 g edible flowers (when available)   1/8 tsp. vitamin/mineral powder**   1-1/2 tsp. protein supplement (rotate regularly): Pro Fuel™, LPP Regular™, non-fat, vitamin A&D fortified powdered milk, strained baby meat (e.g., beef or chicken), raw egg, pollen   1/2-1 tsp. cholesterol-free oil, 1-2 times weekly, (e.g., olive, soy) REMINDER - VARY DIET * or substitute approximately 80 ml Goya®-brand juice. Limit juice substitution to one type. Pour the juice into a small container, and place it next to the other items in the food bowl (FIG. 59). ** Vitamin/mineral powder (mix ingredients thoroughly and store in brown bottle):     45 g bone meal (sterilized; 25% Ca, 12% P) (FIG. 60)     45 g pet multivitamin powder [e.g., Theralin® (FIG. 61)or Vionate®, but not Pervinal® because it contains vitamin D2 instead of vitamin D3]     10 g vitamin E powder, WITHOUT selenium (50 IU/g) Fig. 59.  When substituting fruit juice for whole fruit, place it next to the other foods in a container. Fig. 60.  Bonemeal is used in a variety of animal diets to provide supplemental calcium. Fig. 61.  Theralin® is an excellent dietary supplement for fruit bats, and for fortifying insects to feed to insectivorous bats.

Because some bats are normally more aggressive feeders than others and will select the choice pieces of fruit, the food should be dispersed throughout a cage to insure that all animals have an opportunity to receive adequate portions. Distribute several food dishes within caging so all bats have an opportunity to eat at the same time. To prevent food from becoming contaminated by feces and urine, food containers should never be placed on cage floors. It also may be necessary to feed more than once a day when housing large colonies such as those found in zoological institutions.

Fruit can be distributed more equally among a group of bats if it is cut into relatively small pieces. For example, if halved fruits are skewered on tree branches in the cage, aggressive feeders may defend preferred types, producing dietary imbalances among the group members. By cutting the fruit into cubes with sides ranging from 1/8 inch (3 mm) (FIG. 55a) to 1 inch (25 mm) (FIG. 55b) in size, depending on the species, and mixing dietary ingredients together very well, food may be distributed more evenly among the bats. It is important, however, not to mash or blend the diet, as the bats may not be able to remove indigestible portions. It is unnecessary to peel fruits, but they should be rinsed off in case the skins contain pesticides.

Figure 55.  Small fruit bats require smaller pieces of fruit than large bats.  A) fruit cut into small pieces for Carollia perspicillata;  B) fruit cut larger for Pteropus giganteus.  Coop cups shown in the background are used to supply water for C. perspicillata;  they are hung on the mesh of the bats' cage (also see Figure 50).

The total diet for large pteropodids should range between 50-100% of their body weight per day (as-fed basis), which is dependent on the activity level, age, physiological condition and environmental stress factors. Small fruit bats, such as Carollia spp., should be fed all they will eat.

Although fruit contains abundant water, it should still be provided ad libitum. Pye (1967) reported desiccation and cutaneous ulceration in bats kept in dry environments or given insufficient quantities of water. My fruit bats not only drink water, but also incorporate water in their play. Several nights each week, they travel back and forth between the newspaper-lined cage bottom and the cage top, where their water is located, making paper spitwads. It is not known why the spitwads are made, or what they do with them. In Australia, fruit bats have been observed to drink from the ocean in an apparent attempt to supplement their diet with minerals. To insure fruit bats receive adequate trace minerals, place a mineral wheel in their cages.

Nectarivorous Species
Pollen collects on specialized hairs covering the bodies of nectarivorous bats as they extract nectar from flowers. After nectar forays, the bats gather at their roosts and ingest the pollen during grooming activites. Howell (1974b) reported that Sanborn's long-tongued bat (Leptonycteris sanborni) drank its urine, suggesting that this behavior might aid in the maintenance of water or mineral balance, or in the digestion of pollen proteins. It is important to mention here that although the crude protein of pollen is high, especially in "chiropterophilous" plants (20-43.7%; Howell, 1972, 1974a), nothing has been reported on its digestibility to bats. Also, no one knows for sure just how much protein frugivorous and nectarivorous bats consume in the form of insects because fruit-eating insect larvae are commonly soft-bodied, and they probably would not be conspicuous in a bat's stomach contents or feces. Also, those frugivores and nectarivores that do eat insects may follow the feeding pattern observed in Pallas' long-tongued bat (Glossophaga sorcinia) and the short-tailed fruit bat (Carollia perspicillata). These animals discard chitinous exoskeletons after consuming the soft parts of insects (Ayala and D'Alessandro, 1973).

Diets for nectarivorous bats have been published by Doherty and MacNamara (1977), Greenhall (1976, from pers. comm. by D.J. Howell), House and Doherty (1975), Rasweiler and de Bonilla (1972), and Rasweiler (1973, 1977a,b, 1986). Since the work of these authors, no other diets for captive nectarivores have been published. It would be interesting, however, to experiment with liquid diets (e.g., Nekton-tonic®) currently formulated for nectarivorous birds to see if such diets would also be successful with bats. The major drawback to Nekton® products, however, is their high cost.

ROUTINE FEEDING OF SANGUIVOROUS BATS
Vampire bats are obligatory blood-eaters. Although the common vampire bat (Desmodus rotundus) eats the blood of a variety of animals, it prefers bovine blood. Other blood types offered have included pig, sheep and human. Vampire bats readily eat either fresh or frozen blood. Fresh blood has a refrigerated shelf-life of 5 to 7 days. Frozen blood remains safe to use for 4 to 6 weeks. To minimize trips to the slaughter house, freeze nightly rations of blood in appropriately sized, sterilized plastic bottles (FIG. 56). The blood must be either citrated or manually defibrinated at the time of collection to prevent it from clotting. I prefer to citrate the blood; the formula I use is presented in TABLE 4.

Figure 56. Depending on the number of vampire bats in a colony, blood can be divided into nightly portions and stored in the appropriately sized bottle.  Use bottles that can be sterilized.

Table 4 CITRATED BLOOD PER GALLON Tap or distilled water . . . . . . . . 2 cups (approx. 250 ml) Sodium citrate (FIG. 62a) . . . . . . . . . . . . . . . . . . 11 g Citric acid (FIG. 62b) . . . . . . . . . . . . . . . . . . . . . 4 g Add the ingredients listed above to an empty, plastic gallon jar. The blood must be added to the mixture at the slaughter house. Figure 62. Sodium citrate (A) and citric acid (b) are used to prevent blood from cotting.  Vampire bats cannot eat clotted blood.

There are many ways to present blood to vampire bats. One of the least expensive, most convenient and hygienic methods is to use ice cube trays. The multiple compartments not only allow several bats to eat simultaneously, but also prevent contamination of an entire meal if an animal defecates or urinates in the food. To insure that all bats get enough to eat, allow at least 25-35 ml of blood per bat per night.

Vampire bats do not require drinking water. For over 20 years, Wimsatt (1986) did not provide water for his vampire bats. After three years of maintaining these animals, I also stopped giving them water. It must be noted, however, that vampire bats require water during periods when food is unavailable temporarily. Vampire bats cannot fast for more than three days, after which time they become emaciated and die. During periods of brief fasting, water is critical for these animals, and Wimsatt (1986) suggested giving them 0.9% NaCl (saline) at such times to prevent clinical dehydration. It is also unknown whether vampire bats require supplemental vitamins and minerals. When I stopped offering water to my vampire bats, I also discontinued their dietary supplements; over a 1-year period, no ill effects were observed. When their diet was supplemented, however, 1/2 ml of Avitron® multivitamins and 1 ml of Avimin® multiminerals was added to each 250 ml of blood about 3 times a week. One-half ml of Linatone® was also added to each 250 ml of blood once a week.

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