Care Of Captive Bat Populations

Several species of bats have been maintained in captivity, and there is ample information available regarding the proper care of captive bats. The following is a brief summary of some basic considerations for the captive care of bats. We refer readers to books listed in the Resources section of this chapter for more detailed information. Generally, a researcher interested in maintaining a captive colony must consider roosting and flight needs, climate and lighting needs, nutritional needs, and social needs. How these needs are met depends on the species of bat.

Flight cages and roosting cages Bats need exercise and may lose the ability to fly if deprived of flight space for over a month (Wilson, 1988). Flight cages can be made of a variety of materials to meet the particular needs of the research, but good visibility, easy cleaning, and plenty of perching sites are important considerations. If the cage is made of wire mesh, it is important that the gaps in the mesh are small enough that wings and feet will not get trapped. Also, wire mesh can cause irritation to the wrist and ankle area of the bat as well as tear wing tissue, so it should be coated with a Teflon spray. Alternatively, one could use softer materials such as nylon or rubberized mesh (Lollar and Schmidt-French, 1998). While mesh provides good perching sites, toenails may grow excessively and require clipping. Therefore, it is recommended to provide branches which the bats can use to file their toenails. Other good perching materials include burlap, cork board, bark, plywood with small holes and textured plaster (Wilson, 1988). Lollar and Schmidt-French (1998) provide detailed instructions for well-designed flight cages.

Smaller roosting cages can be placed inside the flight cage to either isolate individuals, provide a location where mothers can keep their young, or accommodate specific roosting needs. There are a variety of different roosting cages ranging from small aquaria with mesh tops to plywood and mesh cages such as those described by Lollar and Schmidt-French (1998). The key is to meet the roosting needs of the species in question. For example, crevice-dwelling bats like to roost in tight, dark spaces. Many bat rehabilitators attach small padded pouches to the walls of roosting cages that bats can crawl into (for patterns see Lollar and Schmidt-French, 1998). Tree-dwelling bats like to roost among foliage typically in relatively high areas. One can tie branches or leaves of the foliage preferred by the species in question to the upper corners of a cage.

Climate and lighting conditions Temperature, relative humidity, and light cycles play key roles in the digestive and reproductive function of bats (Heideman, 2000; Wilson, 1988). The optimal climate and lighting conditions are likely those experienced by the particular species naturally. For example, heterothermic bats in temperate areas experience warm roost temperatures with high relative humidity and long days in the summer but then require low temperatures and short days in the winter for torpor or hibernation. Digestion is most efficient at thermoneutral temperatures, and photoperiod and seasonal temperature changes are critical for reproduction in many bat species. In many species mating takes place in the fall, but fertilization of the ovum or implantation of the zygote occurs in spring. Also, spermatogenesis is likely influenced by photoperiod (Heideman, 2000). Many people working with captive bat colonies mimic natural conditions, while others keep their colonies within sites that bats might normally pick for roosting, such as old barns or attics. This way, the colony experiences natural cycles in temperature, relative humidity and light.

Providing climatic and light cycles that imitate natural conditions may not always be possible. Another option is to use a space heater, heating pad, or a lamp with a 25-W red light bulb to create a temperature gradient in the cage so individuals can choose the temperature they prefer (Lollar and Schmidt-French, 1998; Wilson, 1988). Generally, bats should be kept at a temperature between 24 and 35° C and a relative humidity between 50 and 90% (Lollar and Schmidt-French, 1998; Wilson, 1988), but determining a good climate regime may take some trial and error. Researchers establishing a new colony should consult the literature to find data on the thermoneutral temperature range of the species in question. If breeding is desired, researchers should investigate mating behavior and physiology and determine the ideal conditions for mating and proper fetal and neonatal development (Heideman, 2000).

Nutritional requirements The dietary requirements of bats are easily accommodated in captivity, though at times training may be necessary so bats will accept the offered food. Regardless of the diet, vitamin, mineral, protein and fatty acid supplements should be provided when necessary. Vitamin and mineral supplements may be added by dusting food with vitamin/ mineral powder or fortifying water with liquid vitamins. One should supplement vitamins and minerals with caution as overdoses may result in medical problems (Lollar and Schmidt-French, 1998). Linatone, a veterinary product for birds, dogs and cats, is an excellent source of additional fatty acids for bats.

The most common diet for insectivorous bats is mealworms, the larvae of Tenebrio molitor. Mealworms should be raised on a mixture of bran and oats enriched with a high protein cereal. Wedges of apple or potato provide the moisture mealworms need. Most insectivorous bats will need to be taught to eat the mealworms, and the speed with which they learn varies among species. To train a bat, one should offer a mealworm with a pair of tweezers. Sometimes it may be necessary to decapitate the mealworm to expose viscera but once bats recognize mealworms as food, they will feed independently on mealworms in a bowl. In lieu of live mealworms, bat handlers may use "bat glop,'' a blended mixture of mealworms and other ingredients such as baby food and veterinary vitamin/mineral supplements. Lollar and Schmidt-French (1998) provide excellent recipes for blended mealworm mixtures which can be frozen in ice cube trays and then thawed for a meal.

Suggested food items for carnivorous bats include chunks of beef, rabbit meat, chicken meat, birds, lizards, white mice, rats, bats, chicks, quail, papaya, mango, melon and banana. Piscivorous bats will readily accept small pieces of fish supplemented with red meat and enriched mealworms.

Frugivorous bats will eat several fruits and vegetables including banana, figs, apples, orange, guava, passion fruit, grapes, pineapple, papaya, mango, pear, tomato, lettuce, cooked sweet potato, cooked carrots. This diet should be supplemented with canned feline diet or New World primate diet. Nectivorous bats can be fed instant nectar combinations, though one should ensure that the used combination is properly supplemented and balanced (Wilson, 1988).

The common vampire bat (Desmodus rotundus) does well on a diet of 50 mg of fresh blood per day, which can usually be obtained from a local slaughterhouse. The blood must be defibrinated by stirring or by treatment with sodium citrate or oxalate and is usually served in a shallow dish or ice cube trays. While fresh blood is preferable, frozen citrated blood has been used successfully for extended periods of time (Dickson and Green, 1970).

Different bat species have variable needs for water, depending on the diet provided. However, water should always be provided ad libitum in multiple containers placed throughout a cage. Some bats can be trained to lick water from drinking bottles but all bats will readily drink from open containers. Water in open containers is easily fouled by food and feces, so it is critical to change the water at least twice a day. Also, deep water dishes should be filled with marbles to prevent bats from falling in the container and aspirating water (Lollar and Schmidt-French, 1998).

It is important to keep a systematic record of the health condition of every bat in a captive colony. Individuals should be weighed regularly to assess for weight loss, which may be a sign of illness, as well as hyperphagia, though it is important to remember that hibernating bats will gain weight in preparation for hibernation. Other clinical signs to assess include diarrhea, vomiting, loss of pigmentation and/or dryness of the skin, hair loss, and lethargy. Several of the books listed in the Recommended Resources section of this chapter have helpful information on diagnosing common medical conditions.

Sociality

Bats should be housed in accordance to their natural social behavior (Johnston, 1997). Solitary bats should always be caged separately except for a mother and her pups. Upon weaning, however, the pups should be separated from their mother. Colonial bats should always be housed with roost mates, as they often practice allo-grooming and may thermoregulate by clustering. For most colonial species, the sexes should be kept separate. Species that normally form harems may be housed in groups of multiple females with one male, though regardless of the social system researchers should continually look for signs of aggressive behavior and redistribute individual animals to minimize aggressive interactions.

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