Chapter Two

ASPECTS OF REHABILITATION
Bats are highly specialized animals with complex lives. Many species learn "bat life" from their mothers (Barclay, 1982; Bateman and Vaughan, 1974; Bradbury, 1977; Brigham and Brigham, 1989; Vaughan, 1976; Vaughan and Vaughan, 1987). Young bats observe and mimic their mothers and/or conspecifics to learn how, what and where to hunt, but a high percentage of them still die during their first year of life. Survival requires adequate hunting skills, identification of appropriate shelters (e.g., day and night roosts, hibernacula), knowledge of migratory routes, avoidance of predators and appropriate social skills with conspecifics. Bats must also be in excellent condition, both physically and behaviorally, or their chances for survival are limited.

Captive-reared, insectivorous bats have been taught to catch insects in flight within the confines of a building. Such bug-catching abilities, however, may not translate into survival in the wild. Rehabilitators must hold themselves accountable when releasing handraised or captive-born bats by making every effort to evaluate the success or failure of their release programs. This might be achieved with the use of implanted electromagnetic transponders (Barnard, 1989) in combination with identification bands (FIG. 7) and radiotracking devices (Adkins and Wasserman, 1993; Albrecht and Helverson, 1994; Dicke, 1994).  Until

Figure 7.  Although banding can cause injury to bats, this band style is the least harmful.  Note the proper area for its application (modified from Kowalski, 1955).

2) Species that do not adapt well to captive conditions, such as Lasiurus and Mormoops, might have a better chance of living if displayed to the public in relatively large, naturalistic exhibits.

3) Another option is euthanasia (see Chapter 9, HEALTH, MEDICAL AND NECROPSY CONSIDERATIONS), preferably before the handraising process begins.

Rehabilitation considerations proposed for human-raised orphaned bats also apply to those born in captivity to wild, releasable mothers. Wild, insectivorous bats who give birth in captivity may abandon their pups when released. Any wild animal suddenly taken captive, regardless of the reason, must perceive the situation as "dangerous." Lactating females, therefore, increase their chance of surviving, and reproducing again, by lightening their burden with the abandonment of their young.

Isolate pregnant bats in a quiet area while administering health care. Handle them minimally, and release them as quickly as possible. If a pregnant bat bears young before the targeted release time, feed and house her as described in Chapter 5, ENVIRONMENT AND HOUSING FOR ADULT BATS and Chapter 7, FEEDING ADULT BATS. Avoid interfering with the female's efforts to care for her young, and if she is not injured, release her immediately after the young are weaned. If the female dies or rejects her pups, handraise them according to the information discussed in Chapter 8, HANDRAISING INFANT BATS.

CONSIDERATIONS FOR RELEASE
Bats that are not handreared or injured should be returned to the wild as soon as possible (weather permitting). Check long-range weather forecasts, especially during fall and spring.

Prior to releasing a healthy wild bat, consider feeding it for a few days to a week, especially in the spring and fall. In the spring, bats require fat reserves to sustain them until insects become plentiful. In fall, they also require fat reserves to sustain them during hibernation. Be certain that bats scheduled for release are able to fly well and with reasonable endurance, especially those that have been held for more than a month or two. A wild bat that can remain in flight (FIG. 8) indoors for about 5 to 10 consecutive minutes is probably ready for release (also see Chapter 12, EXERCISING).

Figure 8.  "Fang's" last flight before release.  To insure a bat is ready for release, be sure it is able to fly for 5 to 10 consecutive minutes indoors (photo courtesy of Jay Zuspann, Warner Robins, GA)

Bats will have a better chance of surviving if they are released in the area where they were found originally because they are familiar with these surroundings. A carefully planned release allows them the continued use of their established drinking sites, feeding grounds, roosts and hibernacula. Furthermore, these animals will not expend unnecessary energy, or lose their lives, by attempting to return "home" when released in a new area.

The best time of day to release bats is just before sundown. First check the release area to insure it is free of children and predators such as cats and dogs, then place the bat on a tree trunk about 6 ft. off the ground. Move far enough away from the animal so as not to interfere with its ability to orient itself to the changed environment. Also be sure that there are no obstacles, such as branches, to interfere with a "clean" takeoff. Some bats will orient themselves quickly and fly away within a few minutes. Other bats, however, may require several hours. Always return to the release site the following morning to insure the bat is gone. A bat that does not leave by the following morning should be retrieved. If this problem occurs after several attempts at release, consider one of the options presented above for orphaned and captive-born baby bats.

RELEASE STUDIES
Perhaps the first bona fide release projects recorded in the United States were conducted by Adkins and Wasserman (1993) and Dicke (1994). Adkins and Wasserman released a captive-reared big brown bat, Eptesicus fuscus, and Dicke released a prevolant, juvenile pallid bat, Antrozous pallidus: both bats survived. Factors that may have contributed to the success of Dicke's project was twofold: 1) the animal "knew" it was a pallid bat, being familiar with the appearance, social sounds and biosonar of pallid bats, because it spent up to 6 weeks with its dam and conspecifics; and, 2) the bat was returned to a colony of pallid bats, posibly the one from which it was orphaned. Although these projects each included only one individual, representing only one species, the techniques used by the investigators provided valuable information for future release studies.

In Europe, Gebhard (1988) reported successful releases of juvenile noctule bats, Nyctalus noctula, as part of a larger project encompassing their habits. The following year, Helversen (1989) modified Gebhard's technique to release bats as part of his work on social calls. He placed the study bats in a release box similar to the one shown in FIGURE 9 a-c. The release box was divided into two compartments by a mesh wall to insure contact between unreleasable mother bats and self-feeding, volant juveniles. The mothers were placed in the closed compartment; the juveniles in the one with the exit hole. In 1994, Albrecht and Helversen used the same technique to study the development of foraging behavior of 14 captive-born, mother-reared noctule bats. The behavior of 4 of the 14 bats was recorded by radiotracking them. After leaving the roost, the young bats went through a period of flight practice. As they gained flight experience, feeding strategies improved, allowing them time to explore new feeding grounds. The bats returned to their mothers in the release box after foraging. During the day, the investigators placed the juveniles in the closed compartment with their mothers to reinforce their bonds. Gebhard (1988) showed that juveniles of this bat species could learn to hunt by observing each other, and the works of Helversen (1989) and Albrecht and Helversen (1994) support this theory.

Figure 9.   Release box.  A)  showing access door;  B) showing two-compartment interior.  Mothers, which cannot be released, are placed in the closed right compartment, and the juveniles to be released are placed in the compartment with the exit hole (left);  C) mounted box.  Boxes should be placed in areas that allow the rehabilitator easy access (photos courtesy of Johanna Arnold-Rinehart, Frankfort, KY).

In June, 1986, I undertook what turned out to be an unsucessful release project when over 90 big brown bats were removed from an attic. Fifty-eight orphans were presented to me for hand raising; 47 survived. After the pups became self-feeding and could fly, they were placed in a release habitat shown in FIGURES 10 and 11. The release project had to be discontinued. Nevertheless, the much information was produced about the captive care and social behavior of a captive colony of big brown bats, and the foundation for the original edition of this book (Barnard, 1987a).

Although the work described by Albrecht and Helversen (1994) and Dicke (1994) concerned only the releases of mother-reared juveniles, the concepts can be expanded to rehabilitating handreared infants as was shown by Adkins and Wasserman (1993). For example, we know that it is possible to have successful releases if handraised bats are exposed to their species during the handrearing period. Where a colony of bats (of the species being handreared) is readily available, an infant may be placed in a "Howdy" cage near it. As the infant develops, and becomes self-feeding, the bat can be banded, fitted with a radio, and tracked. Where no wild colony is available, infants may be exposed to unreleasable bats of their own kind, during the handrearing period. In situations like this, either the release box shown in FIGURE 9 a-c can be used, or the release habitat depicted in FIGURES 10 and 11 might be employed.

The discussion on rehabilitation so far has included only colonial insectivorous bats. There is no scientific work published on the release of solitary-dwelling, insectivorous species. At this writing, however, Barbara French in Austin, Texas, has been recording annecdotal information surrounding release possibilities for handreared red bats, Lasiurus borealis.

For information on radiotelemetry, the rehabilitator may wish to read Brigham (1992), Mech (1983), and Wilkinson and Bradbury (1988).

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