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Species: Malayan False Vampire Bat (Megaderma spasma)
Use: General Activity
Authors: Karen Tyrell, University if Illinois at Urbana
Methods: NA
Publications/Presentations: Thesis submission (1990). The Ethology of the Malayan False Vampire Bat (Megaderma spasma), with special emphasis on Auditory Cues used in Foraging.
VocalizationsEcholocation signals: Echolocation pulses (including a Òterminal buzzÓ; sensu Barclay et al, 1981) are produced during navigation around obstacles and during prey capture. Echolocation pulses emitted by M.spasma are similar to those emitted by other megadermatid gleaning bats (Mohres and Kulzer, 1957; Novick, 1958; Mohres and Neuweiler, 1966; Simmons and Stein, 1980; Guppy et al., 1985). They are steeply frequency-modulated and brief, with multiple overlapping harmonics. The number of harmonics present (and thus total bandwidth) vary depending on when the pulse is emitted. Echolocation calls may sometimes be used as communication signals or exploited by others to determine the location of food. However, in most bat species, their primary function is ÒautocommunicationÓ to provide the sender with information about objects in the environment.
Social Buzz: This vocalization is barely audible and is heard as an atonal, Òwhispering buzzÓ sound. It consists of four overlapping harmonics, resulting in a continuous frequency sweep. This vocalization was most often emitted by a bat immediately upon approaching, or being approached by, another individual.
Chitter: The chitter, occasionally emitted prior to feeding and during social interactions, consists of about seven harmonics overlapping in frequency between 128-12 kHz. Chitters occur in two situations: before feeding and during agonistic encounters.
Chuck: The chuck was emitted by bats engaged directly in, or near an agonistic interaction. The call consisted of about 6 overlapping harmonics, resulting in a continuous frequency spectrum with sound energy always evident from about 130-10kHz. The mouth was open when this sound was emitted.
Non-vocal Behavior: Social Behavior
Agonistic Behavior
Wing fan: While the bat is hanging from the ceiling, both wings are abducted, with the leading edges held approximately perpendicular to the long axis of the body. The digits are spread apart. The wings may be held static in this position for up to 3 s, or moved forward then back dorso-ventrally, through an arc of about 30¼. The two wings move in the same direction simultaneously. This movement is about 0.5 s in duration, and may occur once, or be repeated several times during a bout lasting from 1-8 s. The ventrum is usually directed toward one or more bats. Other individuals are at least 25 cm away, and are not contacted by the wing.
Wing slap: The wings are extended as the bat contacts another individual with the anterior face of the wing membrane. Either both wings are extended partially or fully (depending upon the distance between individuals) and contact the other bat in an alternating fashion, or one wing is extended at a time. Both bats hang from the ceiling and are about 15 to 20 cm apart. Repeated wing slaps occur in rapid succession (ca. 6-8/10 s), although they can occur singly. Wing-flapping bats may chitter.
Wrist ÒpunchÓ: While two bats hang in close proximity, one bat ÒjabsÓ at the other individual with the wrist joint. The wing is ÒclosedÓ so that the digits are folded against the anterior face of the wing. Two bats usually wrist punch at the same time. This behavior pattern only occurs when the bats are less than 15 cm apart. Generally, 5-8 wrist punches occur in about 10 s; then, the bats move apart.
Grab at: The wings are held outspread (as in fanning), away from the long axis of the body, and midway between the frontal and sagittal plane. The wings may be moved back and forth at a rate of approximately 4/s through an arc of about 30¼. The bat hangs pendant by one foot; the other is outstretched toward another individual. This behavior pattern was simultaneously executed by two bats approximately 15-20 cm apart. Each bat ÒreachesÓ toward the other with the foot and leg, toes splayed. The foot is moved laterally to medially, perpendicular to the long axis of the body, through an arc of about 90¼. In essence, each bat ÒswipesÓ at the other, and may or may not contact the other bat. This behavior usually lasted about 10 s and was preceded and followed by chase/displace behavior. Because e this behavior was observed rarely, it seems likely that it may occur only during very intense or otherwise unusual encounters.
Supplanting: One bat flies toward and lands within 15 cm of a second stationary, hanging bat. As the approaching bat lands, the roosting bat flies away. The approaching bat may then fly to the location where the previously displaced bat landed; and again that bat flies off. Supplanting involves two individuals, and rarely was the male a participant. Supplanting seems to occur in both agonistic and non-agonistic encounters.
Tumble hit: One bat flies toward a second hanging bat, and momentarily lands in close proximity (the bodies of the two bats touch). Usually after the first bat approaches the stationary bat and lands, the tow exchange 1-2 wing slaps. The two bats then ÒfallÓ about 1 m in distance from the ceiling while in ventral-ventral contact before each flies to the ceiling and hangs at a separate location. The chitter vocalization may be emitted by either bat during the initial approach and wing slapping. This behavior pattern occurs within a duration of about 4 s.
Grapple: Two bats wrap their wings partially about one another for a duration of 3-4 s as both hang pendant. This behavior pattern both precedes and follows chase/display behavior. The bats continue to move their bodies slightly (side-to-side; back and forth; up and down about the long axis) while ÒembracedÓ, and the feet occasionally reposition.
Face-to-face: One bat flies toward another and approaches so that their ventral surfaces are oriented toward each other. The approaching bat then hovers facing the other for about 1 s such that their heads are 10-15 cm apart. This behavior was usually executed by the male and directed toward a female hanging pendant away from other individuals. Occasionally, the male flew and hovered in this posture before one female, then moved (directly and immediately) to repeat the act toward another. Females gave no apparent response.
Nuzzle: Nuzzling occurs after one bat approaches another stationary, hanging bat. The approaching bat placed its ventral surface against the dorsal surface of the approached bat, presses its own muzzle directly behind the ears of the other bat, and moves its own head from side-to-side through an arc of about 15¼. The approaching bat may rotary shake and emit a social buzz briefly before and during the nuzzle. The approached bat shows no overt movement in response to this behavior.
Rotary shake: While in hanging position, the batÕs body rotates very quickly around its long axis through an arc of about 20¼ to either side of the midline. The duration of the rotary shaking ranged from 0.5 to 4.0 s. Individual side-to-side turning movements cannot be seen. The head moves in a similar fashion. As it does, the movement of the ears is more noticeable than the motion of the rest of the head, presumably because of their large size. This behavior is usually shown by one bat after it approaches another and their bodies are in contact (ventrum of approaching bat against dorsum of approached bat). Occasionally, only the approached bat emits a social buzz; usually, both bats do. A bat not close to others rarely emits the call. The social buzz, when heard, always occurred during a rotary shake, but during some rotary shaking, it could not be told if buzzing occurred. As with social buzz, the rotary shake may serve to identify the approach of a non-aggressive bat.Enshroud: One individual approaches another (stationary) individual and wraps its wing membranes around the wings and body of the approached bat as both hang pendant. The approaching bat places its ventral surface in contact with the other batÕs dorsal surface. When the two bats initially make contact, the approaching bat rotary shakes (2-4 s duration) and usually emits a social buzz. Afterward, both bats hang without obviously moving. Enshrouding in M.spasma has only been observed between female pairs; the male never participated as a pair member.
Chirp thrust: One bat hangs pendant, legs separated, its ventral surface in contact with the dorsal surface of a second hanging bat. The first bat remains still for 2-4 s, then jerks its body up (by bending its legs) and toward the other bat, apparently leading with the pelvic region. This position is held for about 1 s, before the bat ÒrelaxesÓ, straightens its legs for 1-2 s, then repeats the motion. As the bat first moves it emits a brief audible, pulsatile ÒchirpÓ, and the wings are briefly ÒopenedÓ, with the forelimbs (but not digits) partially extended. The wing movements look very similar to the wing shrug. This sequence is repeated for 20-60 s.
Penile waving: The male lands about 10 cm from a female, his ventral surfaces facing hers. He extends his erect penis toward the female by holding his pelvic region forward. His wings are fully extended, with the leading edge of the wing approximately perpendicular to the long axis of the body. The two wings are flapped forward and back simultaneously and in the same direction, in an arc of about 45¼. At the same time, the penis is ÒwavedÓ side-to-side in a narrow arc for about 5-8 s. As the wings are moved, the male may take several steps toward the female. However, the pair was never observed to subsequently make contact. Vocalizations were not detected during penile waving.
Non-social (Individual Behavior)Grooming: Bats groom their fur while hanging from one foot; the other foot is used to ÒcombÓ in very rapid, short strokes, too rapid to be seen as individually distinct. Bats have been observed grooming their entire dorsal and ventral surfaces, head, and wing surfaces in this manner. Occasionally, the foot is brought to the mouth and the bat licks between its toes. The body surface may also be groomed with the tongue. A period of grooming lasting several minutes usually begins as feeding sessions terminate. The facial region is groomed first, followed by the pectoral area and the rest of the body. Allogrooming was not observed in M.spasma.
Comfort movements: The term Òcomfort movementsÓ is used to describe behavioral adjustments of body position which apparently make the animal more restful or physically at ease (Eisenbers and Gould, 1966; Winstrand, 1974), or serve Òto remove discomfortÓ by stimulating metabolic activities (e.g. stretching to increase circulation, Bearends and Bearends-Van-Roon, 1950). Comfort movements are not preparatory for the execution of any other observed specific behavior patterns, and as such are a Òunique type of muscular activityÓ (Myrberg, 1972).
Wing shrug: The bat briefly opens, then closes, both wings as it hangs from the ceiling. The forearms are only partially extended and are moved simultaneously. The digits are not extended. This behavior pattern generally occurs as the bat is chewing its food.
Wing stretch: As the bat hangs pendant by one or both feet, one wing with all digits is fully extended and abducted so that the long axis of the wing is nearly perpendicular to the long axis of the body. This position is maintained for 3-4 s. Following the ÒstretchÓ, bats often groom the wing membrane. As with grooming, this behavior pattern follows the cessation of feeding.
Yawn: The mouth is opened wide with the lips pulled back so that the teeth are visible. The gape position is maintained for 1-2 s before the mouth is abruptly closed. This behavior is only observed in bats hanging pendant from the ceiling, after feeding.
Drinking: Individuals were observed drinking (1) while stationary, hanging pendant by both feet from the brick wall adjacent to the water trough, and (2) while hovering in flight over the surface of the water trough. When hanging pendant to drink, the bat lowers its chin toward the water surface and laps at the water with its tongue. The wings are folded against the side of the body. Only the male was observed drinking while in flight. He flew near the water, ÔhoveringÓ 5-10 cm above the water surface. While directly over the water surface, the batÕs head and pinnae were oriented toward the water surface. Then, while in hovering flight close to the water surface, the bat lowers his head so that his chin is near the water, and briefly contacts the water surface. Following a drinking bout, the bat flies higher above the water, then dips down to the water surface again. Typically, 5 bouts of drinking occur during hovering flight.
Feeding: Two foraging styles, surface gleaning and flycatching, have been observed in the laboratory. Both utilize a Òsit-and-waitÓ strategy similar to that described for other bats, especially surface gleaners (Shortridge, 1934; Vaughan, 1976; Buchler, 1980; Fenton et al., 1983b; Guppy and Coles, 1983; Fenton, 1986; Vaughan,1977; McWilliam, 1987; Neuweiler et al., 1987; Norberg and Raynor, 1985). Both are used by Megaderma (Shortridge, 1934) and by certain other surface gleaning species in nature (Vaughan, 1976; Fenton et al., 1983; Bell and Fenton, 1984; Fenton, 1984; Tidemann et al., 1985). Use of the two foraging styles may reflect changes in feeding behavior in response to seasonal fluctuations in abundance of flying and terrestrial prey (Shortridge, 1934; Vaughan, 1976).Urination: Bats have been observed urinating while in two different postures:
Tilted-away urinating: The bat hangs pendant by two feet. The wings are held partially abducted with the digits extended. The palmar surface of each wing is approximately parallel with the frontal plane. The bat Òbends backÓ at the hips so that the genital region is foremost. Once in this position, the bat urinates. This position appears to prevent urine from contacting the batÕs fur.
Rotary-shake urinating: The bat hangs pendant from two feet while the wings are in a folded position at the batÕs side or slightly abducted. The long axis of the body is directly beneath and continuous with the long axis of the legs. As the urine is released, the bat rapidly (too fast to be observed as individual movements) rotates laterally about its long axis through an arc of about 45¼ to either side of its saggital plane. During this movement, the legs are stationary. The effect is to spray most urine out and away (at least 1.5 m) from the bat, but some urine may also partially cover the batÕs fur.
Resting postures: The bats hang pendant from the ceiling, walls, or any structure in the flight cage with one or both feet. The wings are folded and wrapped partially around the ventral surface of the body. Individuals may hang alone or touching others in a contact cluster.
Wing clap: This non-vocal sound is occasionally produced by flying bats after they initiate rapid flight. A ÒslappingÓ or ÒclappingÓ sound is produced, associated with the wing upstroke (when the wings are highest over the body). It is unclear how this sound is produced, but bats flying in rapid bursts only rarely produced this sound. Thus, the sound is apparently not a necessary by-product of this type of flight movement. In M.spasma, wing clap sounds were sometimes produced during agonistic interactions (e.g. by a ÒsupplantingÓ individual), but were not always produced by a bat involved in the aggressive act. Thus, this behavior pattern could be a threat, perhaps an appeasement gesture, or merely indicate an increased level of ÒexcitementÓ.
Wall ÒstrumÓ: The bat hangs pendant from a vertical surface by both feet. It then moves one leg laterally away from the body to an angle of about 40¼ from the body. The foot maintains contact with the surface from which the bat hangs but is moved laterally side-to-side, and toward and away from the surface so that the toes Òpick-atÓ or ÒstrumÓ the surface. Scratching sounds are produced as the bat claws the surface. Only the male exhibits this behavior pattern, and only during agonistic encounters between females.
Looping flight: Following feeding on about 20% of all days, the male bat flies through the enclosure, approaching within 5-10 cm of walls and obstacles, as well as flying through the center are of the cage. The flight pattern is Ò looping and rollingÓ. Flight speed appears no different from thatÕs seen during other behavior patterns. He pauses briefly on the edges of the shelf, interior cages, or cage supports. During these flights, he sometimes hovers over the water dish and Òdips downÓ to touch the water surface with his mouth.