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PubMed1990

Influence of monaural plugging on postnatal development of auditory spatial sensitivity of inferior collicular neurons of the big brown bat, Eptesicus fuscus.

Postnatal development of auditory sensitivity in the big brown bat, Eptesicus fuscus, was studied by determining the auditory spatial sensitivity of inferior collicular (IC) neurons of juvenile bats which were raised under normal (control) or monaurally plugged conditions. The auditory spatial sensitivity of each IC neuron was determined by measuring its variation in number of impulses and minimum threshold to a best frequency sound delivered from different azimuthal angles under free field stimulation conditions. Monaural plugging was performed on different juvenile bats at 7, 14, and 35 days of age. Auditory spatial sensitivity was then determined for IC neurons of monaurally plugged bats at 58-69 days after birth. Monaural plugging did not alter the discharge pattern, distribution of best frequency and latency of IC neurons, but it raised the minimum threshold of IC neurons of plugged juvenile bats by an average of 21-24 dB. Monaural plugging also appeared to modify postnatal development of auditory spatial sensitivity. The auditory spatial sensitivity of IC neurons was sharper when the earplug was intact than when the earplug was removed. Thus, the distribution of response center and the spatial sensitivity of IC neurons of the monaurally plugged bats was more comparable to IC neurons of the control bats before the earplug was removed. These findings suggest that the neural circuits underlying auditory spatial sensitivity of IC neurons of the monaurally plugged juvenile bats have undergone modifications to compensate for the unnatural binaural disparity during postnatal development. The auditory spatial sensitivity was also determined for two control juvenile bats at 49 and 60 days of age and for an adult bat (more than 1 year). Our data show that auditory spatial sensitivity of IC neurons sharpens with postnatal age. Furthermore, the sharpening process appears to be still in progress even at 60 days after birth.

Acoustic Stimulation↗
PubMed1975

Trypanosomes and experimental trypanosomaisis in East African bats.

Using the haematocrit centrifuge technique, four hundred and twenty-seven bats from East Africa were examined for trypanosome infections. Approximately 21% of the bats were found to be infected. The infection rate varied from zero to 73.3%. No trypanosome was found in fruit-eating bats (Megachiroptera). Three species of trypanosomes were found in insect-eating bats (Microchiroptera), none of the trypanosome was infective to mice or rats. The trypanosomes encountered in the survey were Trypanosoma (Schizotrypanum) vespertilionis, T. (Megatrypanum) heybergi, and T. (M). mpapuense. New descriptions based on abundant materials are given for each of the species. Trypanosoma rhodesiense and T. brucei produced a much more chronic infection in insect-eating bats (Tadarida condylura) than in mice. Since it is known that some species of Glossina feed on bats, we raised the possibility of insect-eating bats as potential reservoirs of these trypanosomes. In experiments fruit-eating bats seem to be much more susceptible to T. brucei than the insect-eating bats. T. vivax is not infective to bats.

Africa↗
PubMed1989

Effects of bat composition, grip firmness, and impact location on postimpact ball velocity.

The purpose of this investigation was to examine the effects of bat composition (aluminum and wooden), impact location [center of percussion (COP), center of gravity (COG), and end of the bat (E)], and grip firmness [tight (T) and no tension (NT)] on postimpact ball velocity. With the bats placed alternately in NT and T conditions, baseballs were delivered at a speed of 27.1 m.s-1 from a pitching machine positioned 1.5 m from the bat. High-speed photography (400 fps) was performed using a Locam camera positioned 7.54 m from and perpendicular to the principal plane of ball movement. A three-way ANCOVA revealed significant (P less than 0.01) differences in postimpact ball velocity between the three impact locations, with the COP yielding the greatest values, followed by the COG and E. Moreover, there was a significant (P less than 0.01) grip vs bat interaction. A simple-effects procedure revealed the following results: 1) the T grip produced greater (P less than 0.01) velocities than the NT grip across the aluminum (Al) bat; 2) there was no difference (P greater than 0.01) between the T and NT grips across the wooden (W) bat; 3) the W bat produced greater (P less than 0.01) velocities than the Al bat across the NT grip; and 4) there was no difference (P greater than 0.01) between the Al and W bats across the T grip.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗
PubMed1976

Organochlorine residues in three bat species from four localities in Maryland and West Virginia, 1973.

In 1973, 119 bats of three species were collected from four localities in Maryland and West Virginia. The collection included 43 big brown bats (Eptesicus fuscus), 43 little brown brown bats (Myotis lucifugus), and 33 eastern pipistrelles (Pipistrellus subflavus). The bats were collected from Round Top Mountain, Washington Co., Md.; Trout Cave, Pendleton Co., W. Va.; Montpelier Barn, Prince Georges Co., Md. Residues of sigmaDDT were highest in carcasses of bats from Round Top Mountain, which is surrounded by apple orchards. Bats from Trout Cave had the lowest residues, a circumstance which probably reflects the absence of agriculture and industry in the area. A polychlorinated biphenyl (PCB) and oxychlordane were highest at Montpelier Barn. Sources of the PCB are unknown, but chlordane is used against termites and in gardening at nearby housing developments. Residues in bats from North East Methodist Church were low except for dieldrin. Among species, little brown bats usually had the highest residue concentrations in their carcasses, whereas big brown bats had the lowest. When DDE in carcass fat of all species was above 60-90 ppm, it became measurable in brain tissue. Above 60-90 ppm, DDE levels in brains rose with increasing levels in carcass lipids. Residues of the PCB tended to respond similarly. Residue levels in brains were greatest in little brown bats; the maximum level of the PCB, 7.9 Ppm, was more than twice that of DDE.

Age Factors↗
PubMed1998

Intraspecific responses to distress calls of the pipistrelle bat, Pipistrellus pipistrellus

Responses of the vespertilionid bat Pipistrellus pipistrellus to five recently caught conspecifics confined to a wire-mesh cage, at distances of 50 and 5 m from their roosts, were recorded on 12 separate evenings at three roosts during pregnancy and lactation. When bats were confined 50 m from their roost, an almost 20-fold increase in the number of bats that passed across an open site around the cage was recorded and the strength of response (number of bat passes) increased with time. When the bats were 5 m from the roost there was an 80-fold increase in bat activity above the cage. Playbacks of recorded distress calls produced by single hand-held bats resulted in a more than three-fold increase in bat passes, but the response waned rapidly. The distress calls of recently caught P. pipistrellus were generally similar to those of individuals from the same colony held for longer in captivity, and differences in distress calls between two of the three colonies studied probably reflect differences in the physiological states of recorded bats, rather than the existence of colony-specific vocalizations. Distress calls probably function in attracting conspecifics which perform mobbing behaviour as an anti-predator response. Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Greater spear-nosed bats discriminate group mates by vocalizations.

Individuals often benefit from identifying their prospective social partners. Some species that live in stable social groups discriminate between their group mates and others, basing this distinction on calls that differ among individuals. Vocalizations that differ between social groups are much less common, and few studies have demonstrated that animals use group-distinctive calls to identify group mates. Female greater spear-nosed bats, Phyllostomus hastatus, live in stable groups of unrelated bats and give audible frequency, broadband calls termed screech calls when departing from the roost and at foraging sites. Previous field observations suggested that bats give screech calls to coordinate movements among group members. Prior acoustic analyses of 12 acoustic variables found group differences but not individual differences. Here, we use the same acoustic variables to compare calls from three cave colonies, and find that calls differ between caves. We also report results from field and laboratory playback experiments designed to test whether bats use acoustic differences to discriminate calls from different colonies, groups or individuals. Results from field playbacks indicate that response depends on the cave of origin, indicating that bats can discriminate among calls from different caves. This discrimination ability may be based, in part, on whether calls are familiar or unfamiliar to the listening bats. Laboratory playbacks demonstrate that bats discriminate calls given by their group mates from calls given by other bats from the same cave irrespective of familiarity. However, these experiments provide no evidence that bats discriminate among individuals. Previous field work indicates that females that forage with social group mates may benefit from shared information about food or mutual defence of feeding sites. Indicating group membership is essential, since these benefits appear to be restricted to group mates. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2003

Vision complements echolocation in an aerial-hawking bat.

The northern bat Eptesicus nilssonii normally hunts flying insects in the air using frequency-modulated echolocation calls. It is also known to detect and catch visually conspicuous prey (white moths) hovering low among grass stalks. To overcome the problem with acoustic clutter from the grass, which interferes with target echo detection, the bats make use of visual cues in addition to those of echolocation. We therefore investigated the minimum size of prey that the bats could distinguish by using vision, by presenting the bats with different sized dead and spread moths. We found that vision increased the chance of detection only when the moths had a wingspan of at least 5 cm. Smaller targets were detected using echolocation alone. The mean detection range was 3.5 m, suggesting that the bats need a visual acuity of 49' of arc to detect the prey. This is consistent with results of optomotor response tests and counts of retinal ganglion cells in closely related species. Our results suggest that the visual acuity of Eptesicus bats may not be adequate for prey detection under normal conditions, but that the bats can use vision when the prey is unusually large and conspicuous. The northern bats display a flexibility in prey detection techniques not previously recognised among aerial-hawking bats and they are able to use their full visual capacity in the field.

Animals↗
PubMed2000

Mechanical adaptations for echolocation in the cochlea of the bat Hipposideros lankadiva.

The cochlear mechanics of bats with long constant-frequency components in their echolocation calls are sharply tuned to the dominant second harmonic constant frequency. Hipposiderid bats employ a shorter constant-frequency call component whose frequency is less stable than in long-constant-frequency bats. To investigate to what degree cochlear mechanics in hipposiderid bats are already specialized for the processing of constant frequencies, we recorded distortion-product otoacoustic emissions in Hipposideros lankadiva. Iso-distortion threshold curves for the 2f1-f2 distortion-product otoacoustic emission reveal a threshold maximum close to the second harmonic constant frequency, between 65.0 and 70.0 kHz, and a second insensitivity close to the first harmonic constant frequency. The group delay of the 2f1-f2 distortion is prolonged for both frequency ranges, indicating that a specialized cochlear resonance may act to absorb the constant-frequency call components. Compared to long-constant-frequency bats, the threshold maximum at the second harmonic constant frequency is less pronounced and the optimum cochlear frequency separation is larger. Distortion-product otoacoustic emission suppression tuning curves and neuronal tuning curves recorded from neurons in the cochlear nucleus display an increase of tuning sharpness close to the second harmonic constant-frequency range which is smaller than that reported for long-constant-frequency bats. Our data suggest that the cochlea of hipposiderid bats represents an intermediate state between that of non-specialized bats and long-constant-frequency bats.

Adaptation, Physiological↗
PubMed1997

Temperature regulation and metabolism of an Australian bat, Chalinolobus gouldii (Chiroptera:Vespertilionidae) when euthermic and torpid.

The thermal and metabolic physiology of Chalinolobus gouldii, an Australian vespertilionid bat, was studied in the laboratory using flow-through respirometry. Chalinolobus gouldii exhibits a clear pattern of euthermic thermoregulation, typical of endotherms with respect to body temperature and rate of oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal metabolic rates ascribed to vespertilionid bats. However, like most vespertilionid bats, Chalinolobus gouldii displays extreme thermolability. It is able to enter into torpor and spontaneously arouse at ambient temperatures as low as 5 degrees C. Torpid bats thermoconform at moderate ambient temperature, with body temperature approximately ambient temperature, and have a low rate of oxygen consumption determined primarily by Q10 effects. At low ambient temperature (< 10 degrees C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a higher body temperature at low ambient temperature than do many northern hemisphere hibernating bats. Use of torpor leads to significant energy savings. The evaporative water loss of euthermic bats is relatively high, which seems unusual for a bat whose range includes extremely arid areas of Australia, and is reduced during torpor. The thermal conductance of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid bats at intermediate body temperature and ambient temperature, but increases to euthermic values for torpid bats when thermoregulating at low ambient temperature.

Animals↗
PubMed1999

Absorption of visible spectrum radiation by the wing membranes of living pteropodid bats.

The wing membranes of bats present a large surface area upon which radiation might be taken up, increasing heat load to the animals. This, combined with the high amount of heat produced during flight, has been advanced as one hypothesis explaining the fact that bats are almost exclusively nocturnal. The proportion of short-wave (visible) radiation absorbed by bat wing membrane has previously been measured at between 0.7 and 0.92. These measurements were made on pieces of membrane taken from the wings of dead, mainly insectivorous bats from temperate regions. Here we examined the amount of light transmitted through and reflected off the wing membranes of four species of live pteropodid bats. There were significant differences in wing reflection between species. At 0.68, the average proportion of light absorbed into the wing membranes was lower than previously reported. This might be because we worked with live animals or because ours were tropical bats which are routinely exposed to tropical sun when roosting. Variation in wing tension strongly affected light absorption. It was predicted that the relaxed state of wing membrane through part of the wing beat cycle would increase the absorption of light into the wings of day-flying bats. The proportion of light absorbed into wings was shown to be an important factor in the heat balance of hypothetical bats flying during the day. Our results raise the predicted temperature at which bats flying during the day might experience hyperthermia by approximately 2 degrees C and suggest that variation in albedo of wings between species may make some species more susceptible to overheating than others.

Animals↗
PubMed2005

Folivory in fruit bats: leaves provide a natural source of calcium.

Leaves are an important dietary source of carbohydrates and protein, and an especially rich source of calcium for bats. Most studies of leaf eating by fruit bats have suggested that only male bats feed on leaves. In this study, 23 wild-caught Tongan fruit bats (Pteropus tonganus) were used in feeding trials conducted in an outdoor enclosure. The number of leaves and percentage of each leaf eaten were recorded for each bat on a daily basis, and these data were then multiplied by a calcium constant that was derived from a chemical analysis of leaves from Callophylum neo-ebudicum. Leaves of C. neo-ebudicum that were available in the enclosure were consumed by 82.7% of the bats. Overall, males consumed leaves in greater quantities and with higher frequency than females. Bats that consumed leaves on a regular basis consumed up to 46% more calcium to their diet compared with bats that did not regularly consume leaves. Leaves may represent a readily available, widely used, concentrated source of minerals for foraging bats, and have the potential to contribute significantly to the total amount of ingested calcium.

Aging↗
PubMed2006

Environmental conditions, rather than season, determine torpor use and temperature selection in large mouse-eared bats (Myotis myotis).

We tested whether food availability, thermal environment and time of year affect torpor use and temperature selection in the large mouse-eared bat (Myotis myotis) in summer and winter. Food-deprived bats were torpid longer than bats offered food ad libitum. Bats placed in a gradient of low (0 degrees C-25 degrees C) ambient temperatures (T(a)) spent more time in torpor than bats in a gradient of high (7 degrees C-43 degrees C) T(a)'s. However, we did not observe seasonal variations in the use of torpor. Moreover, even when food deprived in winter, bats never entered prolonged torpor at T(a)'s characteristic of their natural hibernation. Instead, bats preferred shallow torpor at relatively high T(a), but they always maintained a difference between body and ambient temperatures of less than 2 degrees C. Calculations based on respirometric measurements of metabolic rate showed that food deprived bats spent less energy per unit of time in torpor than fed individuals, even when they entered torpor at higher T(a)'s. We conclude that T(a) likely serves as a signal of food availability and daily torpor is apparently an adaptation to unpredictable changes in food availability, such as its decrease in summer or its increase in winter. Thus, we interpret hibernation to be a second step in the evolution of heterothermy in bats, which allows survival in seasonal environments.

Animals↗
PubMed2006

Hearing in large (Eidolon helvum) and small (Cynopterus brachyotis) non-echolocating fruit bats.

Comparing the hearing abilities of echolocating and non-echolocating bats can provide insight into the effect of echolocation on more basic hearing abilities. Toward this end, we determined the audiograms of two species of non-echolocating bats, the straw-colored fruit bat (Eidolon helvum), a large (230-350 g) African fruit bat, and the dog-faced fruit bat (Cynopterus brachyotis), a small (30-45 g) bat native to India and Southeast Asia. A conditioned suppression/avoidance procedure with a fruit juice reward was used for testing. At 60 dB SPL, the hearing range of E. helvum extends from 1.38 to 41 kHz with best sensitivity at 8k Hz; the hearing range of C. brachyotis extends from 2.63 to 70 kHz with best sensitivity at 10 kHz. As with all other bats tested so far, neither species was able to hear below 500 Hz, suggesting that they may not use a time code for perceiving pitch. Comparison of the high-frequency hearing abilities of echolocating and non-echolocating bats suggests that the use of laryngeal echolocation has resulted in additional selective pressure to hear high frequencies. However, the typical high-frequency sensitivity of small non-echolocating mammals would have been sufficient to support initial echolocation in the early evolution of bats, a finding that supports the possibility of multiple origins of echolocation.

Animals↗
PubMed2003

European bat lyssaviruses: an emerging zoonosis.

In Europe, two bat lyssaviruses referred to as European bat lyssaviruses (EBLVs) types 1 and 2 (genotypes 5 and 6 respectively) which are closely related to classical rabies virus are responsible for an emerging zoonosis. EBLVs are host restricted to bats, and have been known to infect not only their primary hosts but also in rare circumstances, induce spillover infections to terrestrial mammals including domestic livestock, wildlife and man. Although spillover infections have occurred, there has been no evidence that the virus adapted to a new host. Since 1977, four human deaths from EBLVs have been reported. None of them had a record of prophylactic rabies immunization. Only fragmentary data exist about the effectiveness of current vaccines in cross-protection against EBLVs. It is clear that EBLV in bats cannot be eliminated using conventional strategies similar to the control programmes based on vaccine baits used for fox rabies in Europe during the 1980s. Due to the protected status of bats in Europe, our knowledge of EBLV prevalence and epidemiology is limited. It is possible that EBLV is under-reported and that the recorded cases of EBLV represent only a small proportion of the actual number of infected bats. For this reason, any interaction between man and bats in Europe must be considered as a possible exposure. Human exposure through biting incidents, especially unprovoked attacks, should be treated immediately with rabies post-exposure treatment and the bat, where possible, retained for laboratory analysis. Preventative measures include educating all bat handlers of the risks posed by rabies-infected animals and advising them to be immunized. This review provides a brief history of EBLVs, their distribution in host species and the public health risks.

Animals↗
PubMed1999

Preparing for inactivity: how insectivorous bats deposit a fat store for hibernation.

During late autumn insectivorous bats must deposit a fat store to cover their energy demands throughout the period of hibernation, yet the density of aerial insects by this time has already declined from its peak in midsummer. Krzanowski (1961) suggested that bats are able to deposit a fat store by manipulating their energy expenditure; specifically by selecting cold roosting locations rather than warm roosts, and depressing their body temperatures during the day roosting period. It was hypothesized that these behavioural changes result in very low daily energy demands, and despite reduced food intake the animals are still able to gain body fat. We made several tests of this hypothesis. First, we explored the thermo-selection behaviour of long-eared bats (Plecotus auritus) in the summer and in the pre-hibernal period. We found that in summer bats preferred temperatures of about 32-35 degrees (about thermoneutral), but in the pre-hibernal period they preferred much colder temperatures of about 10 degrees. Second, using open-flow respirometry we found that in the cold pre-hibernal bats entered torpor for an average of 14 h each day. Compared with bats held at 30 degrees (that did not go torpid), the bats at 7 degrees expended less energy. The extent of saving was sufficient to positively affect their mass balance, despite the fact that bats at lower temperature also had reduced digestive efficiencies. Our findings support the hypothesis that during the pre-hibernal period insectivorous bats manipulate their mass balance primarily by alterations in their energy expenditure, specifically utilizing energy-sparing mechanisms such as torpor.

Adipose Tissue↗
PubMed1999

Ectoparasites of Brazilian free-tailed bats with emphasis on anatomical site preferences for Chiroptonyssus robustipes (Acari: Macronyssidae).

Seven species of arthropods were recovered from 45 Brazilian free-tailed bats, Tadarida brasiliensis (I. Geoffrey), captured from May 1994 to May 1995 from a roost in Jenkins County, GA. Six species of mites were found infesting the bats, representing 5 families: Macronyssidae, Cheyletidae, Sarcoptidae, Rosensteiniidae, and Uropodidae. The macronyssid mite chiroptonyssus robustipes (Ewing) and the hemipteran bat bug, Cimex adjunctus (Barber), were collected from the host and the roost. C. robustipes was the most abundant mite (2,508 specimens) and the macronyssid Steatonyssus ceratognathus (Ewing) (189 specimens) was the 2nd most abundant mite found infesting the bats. The predatory cheyletid mite Cheyletonella vespertilionis Womersley (51 specimens) was also collected from the bats, and this is thought to be the 1st report of this mite from Georgia. In addition, Teinocoptes sp. (Sarcoptidae, 8 specimens), Nycteriglyphus sp. (Rosensteiniidae, 8 specimens), and uropodid mites (5 specimens) were removed from the bats. Of the 45 bats examined, all 30 females and 14 of 15 males were infested with C. robustipes. Twenty-three bat anatomical areas were designated and all C. robustipes mites were counted to ascertain anatomical preference. This mite was significantly more abundant on the ventral wing membrane areas posterior to the radiusulna and on the lower torso. Protonymphs of C. robustipes predominated on the wing membranes of the bats, whereas adult mites were more concentrated on the torso and head.

Animals↗
PubMed2005

Doppler-shift compensation in the Taiwanese leaf-nosed bat (Hipposideros terasensis) recorded with a telemetry microphone system during flight.

Biosonar behavior was examined in Taiwanese leaf-nosed bats (Hipposideros terasensis; CF-FM bats) during flight. Echolocation sounds were recorded using a telemetry microphone mounted on the bat's head. Flight speed and three-dimensional trajectory of the bat were reconstructed from images taken with a dual high-speed video camera system. Bats were observed to change the intensity and emission rate of pulses depending on the distance from the landing site. Frequencies of the dominant second harmonic constant frequency component (CF2) of calls estimated from the bats' flight speed agreed strongly with observed values. Taiwanese leaf-nosed bats changed CF2 frequencies depending on flight speed, which caused the CF2 frequencies of the Doppler-shifted echoes to remain constant. Pulse frequencies were also estimated using echoes returning directly ahead of the bat and from its sides for two different flight conditions: landing and U-turn. Bats in flight may periodically alter their attended angles from the front to the side when emitting echolocation pulses.

Acoustics↗
PubMed2006

Prevalence and genetic diversity of coronaviruses in bats from China.

Coronaviruses can infect a variety of animals including poultry, livestock, and humans and are currently classified into three groups. The interspecies transmissions of coronaviruses between different hosts form a complex ecosystem of which little is known. The outbreak of severe acute respiratory syndrome (SARS) and the recent identification of new coronaviruses have highlighted the necessity for further investigation of coronavirus ecology, in particular the role of bats and other wild animals. In this study, we sampled bat populations in 15 provinces of China and reveal that approximately 6.5% of the bats, from diverse species distributed throughout the region, harbor coronaviruses. Full genomes of four coronavirues from bats were sequenced and analyzed. Phylogenetic analyses of the spike, envelope, membrane, and nucleoprotein structural proteins and the two conserved replicase domains, putative RNA-dependent RNA polymerase and RNA helicase, revealed that bat coronaviruses cluster in three different groups: group 1, another group that includes all SARS and SARS-like coronaviruses (putative group 4), and an independent bat coronavirus group (putative group 5). Further genetic analyses showed that different species of bats maintain coronaviruses from different groups and that a single bat species from different geographic locations supports similar coronaviruses. Thus, the findings of this study suggest that bats may play an integral role in the ecology and evolution of coronaviruses.

Animals↗