Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BATS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed1987

Optimal response of key enzymes and uncoupling protein to cold in BAT depends on local T3 generation.

We have examined the activity of three lipogenic enzymes [malic enzyme (ME), glucose-6-phosphate dehydrogenase (G-6-PD), and acetyl coenzyme A (CoA) carboxylase], the activity of the mitochondrial FAD-dependent alpha-glycerolphosphate dehydrogenase (alpha-GPD), and the mitochondrial concentration of uncoupling protein (UCP) in brown adipose tissue (BAT) of euthyroid and hypothyroid rats, both at room temperature and in response to acute cold stress. These enzymes and UCP are important for the thermogenic response of BAT in adaptation to cold. The basal level of the lipogenic enzymes was normal or slightly elevated in hypothyroid rats maintained at 23 degrees C, but the levels of alpha-GPD and UCP were markedly reduced. Forty-eight hours at 4 degrees C resulted in an increase in the activity of G-6-PD, acetyl-CoA carboxylase, and alpha-GPD and in the concentration of UCP both in euthyroid and hypothyroid animals, but the levels reached were invariably less in hypothyroid animals, indicating that thyroid hormone is necessary for a full metabolic response of BAT under maximal demands. Of all variables measured, the most affected was UCP (only one-fifth of the response of euthyroid rats to cold) followed by alpha-GPD (approximately 50% the euthyroid response). The administration of replacement doses of triiodothyronine (T3) to hypothyroid rats for 5-7 days did not normalize any of the BAT responses, whereas the replacement of thyroxine (T4) for only 2 days sufficed to normalize them all. This effect of T4 was abolished by preventing its conversion to T3 with iopanoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue, Brown↗
PubMed1995

Regulation of beta 3-adrenergic receptor mRNA by sympathetic nerves and glucocorticoids in BAT of Zucker obese rats.

Impaired brown adipose tissue (BAT) thermogenesis in the genetically obese Zucker fatty (fa/fa) rat is restored to normal by adrenalectomy. We investigated the role of the sympathetic nervous system in modulating the effects of adrenalectomy by studying beta3-adrenergic receptor (AR) and uncoupling protein (UCP) mRNA levels in unilaterally sympathectomized interscapular BAT of lean and obese rats. UCP mRNA levels were increased by adrenalectomy. Sympathetic denervation prevented this adrenalectomy-induced increase in lean rats but not in obese rats. beta 3-AR mRNA was decreased in BAT of obese rats. Adrenalectomy decreased and denervation increased beta 3-AR mRNA in lean rats but the opposite response was observed to both of these manipulations in obese rats. beta 3-AR mRNA and UCP mRNA were negatively correlated in lean rats but positively correlated in obese rats. Norepinephrine increased UCP mRNA levels in denervated BAT of both lean and obese rats and decreased beta 3-AR mRNA in lean rats but not obese rats. These data suggest that the regulation of the beta 3-AR gene in response to sympathetic stimuli and glucocorticoids is abnormal in the obese rat.

Adipose Tissue, Brown↗
PubMed1982

Neural representation of target distance in auditory cortex of the echolocating bat Myotis lucifugus.

1. Single- and multiunit recordings were obtained from neurons in the auditory cortex of the echolocating bat Myotis lucifugus, while trains of stimuli designed to simulate the bat's frequency-modulated (FM) orientation pulse and its returning echo were delivered. It was found that many neurons in the cortex responded selectively to pulse-echo pairs only if the time delay separating the artificial pulse and the echo was within a certain range. This response property is called "delay-dependent facilitation." Since echolating bats are known to utilize echo-delay information for the determination of target distance, it is postulated that these neurons are involved in the process of distance perception. 2. Two types of delay-sensitive neurons were characterized on the basis of their response patterns. P-type units had short maximum response delays, narrow delay response functions, and response latencies for pulse-echo pairs that were similar to their response latencies for single loud FM pulses. E-type units had longer maximum response delays, wide delay response functions, and pulse-echo pair response latencies that were time-locked to the echo. Another important difference between these two classes was that changes in the amplitude of the artificial echo caused systematic changes in the delay response of E-type units but not of P-type units. 3. The sharpness and stability of the delay response functions of P-type units suggested that they may encode target distance by responding at discrete echo delays. In contrast, delay tuning may not be an unambiguous determinant of echo delay in E-type units. Here, the most consistent and reliable response parameter for echo delay is the time at which the responses occurred. This suggested that echo delay could be encoded by the temporal pattern of responses in E-type units in relation to the responses evoked by the outgoing orientation cry. The different range of delay of delay sensitivity of P-type and E-type units indicates that these two mechanisms could be operating at different ranges of target distance. 4. P-type and E-type responses may not be due to different populations of neurons but to different response properties of the same population under different conditions. Evidence for this proposition was obtained by showing that in some recordings, decreases in the amplitude of the artificial pulse caused a switch in response from a long best delay, E-type response to a short best delay, P-type response. This suggested that the delay sensitivity of cortical neurons could be under the bat's control based on the intensity of its pulse emissions.

Animals↗
PubMed1989

Distribution of combination-sensitive neurons in the ventral fringe area of the auditory cortex of the mustached bat.

1. The orientation sound (pulse) of the mustached bat, Pteronotus parnellii parnellii, consists of long constant-frequency components (CF1-4) and short frequency-modulated components (FM1-4). The auditory cortex of this bat contains several combination-sensitive areas: FM-FM, DF, VA, VF, and CF/CF. The FM-FM area consists of neurons tuned to a combination of the pulse FM1 and the echo FMn (n = 2, 3, or 4) and has an echo-delay (target-range) axis. Our preliminary anatomical studies with tritiated amino acids suggest that the FM-FM area projects to the dorsal fringe (DF) area, which in turn projects to the ventral fringe (VF) area. The aim of our study was to characterize the response properties of VF neurons and to explore the functional organization of the VF area. Acoustic stimuli delivered to the bats were CF tones, FM sounds, and their combinations mimicking the pulse emitted by the mustached bat and the echo. 2. Like the FM-FM and DF areas, the VF area is composed of three types of FM-FM combination-sensitive neurons: FM1-FM2, FM1-FM3, and FM1-FM4. These neurons show little or no response to a pulse alone, echo alone, single CF tone or single FM sound. They do, however, show a strong facilitative response to a pulse-echo pair with a particular echo delay. The essential components in the pulse-echo pair for facilitation are the FM1 of the pulse and the FMn of the echo.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1997

Neural selectivity and tuning for sinusoidal frequency modulations in the inferior colliculus of the big brown bat, Eptesicus fuscus.

Most communication sounds and most echolocation sounds, including those used by the big brown bat (Eptesicus fuscus), contain frequency-modulated (FM) components, including cyclical FM. Because previous studies have shown that some neurons in the inferior colliculus (IC) of this bat respond to linear FM sweeps but not to pure tones or noise, we asked whether these or other neurons are specialized for conveying information about cyclical FM signals. In unanesthetized bats, we tested the response of 116 neurons in the IC to pure tones, noise with various bandwidths, single linear FM sweeps, sinusoidally amplitude-modulated signals, and sinusoidally frequency-modulated (SFM) signals. With the use of these stimuli, 20 neurons (17%) responded only to SFM, and 10 (9%) responded best to SFM but also responded to one other test stimulus. We refer to the total 26% of neurons that responded best to SFM as SFM-selective neurons. Fifty-nine neurons (51%) responded about equally well to SFM and other stimuli, and 27 (23%) did not respond to SFM but did respond to other stimuli. Most SFM-selective neurons responded to a limited range of modulation rates and a limited range of modulation depths. The range of modulation rates over which individual neurons responded was 5-170 Hz (n = 20). Thus SFM-selective neurons respond to low modulation rates. The depths of modulations to which the neurons responded ranged from +/-0.4 to +/-19 kHz (n = 15). Half of the SFM-selective neurons did not respond to the first cycle of SFM. This finding suggests that the mechanism for selective response to SFM involves neural delays and coincidence detectors in which the response to one part of the SFM cycle coincides in time either with the response to a later part of the SFM cycle or with the response to the first part of the next cycle. The SFM-selective neurons in the IC responded to a lower and more limited range of SFM rates than do neurons in the nuclei of the lateral lemniscus of this bat. Because the FM components of biological sounds usually have low rates of modulation, we suggest that the tuning of these neurons is related to biologically important sound parameters. The tuning could be used to detect FM in echolocation signals, modulations in high-frequency sounds that are generated by wing beats of some beetles, or social communication sounds of Eptesicus.

Acoustic Stimulation↗
PubMed2006

Behavioral flexibility positively correlated with relative brain volume in predatory bats.

We investigated the potential relationships between foraging strategies and relative brain and brain region volumes in predatory (animal-eating) echolocating bats. The species we considered represent the ancestral state for the order and approximately 70% of living bat species. The two dominant foraging strategies used by echolocating predatory bats are substrate-gleaning (taking prey from surfaces) and aerial hawking (taking airborne prey). We used species-specific behavioral, morphological, and ecological data to classify each of 59 predatory species as one of the following: (1) ground gleaning, (2) behaviorally flexible (i.e., known to both glean and hawk prey), (3) clutter tolerant aerial hawking, or (4) open-space aerial hawking. In analyses using both species level data and phylogenetically independent contrasts, relative brain size was larger in behaviorally flexible species. Further, relative neocortex volume was significantly reduced in bats that aerially hawk prey primarily in open spaces. Conversely, our foraging behavior index did not account for variability in hippocampus and inferior colliculus volume and we discuss these results in the context of past research.

Adaptation, Psychological↗
PubMed1994

Cell types in the mustached bat auditory cortex.

Cells in the auditory cortex of the mustached bat were studied with Golgi stains. No cell types appeared to be unique to the mustached bat auditory cortex or to specialized functional areas, but the laminar proportions and distributions of cell types were somewhat different from that reported for primary sensory cortex of other species. Two major cell types were distinguished, those with dendritic spines and those without spines. Non-spiny neurons were concentrated deep in layer III/IV and in layer V, and had three types of dendritic patterns, multipolar, bitufted and bipolar. Many of the non-spiny neurons were large; some nearly equaled the largest pyramidal neurons in size. Five types of spiny neurons were identified, pyramidal cells, extraverted pyramidal cells, 'spiny stellate-like' neurons, and multiform cells. In the narrow, densely packed, 'accentuated' layer II, slightly more than half of the spiny neurons were extraverted pyramidal cells, which are characterized by multiple, widely diverging apical dendrites. The high concentration of layer II extraverted pyramidal neurons is consistent with descriptions of the 'accentuated' layer II previously reported in other bat species and 'basal' insectivores. The remaining spiny neurons in layer II, and the preponderance of spiny neurons in layers III-VI, were typical pyramidal neurons that had single apical dendrites and tufts of basal dendrites. The thalamic recipient zone (deep layer III/IV) contained few candidates for spiny stellate cells, so a major constituent of the thalamic recipient zone in primary sensory cortex of many species is only a minor cellular component in the mustached bat auditory cortex.

Animals↗
PubMed1993

Ultrastructural characteristics of atrial, ventricular and subendocardial (Purkinje) cells of the fruit-eating bat Eidolon helvum.

The ultrastructure of the myocardium of the large (285 gm) fruit-eating bat (Eidolon helvum) provides further evidence that, among mammalian species, different types of cardiac myocytes are morphologically heterogeneous. Atrial cells of this species, like those of smaller bats previously studied, have few of the natriuretic hormone-containing granules. These granules are also small, with a mean diameter of 176 +/- 3.9 nm, in comparison with those of the rat (230 +/- 5.8 nm) and mouse (211 +/- 4.7 nm). In all types of myocytes of the bat investigated, mitochondrial matrix granules are more prominent than in those of the rat and mouse. Also distinctive are the Purkinje cells which, aside from their large size (30 microns) and lack of T-tubules, have atrial granule-like inclusions. These cells are well endowed with mitochondria (28% of cytoplasmic volume) and with lipid bodies but have few glycogen granules. Their myofibrillae (33%) are well aligned. The ventricular cells (average diameter 14 microns) have nearly equal volumes of mitochondria (41%) and myofibrils (47%). Mitochondrial cristae, however, are not compactly organized. Lipid material is found in the matrix of the mitochondria. Extensive evaginations of endothelial cells of the bat endocardium appear continuous with endothelial vacuoles. In these endothelial cells, there are also many dense granules of varying shapes and sizes.

Animals↗
PubMed1984

Perinatal and postnatal patterns of plasma sex steroid-binding protein and testosterone in relation to puberty in the male little brown bat.

The little brown bat (Myotis lucifugus lucifugus) possesses a specific plasma sex steroid-binding protein (SBP) which exhibits high affinity for both testosterone (T) and estradiol. To examine the peri- and postnatal patterns of plasma androgen binding in relation to puberty, concentrations of SBP and total T levels were measured in males at various intervals throughout the first year of life. In addition, reproductive organs were examined histologically over this period. SBP levels were low (less than 7 nM) in near-term fetuses (mid-June) but increased more than 30-fold by 1 week of age (range, 245-602 nM). Elevated titers of this protein were present until 3 weeks of age. By 4 weeks of age (onset of puberty, initiation of the first spermatogenesis), SBP concentrations had fallen significantly, and by 12 weeks, just before the first winter hibernation period, plasma SBP levels had returned to low prenatal-like values (3-12 nM). These levels were maintained throughout winter dormancy. The total plasma T concentrations were also elevated during the early postnatal period and were comparable to or even exceeded those previously measured in spermatogenically active adults. Plasma T levels then declined in parallel to those of SBP and reached a nadir (less than 0.6 ng/ml) by 12 weeks of age. As with SBP, T also remained low throughout hibernation. Although a complete spermatogenic cycle was found to occur in postnatal bats during the summer of their birth, this cycle was greatly reduced compared to that which occurs in sexually mature adults during the same period. Maximal testicular weights from the postnatal males were only one fifth of those previously measured in adult males. In addition, the epididymides in the young bats remained virtually devoid of sperm, and the accessory glands showed little evidence of stimulation. Thus, this first spermatogenic cycle in Myotis does not result in the attainment of sexual maturity and, therefore, appears to be "silent." Since sexual maturity is reached during the following summer when the bats are approximately 1 yr of age, the pubertal process in Myotis is prolonged and appears to be biphasic. Nevertheless, the existence of a perinatal rise in SBP levels (which is repeated in this species when the pubertal process is reinitiated during the second summer) as well as a decline in SBP levels during the onset of puberty resembles that previously described for other mammals.

Animals↗
PubMed2003

Sex differences in the thermoregulation and evaporative water loss of a heterothermic bat, Lasiurus cinereus, during its spring migration.

This study quantifies sex differences in thermoregulation and water loss of a small (20-35 g) insectivorous heterothermic mammal, the hoary bat Lasiurus cinereus, during its spring migration. We measured body temperature, metabolic rate and evaporative water loss, and calculated wet thermal conductance, for bats exposed to air temperatures ranging from 0 to 40 degrees C for periods of 2-5 h. Pregnant females maintained normothermic body temperatures (35.7+/-0.7 degrees C; mean +/- S.E.M.) independent of air temperature. In contrast, males became torpid during the majority (68%) of exposures to air temperatures <25 degrees C. The thermal neutral zone (TNZ) ranged between approximately 30 degrees C and 34 degrees C in both sexes and, within the TNZ, females had lower mass-specific metabolic rates (6.1+/-0.2 mW g(-1)) than males (9.0+/-0.9 mW g(-1)). Wet thermal conductance values in torpid bats (0.7+/-0.5 mW g(-1) deg.(-1)) were lower than those of normothermic individuals (1.1+/-0.3 mW g(-1) deg.(-1)). Mass-specific rates of evaporative water loss in males were consistently higher than in females at most air temperatures and rates of water loss in torpid bats were 63+/-6% of normothermic values. These results suggest that male and pregnant female L. cinereus employ different thermoregulatory strategies during their spring migration. Females defend normothermic body temperatures, presumably to expedite embryonic growth, while males use torpor, presumably to minimize energy and water deficits. These variable thermoregulatory strategies may reflect continental differences in the summer distribution of the sexes.

Analysis of Variance↗
PubMed2005

Echolocation call intensity in the aerial hawking bat Eptesicus bottae (Vespertilionidae) studied using stereo videogrammetry.

Aerial hawking bats use intense echolocation calls to search for insect prey. Their calls have evolved into the most intense airborne animal vocalisations. Yet our knowledge about call intensities in the field is restricted to a small number of species. We describe a novel stereo videogrammetry method used to study flight and echolocation behaviour, and to measure call source levels of the aerial hawking bat Eptesicus bottae (Vespertilionidae). Bats flew close to their predicted minimum power speed. Source level increased with call duration; the loudest call of E. bottae was at 133 dB peSPL. The calculated maximum detection distance for large flying objects (e.g. large prey, conspecifics) was up to 21 m. The corresponding maximum echo delay is almost exactly the duration of one wing beat in E. bottae and this also is its preferred pulse interval. These results, obtained by using videogrammetry to track bats in the field, corroborate earlier findings from other species from acoustic tracking methods.

Animals↗
PubMed1993

What ears do for bats: a comparative study of pinna sound pressure transformation in chiroptera.

Using a moveable loudspeaker and an implanted microphone, we studied the sound pressure transformation of the external ears of 47 species of bats from 13 families. We compared pinna gain, directionality of hearing and interaural intensity differences (IID) in echolocating and non-echolocating bats, in species using different echolocation strategies and in species that depend upon prey-generated sounds to locate their targets. In the Pteropodidae, two echolocating species had slightly higher directionality than a non-echolocating species. The ears of phyllostomid and vespertilionid species showed moderate directionality. In the Mormoopidae, the ear directionality of Pteronotus parnellii clearly matched the dominant spectral component of its echolocation calls, unlike the situation in three other species. Species in the Emballonuridae, Molossidae, Rhinopomatidae and two vespertilionids that use narrow-band search-phase echolocation calls showed increasingly sharp tuning of the pinna to the main frequency of their signals. Similar tuning was most evident in Hipposideridae and Rhinolophidae, species specialized for flutter detection via Doppler-shifted echoes of high-duty-cycle narrow-band signals. The large pinnae of bats that use prey-generated sounds to find their targets supply high sound pressure gain at lower frequencies. Increasing domination of a narrow spectral band in echolocation is reflected in the passive acoustic properties of the external ears (sharper directionality). The importance of IIDs for lateralization and horizontal localization is discussed by comparing the behavioural directional performance of bats with their bioacoustical features.

Animals↗
PubMed1997

A stereological comparison of villous and microvillous surfaces in small intestines of frugivorous and entomophagous bats: species, inter-individual and craniocaudal differences.

The extents of functional surfaces (villi, microvilli) have been estimated at different longitudinal sites, and in the entire small intestine, for three species of bats belonging to two feeding groups: insect- and fruit-eaters. In all species, surface areas and other structural quantities tended to be greatest at more cranial sites and to decline caudally. The entomophagous bat (Miniopterus inflatus) had a mean body mass (coefficient of variation) of 8.9 g (5%) and a mean intestinal length of 20 cm (6%). The surface area of the basic intestinal tube (primary mucosa) was 9.1 cm2 (10%) but this was amplified to 48 cm2 (13%) by villi and to 0.13 m2 (20%) by microvilli. The total number of microvilli per intestine was 4 x 10(11) (20%). The average microvillus had a diameter of 8 nm (10%), a length of 1.1 microns (22%) and a membrane surface area of 0.32 micron 2 (31%). In two species of fruit bats (Epomophorus wahlbergi and Lisonycteris angolensis), body masses were greater and intestines longer, the values being 76.0 g (18%) and 76.9 g (4%), and 73 cm (16%) and 72 cm (7%), respectively. Surface areas were also greater, amounting to 76 cm2 (26%) and 45 cm2 (8%) for the primary mucosa, 547 cm2 (29%) and 314 cm2 (16%) for villi and 2.7 m2 (23%) and 1.5 m2 (18%) for microvilli. An increase in the number of microvilli, 33 x 10(11) (19%) and 15 x 10(11) (24%) per intestine, contributed to the more extensive surface area but there were concomitant changes in the dimensions of microvilli. Mean diameters were 94 nm (8%) and 111 nm (4%), and mean lengths were 2.8 microns (12%) and 2.9 microns (10%), respectively. Thus, an increase in the surface area of the average microvillus to 0.83 micron 2 (12%) and 1.02 microns 2 (11%) also contributed to the greater total surface area of microvilli. The lifestyle-related differences in total microvillous surface areas persisted when structural quantities were normalised for the differences in body masses. The values for total microvillous surface area were 148 cm2g-1 (20%) in the entomophagous bat, 355 cm2g-1 (20%) in E. wahlbergi and 192 cm2g-1 (17%) in L. angolensis. This was true despite the fact that the insecteater possessed a greater length of intestine per unit of body mass: 22 mm g-1 (8%) versus 9-10 mm g-1 (9-10%) for the fruit-eaters.

Animals↗
PubMed2000

The effect of alterations in activity and body temperature on the pulmonary surfactant system in the lesser long-eared bat Nyctophilus geoffroyi.

Pulmonary surfactant is a mixture of phospholipids, neutral lipids and proteins that controls the surface tension of the fluid lining the lung. It is critical for lung stability and function. The amount and composition of surfactant are influenced by physiological variables such as metabolic rate, body temperature and ventilation. We investigated the plasticity of the pulmonary surfactant system in the microchiropteran bat Nyctophilus geoffroyi throughout a natural 24 h cycle. Bats were housed at 24 degrees C on a fixed (8 h:16 h) light:dark photoperiod. At 4 h intervals throughout the 24 h period, bats were lavaged and the surfactant analysed for absolute and relative amounts of total phospholipid (PL), disaturated phospholipid (DSP) and cholesterol (Chol). N. geoffroyi experienced two peaks of activity, at 18:00 h and 06:00 h. The amount of surfactant increased 1.5-fold upon arousal from torpor. The proportion of DSP to PL in the surfactant remained constant. Similarly, the Chol/PL and Chol/DSP ratios remained relatively constant. Surfactant cholesterol content did not increase during torpor in N. geoffroyi. Cholesterol does not appear to control surfactant fluidity during torpor in these bats, but instead the cholesterol content exactly mirrored the diurnal changes in body temperature.

Animals↗
PubMed2000

What it takes to fly: the structural and functional respiratory refinements in birds and bats.

In absolute terms, flight is a highly energetically expensive form of locomotion. However, with respect to its cost per unit distance covered, powered flight is a very efficient mode of transport. Birds and bats are the only extant vertebrate taxa that have achieved flight. Phylogenetically different, they independently accomplished this elite mode of locomotion by employing diverse adaptive schemes and strategies. Integration of functional and structural parameters, a transaction that resulted in certain trade-offs and compromises, was used to overcome exacting constraints. Unique morphological, physiological and biochemical properties were initiated and refined to enhance the uptake, transfer and utilization of oxygen for high aerobic capacities. In bats, exquisite pulmonary structural parameters were combined with optimal haematological ones: a thin blood-gas barrier, a large pulmonary capillary blood volume and a remarkably extensive alveolar surface area in certain species developed in a remarkably large lung. These factors were augmented by, for example, exceptionally high venous haematocrits and haemoglobin concentrations. In birds, a particularly large respiratory surface area and a remarkably thin blood-gas (tissue) barrier developed in a small, rigid lung; a highly efficient cross-current system was fabricated within the parabronchi. The development of flight in only four animal taxa (among all the animal groups that have ever evolved; i.e. insects, the now-extinct pterosaurs, birds and bats) provides evidence for the enormous biophysical and energetic constraints that have stymied volancy. Bats improved a fundamentally mammalian lung to procure the large amounts of oxygen needed for flight. The lung/air sac system of birds is not therefore a prescriptive morphology for flight: the essence of its design can be found in the evolution of the reptilian lung, the immediate progenitor stock from which birds arose. The attainment of flight is a classic paradigm of the remarkable adaptability inherent in organismal and organic biology for countering selective pressures by initiating elegant morphologies and physiologies.

Altitude↗
PubMed2000

Soaring and non-soaring bats of the family pteropodidae (flying foxes, Pteropus spp.): wing morphology and flight performance.

On oceanic islands, some large diurnal megachiropteran bat species (flying foxes; Pteropus spp.) frequently use thermal or slope soaring during foraging flights to save energy. We compared the flight morphology and gliding/soaring performance of soaring versus non-soaring Pteropus species, one pair on American Samoa and one pair on the Comoro Islands, and two other soaring/flap-gliding species and one non-soaring species. We predicted that the soaring species should have a lower body mass, longer wings and, hence, lower wing loadings than those species that use mainly flapping flight. This would give a lower sinking speed during gliding, a higher glide ratio, and enable the bats to make tighter turns with lower sinking speeds than in the non-soaring species. We theoretically calculated the gliding and circling performances of both the soaring and non-soaring species. Our results show that there are tendencies towards longer wings and lower wing loadings in relation to body size in the gliding/soaring flying foxes than in the non-soaring ones. In the species-pair comparison of the soaring and non-soaring species on American Samoa and the Comoro Islands, the soarers on both islands turn out to have lower wing loadings than their non-soaring partners in spite of opposite size differences among the pairs. These characteristics are in accordance with our hypothesis on morphological adaptations. Most differences are, however, only significant at a level of P<0.1, which may be due to the small sample size, but overlap also occurs. Therefore, we must conclude that wing morphology does not seem to be a limiting factor preventing the non-soarers from soaring. Instead, diurnality in the soaring species seems to be the ultimate determinant of soaring behaviour. The morphological differences cause visible differences in soaring and gliding performance. The glider/soarers turn out to have lower minimum sinking speeds, lower best glide speeds and smaller turning radii than the non-soarers. When the wing measurements and soaring performance are normalized to a body mass of 0.5 kg for all species, the minimum sinking speed becomes significantly lower (P<0.05) in the three soaring and the one flap-gliding species (0.63 m s(-)(1)) than in the three non-soaring species (0.69 m s(-)(1)). Interestingly, the zones in the diagrams for the glide polars and circling envelopes of these similar-sized bats become displaced for the glider/soarers versus the non-soarers. The glide polars overlap slightly only at the gliding speeds appropriate for these bats, whereas the circling envelopes do not overlap at the appropriate bank angles and turning radii. This points towards adaptations for better gliding/soaring performance in the soaring and gliding species.

American Samoa↗
PubMed2001

The acoustic advantage of hunting at low heights above water: behavioural experiments on the European 'trawling' bats Myotis capaccinii, M. dasycneme and M. daubentonii.

We have demonstrated in behavioural experiments that success in capturing prey from surfaces in 'trawling Myotis' (Leuconoë-type) depends on the acoustic properties of the surface on which the prey is presented. Two types of surface structure were ensonified with artificial bat signals to probe their acoustic characteristics. We have shown that perception of prey by echolocation is easier if the prey is presented on a smooth surface (such as calm water) than if it is presented on a structured surface (such as vegetation or the ground). This is because the smooth surface reflects a much lower level of clutter echoes than the structured one if ensonified at an angle typical for bats foraging low over water. The ensonification experiments revealed that the sound pressure level of the echo was even higher for mealworms on a smooth surface than for mealworms suspended in air. This might be because waves travelling via the surface also contribute to the echo (e.g. reflection from the surface to the mealworm, back to the surface and then to the receiver). From the behavioural experiments, we conclude that 'trawling Myotis' take isolated objects on smooth (water) surfaces for prey. Those objects reflect isolated, stationary acoustic glints back to the echolocating bats. Conversely, 'trawling Myotis' will not recognise prey if prey echoes are embedded in numerous clutter echoes. We have demonstrated marked similarities between the three European 'trawling Myotis' species M. dasycneme, M. daubentonii and M. capaccinii in echolocation behaviour, search image, foraging strategy and prey perception. We propose that a combination of prey abundance and acoustic advantages could have led to repeated and convergent evolution of 'trawling' bats in different parts of the world.

Acoustics↗
PubMed2002

Implanted electrode recordings from a praying mantis auditory interneuron during flying bat attacks.

Using an implanted electrode, we recorded the responses from the ultrasound-sensitive mantis interneuron 501-T3 during flying bat attacks in a large flight room where the mantis served as the target. 501-T3 responds to each vocalization emitted with multi-spike bursts when pulse repetition rates (PRRs) are below 55 pulses x s(-1). As PRR increases and pulse durations fall below 3 ms, 501-T3 ceases burst activity. On average, spike bursts cease 272 ms before contact (when the bat is 73 cm away from the preparation). The timing of cessation of activity in 501-T3 is similar to the latency for the diving portion of the response of the mantid (242 ms). Experiments using vocalizing stationary bats confirm that 501-T3 responds more reliably to longer pulse durations (> or =3 ms) when intensities are below 90 dB pe SPL. The cessation of 501-T3 activity is probably due both to the increasing PRR and to the decreasing pulse duration that occur in the terminal buzz phase of a bat attack. 501-T3 may be actively shut off at high PRRs and/or intensities to protect the interneuron from habituation while the mantis performs an escape response. The cessation of 501-T3 activity is consistent with the lack of a very late ultrasound-mediated evasive response by the mantis. However, cessation of 501-T3 activity may allow a true 'last-chance' response to be mediated by other neural systems.

Animals↗