Eavesdropping by bats on the feeding buzzes of conspecifics

2007 ◽  
Vol 85 (7) ◽  
pp. 795-801 ◽  
Author(s):  
E.H. Gillam
Keyword(s):  
Echolocation Call ◽  
Tadarida Brasiliensis ◽  
Echolocation Calls ◽  
Insect Prey ◽  
Bat Activity

Echolocation calls of most bats are emitted at high intensities and subject to eavesdropping by nearby conspecifics. Bats may be especially attentive to “feeding buzz” calls, which are emitted immediately before attack on airborne insects and indicate the potential presence of prey in the nearby area. Although previous work has shown that some species are attracted to feeding buzzes, these studies did not provide a well-controlled test of eavesdropping, as comparisons were made between responses to natural and altered signals (e.g., forward versus backward broadcasts of calls). In this study, I assessed the importance of feeding buzzes by conducting playbacks of controlled echolocation stimuli. I presented free-flying Brazilian free-tailed bats, Tadarida brasiliensis (I. Geoffroy, 1824), with echolocation call sequences in which feeding buzz calls were either present or absent, as well as a silence control. I determined levels of bat activity by counting the number of echolocation calls and bat passes recorded in the presence of each stimulus, and found significantly greater bat activity in response to broadcasts that contained feeding buzzes than to broadcasts without feeding buzzes or to the silence control. These results indicate that bats are especially attentive to conspecific feeding buzz calls and that eavesdropping may allow a bat to more readily locate rich patches of insect prey.

scholarly journals Brazilian free-tailed bats (Tadarida brasiliensis) adjust foraging behaviour in response to migratory moths

2018 ◽  
Vol 96 (6) ◽  
pp. 513-520 ◽  
Author(s):  
J.J. Krauel ◽  
J.M. Ratcliffe ◽  
J.K. Westbrook ◽  
G.F. McCracken
Keyword(s):  
Foraging Behaviour ◽  
Ground Level ◽  
Prey Detection ◽  
Echolocation Call ◽  
Tadarida Brasiliensis ◽  
Call Duration ◽  
Above Ground Level ◽  
Bat Activity ◽  
Moth Migration

Insect migrations represent large movements of resources across a landscape, which are attractive to predators capable of detecting and catching them. Brazilian free-tailed bats (Tadarida brasiliensis (I. Geoffroy, 1824)) consume migratory noctuid moths, which concentrate in favourable winds resulting in aggregations of prey that attract bats hundreds of metres above ground. Although T. brasiliensis are known to feed on these aggregations of migratory moths, changes in their foraging behaviours have not been linked to moth migration events. We investigated possible shifts in the bats’ foraging behaviours when moths are migrating with respect to altitude and moth abundance. We recorded 1104 echolocation call passes of T. brasiliensis at ground level and at altitudes of ∼100 and ∼200 m above ground level. We found proportionally more bat activity at higher altitudes when migratory moth abundance was high. We also found that bats decreased call frequency and bandwidth and increased call duration at higher altitudes and behaved similarly with increasing moth abundance even at ground level. Our results support predictions that bats change foraging behaviour in response to seasonal availability of migratory moths and document alterations in echolocation call parameters that are consistent with optimizing prey detection.

scholarly journals Description of Echolocation Call Parameters for Urban Bats in Vietnam as a Step Towards a More Integrated Acoustic Monitoring of Urban Wildlife in Southeast Asia

Diversity ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 18
Author(s):  
Long Kim Pham ◽  
Bang Van Tran ◽  
Quy Tan Le ◽  
Trung Thanh Nguyen ◽  
Christian C. Voigt
Keyword(s):  
Discriminant Function ◽  
Discriminant Function Analysis ◽  
Function Analysis ◽  
Quantitative Description ◽  
Southeast Asian ◽  
Asian Countries ◽  
Echolocation Call ◽  
Echolocation Calls ◽  
Pilot Work ◽  
Southeast Asian Countries

This study is the first step towards more systematic monitoring of urban bat fauna in Vietnam and other Southeast Asian countries by collecting bat echolocation call parameters in Ho Chi Minh and Tra Vinh cities. We captured urban bats and then recorded echolocation calls after releasing in a tent. Additional bat’s echolocation calls from the free-flying bats were recorded at the site where we captured bat. We used the obtained echolocation call parameters for a discriminant function analysis to test the accuracy of classifying these species based on their echolocation call parameters. Data from this pilot work revealed a low level of diversity for the studied bat assemblages. Additionally, the discriminant function analysis successfully classified bats to four bat species with an accuracy of >87.4%. On average, species assignments were correct for all calls from Taphozous melanopogon (100% success rate), for 70% of calls from Pipistrellus javanicus, for 80.8% of calls from Myotis hasseltii and 67.3% of calls from Scotophilus kuhlii. Our study comprises the first quantitative description of echolocation call parameters for urban bats of Vietnam. The success in classifying urban bats based on their echolocation call parameters provides a promising baseline for monitoring the effect of urbanization on bat assemblages in Vietnam and potentially also other Southeast Asian countries.

scholarly journals Rapid jamming avoidance in biosonar

2006 ◽  
Vol 274 (1610) ◽  
pp. 651-660 ◽  
Author(s):  
Erin H Gillam ◽  
Nachum Ulanovsky ◽  
Gary F McCracken
Keyword(s):  
Abrupt Change ◽  
Considerable Effort ◽  
Echolocation Call ◽  
Tadarida Brasiliensis ◽  
Radar Systems ◽  
Spectral Shifts ◽  
Processing Strategies ◽  
Jamming Avoidance ◽  
Sonar Systems ◽  
Behavioural Correlations

The sonar systems of bats and dolphins are in many ways superior to man-made sonar and radar systems, and considerable effort has been devoted to understanding the signal-processing strategies underlying these capabilities. A major feature determining the efficiency of sonar systems is the sensitivity to noise and jamming signals. Previous studies indicated that echolocating bats may adjust their signal structure to avoid jamming (‘jamming avoidance response’; JAR). However, these studies relied on behavioural correlations and not controlled experiments. Here, we provide the first experimental evidence for JAR in bats. We presented bats ( Tadarida brasiliensis ) with ‘playback stimuli’ consisting of recorded echolocation calls at one of six frequencies. The bats exhibited a JAR by shifting their call frequency away from the presented playback frequency. When the approaching bats were challenged by an abrupt change in the playback stimulus, they responded by shifting their call frequencies upwards, away from the playback. Interestingly, even bats initially calling below the playback's frequency shifted their frequencies upwards, ‘jumping’ over the playback frequency. These spectral shifts in the bats' calls occurred often within less than 200 ms, in the first echolocation call emitted after the stimulus switch—suggesting that rapid jamming avoidance is important for the bat.

scholarly journals Don’t believe the mike: behavioural, directional, and environmental impacts on recorded bat echolocation call measures

2018 ◽  
Vol 96 (4) ◽  
pp. 283-288 ◽  
Author(s):  
J.M. Ratcliffe ◽  
L. Jakobsen
Keyword(s):  
Environmental Impacts ◽  
Acoustic Signals ◽  
Bird Song ◽  
Great Flexibility ◽  
Echolocation Call ◽  
Echolocation Calls ◽  
Acoustic Information ◽  
Species Overlap ◽  
Actual Signal ◽  
Nocturnal Mammals

Echolocation calls produced by bats in their larynges allow these flying, nocturnal mammals to orient and find food at night. The acoustic signals are not like bird song, and even individual bats exhibit great flexibility in call design and between-species overlap is common. As a result, identifying bats to species by their echolocation calls even in communities with few bat species can be difficult. Unfortunately, the situation is worse still. As a result of several factors — some to do with microphones, some with environment, some with bats, and the calls themselves — acoustic information transmitted to and transduced by microphones can be dramatically different from the actual signal produced by the bat and as would be recorded on axis, close to its mouth using ideal microphones under ideal conditions. We outline some of these pitfalls and discuss ways to make the best of a bad situation. Overall, however, we stress that many of these factors cannot be ignored and do impact our recordings.

Bat activity over calm and turbulent water

1987 ◽  
Vol 65 (2) ◽  
pp. 219-222 ◽  
Author(s):  
Beatrix von Frenckell ◽  
Robert M. R. Barclay
Keyword(s):  
Water Level ◽  
Frequency Analysis ◽  
Myotis Lucifugus ◽  
Prey Abundance ◽  
Sticky Traps ◽  
Insect Abundance ◽  
Echolocation Calls ◽  
Bat Activity ◽  
Little Brown Bat ◽  
Turbulent Water

A comparison of the activity of the little brown bat (Myotis lucifugus) over calm pools and fast-flowing riffles was performed in southwestern Alberta. Bat activity was assessed by monitoring echolocation calls using ultrasonic detectors. Activity was higher over pools than riffles. This could be due to differences in prey abundance or accessibility in the two habitats. Alternatively, water noise at turbulent sites may interfere with the bats' echolocation abilities. Sticky traps were used to assess prey abundance, and water noise was recorded for intensity–frequency analysis. Insect abundance at the height where the bats flew (< 1 m above the water) did not differ between sites, but insects close to or at water level at calm pools may be more accessible than at fast-flowing riffles. Further, water noise at riffles may decrease the efficiency with which bats detect targets.

Bats are still not birds in the digital era: echolocation call variation and why it matters for bat species identification

2018 ◽  
Vol 96 (2) ◽  
pp. 63-78 ◽  
Author(s):  
Danilo Russo ◽  
Leonardo Ancillotto ◽  
Gareth Jones
Keyword(s):  
Adaptive Significance ◽  
Bird Songs ◽  
Echolocation Call ◽  
Comprehensive Overview ◽  
Echolocation Calls ◽  
Digital Era ◽  
Call Classification ◽  
Acoustic Surveys ◽  
And Behavior ◽  
And Control

The recording and analysis of echolocation calls are fundamental methods used to study bat distribution, ecology, and behavior. However, the goal of identifying bats in flight from their echolocation calls is not always possible. Unlike bird songs, bat calls show large variation that often makes identification challenging. The problem has not been fully overcome by modern digital-based hardware and software for bat call recording and analysis. Besides providing fundamental insights into bat physiology, ecology, and behavior, a better understanding of call variation is therefore crucial to best recognize limits and perspectives of call classification. We provide a comprehensive overview of sources of interspecific and intraspecific echolocation call variations, illustrating its adaptive significance and highlighting gaps in knowledge. We remark that further research is needed to better comprehend call variation and control for it more effectively in sound analysis. Despite the state-of-art technology in this field, combining acoustic surveys with capture and roost search, as well as limiting identification to species with distinctive calls, still represent the safest way of conducting bat surveys.

scholarly journals Anthropogenic noise alters bat activity levels and echolocation calls

2015 ◽  
Vol 3 ◽  
pp. 62-71 ◽  
Author(s):  
Jessie P. Bunkley ◽  
Christopher J.W. McClure ◽  
Nathan J. Kleist ◽  
Clinton D. Francis ◽  
Jesse R. Barber
Keyword(s):  
Anthropogenic Noise ◽  
Activity Levels ◽  
Echolocation Calls ◽  
Bat Activity

scholarly journals An ultrasound absorbing inflorescence zone enhances echo-acoustic contrast of bat-pollinated cactus flowers

2019 ◽  
Author(s):  
Ralph Simon ◽  
Felix Matt ◽  
Vinicio Santillan ◽  
Marco Tschapka ◽  
Merlin Tuttle ◽  
...  
Keyword(s):  
Chemical Signals ◽  
Flowering Plants ◽  
Echolocation Call ◽  
Echolocation Calls ◽  
Columnar Cactus ◽  
Wide Range ◽  
Reflective Surfaces

AbstractFlowering plants have evolved an extraordinary variety of signaling traits to attract and guide their pollinators. Most flowers rely on visual and chemical signals, but some bat-pollinated plants have evolved reflective surfaces to acoustically guide echolocating bats. All known echo-acoustic flower signals rely on the same basic acoustic principles of increased sonar reflectivity. Here we reveal a novel mechanism through which plants acoustically communicate with bats, a principle that relies on increased absorption of the area surrounding the target flower, thereby enhancing echo-acoustic contrast. In a bat-pollinated columnar cactus (Espostoa frutescens) from the Ecuadorian Andes we found a hairy inflorescence zone, a so called lateral cephalium. Flowers of this cactus solely emerge out of this hairy zone. We measured the ultrasound echoes of the hairy zones, the flowers and unspecialized column surfaces with a biomimetic sonar head and recorded echolocation calls of approaching bats. We found that the hairy inflorescence zones act as strong ultrasound absorber, attenuating the sound by −14 dB compared to other parts of the column. The absorption was highest around the echolocation call frequencies of approaching bats. Our results indicate that, instead of making flowers more reflective, plants can also evolve specific structures to attenuate the background echo, thereby enhancing the acoustic contrast with the target. Similar sound absorbing mechanisms may be found in other species that interact with bats across a wide range of ecological contexts.

On the use of ultrasonic detectors for bat species identification and the calibration of QMC Mini Bat Detectors

1984 ◽  
Vol 62 (12) ◽  
pp. 2677-2679 ◽  
Author(s):  
Donald W. Thomas ◽  
Stephen D. West
Keyword(s):  
Species Identification ◽  
Species Level ◽  
Ultrasonic Detection ◽  
Echolocation Call ◽  
Echolocation Calls ◽  
Reliable Identification ◽  
Level Identification

Several ultrasonic detection and analysis systems are currently used to provide information on the echolocation calls of bats, in many cases permitting species-level identification. This note briefly describes these systems and alerts potential users of the inaccuracies of the simplest device, the superheterodyne QMC Mini Bat Detector. Without adequate calibration, the error in this latter detector is such that reliable identification of bats by echolocation call characteristics cannot be achieved.

scholarly journals Variability in echolocation call design of 26 Swiss bat species: consequences, limits and options for automated field identification with a synergetic pattern recognition approach

Mammalia ◽  
2004 ◽  
Vol 68 (4) ◽  
Author(s):  
Martin K. Obrist ◽  
Ruedi Boesch ◽  
Peter F. Flückiger
Keyword(s):  
Pattern Recognition ◽  
Species Identification ◽  
Automated Systems ◽  
Echolocation Call ◽  
Echolocation Calls ◽  
Recognition Algorithms ◽  
Field Identification ◽  
Pattern Recognition Approach ◽  
Species Specific ◽  
Independent Species

Pattern recognition algorithms offer a promising approach to recognizing bat species by their echolocation calls. Automated systems like synergetic classifiers may contribute significantly to operator-independent species identification in the field. However, it necessitates the assembling of an appropriate database of reference calls, a task far from trivial. We present data on species specific flexibility in call parameters of all Swiss bat species (except

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