Wyniki wyszukiwania - Biblioteka Nauki

1

Describing the echolocation calls and behaviour of bats

100%

Fenton M. B.

Acta Chiropterologica

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1999

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tom 01

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nr 2

2

Choosing the correct bat detector

100%

Fenton M. B.

Acta Chiropterologica

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2000

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tom 02

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nr 2

EN

Direct field comparisons revealed that in any time period, a bat detecting system using zero-crossing period meter analysis (the Anabat II Bat Detector with Anabat ZCAIM and Anabat 6 software) detected significantly fewer bat echolocation calls than a time-expansion bat detecting system (Pettersson D980 detector with BatSoundPro software). Furthermore, the features of 81 echolocation calls (highest frequency, in kHz; lowest frequency, in kHz; duration, in ms) recorded and analyzed on both systems differed significantly. Regression analyses indicated no consistent, frequently unpredictable differences between Anabat and Pettersson values for the lowest frequencies in echolocation calls, but a significant correlation for their highest frequencies and durations. In a variety of field settings in Israel and in southern Ontario, Canada involving both foraging bats and bats emerging from a cave roost, the Pettersson system recorded echolocation calls not detected by the Anabat system. When many Myotis bats were emerging from a cave roost in Israel, the Anabat system did not detect the calls of a Rhinolophus species or those of another vespertilionid which were detected by the Pettersson system. The differences in performance between the two kinds of systems reflect differences in sensitivity and operation between zero-crossing period meters and time-expansion systems. Data on bat activity or echolocation calls detected and analyzed by a zero-crossing period meter system like Anabat are not as consistent or as reliable as those obtained by a time-expansion system like the Pettersson. Differences in performance of bat detectors coincide with considerable difference in costs, from about US$ 650 for an Anabat system, to over US$ 2,000 for a Pettersson system, which involves digital time-expansion. A time-expansion system involving a high speed tape recorder will cost over US$ 30,000. When it comes to bat detectors and analysis systems, the quality of data that will be obtained is a direct reflection of cost — buyers get what they pay for.

3

Detecting bat calls: an analysis of automated methods

63%

Skowronski M. D. , Fenton M. B.

Acta Chiropterologica

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2009

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tom 11

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nr 1

EN

Long-term and large-scale acoustic surveys of bats have become possible with the increased availability of recording hardware and advances in battery and memory storage technologies. The volume of data generated in surveys necessitates automated call detection, either in real time via a triggering function or offline, yet researchers are hesitant to replace traditional hand analysis without a thorough understanding of the accuracy and costs of automated detection. We compared detection accuracy and computational cost of the underlying algorithms used in commercial detectors (a zero-crossing detector, a spectral peak detector, and a high-band energy detector) with a model-based analysis method called the links detector. We predicted that the links detector would be more accurate than the other detectors, producing a larger effective detection range, because the links detector uses more information to make detection decisions. We also predicted that the links detector would be the most computationally expensive algorithm because of the processing needed for the extra information. We quantified the performance of the detectors using a synthetic recording environment, which provided an absolute ground truth for the experiments and allowed us to measure the effective detection range of each algorithm. The zero-crossing and high-band energy detectors, the fastest, were about 40 times faster than the links detector. Most of the computational cost was attributed to the filter used to remove low-frequency noise. The links detector, the most accurate, increased effective detection range by 6-12 m compared to the other detectors depending on species. The results will allow bat researchers to better understand the costs and benefits of automated detection methods.

4

Hitting the wall: light affects the obstacle avoidance ability of free-flying little brown bats (Myotis lucifugus)

63%

McGuire L. P. , Fenton M. B.

Acta Chiropterologica

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2010

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tom 12

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nr 1

5

Echolocation and the thoracic skeletons of bats: a comparative morphological study

51%

DesRoche K. , Fenton M. B. , Lancaster W. C.

Acta Chiropterologica

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2007

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tom 09

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nr 2

EN

Using analyses of digital images of the thoracic skeletons of 16 species of bats (7 families) known to produce high intensity echolocation calls, we made qualitative and quantitative comparisons of the associations of thoracic skeletal features to echolocation behaviour and classification by family. The bats we examined showed significant differences in rib, sternal, manubrial and xiphoid morphology. Pteropodids (former Megachiroptera, non echolocating or, in the case of Rousettus aegyptiacus echolocating using orally-generated signals), were distinctly different from species of former Microchiroptera. Among former Microchiroptera, low duty cycle echolocators (Emballonuridae, most Mormoopidae, Vespertilionidae, and Molossidae) were generally more similar to one another than to high duty cycle echolocators (Hipposideridae and Rhinolophidae). Pteronotus parnellii, a high duty cycle echolocator, was more similar in thoracic morphology to other mormoopids than to other high duty cycle echolocators (hipposiderids and rhinolophids). Thoracic skeletal morphology suggests that laryngeal echolocation is associated with some modifications of the thoracic skeleton apparently beyond those related to flight.

6

Echolocation calls of Myotis lucifugus and M. leibii (Vespertilionidae) flying inside a room and outside

51%

Mukhida M. , Orprecio J. , Fenton M. B.

Acta Chiropterologica

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2004

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tom 06

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nr 1

EN

The purpose of this study was to compare the echolocation calls of the same four individual Myotis lucifugus and Myotis leibii flying inside a closed room and when released outside. Echolocation calls were recorded using a Pettersson D980 bat detector, the high frequency output fed into a personal computer via an F2000 Control Filter and an Ines High speed card. Recorded as .wav files, recordings were analyzed with BatSoundPro. We measured call duration (DUR in ms), frequency with maximum energy (FMAX in kHz), highest frequency (HF in kHz), lowest frequency (LF in kHz), and inter-pulse interval (IPI in ms). Multivariate Analyses of Variance (MANOVA) indicated significant differences in call features between species, between settings, between species in each setting, and finally between settings for each individual. Discriminant Function Analyses (DFA) revealed that inside DUR was the most important parameter distinguishing M. lucifugus from M. leibii, with 66.3% correct classification, while outside, the two species were distinguished 78.8% of the time by LF. The data demonstrate that the same individuals flying in confined spaces change the details of their echolocation calls compared to when flying in the open. Calls produced inside are shorter in DUR and are produced at shorter IPIs than calls produced outside. FMAX differed most between the calls of M. lucifugus and M. leibii whether flying inside or outside. Differences between echolocation calls were more pronounced between setting (inside versus outside) than between species.

7

Bat activity and genetic diversity at Long Point, Ontario, an important bird stopover site

51%

Dzal Y. , Hooton L. A. , Clare E. L. , Fenton M. B.

Acta Chiropterologica

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2009

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tom 11

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nr 2

EN

Long Point, Ontario is an important stopover site for a variety of migrating birds and it may also serve migrating bats. While bats often have been caught during mist netting for birds at Long Point, there have been no quantitative studies of migrating (or resident) bats at this location. We monitored bat activity at Long Point using mist-net captures and recordings of echolocation calls in June and August 2006. Bat activity was significantly higher in August than in June, suggesting a peak in bat activity coincident with when migration would be expected to occur. Lasionycteris noctivagans was the only species known from Ontario not present at Long Point in June, but it was the second most abundant bat in August. An increase in L. noctivagans and Lasiurus cinereus abundance between June and August, suggests that Long Point serves as a migratory flyway for both species. Feeding activity of L. noctivagans increased towards the end of August, suggesting that it and not others use Long Point as a stopover and refuelling site. Mitochondrial haplotypes of Myotis lucifugus were more diverse at Long Point than at a swarming site in Ontario, indicating that Long Point is important for bats, regardless of its function as a stopover site during migration.

8

Variation in the use of harmonics in the calls of laryngeally echolocating bats

51%

Fenton M. B. , Skowronski M. D. , McGuire L. M. , Faure P. A.

Acta Chiropterologica

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2011

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tom 13

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nr 1

EN

The echolocation calls of bats may contain a single acoustic element (the fundamental frequency or a harmonic) or multiple acoustic elements that may (or may not) include the fundamental element. We hypothesize that the detection of harmonics is affected by three factors: 1) species, 2) situation, and 3) recording quality. To test our hypotheses, we recorded and analyzed approximately 2,300 calls from 17 species and 1 subspecies in 6 families of bats using a 1-channel and 4-channel microphone array. The percentage of calls with multiple acoustic elements varied from 0 to 83% across species. Furthermore, recordings from a 4-channel microphone array (1 m tetrahedron arrangement) revealed that the percent of calls with multiple acoustic elements varied across channels by up to 50%, indicating the effect of bat position relative to the microphone. In some species, presence of multiple acoustic elements was predicted by call energy: calls with sufficient energy (threshold varied by species) had multiple acoustic elements above the noise floor of the recording system. In the remaining species that produced calls with multiple acoustic elements, we found two clusters of calls. In one cluster, the presence of multiple acoustic elements was predicted by received call energy. In the 2nd cluster, call energy was lower, and almost all calls included multiple acoustic elements. The detection of harmonics independent of recorded energy suggests the intriguing possibility that harmonics are used differently in these species. Finally, to test the effect of situation, we recorded the echolocation calls of big brown bats (Eptesicus fuscus) flying in three settings: an anechoic flight room, during roost emergence, and foraging in an open area. Call energy shifted to lower frequencies and fewer acoustic elements as the recording distance and the volume of the flight environment increased (i.e., as clutter decreased). Comparing flight room with foraging calls revealed that the second harmonic of open air foraging signals decreased by about 30 dB (relative to the fundamental). Overall, our results show that detection of echolocation signals with harmonics varied significantly across species. We also demonstrate that relative harmonic intensity varies according to the flight situation within a species, and when combined with the effects of call directionality and relative position of bat and microphone, these factors influence harmonic detection in echolocation recordings.

9

Data, sample sizes and statistics affect the recognition of species of bats by their echolocation calls

45%

Biscardi S. , Orprecio J. , Fenton M. B. , Tsoar A. , Ratcliffe J. M.

Acta Chiropterologica

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2004

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tom 06

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nr 2

EN

Identification of bat species based on analysis of echolocation calls can be affected by the way data are manipulated, the diversity of species, and call variability. We document the effects of sample sizes and a priori assignment of calls by species on the outcome of discriminant function analysis (DFA) and multinomial logistic regression (MLR) of features of echolocation calls, and determine which features of calls are most useful for identification. We used recorded echolocation calls of eight species readily distinguishable by call features, including molossids, emballonurids and a moormopid recorded at sites in Belize, Brazil, and Mexico. On individual calls, we measured four features: frequency with most energy, highest and lowest frequencies and call durations obtained from sequences consisting of 10 calls. Cluster analysis and multiple analyses of variance indicated significant differences between the calls of different species. Outcomes of DFA and MLR were affected by both sample sizes (numbers of calls, numbers of sequences) and the subjective approach that researchers take to their data (i.e., categorizing calls or sequences of calls by species). Levels of variation in calls of some species in our sample often precluded the use of single calls in making call-based identifications. Accurate documentation of variability in echolocation behavior of sympatric bats is a prerequisite for an effective sound-based bat survey

10

Disassembly of fragmented bat communities in Orange Walk District, Belize

45%

Herrera J. P. , Duncan N. , Clare E. , Fenton M. B. , Simmons N.

Acta Chiropterologica

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2018

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tom 20

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nr 1

EN

The assembly, or disassembly, of ecological communities is thought to be driven by competition, environmental filtering, and dispersal limitation. These processes leave patterns in the functional, phylogenetic, and taxonomic diversity of communities. Bat communities in the tropics tend to have many species that are niche specialists with varying dispersal propensities. We investigated the effects of fragmentation on bat communities in an isolated forest fragment and a nearby larger forest preserve in Belize. Over four field seasons (2014–2017), we captured over 1,480 individuals from 32 species using mist nets and harp traps. The community in the fragment was a nested subset of species (20) compared to the preserve (30), and species richness was relatively stable over time. Functional richness was higher in the preserve than in the fragment, and species in the preserve were more closely related phylogenetically than expected by chance. Closely related species and species with different diet guilds co-occurred at both sites more often than distant relatives and those with the same diet guild. Bat species with flexible roost use had higher abundance in the fragment than the preserve, while closely related roost-specialist species had higher abundance in the preserve. Local extirpation and decreased dispersal are the most likely mechanisms of community disassembly in this system, and variation in roosting habits results in nonrandom community composition. These results have significant implications for the effects of ongoing deforestation and habitat fragmentation in Belize and adjacent dry forest areas.

11

Characterization of the echolocation Calls of Bats from Exuma, Bahamas

45%

Murray K. L. , Fraser E. , Davy C. , Fleming T. H. , Fenton M. B.

Acta Chiropterologica

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2009

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tom 11

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nr 2

EN

The islands of the West Indies are home to 56 species of bats, half of which are endemic to the region. Recently, researchers have begun to characterize the echolocation calls of the bat fauna of the West Indies. However, the majority of species have not yet been characterized and no studies have been conducted on most West Indian islands, including the islands of the Bahamas. Exuma, a small island in the Bahamas, has six species of bats classified in four families (Molossidae, Natalidae, Phyllostomidae, and Vespertilionidae). We used an ultrasonic detector (Avisoft UltraSoundGate 116) to study the echolocation calls of these bats, focusing on three species whose calls have not been previously described, Erophylla sezekorni, Macrotus waterhousii, and Nyctiellus lepidus. Each of these species uses low-intensity, frequency modulated echolocation calls and exhibits intraspecific call variation both among individuals and within individual call sequences. Despite this variation, we were able to accurately classify each species using discriminant function analysis. Accuracy rates varied from 94% (M. waterhousii) to 100% (E. sezekorni, N. lepidus). We also provide a preliminary description of the echolocation calls of two additional Exuman bat species, Lasiurus borealis and Tadarida brasiliensis. The echolocation calls of L. borealis and T. brasiliensis appear similar to their mainland counterparts; however, more study is needed to characterize the calls of these two species on Exuma.

12

Opportunistic use of banana flower bracts by Glossophaga soricina

38%

Murphy M. , Clare E. L. , Rydell J. , Yovel Y. , Bar-On Y. , Oelbaum P. , Fenton M. B.

Acta Chiropterologica

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2016

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tom 18

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nr 1

EN

The evolution of cue reception and cue production is well documented. The ability of species to use cues they did not evolve with is important in understanding flexibility in behaviour. We observed Neotropical nectar-feeding bats (Glossophaga soricina) feeding at Old World banana flowers (Musa acuminata) in a Belize garden. The flowers produce a rich source of nectar that is exposed as a bract lifts before dusk. We tested the hypothesis that the bracts serve as beacons to foraging bats and discuss this approach and the use of acoustic information by bats feeding at flowers. We ensonified a bract with cues like those of echolocating G. soricina, which revealed the production of strong echoes from the bract. Additionally, the removal of bracts from the flowers influenced the bats' flower-visiting behaviour. We suggest that the bats use the echoes from the bract opportunistically as a cue to find the nectar source. Our findings provide an example of an interaction between a plant and flower visitor not reflecting a shared evolutionary past.

13

Conjoined twins in a wild bat: a case report

38%

Urban D. J. , Sorensen D. W. , Maier J. A. , Fenton M. B. , Simmons N. B. , Cooper L. N. , Sears K. E.

Acta Chiropterologica

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2015

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tom 17

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nr 1

EN

There are numerous records of conjoined twinning in humans and domesticated animals, but many fewer for wild animals because of the early death of conjoined twins. We here describe the incidental discovery and skeletal anatomy of a wild-caught bat fetus with two heads. To our knowledge, this is only the second conjoined bat fetus described, and the first conjoined Artibeus phaeotis. We also revisit the anatomy of the first conjoined bat that was described, a stillborn Eptesicus fuscus.