Phylogeny of phyllostomid bats (Mammalia, Chiroptera) : data from diverse morphological systems, sex chromosomes, and restriction sites. Bulletin of the AMNH ; no. 248

Phyllostomidae is a large (> 140 species), diverse clade of Neotropical bats. Different species in this family feed on blood, insects, vertebrates, nectar, pollen, and fruits. We investigated phylogenetic relationships among all genera of phyllostomid bats and tested monophyly of several genera (e.g., Micronycteris, Mimon, Artibeus, Vampyressa) using 150 morphological, karyological, and molecular characters. Results of parsimony analyses of these combined data indicate that all traditionally recognized phyllostomid subfamilies are monophyletic and that most taxa that share feeding specializations form clades. These results largely agree with studies that have used a taxonomic congruence approach to evaluate karyological, immunological, and limited sets of morphological characters, although our finding that Phyllostominae is monophyletic is novel. Our results indicate that several genera (Micronycteris, Artibeus, and Vampyressa) are not monophyletic. We propose a new classification for Phyllostomi...

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Phylogeny of phyllostomid bats (mammalia: chiroptera): data from diverse morphological systems, sex chromosomes, and restriction sites

Bats use echolocation or biosonar to navigate and find prey at night. They emit short ultrasonic calls and listen for reflected echoes. The beam width of the calls is central to the function of the sonar, but directionality of echolocation calls has never been measured from bats flying in the wild. We used a microphone array to record sounds and determine horizontal directionality for echolocation calls of the trawling Daubenton's bat, Myotis daubentonii , flying over a pond in its natural habitat. Myotis daubentonii emitted highly directional calls in the field. Directionality increased with frequency. At 40 kHz half-amplitude angle was 25°, decreasing to 14° at 75 kHz. In the laboratory, M. daubentonii emitted less intense and less directional calls. At 55 kHz half-amplitude angle was 40° in the laboratory versus 20° in the field. The relationship between frequency and directionality can be explained by the simple piston model. The model also suggests that the increase in the emitted intensity in the field is caused by the increased directionality, focusing sound energy in the forward direction. The bat may increase directionality by opening the mouth wider to emit a louder, narrower beam in the wild.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2008.1505

Echolocating bats emit a highly directional sonar sound beam in the field

Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40° to approximately 90° horizontally and from approximately 45° to more than 90° vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals.

https://www.pnas.org/content/pnas/107/31/13930.full.pdf

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit.

The directionality of sound emission by a horseshoe bat (Rhinolophus ferrumequinum) has been determined for the constant frequency component of its orientation sounds. The bat was fixed in the center of an acoustic perimeter and the SPL of the orientation sounds measured with a scanning microphone at different angles compared with the SPL measured by another microphone located in the direction perpendicular to the plane of the horseshoe-like structure of the nose-leaf. The maximum SPL was always found in this direction which also corresponds to the flight direction of a bat in horizontal flight. Above and lateral to this direction the SPL decreases steadily with -6 dB-points at 24 ‡ above and 23 ‡ lateral. Below the flight direction we found a prominent side lobe with a -6 dB-point at 64 ‡.

Directional sensitivity of echolocation in the horseshoe bat, Rhinolophus ferrumequinum

Acoustical beam patterns for emission from several different bats are calculated assuming a piston source in an infinite baffle, both as single and as double emitters. The calculated beam patterns agree well enough with experimental values available in the literature to justify the assumptions used. For those bats which possess no facial appendages to serve as a baffle, the simple acoustical model does not work, as anticipated. The calculated beam patterns are for fixed frequencies in the examples used; however, some aspects of frequency modulated beams are briefly discussed.

G. K. Strother

Papers

Acoustical Beam Patterns for Bats: Some Theoretical Considerations