Volume 195(1): Joshua A. Deily and Johannes Schul (2009): Selective phonotaxis in Neoconocephalus nebrascensis (Orthoptera: Tettigoniidae): call recognition at two temporal scales. J. Comp. Physiol. A 195(1), 31-37.
Abstract: The calls of many Orthopteran species are comprised of a simple trill of pulses, the temporal pattern of which is important for call recognition. Male Neoconocephalus nebrascensis produce pulses with a temporal structure typical for the genus. However, they modify this pattern by grouping their pulses into verses, thereby creating a higher order temporal structure. The importance of the pulse pattern and verse structure for call recognition in N. nebrascensis was determined using a walking compensator. Females required the conspecific pulse pattern for call recognition, responding only when the intervals between pulses were short or absent. Females also required the verse structure for call recognition, and recognized the verse structure only when the amplitude modulation depth between verses and pauses exceeded 18 dB. We discuss that the verse recognition mechanism is a derived trait adapted for pre-mating isolation. We hypothesize that the unusually large amplitude modulation required for verse recognition forces males to synchronize their calls in order to preserve an attractive pattern. Call synchrony appears to be the outcome of cooperation, rather than competition, in this species. URL: http://www.springerlink.com/content/05215478167t316v/ For reprints please contact Johannes Schul (Email: [email protected]) Mariana L. Melcón, Hans-Ulrich Schnitzler and Annette Denzinger (2009): Variability of the approach phase of landing echolocating Greater Mouse-eared bats. J. Comp. Physiol. A 195(1), 69-77. Abstract: The approach phase of landing vespertilionid bats ends with a group of calls, which either consists of buzz I alone or buzz I and buzz II. To understand the possible role of buzz II, we trained Myotis myotis to land on a vertical grid, and compared the flight and echolocation behavior during approach in trials with and without buzz II. During the approach, we did not find any differences in the echolocation behavior until the end of buzz I which indicated whether buzz II was emitted or not. However, bats flying from the periphery of the flight channel, such that they had to make a small turn at the very last moment, finished the sequence with a buzz II. Bats flying on a rather stereotyped trajectory near the center of the flight channel without last instant corrections emitted buzz I alone. Our results indicate that buzz II occurred only on trajectories that implied a higher risk to fail at landing. The information delivered by buzz II reaches the bat too late to be used for landing. Therefore, we hypothesize that buzz II may help the bats to evaluate unsuccessful attempts and to eventually react adequately. URL: http://www.springerlink.com/content/x443p1j593486613/ For reprints please contact Mariana L. Melcón (Email: [email protected]) Sarah A. Stamper, Mary E. Bates, Douglas Benedicto and James A. Simmons (2009): Role of broadcast harmonics in echo delay perception by big brown bats. J. Comp. Physiol. A 195(1), 79-89. Abstract: Big brown bats (Eptesicus fuscus) emit frequency-modulated (FM) echolocation sounds containing two principal down-sweeping harmonics (FM1 ~ 55–25 kHz, FM2 ~ 105–50 kHz). To determine whether each harmonic contributes to perception of echo delay, bats were trained to discriminate between “split-harmonic” echoes that differed in delay. The bat’s broadcasts were picked up with microphones, and FM1 and FM2 were separated with highpass and lowpass filters at about 55 kHz, where they overlap in frequency. Both harmonics then were delivered from loudspeakers as positive stimuli in a 2-choice delay discrimination procedure with FM1 delayed 3.16 ms and FM2 delayed 3.46 ms (300 μs delay split). Negative stimuli contained FM1 and FM2 with the same filtering but no delay separation. These were presented at different overall delays from 11 down to 3 ms to measure the bat’s delay discrimination acuity for each harmonic in the split harmonic echoes. The bats determined the delays of both FM1 and FM2, but performance was overlaid by a broad pedestal of poor performance that extended for 800 μs. Splitting the harmonics by 300 μs appears to defocus the bat’s representation of delay, revealing the existence of a process for recognizing the normally simultaneous occurrence of the harmonics. URL: http://www.springerlink.com/content/3l24032478702qm6/ For reprints please contact Sarah A. Stamper (Email: [email protected]) Volume 195(2): Tobias Riede and Roderick A. Suthers (2009): Vocal tract motor patterns and resonance during constant frequency song: the white-throated sparrow. J. Comp. Physiol. A 195(2), 183-192. Abstract: Bird song is a complex behavior that requires the coordination of several motor systems. Sound is produced in the syrinx and then modified by the upper vocal tract. Movements of the hyoid skeleton have been shown in the northern cardinal (Cardinalis cardinalis) to be extensively involved in forming an oropharyngeal–esophageal cavity (OEC), which contributes a major resonance to the vocal tract transfer function. Here we report that a similar relationship exists between the volume of the OEC and the fundamental frequency in the white-throated sparrow (Zonotrichia albicollis) whose song, unlike that of the cardinal, consists of a series of almost constant frequency notes. Cineradiography of singing sparrows shows that the oropharyngeal cavity and cranial end of the esophagus expand abruptly at the start of each note and maintain a relatively constant volume until the end of the note. Computation of the vocal tract transfer function suggests a major resonance of the OEC follows the fundamental frequency, making sound transmission more efficient. The presence of similar prominent song-related vocal tract motor patterns in two Oscine families suggests that the active control of the vocal tract resonance by varying the volume of the OEC may be widespread in songbirds. URL: http://www.springerlink.com/content/u67w250856147577/ For reprints please contact Tobias Riede (Email: [email protected]) Amanda M. Lauer, Robert J. Dooling and Marjorie R. Leek (2009): Psychophysical evidence of damaged active processing mechanisms in Belgian Waterslager Canaries. J. Comp. Physiol. A 195(2), 193-202. Abstract: Belgian Waterslager canaries (BWC), bred for a distinct low-pitched song, have an inherited high-frequency hearing loss associated with hair cell abnormalities. Hair cells near the abneural edge of the papilla, which receive primarily efferent innervation in normal birds, are among the most severely affected. These cells are thought to support nonlinear active processing in the avian ear, though the mechanisms are poorly understood. Here we present psychophysical evidence that suggests degraded active processing in BWC compared to normal-hearing non-BWC. Critical ratios, psychophysical masking patterns and phase effects on masking by harmonic complexes were measured in BWC and non-BWC using operant conditioning procedures. Critical ratios were much larger in BWC than in non-BWC at high frequencies. Psychophysical tuning curves derived from the masking patterns for BWC were broadened at high frequencies. BWC also showed severely reduced phase effects on masking by harmonic complexes compared to non-BWC. As has been hypothesized previously for hearing-impaired humans, these results are consistent with a loss of active processing mechanisms in BWC. URL: http://www.springerlink.com/content/a872k85176804t04/ For reprints please contact Amanda M. Lauer (Email: [email protected]) Kind regards Sonja ************************** Dr. Sonja Amoser Steinrieglstraße 286 3400 Weidlingbach [email protected]
