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Biomedical subjects

P Marler

Publications and source records attributed to P Marler.

At least 37 records · Page 2Linked to original sources
PubMed1989

Addition of song-related neurons in swamp sparrows coincides with memorization, not production, of learned songs.

During song learning in birds, neurons are added to some song nuclei and lost from others. Previous studies have been unable to distinguish whether these neural changes are uniquely associated with memorizing a song model (sensory acquisition) or vocal practice (sensorimotor learning). In this study we measured changes in neuron number within song nuclei of swamp sparrows, a species in which the two phases of song learning are nonoverlapping. Male swamp sparrows were collected as hatchlings and tape-tutored from approximately 22 to 62 days of age. Swamp sparrows memorize about 60% of their song material during this period, but do not begin practicing this learned material until approximately 275 days of age. Birds were sacrificed at 23, 41, 61, 71, 274, or 340 days of age. During sensory acquisition, neuron number increased drastically in both the caudal nucleus of the ventral hyperstriatum (HVc) and Area X. The period of sensorimotor learning was not associated with any further changes in neuron number within these regions. We were unable to detect any significant changes in neuron number within the magnocellular nucleus of the neostriatum or the robust nucleus of the archistriatum during either stage of song learning. These results raise the possibility that ongoing addition of HVc and Area X neurons may encourage, and thereby temporally restrict, song acquisition.

Aging↗
PubMed1988

Alarm signals in birds: the role of testosterone.

In the laboratory and under semi-naturalistic conditions, male domestic fowl (Gallus gallus) produce more alarm calls in response to predatory birds flying overhead than females. This study tests the hypothesis that testosterone is a factor in the control of aerial alarm call production. Birds were castrated early in life and tested as adults in the laboratory. Aerial predators were simulated by cardboard silhouettes drawn overhead. Blood samples were taken at intervals and plasma testosterone levels were measured by radioimmunoassay. Each subject was tested in four conditions: with an empty Silastic implant, with a testosterone-filled implant, with an additional testosterone implant, and after removal of the implants. Results show that the presence of testosterone increases the production of aerial alarm calls, and that removal of the hormone supply results in a drop in calling rate. As a control a second vocal system, food calling, was considered. In contrast with alarm calling, there was no correlation between testosterone levels and variation in food-call production. We conclude that testosterone plays a specific role in activation of the production by cockerels of vocalizations that signal the presence of aerial predators.

Animals↗
PubMed1988

Audience effects on alarm calling in chickens (Gallus gallus).

The male domestic chicken (Gallus gallus) has been found to modulate the production of vocal signals in response to the presence or absence of a suitable audience. We investigated effects on alarm calling by presenting overhead predator models to cockerels in the presence of a variety of social companions. The production of aerial predator calls in response to hawk silhouettes varied with the presence or absence of a member of the same species. The kinds of audience investigated included the mate, unfamiliar females, other females and males with which subjects had had prior visual and auditory contact, and broody hens with and without young. Domestic chicks, unrelated to the subjects, were almost as effective an audience as conspecific adults. A member of another species, however, failed to potentiate alarm-call production. The subjects gave more alarm calls when they were in the presence of either a male or a female audience than when they were alone. By manipulating the visibility of overhead predator models to the subjects and to the audience, we showed that the subjects were not cued by alarm and escape behaviors of the audience. Comparisons with food calling indicate that, in deciding whether to emit a signal in response to the appropriate referent (e.g., food or predators), chickens respond to subtle differences in the nature of the audience with behaviors that vary from one communicative context to another.

Animals↗
PubMed1987

Response of sparrows to songs of deaf and isolation-reared males: further evidence for innate auditory templates.

Adult song sparrows (Melospiza melodia) were tested for response to songs of conspecific males that had been reared in acoustic isolation or deafened early in life. Territorial males responded more aggressively to playback of songs of isolated males than to songs of deafened males but did not discriminate between songs of deafened males and heterospecific songs. Captive females showed an identical pattern when their response was measured in terms of the number and intensity of courtship displays evoked by song. The results support the auditory template theory of song development in demonstrating that species-identifying features are present in songs of isolates and in showing that males unable to hear their own song production do not incorporate these species-identifying features into their songs.

Animals↗
PubMed1987

Correlations between song acquisition, song production, and plasma levels of testosterone and estradiol in sparrows.

Male birdsong is a sexually dimorphic behavior characterized by learned dialects. In a combined study of learning in relation to steroid levels in the plasma, changes in estradiol and testosterone levels were correlated with the timing of the sensitive period for song acquisition and with successive stages in song development. Male swamp sparrows were trained with a changing series of live singing tutors from 26 days to 1 year of age. Song acquisition was concentrated between 26 and 47 days of age (57%). By 85 days of age 71% of acquisition was completed; some occurred as late as 300 days. There were two major periods when testosterone levels were elevated. The first, from 30-80 days, encompassed most of the period of song acquisition. The second, from 260 to at least 360 days of age, coincided with song development. Estradiol levels were elevated from 18 to 170 days of age, encompassing almost all of the period of song acquisition. A marked estradiol peak between 40 and 50 days coincided with a trough in testosterone levels and a hiatus in song acquisition. The strong correlation between the second period of elevated testosterone and song motor development suggests a causal connection, with levels peaking in mid-development and declining during mature song production. Estradiol levels were elevated at the start of the study and remained so during early subsong production, from 30 to 165 days. They then fell to baseline, remaining there throughout the resumption of subsong and plastic song production at 250-326 days. Both estradiol and testosterone are candidates for possibly affecting song acquisition.

Aging↗
PubMed1983

Song structure without auditory feedback: emendations of the auditory template hypothesis.

Motor patterns of songs of swamp and song sparrows, Melospiza georgiana and M. melodia, deafened early in life display a significant degree of species-specific structure. Normal songs of the two species differ in the degree to which they are segmented. Swamp sparrow song consists of a single segment, and song sparrow songs are multisegmental. Song and swamp sparrows were deafened at 17 to 23 days, prior to the onset of song or subsong. The song sparrows developed more segments in their singing than the swamp sparrows. Species-specific trends were also evident in song durations and frequency characteristics. Abnormalities were found, however, in the morphology of the notes and syllables from which songs of early deafened sparrows are constructed. These results require emendation of the auditory template hypothesis of song learning in birds.

Animals↗
PubMed1982

Developmental overproduction and selective attrition: new processes in the epigenesis of birdsong.

All phases of song development from infancy to adulthood were studied intensively in a group of laboratory-reared birds. Male swamp sparrows, Melospiza georgiana, trained with tape-recorded songs in infancy, developed song some 8 months later, averaging 2.2 song types per bird. Analysis of the intermediate stage of plastic song revealed that the birds generated 4 to 5 times more song material than was needed for the species-specific song repertoire. The excess was discarded at the time of full song crystallization. Indications that the attrition process is selective include tendencies to retain imitated rather than nonimitated elements, and the rejection of heterospecific elements. Attrition may also be influenced by vocal stimulation at the time of song crystallization, providing an opportunity for behavioral adjustment even though new themes can no longer be learned. Attrition has been described in the transition in human infants from babbling to speech.

Animals↗
PubMed1980

Monkey responses to three different alarm calls: evidence of predator classification and semantic communication.

Vervet monkeys give different alarm calls to different predators. Recordings of the alarms played back when predators were absent caused the monkeys to run into trees for leopard alarms, look up for eagle alarms, and look down for snake alarms. Adults call primarily to leopards, martial eagles, and pythons, but infants give leopard alarms to various mammals, eagle alarms to many birds, and snake alarms to various snakelike objects. Predator classification improves with age and experience.

Animal Communication↗
PubMed1979

Species-specific perceptual processing of vocal sounds by monkeys.

Monkeys of four species were trained to discriminate between sets of natural tonal calls of Japanese macaques (Macaca fuscata) by the position of a frequency-inflection peak or by initial pitch. The Japanese macaques consistently performed best on peak position and the other species on pitch. The results imply special strategies for perceptional processing of vocal sounds and suggest parallels with human speech perception.

Animals↗
PubMed1977

Role of auditory feedback in canary song development.

As in other songbirds, early deafening had drastic effects on the song of the roller canary, a cardueline finch, resulting in a song that was much simpler and more variable than the normal. The repertoire of the syllable types, of which the song is made, was reduced from 30 to a mean of 5.0. Loud white noise was successfully used as a reversible method of cutting off auditory feedback from vocal behavior. Although suffering permanent elevation of hearing thresholds, birds reared in noise to 200 days, singing at first like deaf birds, subsequently increased their syllable repertoires significantly. Birds reared in noise to weaning at 40 days, again partly deaf, achieved a normal repertoire size when stimulated with a singing adult. Without such stimulation the repertoire was significantly reduced, showing that canary song is not fully innate, as had been thought. Although abnormal, the song of deaf canaries retained more species-specific features than did the song of emberizine sparrows when the songs developed without auditory feedback. The results are interpreted in terms of a sensory template theory.

Animals↗
PubMed1975

Individuality in a long-range vocalization of wild chimpanzees.

Analysed sound-spectrographically 129 field tape-recordings of the pant-hooting vocalization of seven chimpanzees at the Gombe Stream National Park, Tanzania. Quantitative statistical comparisons revealed that each animal had distinctive differences, sufficient to permit observers and probably chimpanzees to identify individuals. A consistent sexual difference was found, as well as a possible ageclass difference.

Age Factors↗
PubMed1973

Effects of continuous noise on avian hearing and vocal development.

Continuous loud noice was used to mask auditory feedback from vocal behavior of male canaries. Single unit techniques demonstrate partial deafness after noise exposure. Longer exposure caused greater deficits, with losses of high-frequency sensitivity. Males raised in noise to 40 days of age, then deafened surgically, thus totally deprived of auditory feedback from vocalization, developed significantly fewer song syllables than birds similarly raised but left intact, to mature in quiet sound-insulated chambers. Males left longer in noise, to sexual maturity at 200 days of age, sang at first like surgically deafend birds, but then increased their song syllable repertoire after noise termination. Thus, in spite of the considerable deafness resulting from noise exposure, the deficit in syllable repertoire was corrected, presumably as a result of restoration of the birds' ability to hear their own song.

Animals↗