Absence of Kin Discrimination in Hatchling American Alligators, Alligator mississippiensis

Passek, Kelly M; Gillingham, James C.

doi:10.2307/1447624

Cited by 14 publications

(7 citation statements)

References 9 publications

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“…Crocodilians are birds’ closest living relatives, and use low-frequency sound for communication. Additionally, field observations support their ability to localize the contact calls made by their young (Hunt and Watanabe, 1982; Passek and Gillingham, 1999). …”

Section: Introductionmentioning

confidence: 74%

“…Behavioral evidence of sound localization is lacking, but most crocodilians are nocturnal hunters, and produce a loud roaring call (Todd, 2007). Furthermore, females can localize the contact calls made by their young (Hunt and Watanabe, 1982; Passek and Gillingham, 1999), and so we expect that sound source localization is behaviorally relevant to this group.…”

Section: Discussionmentioning

confidence: 99%

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Detection of Interaural Time Differences in the Alligator

Carr

Soares²,

Smolders³

et al. 2009

Journal of Neuroscience

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The auditory systems of birds and mammals use timing information from each ear to detect interaural time difference (ITD). To determine whether the Jeffress-type algorithms that underlie sensitivity to ITD in birds are an evolutionarily stable strategy, we recorded from the auditory nuclei of crocodilians, who are the sister group to the birds. In alligators, precisely timed spikes in the first-order nucleus magnocellularis (NM) encode the timing of sounds, and NM neurons project to neurons in the nucleus laminaris (NL) that detect interaural time differences. In vivo recordings from NL neurons show that the arrival time of phase-locked spikes differs between the ipsilateral and contralateral inputs. When this disparity is nullified by their best ITD, the neurons respond maximally. Thus NL neurons act as coincidence detectors. A biologically detailed model of NL with alligator parameters discriminated ITDs up to 1 kHz. The range of best ITDs represented in NL was much larger than in birds, however, and extended from 0 to 1000 μs contralateral, with a median ITD of 450 μs. Thus, crocodilians and birds employ similar algorithms for ITD detection, although crocodilians have larger heads.

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Section: Introductionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Detection of Interaural Time Differences in the Alligator

Carr

Soares²,

Smolders³

et al. 2009

Journal of Neuroscience

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“…Juveniles of several species [including Alligator mississippiensis (Daudin 1802)] perform both low frequency grunts and higher frequency distress calls (Burghardt, 1977), which reliably attract adults (reviewed by Garrick and Lang, 1977). Vocal communication is thought to be important for maternal care and promoting group cohesiveness among the young (Pooley, 1969;Pooley, 1977;Campbell, 1973;Garrick and Lang, 1977;Hunt and Watanabe, 1982;Passek and Gillingham, 1999) and part of courtship in adults (Garrick and Lang, 1977).…”

Section: Introductionmentioning

confidence: 99%

Biophysics of directional hearing in the American alligator (Alligator mississippiensis)

Bierman

Thornton

Jones

et al. 2014

Journal of Experimental Biology

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Physiological and anatomical studies have suggested that alligators have unique adaptations for spatial hearing. Sound localization cues are primarily generated by the filtering of sound waves by the head. Different vertebrate lineages have evolved external and/or internal anatomical adaptations to enhance these cues, such as pinnae and interaural canals. It has been hypothesized that in alligators, directionality may be enhanced via the acoustic coupling of middle ear cavities, resulting in a pressure difference receiver (PDR) mechanism. The experiments reported here support a role for a PDR mechanism in alligator sound localization by demonstrating that (1) acoustic space cues generated by the external morphology of the animal are not sufficient to generate location cues that match physiological sensitivity, (2) continuous pathways between the middle ears are present to provide an anatomical basis for coupling, (3) the auditory brainstem response shows some directionality, and (4) eardrum movement is directionally sensitive. Together, these data support the role of a PDR mechanism in crocodilians and further suggest this mechanism is a shared archosaur trait, most likely found also in the extinct dinosaurs.

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“…The marsh-dwelling American alligator is considered especially chatty, and vocal communication is thought to be particularly useful in their low visibility habitat (Garrick and Lang, 1977). Behavioral observations show vocal communication during mating, defensive, group cohesion, and maternal care behaviors (Burghardt, 1977; Garrick and Lang, 1977; Hedges and Poling, 1999; Hunt and Watanabe, 1982; Iwabe et al, 2005; Passek and Gillingham, 1999; Young et al, 2014). The 1 KHz peak in the alligator audiogram (Higgs et al, 2002; Nesbitt, 2011) coincides with a major component in the juvenile contact call (Köppl et al, 2014; Vergne et al, 2009).…”

Section: Evidence For Directional Hearingmentioning

confidence: 99%

Sound localization in the alligator

Bierman

Carr

2015

Hearing Research

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In early tetrapods, it is assumed that the tympana were acoustically coupled through the pharynx and therefore inherently directional, acting as pressure difference receivers. The later closure of the middle ear cavity in turtles, archosaurs, and mammals is a derived condition, and would have changed the ear by decoupling the tympana. Isolation of the middle ears would then have led to selection for structural and neural strategies to compute sound source localization in both archosaurs and mammalian ancestors. In the archosaurs (birds and crocodilians) the presence of air spaces in the skull provided connections between the ears that have been exploited to improve directional hearing, while neural circuits mediating sound localization are well developed. In this review, we will focus primarily on directional hearing in crocodilians, where vocalization and sound localization are thought to be ecologically important, and indicate important issues still awaiting resolution.

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Absence of Kin Discrimination in Hatchling American Alligators, Alligator mississippiensis

Cited by 14 publications

References 9 publications

Detection of Interaural Time Differences in the Alligator

Detection of Interaural Time Differences in the Alligator

Biophysics of directional hearing in the American alligator (Alligator mississippiensis)

Sound localization in the alligator

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