Hearing in the Elephant (Elephas maximus). Science 208:518-520
Parsons, New York, New York, United StatesScience (Impact Factor: 33.61). 06/1980; 208(4443):518-20. DOI: 10.1121/1.2017313
Auditory thresholds were determined for a 7-year-old Indian elephant. The hearing range extended from 17 hertz to 10.5 kilohertz. The results indicate that the inverse relationship between functional interaural distance (that is, the distance between the two ears divided by the speed of sound) and high-frequency hearing limit is valid even for very large mammals.
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- "This finding does not, however, imply that elephants do not use BC hearing for seismic detection. The fatty cushion in the feet, the excellent hearing in the frequency range where seismic waves transmit most efficiently, as well as enlarged middle ear bones facilitating independent oscillations of the ossicles relative to the skull make elephants suited for seismic detection/discrimination through BC hearing      . In addition, the spaciously pneumatized elephant skull may act as a resonating chamber for vibrations. "
ABSTRACT: X-ray CT of an Asian elephant's skull suggest that elephants do not have a labyrinthine 3(rd) mobile window. This excludes the concept that elephants benefit from enhancement of bone conducted vibration by an extra opening of the labyrinth. This finding does not, however, exclude that elephants use bone conducted hearing for seismic detection, nor that other species may use an extra labyrinthine opening for improved detection of seismic signals. In man, a pathologic extra opening of the bony labyrinth causes altered hearing with supranormal bone conduction. Theoretically, this variation in auditory performance could be advantageous for detection of seismic waves. The skull of an adult Asian elephant was examined by X-ray computed tomography to investigate whether a natural '3(rd) mobile window' mechanism for enhanced sensitivity of body sounds exist in elephants. Although the entire elephant's skull was otherwise broadly aerated, the labyrinth areas were surrounded by dense bone.Acta oto-laryngologica 08/2015; DOI:10.3109/00016489.2015.1076168 · 1.10 Impact Factor
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- "Recent evidence suggests that coiled cochleae may play a mechanical role in low frequency hearing limit . Across auditory ‘generalists’ high frequency hearing limits correlate with inter-aural distance , whereas auditory specialists such as subterranean mole rats and echolocating cetaceans deviate from this relationship . Other factors determining the morphology of auditory systems include physical and mechanical constraints, as well as phylogeny e.g. "
ABSTRACT: Introduction Many mammals have evolved highly adapted hearing associated with ecological specialisation. Of these, bats possess the widest frequency range of vocalisations and associated hearing sensitivities, with frequencies of above 200 kHz in some lineages that use laryngeal echolocation. High frequency hearing in bats appears to have evolved via structural modifications of the inner ear, however, studying these minute features presents considerable challenges and hitherto few such attempts have been made. To understand these adaptations more fully, as well as gain insights into the evolutionary origins of ultrasonic hearing and echolocation in bats, we undertook micro-computed tomography (μCT) scans of the cochleae of representative bat species from 16 families, encompassing their broad range of ecological diversity. To characterise cochlear gross morphology, we measured the relative basilar membrane length and number of turns, and compared these values between echolocating and non-echolocating bats, as well as other mammals. Results We found that hearing and echolocation call frequencies in bats correlated with both measures of cochlear morphology. In particular, relative basilar membrane length was typically longer in echolocating species, and also correlated positively with the number of cochlear turns. Ancestral reconstructions of these parameters suggested that the common ancestor of all extant bats was probably capable of ultrasonic hearing; however, we also found evidence of a significant decrease in the rate of morphological evolution of the basilar membrane in multiple ancestral branches within the Yangochiroptera suborder. Within the echolocating Yinpterochiroptera, there was some evidence of an increase in the rate of basilar membrane evolution in some tips of the tree, possibly associated with reported shifts in call frequency associated with recent speciation events. Conclusions The two main groups of echolocating bat were found to display highly variable inner ear morphologies. Ancestral reconstructions and rate shift analyses of ear morphology point to a complex evolutionary history, with the former supporting ultrasonic hearing in the common bat ancestor but the latter suggesting that morphological changes associated with echolocation might have occurred later. These findings are consistent with theories that sophisticated laryngeal echolocation, as seen in modern lineages, evolved following the divergence of the two main suborders.Frontiers in Zoology 01/2013; 10(1):2. DOI:10.1186/1742-9994-10-2 · 3.05 Impact Factor
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