Pitch separation as a possible jamming-avoidance mechanism in underwater calls of bearded seals ( Erignathus barbatus)
Bearded seals (Erignathus barbatus) produce simultaneous loud, long, narrowband underwater trills. It is likely that calls separated by 1/3 octave will not mask each other. Three call (trill) types were identified. Pitch separations between nearest-neighbour calls were measured by sampling at 1-s in...
| Published in: | Canadian Journal of Zoology |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1999
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/z99-067 http://www.nrcresearchpress.com/doi/pdf/10.1139/z99-067 |
| Summary: | Bearded seals (Erignathus barbatus) produce simultaneous loud, long, narrowband underwater trills. It is likely that calls separated by 1/3 octave will not mask each other. Three call (trill) types were identified. Pitch separations between nearest-neighbour calls were measured by sampling at 1-s intervals. Calls spanned 5 octaves and were centred near 1 kHz. Mean pitch separations decreased significantly as the number of simultaneous calls increased from 2 to 9-11, but remained relatively constant at about 0.3 octave at higher numbers of simultaneous calls. For 2-12 simultaneous calls, the pitch separations between 0.0 and 0.4 octave were fewer than random. Proportions of the three trill types did not change as the numbers of simultaneous calls increased. All three call types had fewer pitch separations below 1/3 octave than between 1/3 and 2/3 octave. No relationship was found between pitch separation and call duration. Differences in starting pitch and the regular decline in pitch throughout most calls ensured that mean pitch separations of >1/3 octave were maintained even when many calls occurred simultaneously. Bearded seals may use pitch separation as a jamming-avoidance mechanism. |
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