. The Canadian field-naturalist. o >. I t 100 Microseconds Figure 2. Example waveforms of echolocation-like pulses recorded from a stranding Pilot Whale within the five minute period immediately prior to beaching. Maxi- mum energy ranged from 6 to 11 kHz (167 to 100 microseconds per cycle). During this period (1155 to 1157h) several echolocation-like pulses, with maximum energy between 6 and 11 kHz (Figure 2), were emitted by the stranding animal. No other sounds were recorded dur- ing the time that she was away from the pod. By 1159 h respiration was very rapid, with blows occurring every
. The Canadian field-naturalist. o >. I t 100 Microseconds Figure 2. Example waveforms of echolocation-like pulses recorded from a stranding Pilot Whale within the five minute period immediately prior to beaching. Maxi- mum energy ranged from 6 to 11 kHz (167 to 100 microseconds per cycle). During this period (1155 to 1157h) several echolocation-like pulses, with maximum energy between 6 and 11 kHz (Figure 2), were emitted by the stranding animal. No other sounds were recorded dur- ing the time that she was away from the pod. By 1159 h respiration was very rapid, with blows occurring every s (SD = , N = 7). Aground at 1204 h, the whale vigorously flailed her tail stock. By 1206 h the whale had ceased struggling and was lying on her side with the blowhole underwater. I turned her so that the blowhole remained out of the water but respiration had ceased. The animal showed no signs of life by 1215 h (no response to touching on or near the eye). There was a gently sloping mud bottom where the whale stranded. During the stranding there were no potential predators in the area and no boats except for mine which was drifting with the motor off. Winds were from the south-west at about 15 to 20 knots (30 to 40 km/h; waves to m), the sky was partly- cloudy (approximately 15% cloud cover), and the tide had just started to rise when the animal stranded (low tide 1112h). Several aspects of this stranding are noteworthy: 1. The stranding animal emitted echolocation-like pulses shortly before becoming stranded. These pulses had maximum energy at frequencies from 6 to 11 kHz, within the range recorded from other groups of Pilot Whales (McLeod, unpublished data) and from other odontocete species (Popper 1980). Dudok van Heel (1966) has hypothesized that strandings are a result of odontocetes having trouble detecting gently sloping beaches using echolocation signals. This is most likely if the animals are paying attention to the higher frequency components of their e
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