Acoustic analysis of slow click function and foraging in sperm whales (Physeter macrocephalus) off Kaikoura, New Zealand
Sexually immature male sperm whales (Physeter macrocephalus) disperse from their natal areas and move to higher latitude male-only foraging grounds, such as those off New Zealand and Norway. In these areas they are found in aggregations, in which a relatively high concentration of animals congregate...
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| Format: | Other/Unknown Material |
| Language: | English |
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University of Canterbury
2016
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| Online Access: | http://hdl.handle.net/10092/13316 https://doi.org/10.26021/8676 |
| Summary: | Sexually immature male sperm whales (Physeter macrocephalus) disperse from their natal areas and move to higher latitude male-only foraging grounds, such as those off New Zealand and Norway. In these areas they are found in aggregations, in which a relatively high concentration of animals congregate in a specific area. Males within aggregations continuously forage, yet seemingly dive in a solitary manner. The Kaikoura submarine canyon off New Zealand is an area where male sperm whales aggregate. This canyon is among the most productive deep sea regions in the world, and has been used for foraging both by individual male sperm whales over years, as well by transient animals which have only been seen once. Slow clicks are vocalisations only used by males. Typically displayed in bouts with inter-click intervals of 3-9 s, they consist of low frequency (2-4 kHz) sharp clicks with a strong reverberation and apparent source levels around 201 dB peak re 1 μPa at 1 m. Slow clicks have much lower directionality than regular echolocating clicks, resulting in their characteristic strong and lasting seafloor echo. At breeding grounds, slow clicks seem to be displayed in long sequences while males are close to, or at the surface, and these have been suggested to function as vocal display used in competition and/or to attract females. In contrast, at male-only foraging grounds, slow clicks are heard in shorter sequences at the end of foraging dives (and also, at times, during surfacing), with these being heard in almost half of all foraging dives recorded in this study. The diving-phase pattern associated with slow clicks appears consistent across male aggregations recorded here, off Kaikoura, and those found off Norway1. While the function of slow clicks is still unclear, the different social and slow-clicking patterns observed suggests a context-dependent function in communication. I used a towed hydrophone array and photo-identification data from individually-tracked whales during complete foraging dives to further ... |
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