The long-range echo scene of the sperm whale biosonar
Description
Sperm whales use their gigantic nose to produce the most powerful sounds in the animal kingdom, presumably to echolocate deep-sea prey at long ranges and possibly to debilitate prey. To test these hypotheses, we deployed sound recording tags (DTAG-4) on the tip of the nose of three sperm whales. One of these recordings yielded over 6000 echo streams from organisms detected up to 144 m ahead of the whale, supporting a long-range prey detection function of the sperm whale biosonar. The whale navigated this complex acoustic scene by maintaining a stable, long-range acoustic gaze suggesting continual resource evaluation. Less than 10% of the echoic organisms recorded by the tag were targeted for capture and only 18% of the buzzes were emitted within the 50 m depth interval of maximum organism encounter rate, demonstrating echo guided prey selection. Buzzes were initiated >20 m from the prey, showing that sperm whales do not debilitate their prey with sound, but trade echo levels for reduced forward masking and rapid updates on prey location in keeping with the lower manoeuvrability of these large predators. We conclude that the powerful biosonar of sperm whales enables long-range echolocation and selection of prey, but not acoustic debilitation.
Notes
Overview of data and code:
Data:
sw17_196a_buzz:
Contains information about each buzz including start and end time, click detections, duration, numbers of clicks, median depth and median distance to the sea floor of the whale when the buzz was emitted.
sw17_196a_data:
Includes the core data for each dive such as diurnal phase, click detections, buzz starts end ends, timing and depth of detected echoes, numbers of echoes per click, distance to the sea floor for each click and maximum distance to each echo.
sw17_196a_dive:
Contains information about the dives including time of start and end, maximum and median depth, dive duration, the depth trace, timing of descent and ascent phases and pitch data.
sw17_196a_echo:
Contains information about the echoes of each dive including time delay of echoes from potential prey, the sea floor and sea surface, the number of prey echoes, maximum distance to prey echo and depth of echoes.
Scripts:
Supplementary scripts can be downloaded at http://www.animaltags.org
- Finddives:
Locates dives exceeding a custom set depth threshold and provide timing of start and end and maximum dive depth.
- AZ_clickdetection & d3findallclicks & d3findmissedclicks_advanced & d3findmissedclicks_buzz:
Setup and function that enables automatic click detection and verification
- Buzz_threshold & find_buzz_fun:
Find inter-click interval threshold for buzzes and detect buzzes in the click detections
- AZ_run_d3echotool2 & d3echotool2_blind:
Makes spectrograms of recordings for manual echo detection.
- hand_off2:
Gives the distance to the prey when the buzz is initiated
- bottom_ici_stats
Makes generalized linear mixed effect model to test relationship between inter-click interval and echo density
Funding provided by: National Danish Research Council**
Crossref Funder Registry ID:
Award Number:
Funding provided by: Regional Foundation for Science and Technology*
Crossref Funder Registry ID:
Award Number: ACORES-01-0145-FEDER-00057
Funding provided by: National Danish Research Council*
Crossref Funder Registry ID:
Funding provided by: Regional Foundation for Science and Technology
Crossref Funder Registry ID:
Award Number: ACORES-01-0145-FEDER-00057
Files
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(26.4 MB)
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