Abstract
Toothed whales have evolved flexible biosonar systems to find, track and capture prey in diverse habitats. Delphinids, phocoenids and iniids adjust inter-click intervals and source levels gradually while approaching prey. In contrast, deep-diving beaked and sperm whales maintain relatively constant inter-click intervals and apparent output levels during the approach followed by a rapid transition into the foraging buzz, presumably to maintain a long-range acoustic scene in a multi-target environment. However, it remains unknown whether this rapid biosonar adjustment strategy is shared by delphinids foraging in deep waters. To test this, we investigated biosonar adjustments of a deep-diving delphinid, the Risso’s dolphin (Grampus griseus). We analyzed inter-click interval and apparent output level adjustments recorded from sound recording tags to quantify in situ sensory adjustment during prey capture attempts. Risso’s dolphins did not follow typical (20logR) biosonar adjustment patterns seen in shallow-water species, but instead maintained stable repetition rates and output levels up to the foraging buzz. Our results suggest that maintaining a long-range acoustic scene to exploit complex, multi-target prey layers is a common strategy amongst deep-diving toothed whales. Risso’s dolphins transitioned rapidly into the foraging buzz just like beaked whales during most foraging attempts, but employed a more gradual biosonar adjustment in a subset (19%) of prey approaches. These were characterized by higher speeds and minimum specific acceleration, indicating higher prey capture efforts associated with evasive prey. Thus, tracking and capturing evasive prey using biosonar may require a more gradual switch between multi-target echolocation and single-target tracking.
Original language | English (US) |
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Article number | jeb216283 |
Journal | Journal of Experimental Biology |
Volume | 223 |
Issue number | 3 |
DOIs | |
State | Published - Feb 2020 |
Externally published | Yes |
Keywords
- Biosonar strategies
- Deep-water environment
- Echolocation
- Gain control
- Mesopelagic foraging
- Sensory ecology
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Physiology
- Aquatic Science
- Animal Science and Zoology
- Molecular Biology
- Insect Science