Foraging toothed whales must be able to distinguish between targets and selectively keep track of prey items whilst in a multi-target and acoustically cluttered environment. Echolocating animals manage sensory loads from complex scenes by controlling the flow of spatial and temporal information via the adjustment of both their beamwidth and acoustic gaze. However, it is not understood how they control their acoustic gaze to inform changes in motor behaviour during search, approach and interception of multiple moving prey targets. My research focuses on disentangling the basis on which echolocating odontocetes adjust their acoustic gaze to focus on distinct targets.
Specific projects include: (1) Testing the capability of harbour porpoises (Phocoena phocoena) to range and hence delay gate to focus on a target of interest in an environment with a barrage of unwanted echoes. I have used sound-and-movement tags on free-swimming, blind-folded porpoises in a phantom target experiment to define how clutter and the presence of multiple targets impacts the time resolution capability in the porpoise’s biosonar feedback loop. (2) Measuring the functional beamwidth (a.k.a. the acoustic equivalent of peripheral vision) in porpoises. I have worked with trained porpoises in a two-alternative forced choice task to quantify how they steer their acoustic gaze to include and exclude information to accommodate complex acoustic scenes, effectively spatially filtering their acoustic field of view. (3) Testing optimal localisation theory in porpoises to uncover whether they exploit their beam gradient to assist in target localisation. (4) Measuring the 360° beam profile of the harbour porpoise, in relation to its implications for passive acoustic monitoring. And (5) collaborating with the Bahamas Marine Mammal Research Organisation and Ocean Instruments to collect the first deep water acoustic array recordings of pygmy and dwarf sperm whales (Kogia sp.) – a deep diving toothed whale that curiously produces narrow-band high-frequency clicks very similar to that of the harbour porpoise.
I defended my PhD on June 18 2021. A copy of the thesis can be found here: hjttp://www.marinebioacoustics.com/files/2021/Malinka_PhDThesis_2021_AU.pdf