Pernille Tønnesen


More than twenty species of toothed whale, of widely varying morphology, physiology and sound producing systems, use echolocation to forage at mesopelagic depths. This diversity likely results in a large range of different foraging strategies including different adaptations of biosonar behavior. My research focuses on how deep diving toothed whales have adapted their foraging behavior and echolocation to target the mesopelagic prey layer and how these species adjust their biosonar output to overcome challenges presented by their foraging habitat and the targeted prey type.

Specific completed and planned projects:

1) The ontogeny of sperm whale (Physeter macrocephalus) calves

Using sound and movement tags I studied the acoustic activity and diving capability of sperm whale calves. The results show that sperm whales dive to great depths and start echolocating within their first year of life. The data were collected as part of The Dominica Sperm Whale Project and published in Behavioral Ecology and Sociobiology.

2) Adaptation to different foraging strategies in short finned pilot whales (Globicephala macrorhynchus)

With this project, I wish to describe and compare echolocation behavior during two types of foraging modes to examine whether short-finned pilot whales adjust their acoustic sampling rate in accordance to the density and maneuverability of their prey. Data will be collected in The Canary Islands.

3) Adaptation to bottom feeding in sperm whales

Using sound and movement data from male sperm whales from the Mediterranean Sea, I will examine how they adapt their high source level, long-range biosonar system to solve the short-range, high-clutter echolocation tasks of bottom feeding.

4) Sperm whale predator-prey interactions and related echolocation adaptations inferred from prey echoes.

Collaborating with Department of Oceanography and Fisheries, University of Azores, I deployed sound and movement tags on sperm whales. By placing these bio-logging devices very close to the distal part of the whales’ noses, I hope to be able to detect prey echoes and thereby to gain insight on prey availability, prey selection, and prey type related foraging strategy and echolocation behavior of sperm whales.

5) Echolocation of the cryptic deep diving kogias (Kogia sima and Kogia breviceps)

The aim of this project is to study the echolocation and foraging behavior of the elusive kogias to examine how these species use narrow-band high-frequency clicks to locate mesopelagic prey. In collaboration with PhD fellow Chloe Mallinka, Bahamas Marine Mammal Research Organisation, and Ocean Instruments, I deployed a deep-water acoustic array to get recordings of pygmy and dwarf sperm whales.

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