The function of roll in foraging behaviour of sperm whales

Sperm whale--Behavior;Sperm whale--Vocalization;Sperm whale--Food;Echolocation (Physiology)

Hartvig, Eva Christel ; Miller, Patrick ; Miller, Patrick

University:University of St Andrews

Department:Biology (School of)

关键词: Sperm whale--Behavior;    Sperm whale--Vocalization;    Sperm whale--Food;    Echolocation (Physiology);   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/3139/EvaHartvigMPhilThesis.pdf?sequence=3&isAllowed=y

来源: DR-NTU

【 摘 要 】

Though direct experiments to test echolocation in sperm whales (Physetermacrocephalus) remain impossible, the indirect evidence is overwhelming that onefunction of their clicks is echolocation used during foraging, as has been shown for othertoothed whales. In this thesis, the aim was to test: 1) the hypothesis by Fristrup andHarbison (2002) that the sperm whale might be using downwelling light during the day tospot prey or prey patches as silhouettes against the lighter sea surface. 2) A secondhypothesis by Fristrup and Harbison (2002) suggested that the sperm whales use vision tolook for bioluminescence in prey at depth, or during the night when no light is available.3) Indications that the sperm whales changed their roll-behaviour, rolling moreextensively when they were producing regular clicks during the descent as well as for theascent. Data from 51 sperm whales tagged in the Gulf of Mexico, the Atlantic, theMediterranean and northern Norway, were tested to explore how large a proportion of thebottom-interval the whales spent at angles where they were able to see towards the lightersea surface at three different pitch-modes while either searching or buzzing, for eachdive. The majority of whales were found to be swimming predominantly upside down oron the side during both the day and night time. The whales were not found to change theway they use roll at night compared to the day time, when looking at the bottom-intervalwhen the whales were both searching for prey and buzzing.Looking at another function for roll and a possible association with theecholocation of the sperm whales, it was found that during the descent, the whales had atendency to have a higher variance of roll when they were producing regular clicks. Avery similar trend showed for the ascent-phase as well, that they seemed to roll morewhen clicking compared to when they were not, before they reached the sea surface.These analyses of the roll-behaviour of sperm whales used to test the hypotheses putforward by Fristrup and Harbison do not seem to support the use of vision to detect preyduring foraging at depth, but might indicate that the sperm whale was intentionallychanging its roll-behaviour, when they were producing regular clicks during the ascentand descent-phase in the Gulf of Mexico, the Atlantic, the Mediterranean and Norway.