The harbour porpoise, the most numerous cetacean in north European seas, is a highly vocal species which uses only ultrasonic clicks for both echolocation and communication. Their relatively long, narrow band, high frequency (NBHF) clicks are unlike those produced by many other odontocetes. Harbour porpoises are particularly difficult to detect visually, and consequently, researchers have developed passive acoustic monitoring (PAM) techniques to track porpoises in the field. Development of such field techniques was hampered until recently by the very high frequencies of porpoise clicks, and there is still a paucity of information on how porpoises use their biosonar in their normal lives.
Porpoise bio-sonar represents a contrasting echolocation strategy to that taken by many other odontocetes which utilise shorter broad-band clicks. This system has evolved independently at least four times and there are several hypotheses suggesting the functional advantages driving this evolution. (Moriska, 2007; Madsen et al. 2005). The passive acoustic tracking data, allied with a modest degree of in situ acoustic experimentation, will allow some of these hypotheses to be investigated. The student will make detailed studies of how porpoises echolocate and forage in their natural environment. A particular interest will be exploring whether and how porpoise echolocation is adapted to the acoustic habitat these animals operate in and the sonar tasks they need to perform. Specific areas for investigation include:
• Source levels and click patterns used by wild porpoises to explore their environments and forage.
• Diurnal patterns in vocal behaviour and foraging.
• The acoustic characteristics of porpoise habitat, e.g. background noise, reverberation, propagation conditions and whether NBHF clicks optimised as a sonar signal in these environments.
• How porpoises use vocalisations to communicate.
• Other amenable issues may include foraging behaviour, foraging rates, body size.
The successful candidate will need to learn and apply signal processing techniques and achieve a level of knowledge and competence in underwater acoustics.
Funding Notes:
The student will require a minimum of an upper second class Hons Degree.
References:
References
Gillespie, DM., Swift, R., Cailat, M.,Gordon, J.C.D., Hammond, P.S. "Acoustic detection and tracking of harbour porpoise on line transect surveys." J. Acoust.Soc. Am., 2009.
Kyhn, L.A., Tougaard, J., Wahlberg, M., Stone, G., Yoshinaga, A., Beedholm, K., Madsen P.T. "Feeding at a high pitch: Source parameters of narrow band, high-frequency clicks from echolocating off-shore hourglass dolphins and coastal Hector's dolphins." J. Acoust. Soc. Am. 125, 2009: 1783-1791.
Madsen, P. T., Carder, D. A., Bedholm, K., & Ridgway, S. H. (2005). PORPOISE CLICKS FROM A SPERM WHALE NOSE — CONVERGENT EVOLUTION OF 130 KHZ PULSES IN TOOTHED WHALE SONARS ? BioAcoustics: The International Journal of Animal Sound and its Recording, 15, 195-206.
Morisaka T., Connor R.C. 2007:"Predation by killer whales (Orcinus Orca) and the evolution of whistle loss and narrow-band high frequency clicks by odontocetes". J. Acoust. Soc. Am. 1439-1458.
Wilson, B., Batty, R., S., Daunt, F., Carter, C. Collision risks between marine renewable energy devices and mammals, fish and diving birds. Report to the Scottish Executive, Oban: Scottish Association for Marine Science, 2007.