Multivariate analysis of behavioural response experiments in humpback whales (Megaptera novaeangliae)

• Published in: Journal of Experimental Biology
• Main Authors: Dunlop, Rebecca A., Noad, Michael J., Cato, Douglas H., Kniest, Eric, Miller, Patrick, Smith, Joshua N., Stokes, M. Dale
• Format: Text
• Language: English
• Published: Company of Biologists 2012
• Subjects: Research Article; Humpback Whale; Megaptera novaeangliae
• Online Access: http://jeb.biologists.org/cgi/content/short/jeb.071498v1; https://doi.org/10.1242/jeb.071498

The behavioural response study (BRS) is an experimental design used by field biologists to determine the function and /or behavioural effects of conspecific, heterospecific or anthropogenic stimuli. When carrying out these studies in marine mammals it is difficult to make basic observations and achieve sufficient samples sizes due to the high cost and logistical difficulties. Rarely are other factors such as social context or the physical environment considered in the analysis because of these difficulties. This paper presents results of a BRS carried out in humpback whales to test the response of groups to one recording of conspecific social sounds and an artificially-generated tone stimulus. Experiments were carried out in September/October 2004 and 2008 during the humpback whale southward migration along the east coast of Australia. In total, 13 ‘tone’ experiments, 15 ‘social sound’ experiments (using one recording of social sounds) and three silent controls were carried out over two years. Results (using a mixed model statistical analysis) suggested that humpback whales responded differently to both stimuli, measured by changes in course travelled and dive behaviour. Although the response to ‘tones’ was consistent, in that groups moved offshore and surfaced more often (suggesting an aversion to the stimulus), the response to ‘social sounds’ was highly variable and dependent upon the composition of the social group. The change in course and dive behaviour in response to ‘tones’ was found to be related to proximity to the source, the received signal level and signal-to-noise ratio SNR. This study demonstrates the complexity of behavioural responses by a marine mammal to acoustic stimuli, the need to replicate stimuli to generate a sufficient sample size, and to measure as many other factors as possible culminating in a multivariate analysis in order to tease out complex interactions.