Behavioural response studies

Multi-study OCean acoustics Human effects Analysis (MOCHA)

Mocha was a 3.5 year (2012-2015) collaborative research project that aimed to develop and implement innovative methods for the analysis of cetacean behavioural response studies (BRSs).

Behavioral response studies (BRSs) are experiments aimed at directly quantifying the relationship between potential anthropogenic disturbances and their effect on specific marine mammals. The US Navy is making a substantial investment in BRS studies, aimed at understanding the effect of active sonar on species of concern.

Studying these species in ecologically valid settings often requires field experiments. BRS studies are difficult and expensive to conduct, and so sample sizes are necessarily small. Traditional statistical methods for analysis, based on null models and hypothesis testing, do not make best use of the available data, and make it hard to represent accurately the complexity of BRS experimental protocols. With traditional approaches, small sample sizes result in insufficient power for all but the most extreme effects. This creates a risk of biased reporting, where clear responses from the most sensitive species will be publishable, while responses (or lack of responses) from less sensitive species are harder to detect and results are more difficult to interpret and publish. There is therefore a need for analytical approaches where every outcome contributes equally to our understanding. The outputs of this project will substantially enhance our ability to quantify the response of marine mammal species to navy sonar and other acoustic stimuli, make best use of available data, and provide guidance for future studies.