Spatial clustering of trumpetfish shadowing behaviour in the Caribbean Sea revealed by citizen science

Abstract

Abstract: The West Atlantic trumpetfish (Aulostomus maculatus) performs an unusual hunting strategy, termed shadowing, whereby a trumpetfish swims closely behind or next to another ‘host’ species to facilitate the capture of prey. Despite trumpetfish being observed throughout the Caribbean, observations of this behaviour appear to be concentrated to a handful of localities. Here we assess the degree of geographical clustering of shadowing behaviour throughout the Caribbean Sea, and identify ecological features associated with the likelihood of its occurrence. To do this, we used a citizen science approach by creating and distributing an online survey to target frequent divers across this region. While the vast majority of participants observed trumpetfish on nearly every dive across the Caribbean, using random labelling spatial analyses, we found the frequency of shadowing behaviour was geographically clustered; participants that were within ~ 120 km of each other reported observations of shadowing that were more similar than would be expected by chance. Our survey also highlighted that trumpetfish were more likely to be observed shadowing than observed alone in a particular habitat type, and with particular host species, suggesting potential ecological factors that could drive the uneven distribution of this behaviour. Our results demonstrate that this behavioural hunting strategy is spatially clustered and, more generally, highlight the power of using citizen science to investigate variation in animal behaviour over thousands of square kilometres.