The three-dimensional (3D) structure of habitats influences how prey detect and respond to predators, but the specific roles of different aspects of structural complexity remain poorly understood, particularly in coral reef ecosystems. We used 3D models of three Caribbean reef sites to quantify three structural metrics at site-level: field of view (the extent of observable area), refuge density (density of holes), and rugosity (reef surface roughness). We then observed the anti-predator behaviour of damselfish, parrotfish, and wrasses at each site. Refuge density was similar across sites, likely reflecting long-term regional loss of fine-scale complexity in the Caribbean. Territorial damselfish showed species-specific responses to habitat structure, especially in relation to field of view. Stegastes adustus, for example, exhibited shorter flight initiation distances (FIDs) at the site with the highest field of view, consistent with expectations from optimal escape theory. In contrast, wrasse and parrotfish species showed little variation in behaviour across sites, though larger individuals tended to have longer FIDs and flight distances. While rugosity is widely used as a proxy for reef complexity, our results suggest that field of view may be more strongly associated with differences in anti-predator behaviour, particularly in damselfish. These findings highlight the need to assess multiple dimensions of habitat structure, as even closely related species may exhibit distinct behavioural adaptations to their 3D environment.

Funding provided by: Natural Environment Research CouncilROR ID: https://ror.org/02b5d8509Award Number: