Abstract
Commensal foraging is a positive interaction which occurs when one species benefits another's foraging activity without affecting their own. Though commensal relationships are widely recognized as ecologically important, instances of predator-predator commensalism remain relatively under documented in marine systems. Here, we report a predator-predator commensal foraging relationship between cobia (Rachycentron canadum), a pelagic marine ray-finned fish, and southern stingray (Hypanus americanus), a benthic whiptail stingray. While similar relationships have been documented between other teleost species and rays, there are few documented observations between cobia and southern stingrays. We observed this interaction during aerial drone surveys in a shallow, sandy-bottom habitat in Biscayne Bay, Florida, an atypical foraging environment for the offshore-associated cobia. Over the continuous 7-min and 13-s aerial observation, the cobia followed the stingray for > 90% of the time, closely tracking its position and shifting behavior based on the ray's activity. Notably, the cobia was observed consuming small prey items displaced but not consumed during stingray foraging. To assess whether similar associations have been observed elsewhere, we conducted a semi-structured Internet-based survey that compiled 14 additional observations of cobia-ray commensalism from public web sources. This behavioral evidence suggests that commensal foraging may represent an understudied foraging strategy for cobia in nearshore habitats and highlights the ecological importance of positive interspecific interactions in marine predator communities.