Tactile behaviour in a marine producer–scrounger feeding aggregation

Territorial behaviour can facilitate the defence of resources but becomes disadvantageous when resources are mobile and move beyond territory boundaries. In such cases, animals may develop strategies to retain access to these resources within their territory. Here, we describe a novel behaviour in the territorial Mediterranean rainbow wrasse, Coris julis , which joins producer–scrounger aggregations with a goatfish species, Mullus surmuletus , that disturbs benthic prey during foraging. Wrasse remained within their territories and did not follow producers beyond these boundaries but repeatedly engaged in tactile interactions (brief physical contact using their ventral side and pelvic fins or caudal fin) with goatfish while they were present. Events involving tactile interactions were associated with longer feeding durations of goatfish and therefore, indirectly, a higher overall food uptake for wrasse. During these events, wrasse also had increased rates of food uptake, possibly due to the close proximity to the producer and the disturbed prey. In general, feeding with goatfish was beneficial for wrasse when compared to foraging alone. Although goatfish feeding durations were longer when tactile interactions occurred, their movement patterns through the environment were unaffected by the presence or tactile contact of wrasse. While a causal relationship between tactile contacts and length of feeding time could not be established, the underlying mechanism may involve a physiological effect on goatfish, such as by reducing stress or functioning as a reassuring safety cue. Our findings describe a novel example of tactile interactions in a marine system and may suggest a behavioural strategy that could increase access to food resources within territorial boundaries, ultimately mitigating a cost of territoriality. • Territorial scroungers show tactile interactions with heterospecific food-producers. • Tactile interactions were associated with longer feeding aggregations. • Scroungers did not follow mobile producers beyond their territorial boundaries. • Scrounging with producers resulted in higher food uptake than foraging alone. • Tactile contact further increased food uptake rates, likely due to close proximity.