Intraspecific kleptoparasitism and counter-tactics in the archerfish (Toxotes chatareus)

Abstract

The mechanics of the archerfish’s remarkable ability to spit down aerial prey is well studied. Relatively unknown, however, are the social consequences of this hunting method. To explore how physical factors and behavioural choices affect the use and success of intraspecific kleptoparasitism in socially foraging archerfish, 10 tagged, juvenile archerfish (Toxotes chatareus) were presented in groups of 3, 5, and 7 with single crickets of 3 sizes overhanging the water by either 15 or 30 cm. Video review revealed all spits, jumps, attempted thefts, and consumptions. Kleptoparasitism attempts were common, resulting in a 43.6% loss rate to the fish that successfully brought down the prey. Group size affected the probability of kleptoparasitism asymptotically: loss rate increased as group size increased from 3 to 5 members, but with no further increase at 7 members. As observed with other kleptoparasitic species, the rate and success of kleptoparasitism increased with both prey size and prey height (analogous to handling time). Several counter-kleptoparasitism behaviours were observed, including jumping to grab prey directly, aggression, spitting technique, and positioning.