Male sticklebacks can distinguish between familiar rivals on the basis of visual cues alone

Abstract

Abstract. One-way mirrors were used to determine whether male three-spined sticklebacks, Gasterosteus aculeatus, could use visual cues to distinguish between pairs of neighbours that had similar social and physical attributes. Neighbours were enclosed in identical tanks that had no physical landmarks. The tanks had opaque side-walls and one-way mirrors (reflecting inward) placed along end-walls; thus, neighbours could not see outside of their tanks. Neighbour tanks were positioned at the ends of a test tank so that a resident could view both neighbours. Tanks were left undisturbed until residents completed a nest (ca 4-6 days). If neighbours were then switched from one end of a residents' territory to the other, residents charged toward and bit at the neighbours more often than they did following a 'mock' switch (i.e. neighbours were moved but then returned to their original position); following actual switches, males also devoted less effort to nest maintenance. Furthermore, the amount of effort devoted to defending a given side of the tank depended on which neighbour was there. The neighbours' surroundings did not change after switches, nor did their behaviour. Thus, male sticklebacks can distinguish between familiar rivals using visual cues alone. The ability developed in 4-6 days (i.e. the time required to build nests) and did not require physical interaction with the neighbours.