Social recognition in wild fish populations

Abstract

The ability of animals to gather information about their social and physical environment is essential for their ecological function. Odour cues are an important component of this information gathering across taxa. Recent laboratory studies have revealed the importance of flexible chemical cues in facilitating social recognition of fishes. These cues are known to be mediated by recent habitat experience and fishes are attracted to individuals that smell like themselves. However, to be relevant to wild populations, where animals may move and forage freely, these cues would have to be temporally flexible and allow spatial resolution. Here, we present data from a study of social recognition in wild populations of three-spined sticklebacks (Gasterosteus aculeatus). Focal fish preferentially associated with conspecifics from the same habitat as themselves. These preferences were changed and updated following translocation of the focal fish to a different site. Further investigation revealed that association preferences changed after 3 h of exposure to different habitat cues. In addition to temporal flexibility, the cues also allowed a high degree of spatial resolution: fish taken from sites 200 m apart produced cues that were sufficiently different to enable the focal fish to discriminate and associate with fish captured near their own home site. The adaptive benefits of this social recognition mechanism remain unclear, though they may allow fish to orient within their social environment and gain current local information.

Figure 1

Median time±quartiles spent by focal fish with each of two stimulus shoals: (a) Focal fish taken from sites 1 and 2 were given a choice between stimulus fish from their home site and stimulus fish from the alternative site, n=24; (b) Focal fish taken from site 2 were transplanted to site 1 overnight before being given a choice between stimulus fish from their site 1 and stimulus fish from site 2, n=16 and (c) Focal fish taken from sites 2 and 3 were given a choice between stimulus fish from their home site and stimulus fish from the alternative site, n=24. Differences in time spent shoaling by focal fish with the two stimulus shoals in binary choice tests were derived by subtracting time spent with shoal ‘b’ from time spent with shoal ‘a’ and comparing the results against a null expectation of 0. Significant differences are denoted as follows: ^*p<0.05; ^**p<0.01.

Figure 2

Median time±quartiles spent by focal fish with stimulus fish from their home site where the other stimulus fish was taken from the alternative site as a function of time spent in mixed water, n=24 for each treatment. Differences in time spent shoaling by focal fish with the two stimulus shoals in binary choice tests were derived by subtracting time spent with shoal ‘b’ from time spent with shoal ‘a’ and comparing the results against a null expectation of 0. Significant differences are denoted as follows: ^*p<0.05.