The social organization of animals is reliant on recognition. However, the precision and specificity with which an individual animal recognizes another in a social context, and the sensory mechanisms that it employs, may vary both within and between species. Differences in the ecology and in the mating systems of species may drive the evolution of different recognition abilities, ranging from individual-specific recognition to more general forms of recognition. We examined social recognition in two important model species in behavioral ecology, the guppy (Poecilia reticulata) and the three-spined stickleback (Gasterosteus aculeatus). We found that guppies were capable of individual recognition of conspecifics, as well as being able to differentiate between groups of conspecific based on cues relating to resource use and habitat use. By contrast, sticklebacks showed no ability to recognize individuals in a social context after prior interactions. Nonetheless, two out of three populations of sticklebacks demonstrated general recognition abilities, based on cues relating to resource use. We discuss the potential relationship between social recognition mechanisms and the ecological and life-history parameters of species and populations. Copyright 2009, Oxford University Press.