Kin recognition in Rana cascadae tadpoles: effects of rearing with nonsiblings and varying the strength of the stimulus cues.

Experiments with two clutches of Rana cascadae tadpoles were undertaken to determine if (1) rearing tadpoles exclusively with nonkin affects sibling recognition behavior and (2) if tadpoles are capable of distinguishing between groups of varying sibling/nonsibling composition. Individual tadpoles reared from embryonic stages with 12 nonsiblings behaved as tadpoles reared with siblings by exhibiting a preference for siblings over nonsiblings in choice tests. This suggests that experience with siblings is not a necessary prerequisite for the development of sibling recognition in this species. Tadpoles reared with siblings preferred to associate with a group composed of 50% siblings and 50% nonsiblings over a group of 100% nonsiblings, but exhibited no preference for a group composed of 25% siblings and 75% nonsiblings versus one composed of nonsiblings only. Thus tadpoles are capable of discriminating between mixed groups of siblings and nonsiblings, but probably require some minimum proportion of siblings to do so.