Kin recognition in wood frog tadpoles (Rana sylvatica): factors affecting spatial proximity to siblings

In blind laboratory observations, we investigated three factors affecting spatial proximity to full siblings in wood frog (Rana sylvatica) tadpoles. In the first set of observations, we provided tadpoles the opportunity to associate with (i) siblings or no larvae and (ii) nonkin or no larvae. Tadpoles associated preferentially with siblings over no larvae, but showed no preference for either nonkin or no larvae. Thus tadpoles associate with siblings because they are attracted to kin rather than repulsed by nonkin. In a second set of observations, 10-day-old tadpoles failed to display sibling recognition, while 17-day-old tadpoles displayed a significant sibling preference. Furthermore, 17-day-old tadpoles spent significantly more time with siblings than did 10-day-old tadpoles. Thus, age affects sibling preference in wood frog tadpoles. When retested several days later, the former 17-day-old tadpoles again displayed a significant kin preference. However, there was no significant correlation in kin preference between a tadpole's first and second test. This and another comparison indicate that all wood frog tadpoles possess recognition ability, and that the failure of some tadpoles to manifest sibling preference is not due to a lack of recognition ability.