Some of the anuran species are known to live in social aggregation in the larval stage (tadpole). Intriguingly, tadpoles possess a manner of association preferences. Previous studies reported that schooling/aggregation behavior of tadpoles would be controlled by evolutionary and ecological factors: the ability of kin recognition, population density, the presence of a predator.
To investigate whether frog tadpole exhibits size-assortative preference or not, we tested schooling behavior of Rana ornativentris tadpoles, hatched from egg masses collected in the field. For considering size difference, the tadpoles were sorted two groups based on body length and developmental stage: small (＜32mm, no hind limb) and large (＞36mm, with hind limbs). Our results indicated that small tadpoles had size-assortative preference, whereas larger ones did not show it. Moreover, the tendency was modified with whether the other side was kin or non-kin. These findings suggest that in general, Rana ornativentris tadpoles use information both body size and relatedness on making a decision about social preference.