On 3 July 2003, more than 20 foam-nests of Z. arboreus were recognized at branches expanded over the pond or trees fallen into the pond. At this time, a series of choruses (i.e., mating calls) by several male frogs were harmonized clearly around the pond. Some tadpoles of Z. arboreus were collected from the pond, but there was no larva of H. nigrescens in the pond. This was out of imagination because the present pond has both the deposition of 700-800 pairs of egg sacs of H. nigrescens every year and the usual occurrence of overwintering larvae, though their occurrence varies by year.

In another breeding pond, which is located near this site, larvae of H. nigrescens and tadpoles of Z. arboreus were numerously found on the same day. The salamander Onychodactylus japonicus and the frog Rana tagoi tagoi inhabit a torrent nearly bordered by this site. Several larvae of O. japonicus with 2-3 years old were captured from the torrent on the same day.