At Inokashira Park Zoo, the "Creature Plaza," which is open every Sunday from 11:00 to 12:00, offers the chance to encounter a variety of creatures. We will be introducing some of the creatures you can encounter there on an irregular basis.

This time, we're featuring the tadpoles of Eastern Japanese Common Toad which have been enlivening the pond in the plaza since spring. Some of them underwent dramatic changes as early as the first week of May 2012, with hind legs appearing, then forelegs, and their tails being absorbed. By May 9th, we were able to observe tadpoles that had come ashore. Then, when the park opened on Sunday, May 13th, tiny brown tadpoles, no bigger than the tip of a little finger, were swarming around the pond. There were hundreds of them, but because they were so small and the color was so similar to the soil, children would pass by without noticing them. When we pointed them out, some children would stare in silence, while others would cheer. Their reactions varied, but in any case, the sight was truly moving.

What also puzzles everyone is how incredibly weak the tadpoles look right after metamorphosis. In the plaza, you can also see large adult toads under the "observation board" and in the crevices of the rocks. Even when you explain "this is what they'll look like," it seems they just can't connect the stocky adult toads with the tadpoles with their needle-thin legs.

In fact, baby frogs grow very quickly. According to research conducted at the National Museum of Nature and Science's Natural Education Garden in Minato Ward, their body length, which was 7-9 mm, increases to about 5-6 cm (6-7 times) in about three months after metamorphosis, and by next spring, it will be about 7 cm (9-10 times) longer. Even baby frogs that look weak will grow rapidly from now on.

At the end of May, the baby frogs move out of the pond and can be seen under the fallen leaves in the plaza and under the observation board. They are still weak, but they seem to be getting a little bigger each week.
There are still tadpoles in the pond, so you should be able to observe newly metamorphosed froglets for a little while longer. Now is the best time to look for froglets.

Speaking of which, I noticed several women who were worried about the multitude of baby frogs, saying things like, "What will happen when they all grow up...?" I wonder how many of the baby frogs will survive?
According to "Toads of Kanazawa Castle" by Ryunosuke Okuno, a renowned book that tracked 1,526 toads living at the Kanazawa Castle ruins in Kanazawa City for nine years, the mortality rate during the tadpole stage is 90%, the mortality rate for young toads after they emerge from the water is 97%, and a further 99.7% die before they reach one year old. Hang in there, young toads!

Photo above: Baby frogs huddled together after coming ashore
Photo below: A still weak baby frog

[Inokashira Park Zoo Zoo]

(June 1, 2012)