Re: Why do some tadpoles change to frogs and some never do?

Gini -

The answer to your question is not a simple one. I submitted the question to Erika R. Halvorsen, a frog expert at A Thousand Friends of Frogs. Here is her response:

"It is important to provide an area of dry land for metamorphosing amphibians to climb onto. However, there could be many factors that may have led to the underdevelopment of the tadpoles. The food supply may have been inadequate, the water tamperature may have been too high/low, the level of dissolved oxygen in the water may have been too low, etc. It also depends on what species of tadpoles the children had. It could be that they had different species, that develop at different rates and times. For example, Bullfrogs remain as tadpoles for several years before turning into adult frogs."

So, it is quite possible that you are correct. The beach was necessary for the final metamorphosis from tadpole into frog. The change from tadpole into frog is controlled by hormones and it is known that in some frogs, the release of these hormones is controlled by stress. If the water level in your container went down (from evaporation), the tadpole would have run into your beach more often. This would make the tadpole think that the pond was drying up and it was time to turn into a frog.

Your cousin's tadpoles never realized that the 'pond' was drying up (because there was no beach) and did not change.

I hope that this helps.

James Powell