Frog Story

The froglet in the last post was set free later that evening. It had glued itself to the glass above the water line, up near the top, clearly wanting nothing more than to leave. Its nutrition-filled tail was shrinking by the hour. When I reached in, the froglet practically jumped right into my net, as if it knew I was offering a path to freedom. I put it into a plastic food box with a little water, foliage, and some algae, put the lid on, and carried the box outside to the Big Tank.

Dusk was falling and I hoped it would be a time of increased bug activity. I didn’t see any, but tiny froglets need miniscule bugs, and my eyes aren’t that small. But the froglets must have bugs! And there must be LOTS of them! because once they’ve tasted bugs, there’s no going back to salad. They’re not going to go back into the water for an algae snack if they can’t find any bugs. They go from vegetarian tadpoles to carnivore froglets almost overnight. 

That’s why the right timing of their transfer to the outdoors is crucial. Once they lose interest in algae, they could starve to death without bugs to replace it. And as I pointed out, I live in a bug-free home. Fortunately they get nutrients from the gradual absorption of their tails (no, they do not fall off) while they’re honing their hunting skills. They have only a few days to learn, and their parents haven’t stuck around to teach them. 

I floated the box on the surface of the water and watched for a bit. The froglet stayed in the box even though I took the lid off. After watching a while, I went inside to bed. In the morning the froglet was nowhere to be found – and I really looked, both in the water and out. 

What exactly happens to them? Well here’s one theory, but Warning: some viewers may find this disturbing. (I know I do.) A google search of “Why are my tadpoles dying?” turned up cannibalism, among other things. I hesitate to believe it. One, it’s gross. And two, I’ve never seen them so much as nibble on each other, and I’ve been watching very closely. I mean how would they even kill each other? They don’t have teeth, or other weapons. The Tiny Tank has a bare floor and not too much foliage, on purpose so I can see what’s going on. Still, those last three bodies never turned up, so … where’d they go? (Recall that I placed fifteen tads in the Tiny Tank, found two dead on the floor the next day, and only ten remain.)

Do they just up and die when they look around and see that it’s over-crowded? And THEN the other tads eat them? I saw no tads nibbling away at the two bodies on the floor. If an animal is consumed by its peers after death, is that still considered cannibalism? (I know it is with humans. Remember that plane crash in the Andes? )

Besides, how would they do it? They can’t exactly drown themselves. I’m not sure I even believe that each tadpole needs a gallon and a half of water. If that were true, in the wild they would stay further away from each other than they do. Nor are the mass suicide or cannibalism theories making much sense. I’m exploring other possibilities.

After only a day or two of Tadpole ICU, I found two tads on the floor of the tank.

This was so upsetting. Was I now going to have to helplessly watch them die off one by one, as they seemed to be doing outside? I’d had the water tested for everything, more than once, so I knew that wasn’t the problem.

I filled their Tiny Tank with water from their Big Tank outside, so they wouldn’t be shocked by a change in bacteria or temperature. I asked at the fish store — they were helpful with my indoor setup but mystified about the deaths. (They specialize in fish, not tadpoles.) The pond & water-garden store people, who have provided me with tadpoles in years where I didn’t get any eggs, know literally everything about these frogs — except this. They seemed as puzzled as I was.

By coinkidink, my Other Three-Quarters was reading a book called Simple Fountains, by Dorcas Adkins. She came across the following simple paragraph in a sidebar entitled Stocking Limits. “You don’t want to overstock reservoirs with animals that can’t simply get up and leave overcrowded situations, such as fish and tadpoles. A good rule of thumb is to allow 3 gallons (11 liters) per inch (2.5 cm) of aquatic creature.”

I am horrified. This alone could well be the problem — which would explain not only this death of the masses, but others occurring in previous years. And now it seems so obvious. Why didn’t I think of it before?

We did the math. According to that equation, these half-inch creatures need a gallon and a half of water each — meaning that this five-and-a-half gallon tank could accommodate three or four tadpoles. That might explain why two of the fifteen died right away, and why the population of the Tiny Tank has since dwindled to ten since I put them in there. Are six more of them doomed to die?

And all of this means that my outside tank — of thirty-five gallons — can accommodate twenty-three tadpoles. Not a hundred.

I might be a frog murderer — rather a far cry from being the Jane Goodall of tree frogs.

A blog about the breeding and care of the Pacific Tree Frog, or Hyla Regilla, native to Oregon, USA