Handbook of Nature-Study · Lesson XLIV · Topic 4: Batrachian study: toads, frogs and newts
44. The tadpole aquarium (toads' eggs and tadpoles)
Goal: Your child can set up a small pond-water tank for a few tadpoles and follow, week by week, how a tadpole grows legs, loses its tail and becomes a tiny toad.
You'll need
- A wide, shallow pan or tub (Comstock used a tin or agate pan or an earthenware washbowl)
- A bucket of pond water, a few pond stones, a little pond mud and some water plants
- A small net
- A hand lens
- Boiled lettuce or spinach and a hard-boiled egg yolk for food
- Nature notebook (this becomes a tadpole diary)
What's in the book
Two lessons in one: the leading thought and ten "things to be done" to make a tadpole aquarium (pond stones, mud, plants and water, out of the sun, no more than a dozen tadpoles, weekly fresh mud, food); then "Toads' Eggs and Tadpoles", with its own leading thought, method (eggs from a pond about May 1st; keep a dozen, return the rest) and eleven questions on the eggs, hatching, gills, the breathing hole, tail, legs, the loss of the tail and the change in habits. Photographs show toad development through one season.
The lesson, step by step
When and where
Spring. Toads lay long strings of eggs in shallow ponds and puddles in April and May (earlier in the South); Comstock says "about the first of May." Frog eggs come in round jelly clumps. Tadpoles turn into tiny toads in early summer. Safety: an adult stays within arm's reach near any water, and keep off steep or slippery banks.
Some states protect certain frogs, toads and salamanders, or limit collecting. Check your state's wildlife rules before you take any eggs or tadpoles home.
Keep the big idea in mind
Read these to yourself:
The children should understand how to make the tadpoles comfortable and thus be able to rear them.
The toad's eggs are laid in strings of jelly in ponds. The eggs hatch into tadpoles which are creatures of the water, breathing by gills, and swimming with a long fin. The tadpoles gradually change to toads, which are air-breathing creatures, fitted for life on dry land.
Make the "pond"
Follow Comstock's steps at the pond:
Go to some pond where tadpoles live.
Take some of the small stones on the bottom and at the sides of the pond lifting them very gently so as not to disturb what is growing on their surface.
Build them up on one side of the pan so some water is shallow and a stone or two sticks out. Add a little pond mud and a few water plants, carry it home, set it where the sun will not shine on it, and gently pour in pond water.
Just a few tadpoles
When the water is clear, add a few tadpoles or a short piece of an egg string. Comstock says:
Not more than a dozen should be put in a pan of this size
For a home pan, six to ten is plenty. Leave the rest in the pond. Never use tap water straight from the faucet; use pond water, or tap water that has stood for a few days.
Care each week
Every week add a little more mud from the bottom of the pond or another stone covered with slime
Care should be taken that the tadpole aquarium be kept where the sun will not shine directly upon it for any length of time, because if the water gets too warm the tadpoles will die.
Comstock fed tulip leaves and bits of hard-boiled egg. Today's keepers use a pinch of boiled lettuce or spinach instead, plus a crumb of egg yolk now and then. Take out leftover food so the water stays clean.
Watch them change
Look every few days with the hand lens:
Can you see with the aid of a lens the little fringes on each side of the neck? What are these?
Which pair of legs appears first?
After both pairs of legs are developed what happens to the tail? What becomes of it?
As the tadpole gains its legs and loses its tail how does it change in its actions?
Let them go
When the front legs show and the tail starts to shrink, the young toads will need to climb out, so make sure a stone sticks out of the water. As soon as they have four legs, carry them back to the edge of the same pond they came from and let them go. Wash hands after handling pond water, mud and tadpoles.
Nature notebook
Keep a tadpole diary: date, a quick drawing, and one sentence each time you look. Comstock's photographs on the page show the whole change; compare your drawings with them.
Afterwards
Look at the tadpoles for a few minutes every day or two until they leave. The whole change takes about one to two months for toads.
Tip
If you can't keep tadpoles, visit the same pond edge once a week with a net and a white dishpan, look, and let them go. You will see the same story.