Not long ago I wrote about how to make a pond for tree frogs
so they could breed
without the predation and competition of larger frogs.

Since then I’ve learned a few things about how to make such a
pond. I learned much of
it from a particularly intelligent green frog.

I had two little plastic ponds, each about a yard across, set
flush with the ground in
the front yard. A young bullfrog moved into one. Grey tree frogs
colonized the other until
this particular green frog moved in.

When he showed up, the tree frogs disappeared. So one day I
caught the green frog and
carried him over to the pond with the bullfrog.

He seemed to sense danger and didn’t linger long. Two days
later he reappeared in the
other pond. He must have hopped 15 yards across the lawn and
through the weeds.

This quickly became an experiment. I would put the green frog
back in pond No. 1 and he
would move back to pond No. 2, which he saw as his pond.

At first the transfer took one or two days. I never saw the
frog make this trip. With
practice he covered the route faster. Obviously he could find
pond No. 2, which he
couldn’t see.

I started raising pond No. 2 on a support of bricks and
stones. My goal in the
beginning was to find out how high a pond’s edge had to be to
admit the tree frogs and
exclude green frogs.

Green frogs aren’t made for climbing. Each time I would raise
the level the tree frogs
would move back.

And then the green frog would somehow get back in. Every time
the green frog got in and
spawned, the tree frogs would give up and leave.

Today the pond is set on pillars of stones at about 20 inches
above the ground. And the
green frog and his girlfriend are its only residents, along with
their current crop of
tadpoles.

How do they get in? I wondered.

So one Saturday morning I caught the green frog and carefully
put him on the ground
where I could watch him. Then I retreated to the deck with a cup
of coffee to observe.

After about two minutes, the green frog hopped toward the
pond and disappeared into the
surrounding thicket. After several minutes’ rest, he began to
clumsily climb the pile of
rocks.

He struggled, fell back and tried again. About two-thirds of
the way up, he took refuge
in a crevice for about 15 minutes. Then he reemerged to go up
over the top and into his
pond.

He’s still there today, king of his little pond.

Clearly this frog remembers where his pond is and can get in
even though he can’t see
the water from the ground. I also found that the rockpile makes
a structure with ideal
hiding places.

I think I could exclude green frogs by making a smooth-sided
barrier instead of the
rocks. But I’ve decided I like this intelligent frog.

What can we learn from this? One idea is the concept of home
range. Once established,
most animals have an area they know. They learn its feeding and
hiding places. Animals
with a known territory live much longer than those traveling
through an unfamiliar place.

If you’re making a backyard wildlife habitat, try making
ponds. Several little ones
will increase the diversity of residents.

Elevated ponds will favor certain kinds of frogs. Add
structures like rockpiles to
provide hiding places. If you make the habitat good enough, your
transients will establish
themselves and stay.