I pulled the car into my driveway on February 28. Mrs. Redwoodwoman opened the car door, and an uneasy expression spread across her face. She turned to me.
“Is all of that, ah, ours?” She asked me.
The tree frogs’ chorusing, from 100 feet away, was louder that a revving motorcycle, if more pleasant. Their overwhelming pulse of ribbets, chirps and croaks signaled that dozens of the past summer’s tree frog tadpoles had morphed, matured and now returned to the Frogs’ Mitigation Area (FMA). All that frog noise was ours.
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A year ago last Fall. I dug out a pond and shallow creek in my side yard, providing 150 square feet of open water, and replanted an adjacent 500 square area with ground cover, to accommodate the native tree frogs I occasionally found in my garden.
An Oregon tree frog (Pseudacris regilla) would fit onto a 25-cent piece. Its colors are either brown or green, with a bandit-mask-like black line across its eyes.
While locally abundant, frog populations worldwide are crashing. I didn’t put any fish in the FMA pond, to reduce preying on the frog eggs. Over 100 tadpoles hatched last summer, and most morphed into tiny frogs.
Tree frogs are unusually loyal to their birthplace and like salmon, frequently return to that pond to mate and lay eggs. One heartless researcher moved 83 tree frogs over 300 yards from their home pond, yet 67% returned within 9 days.
Judging from the sound, I wonder if all 100 frogs have returned to the FMA to breed and start a new generation of these tiny critters?
I walked towards the FMA at dusk. The frogs’ deafening calls seemed to double in intensity as I approached. Although there are 3 ponds in my backyard, all of the frogs are vocalizing from the smallest water body; the 6 x 6 foot Pear Pond in the FMA.
The frogs seemed so vociferous at 30 feet, that I was a little unnerved. Certainly that volume of noise could only come from hundreds of frogs, teeming on every surface. But when I crept to just 20 feet from the FMA, the croaking ceased abruptly. And once silenced, I could not find a single frog in the failing sunlight.
A week later, the frogs’ chorus still echoes, louder after dark, even as I type this tome.
I am surprised at the frogs’ early return, and the vehemence of their croaking, because one study opined that the tree frogs preferred water over 50 degrees F.
However the air temperature was just 45 F, on its way down to 39, when the croaking first reached cacophonic levels a week ago. The water temperature was within a couple of degrees of air temperature, and soil temperatures were about 5 degrees below peak air temperatures.
Tree frogs croak in different tones; a two-toned (diphasic) pitch to attract mates, and a trill to warn off competitors from an already-occupied corner of the pond, and thus avoid fighting. Their croaking volume carries for up to one-half mile, and attracts mates from a large area, but makes it difficult to estimate how many frogs are actually present.
Mating isn’t supposed to begin until water temperatures reach 54 degrees. However, when this croaking started, water temperature was below 50 degrees.
The frogs’ vigorous croaking seemed to waste energy, and reveal their position to predators for no good reason, if the water was potentially too cold for breeding.
By now, a week later, air temperatures exceed 60 degrees during the day, and water temperatures may be exceeding 54 degrees. The croaking continues.
I theorize that the current batch of FMA frogs have adapted to local temperatures and are prepared to mate and lay eggs in February even when the water is not quite 54 degrees.
Tree frogs are apparently tolerant of colder conditions. One study found tree froggies croaking their seductive song when water temperatures were just 35.6 F (2 degrees C).
Last year at this time, I have no notations regarding tree frog croakings in the FMA. In fact, I wrote a Bucket on April 20, bemoaning the lack of tree frogs in the FMA. Perhaps I didn’t notice a smaller chorus then. This year, you cannot avoid the chorus.
The action kicks off when male tree frogs gather at a water body and begin croaking. They gather volume by ballooning out their flexible throats, like tiny versions of Louis Armstrong.
The female frogs then hear the alluring call, and join the party. If the water is warm enough, the females get in, and submit to the pimply embrace of their soul mate.
Tonight, I can hear a tree frog for the first time this season at another, larger and deeper pond, ten yards from the FMA. I imagine the banter between that frog and his prospective mate.
”Come here often?”
“Every February, but just between you and me, the FMA is just a meat rack. All the males here are after just one thing.”
“I know what you mean, plus this place is so noisy you can’t hear yourself think. Let’s go for a hop.”
A dozen hops and thirty feet later, they are the only frogs at the larger pond.
“Oh, look at the submerged emergent aquatic vegetation!” She says,” It’s so lovely, and a perfect spot to deposit an egg cluster! There’s aren’t any fish around, are there?”
“Oh no,” he lied, ”And the water’s over 54 degrees,” he lied again.
Tree frog mating lasts several hours, during which the male helps the female squeeze out 9-70 eggs, which he fertilizes. The frogs attach the eggs to stems of underwater vegetation. The female can deposit numerous clusters which total 700 eggs. The female leaves the vicinity. The male hangs around the FMA for a couple more weeks.
Eggs take 1-5 weeks to hatch depending on water temperature. I’ve never seen a frog egg cluster in my yard ponds.
I Bucketed last June 11 about the many tadpoles then visible in the FMA. Given a 1 to 3-month typical tadpole growth period, a March egg laying was possible then.
Tree frogs are terrestrial. They only enter the water to mate, and spent the rest of the year throughout my garden, under the strawberries and Lamb’s Ear, mostly eating flying insects, and the occasional slug.
No bullfrogs have appeared yet. There were several by this time last year, including two in the FMA. I think the raccoons nailed those two; they disappeared suddenly.
The City of Portland surveyed several of its wetlands, and found far fewer amphibians in areas where bullfrogs were abundant. www.portlandoregon.gov/…
I’ve been discouraging bullfrogs.
One setback is that all of our lemon thyme ground cover in the FMA has died. It flourished and was even a little weedy last year, but this winter all of it died.
As a result I am in violation of my FERC Record of Decision, clause 1538.5, which requires ..”The project developer must spend every waking hour making the FMA look as pretty as possible.”
Hopefully, the Citizens Against Everything will not file another complaint with FERC (the Frog Environmental Mitigation Commission) about my non-compliance.
My main source material is the following study, chosen because of the pretty drawing of a tree frog on its cover.
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