I’ve been maintaining chorus frog friendly ponds in my back yard in Washington County Oregon for some time now, so when I found a 1956 study about frogs in Washington County, I read it as avidly as some folks might read the latest John Grisham potboiler.
I want to make my ponds as welcoming as possible for the frogs, who are migrating into my backyard now, as they do every March. The chorus frogs have a strong homing instinct for their birth ponds. Scientists tried moving frogs 1000 yards away, but the frogs returned, often to the very spot by their birth pond where they had been captured.
I hoped this 1956 study would provide some hints to help me make the frogs happy. I’d been getting mixed review on Yelp from the frogs, they said I was feeding swill to the tadpoles. Well, the lettuce might of been a little limp.
I want a 5 star establishment for my frogs.
In the 1956 study, the scientists had put toe tags on 373 adult frogs, and 1156 juvenile frogs, and tracked their development at the Thatcher Road ponds in Forest Grove, about 30 miles southwest of Portland. They recorded how far the frogs dispersed from their birth pond, the habitats they preferred, and the factors that give frogs a leg up on survival.
Western chorus frogs are tiny, their bodies are only 1-1 ½ inches long. These researchers must have spent countless hours hunting these diminutive frogs near the bogs.
The frog colonies in the Study seemed to barely survive from season to season. Only 2 of the 1156 tagged juveniles reappeared eight months later at their birth pond to breed. Likewise just 30 of the 373 tagged adult frogs was still around to ribbet after just a few months.
For these frogs, the mating season started as early as December 16th and January 7 in 1953-4. That’s much earlier than the March arrivals in my own ponds.
I’d noticed low survival and return rates at my own ponds. Hundreds of juveniles set out very summer, but barely a dozen or more returned to mate and spin the cycle of life for another turn. Yet just a few returning frogs can restore the population, because a single female frog can lay hundreds of eggs.
The 1956 Study offered another provocative finding; the apparent dearth of lady frogs. The scientists in the 1956 Study said, “Adult females were seldom recovered.” Why?
Female chorus frogs are steathier than the males. They don’t croak, so they are harder to find. But still, why the lack of females? The study contended that the female frogs just didn’t hang out in the mating ponds where the scientists gathered frogs, instead the females mated and vanished. Of the hundreds of tagged frogs, only 22 were female.
The scientists did find another 20 female frogs by cruising two-lane blacktop in Lane County for 50 miles during a warm rain.
I’d found similar low female counts. In the early fall, when there are many recently morphed juvenile frogs hopping around, I captured several and flipped them over, to identify their sex by the presence or absence of the expandable throat sac, which only males have. I’m not sure I identified even one or two females out of ten frogs checked.
In a typical mating scene I’ve watched, there might be 10 male frogs spaced around a pond’s edge, all croaking. But an hour may pass before a single female frog ventures forward to pick a mate. Nonetheless, the Study theorized that “During the entire breeding season the number of females may equal the number of males.”
Unfortunately I don’t know how to compensate for the lack of female frogs. I will try advertising a lady’s night with half price drinks to see if that helps.
The study did note that recently morphed frogs and froglets do hang around near their birth pond in moist areas for a few days before dispersing. I’d noticed newly minted frogs often hidden under the squash vines near my pond, still learning to jump.
If a coon or skunk were to stake out that area for the arrival of newly morphed froglets, they could eat them like they were cheetoes.
The Study also discussed how bullfrogs had completely wiped out chorus frog populations at a neighboring mill pond. In response the scientists removed 17 bullfrogs (and 20 garter snakes) from their own studied pond. That facilitated an increase in chorus frogs from 373 to 630 the following year.
At one point I had ten or more bullfrogs in my own back yard ponds before I lost patience and began eradicating them, in concert with the herons and coons. I’ve never had garter snakes in my yard, fortunately for the frogs. The scientists found 52 juvenile frogs in the tummy of a single garter snake.
Oddly, the 1956 study ground to a halt, stating only that “The area was visited again in May when it was found the pond had been filled.” Today Thatcher Road wends by the suburbs in the foothills of wine country, with not a pond in sight.
You’ve been reading The Daily Bucket,
a nature refuge.
We amicably discuss frogs, animals, weather, climate, soil, plants, waters, and life’s patterns.
Phenology is how we take earth’s pulse.
We discuss what we see in each Bucket. I usually see frogs.
Each note adds to our understanding. Please comment about your own natural area, and include photos if possible. We love photos!
To have the Daily Bucket in your Activity Stream, visit Backyard Science’s profile page and click on Follow, and join to write a Bucket of your own observations.
Thanks for reading;
Now its your turn--
What have you noted in your area or travels?
Hearing any frogs? Please post your observations and general location in your comments. I’ll check back by lunchtime.
Be sure to read, recommend and comment in Meteor Blade’s valuable "Spotlight on Green News & Views,” every Saturday at 5pm Pacific Time and every Wednesday at 3:30 Pacific Time on the Daily Kos front page.