Chorus frogs and other amphibians fill Alberta's wetlands with sound
Naturalist Brian Keating discovers a symphony of song from southern Alberta's frog population
Homestretch naturalist Brian Keating often makes his weekly appearance on the program via satellite phone, from the farthest corners of the planet.
However, on Monday's show Keating rode his bicycle into the studio, stopping en route in Calgary's Edworthy Park to check out the frogs.
Q: What did you discover, Brian?
A: I came across a city wetland last week and it was alive with sound. It [was the sound of] a boreal chorus frog. It's actually a tree frog that lives here in Alberta. It's not really a high climber. It's not really designed like some of the other tree frogs you'll find here in the tropics, but it's still classified as a tree frog. And it's got the widest distribution of any amphibian in the province.
Q: Are these frogs found throughout the province?
A: Historically, it's found everywhere in Alberta — except of course in the alpine environments. Now, it's excluded only from areas where there's higher pesticide use.
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Q: Are there other, similar frogs in Alberta?
A: There's only one other frog that's similar to the boreal chorus frog and that's the wood frog, which also lives in Alberta. And it also has a stripe through the eye, which the boreal chorus frog also has.
But it's larger and has two ridges down the back.
There's not a lot of frog species in Alberta, but that boreal chorus frog is the one that is the most common.
Q: Are they easy to find?
A: No they're not. They're easy to hear.
Actually when I biked to the studio today, I went via Edworthy Park because that's where I came across the pond, and I stopped there just a few minutes ago, and it was quiet. So they may have finished their breeding cycle.
Or maybe because it was just too darn hot for them.
The best time to hear them is early in the morning, or late in the evening — but they'll even call all night.
But they're very difficult to find — as soon as you start to approach to where the call is coming from, they stop.
Q: What do they look like?
A: They're the smallest amphibian in Alberta. They're less than an inch-and-a-half long at their longest — they're usually about an inch or so. And they're also known as the striped chorus frog, because of the three dark stripes that are on their body and a stripe through the eye and along the side.
They produce that sound, like all frogs, by expelling air out of their lungs, over their vocal chords — but they fill up an air sac on their throat.
It's absolutely amazing.
That balloon acts as a resonator and they just recycle the air back and forth over top of their vocal chords. That's how they make the sound.
I remember one time down in South America, I was camping in the woods, and a frog jumped in our canoe, in the night. There was a 50 gallon drum — it was a riverboat — and the 50 gallon drum was empty. The frog sat under the drum and it amplified his call about 50-fold. I'm sure he was the proudest frog in the forest.
That's why they have those air sacs — to amplify the sound.
Q: And the lady frogs love it?
A: Absolutely, 100 per cent. It's a nuptial call — and that's why they were calling last week, and are probably still calling now, in some areas. It attracts females. Discourages males from coming into the area.
So if you've got a good, robust call, like that one in that canoe in South America, I'm sure no male came close — if the call is robust and strong — that'll discourage other males from coming into his territory.
The problem with doing all that calling is it potentially attracts predators, so it's a delicate balance: should I mate, or should I get killed?
Q: How are they doing here?
A: When I was a kid, I remember seeing leopard frogs everywhere! And now, you're hard pressed to find — in fact, a number of years ago, the Calgary Zoo started a program — when I was working at the zoo — and they started to monitor leopard frogs.
They've got an ongoing leopard frog program, looking at 68 different wetlands around southern Alberta — they're even testing the water to see if there's frog DNA in the water. That way, they can figure out if there's frogs in a certain body of water without having to catch the frogs.
Interesting method — but yeah, they're looking at it. They've been in decline since the 1970's. It's one of those things. Obviously we're having an effect on the environment and it's probably due to a number of different reasons — but all the more reason to kiss a frog next time you see one.
With files from The Homestretch