Green Frog at Lake Perrault

2023 February 5

Back on August 27, 2022, Sam and I were hiking around Lake Perrault while Sandy was testing her new fishing kayak in the lake. At one point, we spotted this pretty good-sized frog on the beach. See her there, right in the middle of the picture?

That was a “contingency shot”, in case she jumped away as I moved in. So I got significantly closer, and took another shot:

Hm. Still unperturbed. I wonder how close she’ll let me get? As it turns out, pretty close!

OK, that’s maybe too close. Let’s back up a little . . .

OK, that’s good. There are only a few species of frog around here, and this one looks like a Green Frog, Lithobates_clamitans. These don’t get as big as a bullfrog, but they are several inches long and are generally bigger than our other common frogs. The color varies a bit, with more or less of the bronze coloration on their hindquarters, but the head is generally pretty green.

The circular structure behind the eye is the tympanum, which is basically an exposed eardrum. We have a female here, because her tympanum is the same diameter as her eye. Males have tympanums almost twice the diameter of their eyes, and also tend to have greener lips and yellower chins.

The males are highly territorial, and will call both to warn off other males and to advertise for females. Their call is a kind of deep “plonk” sound, kind of like plucking the low string on a banjo. If a male is not warned off by the call, and instead goes in to challenge the calling male, they apparently will “plonk” vigorously at each other, and then if neither one retreats, they will proceed to wrestle. This continues until one of them basically gets the other in a chokehold and holds him underwater until he “cries Uncle” – they have a separate “submission” call that is used by defeated males to indicate that they give up.

Aside from the size of the tympanum and the behavior, there isn’t much visible difference between male and female green frogs, as they are both about the same size and general coloration. One interesting thing is that they can apparently change sex as a result of as-yet-undetermined environmental factors. This was just discovered in 2019 (, so it isn’t yet known whether sex-changed frogs can breed or not, but genetic analyses of the frogs showed that anywhere from 2% to 16% of the frogs in a population may be sex-reversed. It also doesn’t appear to correlate with pollution or other abnormal conditions, it just appears to be something that Green Frogs do.

One Response
  1. February 22, 2023

    Gorgeous close up! I’m guessing she was relying on her camouflage.

Comments are closed.