frogboy or girl? telling frogs’ sexes apart

‘HE’S HANDSOME,’ I’ll say, or “Doesn’t she have have great markings?” when someone is here visiting, and we’re at the edge of the water gardens. “How do you know he’s a he or she’s a she?” people always ask, and with the most common species in my yard–green frogs (Rana clamitans) and bullfrogs (Rana catesbeiana)–it’s pretty easy, even out of mating season: It’s all in the ears.

The guy up top is a dead giveaway: He’s a green frog (I know, he’s all yellow right now, but his species is green frog). The yellow coloration he adopts in mating season can be just underneath, on the chest (with his back staying greenish or brownish), or it can go all-out, as with this ultra-sexy individual. The frog below? It’s a green frog, too–but look at her ear, or tympanum–that flat disc on each side of the head, behind the eye (not the architectural element by the same name).

If the tympanum in green frogs (or bullfrogs) is larger than the eye, it’s a male. About the same size as the eye or smaller? A female, and this one’s hiding in the semi-shade of some pondside vegetation, watching the antics of the males who are violently competing for her attentions.

In some species (in the tropics, for example) it’s more like it is with many birds: males and females have different coloration. (That’s called being sexually dimorphic, or having two morphologies–physical forms–per species, according to which sex you are.)

And then sometimes, it’s all about size–of the thumbs, that is. In certain species of frogs and toads, sexually mature males in breeding season have enlarged pads on their thumbs. They’re called nuptial pads, and no wonder: The better to clasp their brides with, when it’s time for amplexus. I don’t know if the forward young male in the photo below has nuptial pads, but he sure did get himself a big, beautiful bullfrog girl.


  1. narf7 says:

    I have to say that I identify strongly with frogs and that amongst our 900 potted plants (that we are hopefully going to get into our newly freed up garden beds over winter) we have a small but most determined posse of frogs ruling the roost and eating our pests along with the local wren population. Cheers for a delightful post and some really lovely photos to share that frogs are sexy little round beasts :)

  2. MLFK says:

    Regarding pond cleaning – I leave all the natural litter that builds up over the spring, summer and fall for overwintering my fish and native salamander and dragonfly nymphs. Then, come spring, I have a pond guy who comes and sucks out some of the muck and restarts the pump. We suspend the biological filter bag (that is in the waterfall during the warmer months) in the pond so the bacteria survive over the winter. The pump is submerged in a bucket of water in our basement so it doesn’t freeze. I use a “stock tank heater” from a local farm supply store to keep a hole in the ice for the health of the fish. They need fresh oxygen and my local birds and mammals (even foxes) use that source of drinking water when the local river freezes solid. This summer with our drought the waterfall is in constant use as a source of drinking and bathing water.

  3. Dahlink says:

    I am loving this discussion!

    MLFK, we also have a heater we suspend over the pond during the winter months. We only turn it on when we are iced over. There was one horrendous winter when we got several feet of snow (all at once!) and couldn’t get to the outdoor plug for quite some time. I feared for our poor fish under all that ice and snow, but they all survived somehow.

    We bring the tender pond plants indoors in the fall. I give them a trim before putting them in big rubber trugs and dragging them inside. A couple of years ago I was tidying up one of the pots when a frog emerged from the greenery and almost hopped out in my face. I was SO grateful he didn’t stow away and come indoors with the plants!

  4. Veleta says:

    Interesting…..are toads the same? Another interesting thing; last summer I had 78 (honestly, 78) toads in my swimming pool!! At first I thought they were mating as many were riding “piggyback”. But in the strainer they were 3, 4, 5…as many as 8 getting a free ride! We had to relocate all of them because when we gathered them out of the water they just jumped back in! That’s how we were able to count them. I don’t know what the caused this??? I’ve been in this house for 27 years and this was a first. I’ve deeply regretted that I didn’t take in pix .

    1. margaret says:

      Hi, Veleta. With the American toad, Bufo americanus, I think it’s easier during mating season and with mature individuals than youngsters. The mature males have noticeablelittle horny bits on the first couple of front toes as I recall, if you can get close enough to see; the males call in mating season (females don’t), and the males have darker throats (again in mating season). Males can actually be a little smaller than females of the same age; a female that is ready to mate may look very fat, as she is “gravid,” or full of eggs.

  5. Maddybee says:

    OK, a question for the frog mavens here. For the first time I have witnessed the aggression and fighting by the males frogs in our pond that Margaret has written about and photographed. Wow. Today one of the males, still quite yellow, is no longer croaking, honking or twanging….his voice has changed to a chirp. Seriously, he has a high pitched chirp now instead. It is a little disturbing and I’m wondering what happened to his voice. I mentioned the fighting because I’m wondering if he has been injured in one of the brawls? Any thoughts?

  6. Carol says:

    Here at my pond in Western Oregon I have the Pacific chorus frog. During breeding season the males turn a darker color under their chins. My pond is three years old and has been in biological balance the past two years. I don’t do anything to it. The main thing that keeps it in balance, I think, are snails. They are little algae munching machines that appeared on their own — probably from some water lilies I bought. I also have a floating plant called frogbit on about half the water surface. The frogbit gives the fish a place to hide and keeps the algae down by shading the water surface. For the first two years I added liquid Microlift to the water to build up beneficial bacterial but I didn’t add any this year and everything seems to be fine.

  7. Nancy Carow says:

    Regarding the frogs in amplexus—Isn’t that a male green frog with the bull frog? The (smaller) male appears to have a dorsolateral ridge, thus making him a Lithobates clamitans or green frog. The dorsolateral ridge is said to be the defining characteristic to discern green frogs from bull frogs. What do you think?

    1. margaret says:

      Good call, Nancy. I hadn’t even looks carefully I guess, being wowed by his heroic attempt with such a big girl. : ) Thanks, and yes, the ridges (and I think the shape of the “nose” is different, too, when I look at the two species together here in my pond, and of course the size when you have older adults).

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