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. emily says:

    Thanks for sharing this information. I have frogs in my koi pond. They are all different sizes and colors and I have no idea how they got there. A week after we dug and filled the pond, the first one appeared and there have been more every year. I love when I can have the window open at night and hear them when I’m lying in bed. It’s really interesting to learn more about them.

  2. Pat in Belgium says:

    Of course, of course! I should have guessed. Even in the frog “kingdom”, when it comes to the males, it’s all about size!

    1. margaret says:

      You are so right, Pat…the same as with everything! :) Nice to “see” you all the way from across the big frogpond.

  3. Maddybee says:

    Great job, Margaret, this helps a lot. This year our frogs are pretty much driving us nuts with all the commotion they are making in a small property closely surrounded by neighbors. I figure they are going to come by and complain pretty soon with all the racket, not to mention the tree frogs (Eastern Gray) who have settled down, thankfully. I learned that frogs may not become sexually mature for a few years which might explain why this is the LOUDEST year yet.

  4. Wendy says:

    We moved into a house with a pond (no fish) almost 4 years ago and only one frog has visisted.
    Is it because we have a small waterfall and a spray that keeps the water moving or because it is a man made pond that we don’t get frogs?
    I love these creatures and was looking forward to seeing them.

  5. Maddybee says:

    Wendy, I have a man made water feature with two waterfall and a pump and we have had frogs for the past 5 of the 6 years its been here. Do you put any chemicals in your water for algae control?

  6. Wendy says:

    Maddybee oh how I envy you!!!

    We did put chemicals in the pond to control algae about 4 years ago, non since, I remove the algae with a net now.

    Am wondering if I should leave it. Anything to attract these lovely creatures.

  7. Maddybee says:

    Hi Wendy. I am a city girl and have had a lot to learn about this water garden and what a totally cool ecosystem it is. You definitely don’t need any chemicals to control the algae if you have the right balance of plants, skim the excess leaves/algae that you see and clean it annually. Even during times I was distressed about the amount of string algae I had, it straightened itself out. With that said, I am now dealing with water that is too green so….waiting that out a bit and will see what happens. In the meantime, keep the faith! The frogs will probably return and even if you don’t see more than one right now there may be more that appear later or next year. And thanks to Margaret for her wonderful information about frogs and of course her amazing photos.

  8. Wendy says:

    Thks Maddybee, now I feel hopeful.

    Yes Margaret is a great inspiration and seeing the photos of her frogs makes me what to make the pond more acceptable for them.

  9. Dahlink says:

    Wendy, we also have a small manmade pond with a waterfall, and we have loads of green frogs, plus the occasional visiting bullfrog or tree frog. Our pond is about 10 years old now. When we first built it, we stocked the pond with some koi from a friend, a few goldfish and some tadpoles from the garden center. Those tadpoles turned out to be bullfrogs, but they all grew up and hopped away (in search of bigger ponds, we assume). The green frogs found us on their own. We almost never use chemicals–skimming with a net (and occasionally yanking out string algae in late summer) seems to work pretty well. One year predators (we assume it was a Great Blue Heron and raccoons) wiped out all the bigger koi. I was distraught, but a friend with a pond assured me that Mother Nature would make corrections. Sure enough, we had a bumper crop of baby fish that year. It all works out if we don’t interfere too much.

  10. Maddybee says:

    Hi Dahlink, love your story and can identify. Question, do you drain and clean your pond annually? We did at first but last year we drained only half of it, cleaned and refilled and this year we didn’t drain and clean at all. For the first time we have green water and we were wondering if its because we didn’t properly clean the pond. How do you maintain your pond? Thanks!

  11. Dahlink says:

    Hi, Maddybee. True confession: we have never drained and cleaned our pond. It is always on the “to do” list, but somehow it never gets done. The closest we ever came was when the pump somehow started running backward and almost emptied the pond completely before we discovered the problem. We simply refilled the pond (and counted our fish and our blessings!) Our water is usually a little murky early in the summer, but it clears up over the season. Cleaning out the pump filter may help. We use a bio-filter and have plants that are supposed to help keep the water clear. I also think that not over-feeding the fish helps with water quality. Anyone have any other ideas for pond hygiene?

  12. Maddybee says:

    Thanks for the ‘true confession’, Dahlink, I really appreciate it. When our water feature was built the landscape architect said to drain and clean every year. We did it for a few years and then reverted to our own methodology based on not really wanting to use all of that water unnecessarily. We have an ultra-violet light on our pump but because we’ve never had fish of any kind (this was intended to be solely a water garden) so we don’t have a filter that I know of but I’ll ask my husband who is really the mechanic/caretaker of the pond. The landscaper placed 5 water lilies and 1 arrowhead that are supposed to help keep the water balanced, do you know the names of your plants? I also put a barley bale in last year….not sure if it helped or not but…I will have faith that the green-ness will self correct..Appreciate the response!

    1. margaret says:

      Dahlink and Maddybee: I have never cleaned my 2 inground pools (made with thick rubber “fabric” liners) in more than 20 years. True. I skim out some extra debris (fallen leaves) and add natural materials like barley straw pellets to help things break down…but that’s it. I have biological filters in both ponds, and I clean those a couple of times a year when they need it.

  13. Maddybee says:

    Margaret, thanks for weighing in and confirming my instincts to not follow the landscaper’s advice. Draining and cleaning this pool is an onerous task and I do hate wasting water. This is the first year we have had green water after the initial string algae and I don’t like it. We are used to some string algae of course but we’ve always had fairly clear water. Do you add barley straw pellets throughout the Spring and Summer on a regular basis?

  14. Dahlink says:

    Margaret, thanks for making me feel better about my sloth! I think the more biological our approach, the more successful we are going to be in imitating nature, don’t you?

    Maddybee, I have a big pot of “Red Scarf” lotus, and two hardy waterlilies. The newer one is “Barbara Dobbins.” These stay in the pond all year long. When winter approaches we lower them to the bottom of the pond and then bring them up when we’re sure Spring has arrived. Then we have floating greenery that the fish adore–it provides them cover from predators and seems to be a nursery for tadpoles and baby fish. I also have a dwarf papyrus and a couple of pots of taro (aka “elephant ears”), one green and one purple. These come indoors for the winter in big rubber trugs. In the upper pond, above the waterfall, we have a kind of wild celery that was recommended to help keep the water clean. We used to use water hyacinth, which has pretty lavender blossoms, but it multiplies like crazy, so we have stopped using it. In the south it is banned, I gather, because it could cause a real problem if it got loose into the waterways.

    My major pond chore is to fertilize the pond plants regularly (every 2 weeks during the hot months) with special pond tablets. Last year I got a little neglectful, and the lotus never bloomed. My fingers are crossed for blooms this year!

  15. Maddybee says:

    Thank you for the plant info, Dahlink! So my confession is that I have never fertilized my water plants….yikes. They seem to be doing fine although the waterlilies have less blooms this year. My thinking was that all the ‘stuff’ in the pond would provide the appropriate nutrients for the plants. To be completely honest the landscaper told me to fertilize and to divide the plants and I never have done either. The plant I believe is an arrowhead is a little invasive – it has spread to the waterlilies so I should maybe divide them. We are in central/west NJ and we leave our plants in the water all winter.. no prob.

  16. Dahlink says:

    Okay, Maddybee, we are even on the confessions now!

    I have divided some of our plants, when they get so overcrowded that they plop outside of their pots or when critters knock the plants over in smaller pots (a bigger pot solves that problem). When we first had the pond I used a special heavy pond soil, but when I had to repot my Barbara Dobbins recently the water center I use recommended a special potting medium that was like very fine gravel. That was much easier to use.

    1. margaret says:

      Hi, MLFK. I know other species are sold for science projects (UGH) and so on, but I don’t recall seeing green frogs (more bull or leopard I think?). Sorry not to know.

    1. margaret says:

      Glad you liked it, Patina. They are my dear little friends here. Each one a unique individual in appearance and temperament, I swear. Fascinating.

  17. LInda says:

    I really wish I’d known this yesterday. I’m in the Yukon and we have very few frogs!! But, yesterday there was one on the lawn at the edge of the garden. I’d love to have known whether it was male or female.
    Thanks for the interesting piece of information.

  18. Alice K. says:

    delighted to be learning about frogs. alas, i don’t have a pond or any kind of watering hole.
    my question, margaret, is what to bring my friends in the berkshires (a house away from stockbridge bowl where we swim) to plant in their not too well tended lawn and shrub area. we always visit for a weekend in july. they are there for weekends in spring and fall and for weeks in the summer. we have brought them little trees that have grown happily throughout the years…suggestions? thanks so much.

    1. margaret says:

      Hi, Alice. Nice to hear from you here. There is a very nice nursery called Windy Hill in Great Barrington, on the Stockbridge Road (Route 7); what about a certificate for there? Since I don’t know what they have, and if they have deer, and sun/shade and so on, it’s hard to suggest anything, or you could browse through my tree and shrub archive here. Another possibility: What about a really good lightweight garden hose? My recent favorite things, including the Water Right Inc. hose. Enjoy your visit!

  19. Dahlink says:

    I am hoping to share frog eggs with some frog-less friends next spring, but there is a very small window for sharing before they disappear from view (in my pond, anyway).

    I’ve been thinking more about pond cleaning, and I think over-cleaning may discourage the frogs. They need some muck for their winter snooze!

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