News of this frog’s unique mating technique auto-links to my name apparently, based on a message I received from someone* who sent me this story on innovative froggy sex: Bombay frog’s mating position is unlike anything seen before. I was interested and found photos to share, no small deal given these frogs mate at night (you know, only with the lights out). Also, they don’t touch each other during fertilization. And if that isn’t thrilling enough, they do it high up in trees during a monsoon! All this excitement from one species of the animal type (anurans — frogs and toads) scientists claim has the highest diversity of mating styles of any vertebrate. (Really? Really?) Helpful hint: you’re a vertebrate so get busy with the Kama Sutra or the illustration below and try to keep up.
The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of animals, vegetables, or rocks mating around you. Please let us know what is going on in a comment. Include, as close as is comfortable for you, your location and preferred amplexus position. |
First, to set the stage of anuran sex we need to talk about amplexus, amphibian sex. Most frogs (and many other amphibians) have a type of external fertilization with the male gripping the female, usually with his front legs, to stay close so when she releases eggs he can drop sperm directly on them.
Some do it in the water, others on land. How and where the males cling to their female partners varies (see illustration below).
They grab the female by her middle abdomen (A), arm pits (B), hang onto (C) or sit on (D) the female’s head (yikes), glue themselves to the female’s back (E, dude, get a grip), or demurely sit back to back (F).
Scientists have described six mating positions among the world’s 6,650 frog species.
Okay — got it? The top figures A though F show the mundane everyday six froggy sex positions. No one was sure how the Bombay night frogs did it. These frogs, endemic to the Western Ghats of India, have been the subject of biologists’ fevered speculations but it wasn’t until 2002 that a scientist first witnessed Bombay night frogs mating.
Sathyabhama Das Biju from the University of Delhi, an expert on amphibians, spent 40 nights in the forest, taking notes, photos and infra-red videos of 13 mating events and finally discovered details on a seventh mating style for anurans.
High in a tree on a branch, the female backs up and touches her toes to the head of her chosen mate. The male climbs atop her and hangs onto the branch (G in previous illustration), then squirts out his sperm on the female froggy and dismounts. Next, the female lays eggs and sperm runs down her back onto each egg as it’s released.
So romantic!
And it has a sexy new scientific term: dorsal straddle. Here are photos of the dorsal straddle from the research article: A unique mating strategy without physical contact during fertilization in Bombay Night Frogs (Nyctibatrachus humayuni) with the description of a new form of amplexus and female call. If you go to that link, you can hear the new form of female call, too, audios are at the bottom of the article. This is a special treat as less than 0.5 percent of female anurans have any call at all. Perhaps that dorsal straddle — sex while hanging from a branch — is worth yelling about?
If all this is still intriguing and you want more of the Bombay frog’s night life, there’s a Youtube video showing the habitat and actual mating along with a detailed narration.
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* Thanks to Crimson Quillfeather who thought I’d enjoy the news plus be willing to write about it.