Tell me more about our neighborhood frogs

May 11, 2018 4:19 AM

We (myself and Mr. Sacchan) live in northern Honshu, Japan (also known as Tohoku) and are surrounded by rice fields. When the paddies are filled with water, the frogs go nuts croaking. We want to know the specifics on what they're up to.

For one, how many species are around here living in these paddies? What are they croaking about? Is this a territory thing or a prolonged finding mates thing? And furthermore, the frogs seem to start croaking like crazy when the paddies get filled with water, almost completely shut up when rice plants are planted (last night) and then are back to business as usual tonight.
Why???
Where can we ask these important frog questions, in Japanese or English? Or, do you happen to have an idea?

posted by sacchan to Science & Nature (2 answers total)

Best answer: Frogs pretty much croak about sex. The females use croak volume as a proxy for body size which is in turn a proxy for overall physical condition which is finally a proxy for genetic quality. Generally males will try to find a good place to croak from, and then females will gravitate toward the loudest croaker in the area. Quieter males may or may not try to intercept them en route.

They go croak crazy when the paddies get filled because full paddies are what they want to lay their eggs in. They like that shallow, still, mucky water for their tadpoles. Planting probably disrupts them and scares them off for a bit; lots of huge animals walking around and messing things up. After a while, they feel OK again.

I have no idea how many species of frogs like to hang out in Tohoku rice paddies (although someone might; there's several PhD theses worth of work to be done there, it's fertile ground for natural experiments) but my default assumption is that it's mostly one or two species and then lots of less-common ones. Probably some invasive bullfrogs in there too; bullfrogs get everywhere. If you hear mostly one type of croak, that's your dominant frog species right there.

Some very cursory research suggests that two of the most common frogs in rice paddies in your area are Pelophylax nigromaculatus and Rhacophorus schlegelii.
posted by Anticipation Of A New Lover's Arrival, The at 2:34 PM on May 11, 2018 [5 favorites]

Response by poster: Thank you thank you. They are all croaking away like mad right now, so we managed to compare with recordings of the species you suggested!

I think we do have Pelophylax nigromaculatus, and the main croakers are Japanese Tree frogs. Not sure who else but I found a site with recordings and some info on who hangs out in rice paddies. (albeit in another prefecture)

For those curious, you can listen to our croakers on these pages (click the "mp3" or "wav" buttons)

トノサマガエル (Pelophylax nigromaculatus)
http://www.hitohaku.jp/material/l-material/frog/zukan/tonosama.html

ニホンアカガエル (Japanese Tree Frog)
http://www.hitohaku.jp/material/l-material/frog/zukan/nihonama.html
posted by sacchan at 5:13 AM on May 12, 2018