Finding a Frog on the Mountain

29 Apr

Hunting for herps can involve looking in every nook and cranny where something might be hiding.  Waterfalls have more crannies than most.  One March in Doi Suthep, I spent significant time exploring such a waterfall in breathtaking habitat.


Berdmore’s Water Skinks showed up in the nooks often enough:

Berdmore’s Water Skink Tropidophorus berdmore

But this time, it was not a Water Skink I found, but a little frog:

Inthanon Stream Toad Ansonia inthanon

Inthanon Stream Toad Ansonia inthanon

As you can see, it was a tough place to get a photo – dealing with water spray, darkness, a low-quality camera, and a frog that often hopped away after the first photo. The saving grace was that the frog loved this little spot. On the way back down the mountain, I found him again in the same spot.

Inthanon Stream Toad Ansonia inthanon

And on a different day, yet again in the same cavity but on a different rock – this time looking right at me!

Inthanon Stream Toad Ansonia inthanon

At first I thought it might be a juvenile Green Cascade Frog, a frog I had seen on the same waterfall earlier, as in this photo.

Northern Cascade Frog Amolops marmoratus

However, it was hard to tell if the identification matched matched. My frog was the right size, it had somewhat rough skin, and the color looked like it could potentially match. But the shape looked a bit different, the roughness of the skin seemed like a different kind of roughness, and the colors weren’t exact. Body/head/leg shape is really the #1 clue to look at when identifying frogs. So when I wrote a post showing the frogs I had seen recently on Doi Suthep, I posted a picture of the little guy I’d seen in the cave and asked whether I’d gotten any of the ID’s wrong. Stephen Mahoney, an Irish herpetologist who often works in Asia, told me I was certainly incorrect and the photo looked more like an Ansonia.

I looked up Ansonia and found that they were a genus of “stream toads”, small toads found in fast-moving streams in southeast Asia. Here’s one example of a colorful species of Ansonia from Borneo (photo from Frogs of Borneo).

The body shape and rough skin looked correct, as well as the manner of moving. So I went to look – what species of Ansonia might be found in northern Thailand?

A bit of internet research revealed that there was only one. The Inthanon Stream Toad (Ansonia inthanon), a small dark frog with yellowish markings, matched my frog find perfectly. You can see pictures of the frog here and here and here.

There were two especially interesting facts I learned about the species. First off, it was a recent discovery, having only been known to science since 1998. Even more fascinating, it was only known from two spots in the world! The species was first found in streams on the tallest mountain in Thailand, Doi Inthanon, and later in Thongphaphum in Kanchanaburi Province. And nowhere else.

I had found the third locality ever for the species. Since Doi Suthep is only 50km away from Doi Inthanon, it isn’t exactly a surprising find. It is still neat to be able to expand the known range of the species. With a little bit of luck, the Inthanon Stream Toads will survive in all three locations for many decades and centuries to come.


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