I noticed the large structure below today at the edge of a very small pond in northern Taiwan lowlands. It is June and it has rained a bit the past few days, and this 15 cm mud dome with a 5 cm diameter hole going straight down looked fresh and wet and glistening.

It is hard to tell for sure but it looks like the borough went deep enough to reach the water line of the pond next to it, but I could not tell because it's dark inside and I did not have a flashlight.

The mound is large, perhaps 15 cm tall and wide, which suggests that a lot of material has been removed and the tunnel could be quite deep.

The pond is only about 3 x 5 meters in diameter.

Question: Snake? Crab? Mole? What further information can I collect about it that would help to identify what produced this?

click images for full size view

large burrow next to a pond large burrow next to a pond


1 Answer 1


A crustacean (land crayfish). There are a lot to choose from.


  • 1
    $\begingroup$ Cool link, thank you! I certainly do see land crabs around from time to time. Can you add a little more to your answer though, perhaps a link demonstrating that they do indeed build chimneys or whatever this is? I found this while googling after your answer, perhaps it can help semanticscholar.org/paper/… $\endgroup$
    – uhoh
    Commented Jun 9, 2020 at 10:32
  • $\begingroup$ I haven't found a ref for this, just now talked with an old farmer from Taiwan, he says they are shaped more like crayfish, with a tail. $\endgroup$ Commented Jun 12, 2020 at 10:35
  • $\begingroup$ I'm quite sure this is the right answer, thanks for checking on that! $\endgroup$
    – uhoh
    Commented Jun 12, 2020 at 10:48

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