As they touch upon, it’s more than likely they ended up there accidentally. I recently dug a series of vertically walled pits in a forest, for a foundation. I

As they touch upon, it’s more than likely they ended up there accidentally. I recently dug a series of vertically walled pits in a forest, for a foundation. It rained. I came back to find several of them absolutely heaving with toads and salamanders, who I of course rescued. It’s easy to see how, in a past when wildlife was radically more abundant than it is now, a single step sided ditch could have ended up a mass amphibian grave.