Matt J wrote:
Toads are darn good diggers, enough so to get below the frost-line for the winter.
Frost-line? What's that? Hahaha. Down here, the frost-line is generally considered to be one inch. In truth it is probably less. The heat line on the other hand is probably over a foot. If you don't bury your water lines deep enough, your "cold" water will be nearly as warm as your hot water in summer.
Down here, I'm assuming they either need to dig nearly two feet OR find a shaded and vegetated location that holds the humidity and cooler temps at shallower depths.
I'm wondering if the ones that Paul found were drawn there by an undetected slow leak in that water line.
I guess the short answer is, "they dig as deep as they need to". That need will be determined by humidity, temps, soil conditions, and probably some other less obvious factors. As for the one reported to be 15 feet down, I suspect it didn't truly "dig" that deep. It likely took advantage of burrows, fissures, or other pre-existing voids. The ground in many places out here is full of all sorts of small voids.