I found this blurb in the USAir Gift Catalog (This catalog is yours to keep.
Please take it with you!) recently. Quoted without permission:

GOPHER-IT

Prevent damage to garden and lawns from burrowing rodents
with Gopher-It, the electronic stake that emits vibration
and sound thats intensely annoying to underground rodents
up to 100 feet in diameter.

Requires 4 D batteries, not included.

#26284 Gopher-It $49.95 (3.95)

I suppose for rodents of greater than 100 feet in diameter you need the
nuclear powered version.