I'd have thought so keberoxu. They have glands on their necks which exude a poisonous substance. And their skin is known to deter predators, so I imagine the dog's water dish would be pretty revolting.

The common toad has the Latin name Bufo bufo (Sounds like Boris Johnson!)

While the common frog is called Rana temporaria, as if it's not planning to hang around for long..