Adults can grow to 18 cm (7 in) and their skin has a warty appearance and ranges from green to brown. As a defense against predators they secrete a toxic, foul tasting substance called bufagin. This is enough to deter many predators although Grass Snakes and hedgehogs are immune. Although the adults spend most of their time on land the females enter ponds and other still waters to lay their eggs, toadspawn, which can be distinguished from the spawn of the common frog as it forms strings rather than a large mass of eggs. Eggs are laid in the spring, with the females attempting to return to the water in which they were born. The young tadpoles resemble other tadpoles in their appearance except that toadpoles have a larger, rounder blacker head and shorter tail.
Common Toads eat invertebrates such as insects, larvae, spiders, slugs and worms, which they catch on their sticky tongues. Larger toads may also take slow worms, small grass snakes and harvest mice, which are swallowed alive. Toads generally hunt at night, and are most active in wet weather.
In Germany, Great Britain and Poland many toads are killed on the roads while migrating to their breeding grounds, in some places special tunnels have been constructed so they can cross under roads and local wildlife groups run toad patrols carrying them across busy crossing points in buckets.