Amphibians
Common Spadefoot Toad
Pelobates fuscus · also called common spadefoot, garlic toad, European spadefoot
The common spadefoot spends almost its whole life underground, and it gets there fast. A hard, blade-like tool on each hind foot lets it shovel itself backwards into soft soil and disappear in under a minute. Handle one and it screams, puffs up, and smells strongly of garlic.
Overview
Common spadefoots live in loose, sandy soils near still, fish-free water across the lowlands of central and eastern Europe. They are 4.5–8 cm, pale and marbled, with a high domed head and large vertical-pupilled eyes. They emerge only on warm, damp nights to hunt beetles, worms, spiders, and millipedes.
The spade
A hard, sharp-edged keratinised “spade” sits on the inner edge of each hind foot. The toad works it into the soil and shuffles straight down backwards, vanishing in 30–60 seconds. It stays buried by day and through cold and drought, sometimes for weeks.
Garlic and screams
Stressed, the spadefoot’s skin gives off a strong garlic smell — hence “garlic toad” — and a threatened toad also inflates, rears up, and screams.
Giant tadpoles
The tadpoles are exceptionally large, often 10 cm and sometimes 18 cm — bigger than the adult toad — losing much of that bulk at metamorphosis.
Status
The common spadefoot is Least Concern overall but declining, and locally rare, as sandy grassland is farmed and its breeding ponds are drained or stocked with fish.
Common Spadefoot Toad: common questions
What is the "spade" on a spadefoot toad?
It is a digging tool built into the foot. On the inner edge of each hind foot, where other frogs and toads have a small soft bump (the metatarsal tubercle), a spadefoot has a large, hard, sharp-edged, pale structure reinforced with keratin, shaped rather like a garden trowel or the blade of a spade. The toad presses the spade into loose soil and rocks its hind legs alternately, shovelling the earth aside and sinking straight down backwards, so that it appears to melt into the ground. A common spadefoot can bury itself completely in well under a minute. American spadefoots (genus Spea and Scaphiopus) have the same adaptation, evolved independently.
Why does it smell of garlic?
When a common spadefoot is picked up, alarmed, or attacked, glands in its skin release a secretion with a pungent smell that most people describe as garlic, leek, or onion, and this has given the species its folk names in several languages, such as the German Knoblauchkröte, "garlic toad." The secretion is a mild defence — it tastes and smells bad to a predator and may irritate the mouth. Along with the smell, a threatened spadefoot will often inflate its body with air to look bigger, raise itself up on straight legs, and give a loud, sharp scream or squeal, which is startling from such a small animal.
How can the tadpoles be bigger than the adult toad?
Common spadefoot tadpoles are among the largest of any European amphibian, commonly reaching 10 centimetres and occasionally 15 to 18 centimetres, while the adult toad they become is only 5 to 8 centimetres long. This happens because the tadpole packs on size and fat while it has the chance, and much of that bulk is then lost during metamorphosis as the tail is reabsorbed and the body reorganises for life on land. Growing large as a tadpole is an advantage in the temporary and semi-permanent ponds spadefoots use — a big tadpole is harder for predators to eat, can outcompete smaller larvae, and emerges as a well-provisioned young toad. If the pond starts to dry, spadefoot tadpoles can also speed up their development to get out in time.
Why is the common spadefoot so rarely seen?
It is one of the most fossorial (burrowing) amphibians in Europe and spends the overwhelming majority of its life underground. Adults emerge only on warm, damp nights to feed, and concentrate their above-ground activity into a short spring breeding period at ponds, after which they scatter and dig back in, sometimes hundreds of metres from water. They are inactive underground through cold weather and drought, and their pale, marbled colouring and smooth skin make them easy to mistake for a young common toad on the rare occasions they are found. As a result, even in areas where the species is present, most people and even many naturalists never encounter one.