European common spadefoot

Description

Adult males reach a maximum body length of 6.5 cm, females a maximum of about 8 cm; on average, however, both sexes remain slightly smaller. The coloration of the European spadefoot toad varies depending on the way of life, regional occurrence and sex. Mostly the animals show irregular dark brown, often elongated spots on a light gray to beige-brown ground. Almost every animal is thereby individually distinguishable. In addition, reddish or brown warts can appear, on the flanks also red spots. Females are usually more reddish brown in color, males tend to be more gray or clay yellow. In addition, the latter exhibit thickened upper arm glands at mating time. Some specimens lack the spotted pattern almost completely. While in the water, many individuals darken and thus have temporarily lower contrast markings.

The belly is whitish in color, often with light to dark gray speckles. Occasionally, albinotic forms also occur. Other distinctive external features are a helmet-like "parietal hump" on the back of the head and the vertical slit-shaped pupils, which are otherwise only found in the common midwife toad among Central European frogs. The metatarsal tubercle (callus internus) on the soles of the feet, which is present in all frogs, is particularly enlarged, sharp-edged and hardened in the spadefoot toad. It serves the animal as a "digging shovel" (digging callus).

The garlic odor, which gives this frog its name, is at most perceptible during a strong startle reaction. The secretion emitted serves as a defense against the predator. The behavioral repertoire of defense against predators is said to include active attacking and biting of the opponents as well as emitting a cry of fright similar to a toddler's scream. However, passive behaviors such as inflating the body or crouching are much more regularly observed in threatening situations.

Habitat

Adult toads are ground-dwelling terrestrial animals, except during the spawning season. They particularly prefer landscapes with loose, sandy to sandy-loamy topsoil (e.g. heaths, inland dunes, rough grasslands, steppes). Here, the animals can burrow quickly by means of their metatarsal tubercle " shovels" on the hind feet and the specially adapted leg musculature. The burrows dug are used several times by the animals. Under optimal environmental conditions, the subterranean daytime hiding places are literally turned into living caves, as the walls are mechanically stabilized and strengthened by the European spadefoot toad. In very dry summers, there may occasionally be prolonged periods of inactivity during which the toads rarely leave their burrow.

As soon as evening dusk falls, they dig themselves free from their underground hiding place to forage on the surface. 

Agriculture and its tendency to increase acreage have benefited European spadefoot toads in some ways. The more open, tilled soil areas with loose grains are present, the more frequently the animals migrate into these habitats. European spadefoot toads are particularly fond of colonizing sandy potato and asparagus fields ("potato toad").

Small to medium-sized, eutrophic still waters such as ponds and pools with a minimum depth of about 30 cm are preferred as spawning biotopes. They also like to colonize so-called secondary biotopes such as gravel, sand or clay pits, but also extensively managed carp pond areas. A riparian zone rich in vegetation, for example overgrown with swath reed, cattail reed or flood lawn, meets the needs of the animals. More often, spawning sites are located near or even in the middle of cultivated farmland. For hibernation, European spadefoot toads burrow up to one meter deep into the ground. Found earth cavities, such as mouse holes or mole tunnels, are preferably accepted as winter habitats and remodeled according to their own needs. Topsoil in fens and floodplains is usually avoided by European spadefoot toads - unless the floodplain is interspersed with drifting sand dunes, geest islands or fluviatile sand deposits.

The text is a translation of an excerpt from Wikipedia (https://de.wikipedia.org/wiki/Knoblauchkröte). On wikipedia the text is available under a „Creative Commons Attribution/Share Alike“ licence. Status: 25 June 2021