How to recognize a common
spadefoot toad tadpole?
Onion beds and garden plots are good foraging grounds
for the common spadefoot toad.
Habitat
The common spadefoot toad has vertical pupils.
Common spadefoot toad
The Pelobates genus includes four species, one of which,
the common spadefoot toad, lives also in Estonia. The
species’ distribution area extends from northwestern
France to Kazakhstan. Estonia is at the northern border of the distribution area, with the northernmost
locality being situated in Lääne-Viru County. The
common spadefoot toad is quite a common species in
parts of southern and southeastern Estonia.
Distribution of the common
spadefoot toad in Estonia.
The common spadefoot toad lives in areas with sandy
soil, in dunes, heaths, sparse pinewoods and cultivated
landscapes. It also populates agricultural landscapes
where farming is not intensive. Agricultural land has
loosened light soil, which is easy to dig into, and ample
sources of food. However, the use of agricultural toxins
and artificial fertilizers has a lethal effect on amphibians, as the dissolved chemicals are easily absorbed
through the thin moist skin.
The common spadefoot toad is a small (up to 8 cm
long) amphibian with a round body. It has smooth skin
and large eyes. Colour-wise, individuals vary greatly
– some are completely grey, while others feature a pattern with brown spots and smaller red dots. While it
may seem difficult at first to tell the common spadefoot
toad apart from other frogs, everything becomes clear
once we look into its eyes – it is the only frog here that
has vertical pupils. The common spadefoot toad also
often smells quite strongly of garlic.
Feeding habits
The common spadefoot toad is an amphibian with a terrestrial lifestyle, using water only for breeding. It leads
a very hidden life, digging itself into the ground during
daytime and emerging only at nightfall to search for
food. For digging the toad uses the spade-shaped inner
metatarsal tubercles on its hind feet. It only takes it a
couple of minutes to dig itself into the ground, posterior body end first. The soil has to be light and grainy.
This is why the common spadefoot toad can be often
found in garden plots, flower and vegetable beds (e.g.
onion beds at Piirissaar) and in small fields.
The common spadefoot toad begins its breeding period
in the spring, when ice has thawed in small water bodies and the sun has warmed them for some time. Breeding usually takes place in early May. For breeding to
take place, adults leave their hibernation sites and enter water bodies, where males start calling to attract
females. The common spadefoot toad is the only amphibian in Estonia that “sings” at the bottom of ponds,
under water. It does not croak, but makes a very silent
sound resembling clicking or the bubbling of water.
Once the female has chosen a suitable male, they form
The common spadefoot toad hunts for food at night. It
especially prefers potato fields and small garden plots
as feeding grounds, as there is abundant prey, mainly
various invertebrates, which can be spotted easily. The
prey are made up of mainly ants, ground beetles and
spiders, but also other non-flying invertebrates.
Breeding and life cycle
Spawn string of the common spadefoot toad.
a couple for the duration of the breeding, and the male
grasps the female by the loins. The female spawns a
sausage-like thick spawn string with 1,000–2,500 eggs
around aquatic plants or underwater twigs, which the
male then fertilizes. Once breeding is complete, the
adults leave the water.
From the eggs emerge tadpoles, which grow fast and
take considerably longer (up to 100 days) to develop in
the water body than the tadpoles of other amphibians.
Metamorphosis takes place in late July / early August.
Prior to metamorphosis a tadpole can grow up to 15 cm
long – a true giant compared to tadpoles of other amphibians in Estonia. The higher the water temperature,
the faster the tadpoles develop, which is why the preferred water bodies are up to 1.5 m deep and heat up
quickly. Metamorphosed juvenile toads leave the water
and look for good terrestrial foraging grounds in order
to store up sufficient amounts of energy before hibernation. The common spadefoot toad hibernates on dry
land. It digs itself into the ground, uses the burrows of
other small animals or finds suitable hibernation conditions in places such as old cellars.
A common spadefoot toad tadpole
may grow up to 15 cm long.
Recognizing a common spadefoot toad tadpole
among other tadpoles may seem easy at first sight. It
is after all the largest tadpole among our amphibians
– a ­giant reaching up to 15 cm in length. Still, it should
be kept in mind that tadpoles of green frogs may also
grow up to 10 cm long, and also that tadpoles do not
reach their maximum size until right before metamorphosis (in July/August).
A young, still small common spadefoot toad tadpole
can be recognized quite easily, namely by the position of its eyes – these are located on the sides of the
tadpole, making the common spadefoot toad tadpole
look slightly square when viewed from above. The
tadpoles of other frogs have their eyes located more
towards the back of the body, so that they do not protrude from the body.
Larger (> 3 cm) common spadefoot tadpoles are more
oval. The dorsal fin is high and transparent, without
spots or flecks. A unique “fish-tail pattern” can be
­detected on closer inspection.
The common spadefoot toad often has reddish dots on its sides.
Common spadefoot toad tadpoles have their eyes located
on the sides of their bodies, which makes it easy to distinguish them from the tadpoles of other frog species.
The tadpole is soft and tender, surrounded with
a transparent gelatinous mass. Upon being taken
out of water, it expands slightly in the palm. Both
younger and more mature tadpoles are brownish,
greyish brown or greyish green in colour.
Do not populate small water bodies
with fish!
If you still want to grow fish, leave some ponds empty,
so that amphibians and various aquatic invertebrates
could breed in them.
FOR MORE INFORMATION
Homepage of the
Estonian Environmental Board:
www.keskkonnaamet.ee
Homepage of the DRAGONLIFE project:
www.keskkonnaamet.ee/dragonlife
Photos: Maris Markus, Piret Pappel,
Roland Tischler, Riinu Rannap, Siim Veski
Drawing of tadpoles: Urve Sinijärv
Layout: OÜ NeoArt
The publication of the folder was funded
by the LIFE programme and the Estonian
Environmental Board.
A scrub-invaded water body.
Why has the common
spadefoot toad become rare?
A large number of small water bodies in Europe were
destroyed in the 20th century. The remaining water
bodies often suffer from deteriorated quality – they
become polluted, muddy or invaded by fish. The common spadefoot toad is strongly affected by the loss of
water bodies and deteriorated water quality, as it needs
water for breeding and for tadpole growth. In addition to water bodies the toad also needs high-quality
terrestrial habitats – a mosaic landscape with small
fields, garden plots, meadows and small woods. Scrub-­
invaded areas or intensively farmed landscape rob the
toad of the possibility to move among water bodies and
to find sufficient food and places for burrowing. Thus,
most of the remaining common spadefoot populations
are small and isolated and therefore very threatened.
What has happened to water bodies?
The most common reasons for the loss or deteriorated
quality of small water bodies are the following:
• scrub invasion and overgrowth
• excessive use of agricultural toxins and fertilizers
• landfills and drainage of water bodies
• populating water bodies with fish
Fish feed on the spawn and tadpoles of amphibians
and on aquatic invertebrates. Fish also stir up the bottom sediment in water bodies and destroy aquatic
plants, thus throwing the ecosystem of small water
bodies out of balance. The water becomes opaque and
oxygen-deficient. Such a water body is no longer suitable for amphibians and various aquatic invertebrates
to live and breed in.
Restoring small water bodies.
Protection of the common
spadefoot toad in Estonia
Due to its shrinking distribution area and decreasing numbers, the common spadefoot toad has been
included in Annex IV of the European Union Habitats Directive as a species in need of strict protection.
In Estonia, the common spadefoot toad is a category
II protected species. Active protection efforts of the
species in Estonia began in 2001, when first breeding
ponds were restored. Since 2004, small water bodies
have been managed annually in the various regions of
Estonia, contributing also to the breeding of the common spadefoot toad.
In 2010, the project “Securing Leucorrhinia pectoralis and
Pelobates fuscus in the northern distribution area in Estonia and Denmark” (DRAGONLIFE) was launched
under the European Union LIFE+ Nature programme,
with the aim to protect the small and isolated populations of these two species. The project runs until the
year 2014, and during this time 111 small water bodies
are created or restored in Estonia. The project’s activities in Estonia are funded by the LIFE programme and
the Estonian Environmental Board.
A newly-restored pond.
A restored breeding pond in good condition.
How can I help the common
spadefoot toad?
Our daily routines have an impact on many living
­beings – we can provide them with favourable living
conditions or destroy them. Every pond-owner can
actu­ally take certain steps so that the small pools of
water could please the owners and at the same time
provide suitable living conditions for lots of species.
Keep in mind that helping one species will also benefit ­others, as many species need good-quality water
bodies with clean water!
Preserve small ponds and pools of water
and keep scrub away from the pond banks.
This way you will preserve the diverse aquatic biota
and the lovely landscape.
Leave areas of uncultivated land around
ponds that are situated in the fields.
An unploughed stretch of only 5 m already prevents
fertilizers from entering water bodies and leaves a foraging area for amphibians at the edge of water bodies.
Restore small water bodies, clean them of
excessive vegetation and remove scrub from
the banks.
Before creating new water bodies, be sure to let the
­local government know of your wish, and in protected areas, also inform the Environmental Board –
www.keskkonnaamet.ee.
Common
Spadefoot
Toad
Pel oba tes f uscus