Great Basin Spadefoot
|Common Name:||Great Basin Spadefoot
|Scientific Name:||Spea intermontana
At a Glance
The Great Basin Spadefoot is a small, rather rotund amphibian, grey or olive green in colour.
The eyes are very large, golden yellow, and set on the sides of the head; the pupils are
vertical. The tympana (“ears”) are small and inconspicuous. They have a bump between the
eyes, giving the head a distinctive shape.
Adult spadefoots are 4 to 6.5 centimetres long; males are smaller than females. The limbs
are relatively short and stubby and the body rather plump; a Spadefoot sitting still on the
ground can give a very convincing impression of a large pebble.
Spadefoots have a bumpy skin but are not quite as “warty” as Western Toads. The bumps,
or tubercles, are small and dark brown or reddish in colour; the skin also has other
spots and patches of colour that are not raised. There are light-coloured stripes
down the sides of the spadefoot's back, and the skin on the tummy is pale.
The most distinctive feature is the source of their name: the small, black "spade" on
the first toe of each hind foot. This hardened tissue allows them to dig into loose soil
The spade and cat-like vertical pupils set the Great Basin Spadefoot apart from the
Western Toad, which has horizontal pupils. Western Toads also have distinct parotoid
glands, which appear as large swellings at the back of the jaw.
Male Spadefoots have a call that sounds rather like “gwaa, gwaa”, which they use to
attract females during the breeding season. Male spadefoots also call in response to
each other, forming a chorus of voices that can be heard several hundred metres away.
Home Sweet Home
The Great Basin Spadefoot likes drier habitats than most amphibians. Adult spadefoots
live in dry grasslands and open woodlands. They need loose soil for burrowing, or access
to rodent burrows, to shelter in during the day. They do need ponds for breeding, however,
so their habitat is limited by the availability of water.
This is the Life
Spadefoots hibernate in snug burrows, but emerge in early April to breed. Males gather
and call at small ponds. The females join the males at the ponds, mate, then lay hundreds
of eggs, which they attach to sticks and pebbles underwater. The eggs hatch within a week
in cool weather, or as quickly as two days if it is warm, and the tadpoles transform into
toadlets six to eight weeks after hatching. Great Basin Spadefoots become mature in their
second or third year, and may live up to ten years.
What’s on the Menu?
Great Basin Spadefoots feed on insects and small invertebrates. The adult spadefoots
forage at night for earthworms and insects, especially ants, beetles, and grasshoppers.
They are especially active on rainy or damp nights. The spadefoots are themselves on the
menu for Burrowing Owls, herons, crows, snakes and coyotes.
Spadefoot tadpoles are efficient scavengers, munching on algae and aquatic plants as
well as the occasional dead fish. Some spadefoot species have carnivorous larval morphs
(a genetic variant) that eat brine shrimp and sometimes even their own kind. This
behaviour has not been found in Great Basin Spadefoots.
Where and When
In B.C., Great Basin Spadefoots are found in the dry southern interior. Elsewhere, they
are widely distributed in Oregon and Washington, between the Rocky and Coast mountain ranges.
Spadefoots hibernate from October to early April. They remain dormant until warm weather
and rain return; during extremely hot and dry weather they retreat again to wait for more
comfortable conditions. They are primarily nocturnal even when they are not hibernating,
so are rarely seen. Spadefoots may travel long distances between foraging, breeding, and
hibernation sites, but little is known about their movement patterns.
How Are They Doing?
The Great Basin Spadefoot is on the provincial Blue List (species considered vulnerable to
human actions) and has been designated Special Concern by the Committee on the Status of
Endangered Wildlife in Canada (COSEWIC). Their habitat is under great pressure, since human
beings also enjoy living in warm dry areas. The dry grassland habitat is one of the rarest
habitat types in B.C., making up only six percent of the province's land area. Within the
dry grassland, Spadefoots are restricted to those areas with access to breeding ponds. Just
three such ponds were found to contain over half the total population of calling males in
one survey. Fortunately, two of those ponds are protected.
Current population estimates put the number in the province at about 10 000 adults, but
this number is thought to be declining due to the loss of breeding and foraging habitats
in the Okanagan Valley.
Fragmentation of the habitat is a serious concern, since breeding and foraging sites
must be connected by movement corridors to be useful to the spadefoots. Grazing cattle
may compact the soils, making it difficult for the spadefoots to burrow, and have a
detrimental effect on water quality in breeding ponds. Perhaps most disturbing of all,
intensive human demands on water resources in the Canadian range of the Great Basin Spadefoot
have lowered the water table significantly at many sites, thus reducing the number of breeding
How We’re Helping
The Great Basin Spadefoot is protected from being killed, captured or harmed under the
British Columbia Wildlife Act. Much of their range is privately owned land. Several critical
breeding areas, however, are protected: for example, the Haynes Lease Ecological Reserve and
the South Okanagan Wildlife Management Area provide some secure habitat for breeding spadefoots
at the north end of Osoyoos Lake, and the Nature Trust of British Columbia has acquired several
properties with Great Basin Spadefoot habitat in the South Okanagan.
How You Can Help
You can help by learning more about Great Basin Spadefoots and raising awareness about
them. Stewardship arrangements for spadefoot habitat are needed. Local land use planning
meetings are a good place to get involved. Landowners with spadefoot habitat should be
encouraged to fence their ponds and otherwise try to minimise the impact of their livestock
on the habitat. You can also help with surveys to learn more about the distribution of the
spadefoots and how the populations are doing, by volunteering with B.C. Frogwatch.
- Great Basin Spadefoots can lose up to 48% of their body moisture without ill effect
- Spadefoots can estivate (enter a state of torpor during summer dryness) or
hibernate (in winter's cold) for seven to eight months of the year
- A frightened Great Basin Spadefoot is able to dig itself rapidly into the
soil, disappearing from sight in just a few minutes
- Some spadefoot species can gather enough food energy for a year of dormancy
in just a few feedings
Photo © Wally Edwards. No reproduction or distribution without permission.