The Great Basin Spadefoot Toad is found in BC in the dry southern interior. It is not often seen and spends most of its time burrowed in the ground (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008). It is well adapted to dry conditions and can survive droughts by burying itself--it is active on the surface after rains (Nafis 2009). Although born in water, these toads migrate to nearby terrestrial sites (usually within 500 m) and juvenile and adult toads spend the remainder of the year on land (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008).
The Great Basin Spadefoot is a primarily nocturnal, secretive, distinctive small toad, that is grey, brown or olive green in colour (Matsuda et al. 2006, Nafis 2009, British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008). It has large golden yellow or 'brassy' eyes with vertical pupils that are set on the side of the head (Matsuda et al. 2006, Nafis 2009). Legs are short (Nafis 2009) and it 'has a short, upturned snout' (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008). It is often described as plump, round or stout (Matsuda et al. 2006, Nafis 2009, and others). According to Matsuda et al. (2006), this species has 'two indistinct and irregular bands bordering the back, and has small tuberacles or reddish-brown spots covering the back'. The tympana are small, and there is a distinctive bump between the eyes (BC Ministry of Environment 2009). The skin is bumpy but not warty as it is in Western Toads. Adult Great Basin Spadefoot Toads range from 4 -6.5 (7.0-7.5) cm long (BC Minisry of Environment 2009, Matsuda et al. 2006, Nafis 2009); males are smaller than females.
This species has a distinctive 'sharp-edged dark ridge (“spade”)' on the inner side of the hind feet which allows individuals to dig or buurrow into loose soil for shelter (BC Ministry of Environment 2009, BC, British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008 ). This spade, and the vertical pupils, separate the Great Basin Spadefoot from the Western Toad, which has horizontal pupils.
Accordng to Morey (2009), after hibernation, Great Basin Spadefoot Toads become active on the surface after the first warm spring evenings and move from winter habitat to breeding ponds, where they will breed in springs, sluggish streams, and other permanent or ephemeral water bodies. Reproduction in this species is aquatic. In BC, they will breed in a variety of habitats, 'such as irrigated depressions, ponds, pools, or ditches, but seem to prefer small vernal pools that fill in and dry up each year' (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008). BC Frogwatch (BC Ministry of Environment 2009) provides the following reproductive information: 'males gather and call at small ponds, females join the males at the ponds, mate, then lay hundreds of eggs, which they attach to sticks and pebbles underwater, 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, toads become mature in their second or third year, and may live up to ten years'. Further detailed information on reproduction, including clutch size, is provided by AmphibiaWeb.
This species feeds on insects and smal invertebrates.
The Great Basin Spadefoot toad occupies drier habitats than most toads. They live in dry grasslands and open woods with loose soil, near water, and hibernate in burrows, with emergence in early spring. Morey (2009) indicates that they are 'found primarily in sagebrush country, in bunchgrass prairie, alkali flats, semi-desert shrublands, pinyon-juniper woodland to open ponderosa pine communities, and high elevation (2,800 m) spruce-fir forests'. Research has shown that they are primarily found below the 1600 m elevation, in neutral to basic soils that range from a pH of 7.2 to 10.4 (Hovingh et al. 1985). In BC, they are found up to 1800 m (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008).
This species is found from southern British Columbia south to east California, east to Colorado and nw. New Mexico. In B.C., Great Basin Spadefoot Toads are found in the dry southern interior (BC Ministry of Environment 2009), in the Okanagan, Similkameen, Kettle-Granby, Fraser, Thompson and Nicola Valleys and South Cariboo Region (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008).
The Great Basin Spadefoot Toad is considered vulnerable to human actions (blue-listed in BC), and has been influenced considerably by human action (Morey 2009), including damming of springs and streams, draining, grazing, lakeshore development and more. The grasslands that the toad occupies are one of the rarest habitat types in BC, and the toads are restricted within this to areas with breeding ponds (BC Ministry of Environment 2009). Population numbers in BC are estimated to be about 10,000 adults, but numbers are thought to be declining (BC Ministry of Environment 2009). Trampling of soils by grazing cattle may compact it to the point that it is difficult for the toads to burrow into the soil; cattle can also affect water quality in breeding ponds through increased siltation and distrubance, and increased nutrient loading leading to reduced habitat quality (BC Ministry of Environment 2009). Lowering of the water table in grasslands regions resulting from increased human use can result in loss of breeding ponds. Contrarily, creation of reservoirs can benefit them and create new habitat (Morey 2009). Introduced fish may be a threat (British Columbia Southern Interior Reptile and Amphibian Recovery Team 2008).
British Columbia Southern Interior Reptile and Amphibian Recovery Team. 2008. Recovery Strategy for the Great Basin Spadefoot (Spea intermontana) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC
Matsuda, Brent, David M. Green, and Patrick T. Gregory. 2006. Amphibians and Reptiles of British Columbia. Handbook. Royal BC Museum, Victoria.
Morey, Steven R. 2009. Spadefoot Toad (Spea intermontana) Fact sheet. In: AmphibiaWeb: Information on amphibian biology and conservation. [web application]. 2009. Berkeley, California: AmphibiaWeb. Available: http://amphibiaweb.org/. (Accessed: Jul 24, 2009).
Nafis, Gary. 2009. CaliforniaHerps.com. California Reptiles and Amphibians: Spea intermontana:--Great Basin Spadefoot Toad. Available: http://www.californiaherps.com/index.html.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
19/10/2019 10:58:14 AM]
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