Montana Field Guide

Great Plains Toad - Bufo cognatus

The skin of adult Great Plains toads is covered with numerous small warts; cranial crests are prominent, and diverge posteriorly from a hard lump (boss) on top of the snout. The parotoid glands posterior to the eyes are elongate. The back exhibits a somewhat symmetrical pattern of large, light-edged dark spots or patches. The underside of the hind foot often has a sharp-edged tubercle and a smaller dark-tipped tubercle. Females can reach 11.4 centimeters snout-vent length (SVL); males are usually less than 9.5 centimeters SVL. Males have dark, loose throat skin and a dark patch on the inner surface of the innermost digit of the forefeet during breeding; the vocal sac when inflated may extend beyond the front of the face. The breeding call is a long continuous trill or pulsating ringing sound.

Juveniles have reddish warts. Tadpoles are initially blackish on the dorsum with light or gold flecking, then become paler and mottled brown; the dorsal pattern of large, paired blotches appears before metamorphosis is complete. The eyes are dorsal, and the dorsal fin is highly arched with some black dentritic lines. The upper mandible is highly arched, and labial tooth rows are usually 2/3, with oral papillae restricted to the sides of the mouth. Total length ranges from 25 to 35 millimeters. Eggs are black above, white below, and about 1.2 to 1.3 millimeters in diameter, usually in a single row in long strings of two-layered jelly that is constricted between individual eggs.

Boreal toad (Bufo boreas) lacks cranial crests and is found only in mountainous parts of Montana. On Woodhouse's toad (Bufo woodhousii), the cranial crests are parallel between the eyes, forming two back-to-back L shapes (not convergent between the eyes in a V), and do not merge on the snout in a bony lump or boss. Both boreal and Woodhouse's toads lack on the back and sides the symmetrical black-green spots with light halos. Boreal toad tadpoles are dark to black on the back, lack any gold flecking, and are found only in mountainous parts of the state. Woodhouse's toad tadpoles lack the strongly arched tail fin. Woodhouse's toad eggs are enclosed in a single jelly layer; boreal toad eggs are in strings that are not pinched between eggs, and are present only in the mountainous parts of the state.

Montana Range

No information is available specific to Montana. Elsewhere the species is known to migrate up to several hundred meters between breeding pools and nonbreeding terrestrial habitats.

Little specific information on the habitat of Great Plains toad is available. It has been reported from sagebrush-grassland, rainwater pools in road ruts, in stream valleys, at small reservoirs and stock ponds, and around rural farms; breeding has been documented in small reservoirs and backwater sites along streams (Mosimann and Rabb 1952, Dood 1980, Hendricks 1999, Hossack et al. 2003, P. Hendricks personal communication).

Information gathered from other locations indicates that when inactive, the Great Plains toad is found in burrows, and under rocks or wood. During the active season, it occupies burrows during the day that are quite shallow. This species enters water only to breed. It breeds in rain pools, flooded areas, and ponds and reservoirs that fluctuate in size, and appears to prefer stock tanks and roadside ponds rather than floodplains (Baxter and Stone 1985). Eggs and larvae develop in shallow water, usually clear or slightly turbid, but not muddy.

Although food habits in Montana have not been studied, adult and juvenile toads are generally known to eat a variety of small terrestrial arthropods, including spiders, moths, caterpillars, flies, beetles, termites, and ants (Dimmitt and Ruibal 1980, Hammerson 1999), and require 11 to 22 feedings per year to survive. In the playa wetlands of northwest Texas, carabid beetles were the most common food (Anderson et al. 1999). Larvae eat suspended matter, organic debris, algae, and plant tissue.

Great Plains toads are uncommon near human habitation (Black 1970). They are mainly nocturnal (Bragg 1940, Black 1970). Postmetamorphic young may form aggregations (Graves 1993).

Great Plains toads breed only after rain in clear, shallow, temporary pools of flooded grasslands, probably May to July in Montana (Bragg 1940, Black 1970). Two of three females collected in north-central Montana on July 20 had well developed eggs (Mosimann 1952).

From information gathered in Oklahoma, breeding choruses usually last a few days but are of variable duration. They lasted up to 14 days in March but only 1 to 2 days in June (Krupa 1994). Clutch size was usually several thousand eggs that hatch in a few days. The larval period was short (as few as 18 days) in June, long (up to 49 days) in early spring; pools rarely held water long enough for larvae to reach metamorphosis (Krupa 1994). Great Plains toads are sexually mature in 2 to 5 years. The species commonly exhibited communal egg deposition (Krupa 1994).

No special management needs are currently recognized. However, at permanent and semi-permanent water bodies (reservoirs and stock ponds) where breeding has been observed, portions of the shoreline with emergent vegetation could be fenced to create exclosures that protect breeding adults, eggs and tadpoles from trampling and the removal of emergent cover by livestock. Another option would be the creation of ponds designed for use by prairie amphibians as breeding sites, with the perimeter surrounded by fencing to prevent access by livestock. Game fish should not be introduced to any of these ponds.