Western Toad

Contents:
 
Links:
Taxon, Status, and Ranks Habitat Photos
General Description State Status Comments
Identification Tips Inventory & Research Needs Key Features
Phenology Threats & Mgmt Concerns
Range References Distribution Map

Taxon, Status, and Rank

Species Bufo boreas     Baird and Girard, 1852
Family Bufonidae
(True Toads)
Status State Candidate
State Rank S3S4
Global Rank G4

General Description

This is a medium-sized to large toad with a blunt head, stout body, broad waist, short legs, and “warty” skin. Adults range in size from 5.1 to 12.7 cm (2-5 in.) snout-vent length. Females attain larger sizes than males. Prominent oval glands, called parotoid glands, are present on the head posterior to the eyes. The dorsal body color is usually brown or green, but can also be gray, reddish-brown, or olive. The warts are usually surrounded by dark blotches and may be reddish in color. A distinct, thin, light middorsal stripe is present on all except some of the smallest juveniles. The ventral surface is light with irregularly distributed dark markings. The pupil is horizontally oval. Two yellow rounded knobs, called tubercles, exist on the underside of the hind feet. During the breeding season, males develop a smoother skin than females. Newly metamorphosed toads emerge from the water with remnants of the tail and dark skin. Within days they develop the appearance of miniature adults except the parotoid glands are not as obvious and the dorsal stripe may be subtle or absent.

The tadpole is uniformly dark and appears black in water. Varying degrees of fine lighter flecking are present on the body. The body is dorsally flattened with a low tail fin that originates at the dorsal tail-body junction. The eyes are dorsally situated relatively high on the head. The spiracle is on the left side of the body and the vent is medial at the tail-body juncture. The tail musculature is dark and the fins are slightly pigmented with the dorsal fin darker than the ventral. The tail tip is rounded. The underside of the body is slightly paler than the dorsal surface. The fine lighter flecking on larger tadpoles gives them a fine golden shimmer over the belly when viewed in bright light. Tadpoles grow to approximately 5.0 cm total length (2 in.). The tadpoles form dense aggregations or “schools” composed of thousands of individuals that consist of kin groups (sibs from the same clutch).

The eggs are laid in long strings on bare sediments or intertwined in vegetation in shallow water near shore. Individual females produce approximately 12,000 eggs per clutch on average (estimated counts range 6,000 – 20,000). Toads have been observed to wrap their eggs around vegetation in deeper water (> 1 m) away from shore, but this is not typical.

Voice: A mellow chirruping or soft, high pitched plinking sound like the peeping of a chick. These vocalizations are produced with notes in rapid succession. Multiple males vocalizing at the same time sound rather like a distant flock of Cackling Canada Geese. Vocalizations are produced day and night. One must be relatively close (less than 30 m) to hear them. Both males and spent females give a “release call” when grabbed by an indiscriminant male or when handled by humans. This call is a rapid chirping accompanied by a pulsing of the body.

See Photos Page.

Identification Tips

Presence of parotoid glands distinguishes True Toads (Bufonidae) from all other frogs. Woodhouse’s Toads (Bufo woodhousii) have elongate parotoid glands that are distinctly longer than the eye and have “L”-shaped cranial crests located between and posterior to the eyes. These traits are not present in newly metamorphosed toads and may not be prominent in juvenile toads. The tadpoles of both toad species are similar, but Woodhouse’s Toad tadpoles have patches of white and gold pigment on the body and the underside of the tail musculature and the tail fin lacks pigment except for some dark flecking. The egg strings are also similar but those of Woodhouse’s Toads have only one gel layer. The call of Woodhouse’s Toads is a loud, explosive “w-a-a-a-a-ah” lasting about 1-1 1/2 seconds. See Key Features Page.

Phenology

In general, breeding starts in mid-April at low elevation sites in western Washington and in late April or early May at low elevation sites in eastern Washington. Toads at higher elevations tend to breed later. Onset of egg laying at each location varies from one to three weeks each year depending on site conditions such as snow melt.

Development of the embryos to hatching takes less than two weeks. Tadpole development to metamorphosis takes approximately two months depending on temperature and food availability. Newly metamorphosed toads (toadlets) vary from approximately 9-10 mm to 18 mm snout-vent length. The toadlets disperse from the breeding sites en masse for one to two weeks. These dispersals are remarkable, with tens of thousands of tiny toads covering the ground and gathering in huge piles while basking in the sun.

Range

Western Toads occur in all Washington ecoregions. Within the Washington portion of the Columbia Plateau, their distribution is limited to the edges of the ecoregion except in the southeast corner of the state. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

Western Toads occur in a variety of terrestrial habitats including prairies, forests, canyon grasslands and ponderosa pine-Oregon Oak habitat. They appear absent from most of the shrub steppe and steppe zones with the exception of the canyon grasslands in southeast Washington.

Transformed toads are primarily terrestrial, but often occur near water bodies, especially in drier climates. Overwintering habitat has not been described for Washington. In Thurston County, individual toads have been found in mid-February within duff under sword ferns suggesting that some individuals overwinter terrestrially in areas with mild winters or at least occur terrestrially during the mild portions of winters.

Breeding waters are usually permanent and include wetlands, ponds, lakes, reservoir coves and the stillwater off-channel habitats of rivers. Anecdotal reports indicate that many populations return to the same egg laying location every year. Males gather at breeding sites days to weeks before egg laying commences. Males swim rapidly towards other toads moving in the water. Males being approached by another male release a rapid succession of vocalizations; these are the most common vocalizations heard at breeding sites during the day. Males spend a great deal of time on logs and floating vegetation around the breeding site. Females are much more cryptic and secretive and are uncommon at breeding sites until breeding is about to commence. Western Toads are explosive breeders; most toads at each breeding site lay all eggs within a week.

State Status Comments

General concern about this species is due to rapid and unexplained declines in California, Colorado, New Mexico, Oregon, Utah, Washington and Wyoming. In Washington, Western Toad declines have been documented in the Puget Trough and lower Columbia River. Of 86 historical sites in the Puget Trough Ecoregion, only 21 have been confirmed extant since 1980. Of those populations known extant since 1980, the populations at Beaver Lake (King County), Nisqually Lake (Pierce Co.), and Nisqually National Wildlife Refuge (Thurston Co.) are now extirpated. Of 21 historical sites along the lower Columbia River below Bonneville Dam, none have been confirmed extant, and only one extant site is currently known to exist along this reach.

The relatively low Washington Natural Heritage S-rank of S3S4 is due to the species’ large range in Washington and the fact that the species remains locally common in many areas. However, local declines have been documented and give cause for concern. If populations continue to decline or disappear, the rank will be re-evaluated. Additional, taxonomic research may revise species boundaries (see Inventory and Research Needs below).

Inventory and Research Needs

Breeding site information, locations and use, is needed throughout the state. The following counties are of special concern because of the lack of recent Western Toad reports. The date in parentheses is the most recent report documented in the Washington Department of Fish and Wildlife reptile and amphibian database: Asotin (1958), Clark (1940), Island (1938), San Juan (1939, for all islands except Cypress Island where more recent reports exist), Wahkiakum (1969) and Walla Walla (1974). Observation reports can be submitted to Lori Salzer at salzeljs@dfw.wa.gov.

Several investigators have long been aware that what is now termed Bufo boreas is badly in need of taxonomic revision. Whether all Washington populations belong to one taxon awaits this taxonomic evaluation.

Threats and Management Concerns

This species is especially vulnerable to road traffic during adult movements to and from breeding sites in the spring, and dispersal of newly metamorphosed toads away from breeding sites in the summer and fall. Anecdotal observations suggest that many populations return to the same egg laying location every year. Alteration of these sites may lead to population declines or population extirpation. Because population declines have been rapid, Western Toad breeding sites should be monitored every five to ten years to confirm presence.

Breeding sites, especially in western Washington, appear to be vulnerable to successional changes in vegetation, i.e., a tendency for more open wetlands to succeed into shrub-scrub wetlands that provide unsuitable breeding habitat. The basis of these changes is unclear; hydrological alteration and modification of the grazer assemblage are suspected. This is a critical study need.

Results of a recent Western Toad telemetry study in southeastern Idaho suggest that establishing a buffer large enough around breeding ponds to protect the integrity of the breeding pond and promote connectivity between wetlands and terrestrial habitats, as well as leaving sufficient amounts of cover to provide moist microsites, may be important timber harvest practices needed for conserving toads.

References

Bartelt et al. (2004), Davidson (1995), Hallock and Leonard (1997), Maxell et al. (2002), Nussbaum et al. (1983), Samollow, P.B. (1980), Stebbins (2003), Stebbins and Cohen (1995).


Personal communications: C. Crisafulli, T. Chestnut, M. Hayes, W. P. Leonard, R. Milner.




Hallock, L.A. and McAllister, K.R. 2005. Western Toad. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/

Last updated: February 2005


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