Anaxyrus boreas

This species occurs along the Pacific Coast of North America from southern Alaska (Wiedmer and Hodge 1996) to Baja California, and ranges eastward to the Rocky Mountains in west-central Alberta, Montana, Wyoming, Utah (Ross et al. 1995), Colorado (Hammerson 1999), and (formerly) northern New Mexico (Degenhardt, Painter and Price 1996). It is absent from most of the desert south-west (Stebbins 1985b). Its altitudinal range extends from sea level to at least 3,640m asl.

The range of western toad extends from western British Columbia and
southern Alaska south through Washington, Oregon, and Idaho to northern
Baja California, Mexico; east to Montana, western and central Wyoming,
Nevada, the mountains and higher plateaus of Utah, and western Colorado
[15]. Occurrences of the boreal toad from Yukon Territory, the
Northwest Territories, and northwestern and north-central British
Columbia have been reported [36]. Southern records of boreal toads in
New Mexico have been published [35].

The ranges of subspecies are as follows [13,15]:

boreal toad: western British Colombia and southern Alaska south from
Washington, Oregon, Idaho, western Montana and western Wyoming to northern
California, Nevada, western Colorado, and western Utah.

California toad: extreme western Nevada through the Central Valley of
California and coastal California south to Baja California Norte.

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau

Populations of A. b. halophilus are found in California, w. Nevada, and n. Baja California. Populations of A. b. boreas are found in southern Alaska, British Columbia, Alberta, Washington, Oregon, Idaho, Montana, Wyoming, Colorado, northern California, Nevada, New Mexico, and Utah. This toad frequents a wide variety of habitats such as, desert streams, grasslands, woodlands, and mountain meadows, and can be found in or near a variety of water bodies (Stebbins 1985).

AK CA CO ID MT NV NM OR UT WA WY BC Mexico

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) The range extends along the Pacific Coast from southern Alaska (Wiedmer and Hodge 1996) to Baja California, and eastward through the Rocky Mountains to west-central Alberta, Montana (Werner et al. 2004), Wyoming (Baxter and Stone 1985), Utah (Ross et al. 1995, Thompson et al. 2004), Colorado (Hammerson 1999), and (formerly) northern New Mexico (Degenhardt et al. 1996). The species is absent from most of the desert Southwest (Stebbins 2003). Elevational range extends from sea level to more than 11,000 feet (3.355 meters) in some areas in the Rocky Mountains.

Distinguishing characters include a white or cream dorsal stripe and lack of cranial crest. This species has two known subspecies, Anaxyrus boreas boreas and A. b. halophilus. A. b. boreas is dusky gray or greenish above with warts set in dark blotches, often mixed with a bit of rusty color. Males are usually less blotched with smoother skin and are smaller than females (Stebbins 1985).

It has been known to occasionally hybridize with the red-spotted toad (Anaxyrus punctatus) and the Canadian toad (Anaxyrus hemiophrys) (Stebbins 1985).

See other subspecies accounts at www.californiaherps.com: B. b.boreas and B.b. halophilus .

Length: 13 cm

More info for the term: cover

Western toads are terrestrial. Their body temperatures are largely
controlled by basking and evaporative cooling. In order to avoid
evaporative conditions, they usually spend the daylight hours on the
forest floor in the soil under rocks, logs, stumps, or other surface
objects or in rodent burrows [8,11,15,16,24]. Individuals have been
observed to use the same retreat repeatedly. In locations where there
is little or no hiding cover, western toads may spend most of the day in
the water [15]. Under more humid conditions, western toads may become
active during the day [11].

Breeding Cover: western toads lay their eggs in water; they require
some form of surface cover near the egg-laying location. Woody debris
or submerged vegetation is used to protect egg masses [10,24].

Western toads are widespread throughout the mountainous areas of
northwestern North America, ranging from sea level to elevations near or
above regional treeline, or 10,000 feet (305-3,050 m) in elevation
[15,20]. It is uncommon at the higher elevations [20]. Elevational
range in Colorado is from about 7,000 feet to 11,860 feet (2,131-3615
m). In the mountains of Colorado, the largest western toad populations
usually occur from about 9,500 feet to 11,000 feet (2,896-3,353 m)
elevation [34]. Western toads occupy desert streams and springs,
grasslands, and mountain meadows; they are less common in heavily wooded
regions. They are usually found in or near ponds, lakes (including
saline lakes), reservoirs, rivers, and streams within the above
mentioned habitats [15,16]. Under laboratory conditions western toads
were able to survive in 40 percent seawater, but died within a week when
exposed to 50 percent seawater [11].

In Colorado, individual western toads typically maintain distinct ranges
which vary greatly in size according to the condition of the habitat.
Breeding males may exhibit territoriality, especially in areas where
breeding sites are scarce [41].

Populations of western toads have very limited dispersal, particularly
in rugged terrain [10].

Breeding Habitat: Western toads require open water for breeding [20].
All breeding members of a local population tend to lay their eggs in the
same location, which is used repeatedly from year to year. For example,
at one site on a permanent lake in the Oregon Cascade Range, western
toads returned each year to the same submerged willow clumps [10]. Eggs
are usually laid in shallow water (not deeper than 12 inches [30 cm] but
usually at least 6 inches [15 cm]) [10,24]. The warmth of shallow water
increases the rate at which development occurs; shallow water and
vegetative matter may contribute to protection of eggs from predation by
fish [10]. In western Montana, breeding western toads used gravel pits
that were only filled with water during spring runoff. These gravel
pits contained cattails (Typha spp.) but no other vegetation, and were 5
feet (1.5 m) deep in the center [33].

The boreal toad is found in the Rocky Mountains in aspen (Populus spp.)
groves and riparian forests [8]. In Colorado, the largest populations
are typically found in areas characterized by willows (Salix spp.), bog
birch (Betula glandulosa), and shrubby cinquefoil (Potentilla fruticosa)
[41]. In the Pacific Northwest, the western toad occurs in mountain
meadows and less commonly in Douglas-fir forests (Pseudotsuga menziesii) [8].

In California, optimum habitat for the western toad includes wet or dry
mountain meadows or riparian deciduous forest with available open water
for breeding. Suitable habitat includes blue oak (Quercus douglasii)
savanna, gray pine-oak forest (Pinus sabiniana-Quercus spp.), mixed
conifer forest, and alpine meadows. Marginal habitats include annual
grasslands, chaparral, ponderosa pine forests, California black oak
woodlands, Jeffrey pine forests, and red fir forests [20].

In the Sierra Nevada, the western toad occurs in mid-elevation pine
forests (including Jeffrey pine [Pinus jeffreyi] at higher elevations
and ponderosa pine [Pinus ponderosa] at lower elevations), California
black oak woodlands [Quercus kelloggii], giant sequoia groves
(Sequoiadendron giganteum), montane fir forest (which includes white fir
[Abies concolor], red fir [A. magnifica], and western white pine [P.
monticola]), and redwood forest (Sequoia sempervirens). It is also
found in riparian areas within sagebrush-pinyon communities (Artemisia
spp.-Pinus spp.), oak-pine woodland and savanna (including coast live
oak [Q. agrifolia], interior live oak [Q. wislizenii], and canyon live
oak [Q. chrysolepis]), and California coastal forest and scrub [8].

Western toads have been collected from sedge meadows near a pond
occurring in a creosotebush (Larrea tridentata) community, and from
aspen (Populus spp.)-willow groves within big sagebrush
(Artemisia tridentata)-grassland [15].

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir-spruce
FRES24 Hemlock-Sitka spruce
FRES25 Larch
FRES27 Redwood
FRES28 Western hardwoods
FRES29 Sagebrush
FRES30 Desert shrub
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES37 Mountain meadows

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

207 Red fir
211 White fir
215 Western white pine
217 Aspen
222 Black cottonwood - willow
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
239 Pinyon - juniper
241 Western live oak
243 Sierra Nevada mixed conifer
246 California black oak
247 Jeffrey pine
250 Blue oak - Digger pine

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K005 Mixed conifer forest
K006 Redwood forest
K007 Red fir forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K014 Grand fir - Douglas-fir forest
K018 Pine - Douglas-fir forest
K023 Juniper - pinyon woodland
K025 Alder - ash forest
K029 California mixed evergreen forest
K030 California oakwoods
K038 Great Basin sagebrush
K041 Creosotebush

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Comments: Western toads occur in a wide variety of habitats ranging from desert springs to mountain wetlands. They range into various upland habitats around ponds, lakes, reservoirs, and slow-moving rivers and streams; sometimes they move up to a few kilometers through uplands. For shelter, they dig their own burrow in loose soil or use those of small mammals or seclude themselves under logs or rocks. Egg laying sites include shallow areas of ponds, lakes, or reservoirs, or pools of slow-moving streams.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Migrates seasonally between aquatic breeding and terrestrial nonbreeding habitats.

In Colorado, Muths (2003) found that radio-tracked toads moved up to about 2 km from their breeding sites. Average maximum distance from the breeding site was 905 m in six females and 462 m in 8 males; mean distance of all locations was 721 m in females and 218 m in males; mean minimum distance was 392 m in females and 131 m in males. The longest distance was by a female that moved 2,324 m from her breeding site.

In Idaho, males moved an average of 581 m from the breeding pond and females moved an average of 1,105 m; the greatest total seasonal distances traveled by a male and a female toad were 0.94 km and 2.44 km, respectively (Bartelt et al. 2004). Some individuals remained in the breeding pond area, even after the pond dried.

In northwestern Utah, Thompson (2004) recorded movements of up to 5 km across upland habitat between two springs; the movement occurred between June of one year and January of the next year. Another toad moved 1.3 km between May of one year and May of the next year; the following June it was back at the original breeding location (Thompson 2004).

In Montana, individuals moved along stream corridors; based on recaptures (not radio-tagging), the longest documented movement was 1.5 km upstream in 6 days (Adams et al. 2005).

Western toads wait for their prey on the surface of the ground or in
shallow burrows dug by other animals. Their diet consists largely of
bees, beetles, ants, and arachnids. Other foods include crayfish,
sowbugs, grasshoppers, trichopterans, lepidopterans, and dipterans
[15,20].

Comments: Metamorphosed individuals feed on various small terrestrial invertebrates. Larvae filter suspended plant material or feed on bottom detritus (Nussbaum et al. 1983).

Tadpoles are preyed upon by fish, herpetiles, birds, and mammals [11].

Toads in general tend to walk or hop rather than jump (like frogs).
Their slow movement renders them vulnerable to predators; however, the
western toad (like other toads) produces skin toxins that are avoided by
many predator species. The nocturnal habit may help reduce predation
[8]. Adult western toads are preyed upon by common ravens (Corvus
corvax) and probably by other birds, herpetiles, and mammals as well
[10,11]. A badger (Taxidea taxus) was recorded as having consumed five
adult Anaxyrus (probably western toad, as it was the only Anaxyrus species in
the area) in Wyoming [37].

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Represented by many and/or large occurrences throughout most of the range.

100,000 - 1,000,000 individuals

Comments: Total adult population size is unknown but likely exceeds 100,000. Still common in much of the range.

More info for the terms: cover, top-kill

Western toads occupy diverse habitats, some of which experience fire
relatively frequently (Douglas-fir forests in drier areas [31]), and
some of which rarely experience fire (riparian zones tend to act as fire
breaks but will burn during extended dry conditions [30]).

No specific information describing the response of western toads and
their habitat to fire was available in the literature. Western toads
are vulnerable to changes in both terrestrial and aquatic habitat. They
are, however, found in slightly higher abundance in early seres of
Douglas-fir forests [28]. Severe fires that burn surface objects such
as logs and stumps would immediately decrease available hiding cover for
western toads, but postfire sprouting of shrubby species would result in
a longer-term, overall increase in low hiding cover [30]. Most willow
species sprout after top-kill by fire [29], so the amount and thickness
of willow clumps increases after fire. Crown fires would reduce shade
and surface humidity and decrease the amount of daylight time toads
could spend active after a fire. Fires during early spring could affect
egg masses by reducing shade and increasing water temperatures. Any
substantial change in runoff rates, erosion, or water tables caused by
fire could degrade breeding sites.

It is likely that there is a change in the relative amounts of different
types of prey organisms in the postfire diet of western toads.
Immediately after fire, many insects are present but those requiring
shade do not adapt well to the more open conditions. In the longer term
there are differential responses to fire among prey organisms; ant
populations were one-third higher in burned areas than in unburned
areas, but beetles tend to decrease on burned areas [32].

More info for the terms: hibernaculum, hibernation, natural

Seasonal Activity: Western toads are active from January to October,
depending on latitude and elevation [16]. Boreal toads in one Colorado
population used natural chambers near a small stream bed. The high
water table, constantly flowing stream, and deep winter snow served to
maintain the air temperature within the hibernaculum at a point slightly
above freezing. Emergence from hibernation followed a few days of warm
temperatures that freed the entrance and increased temperatures within
the chamber to about 39.2 degrees Fahrenheit (4 deg C) [40,41].

Diurnal Activity: At low elevations western toads are active at night;
at high elevations and in the northern parts of their range they are
diurnal [16]. Body temperature of western toads is closely correlated
with the substrate temperature. Basking and conduction from the
substrate are primary means of increasing body temperature and cooling
is achieved by evaporative cooling and conduction of heat to a cooler
medium. Diurnal and nocturnal activity are often related to seasonal
changes in temperature; most western toads are diurnal during the spring
and fall but are nocturnal during the warmer summer months [41].

Minimum Breeding Age: In central Oregon, the minimum breeding age for
male western toads is 3 years, and probably 4 or 5 years for females
[10]. California toads are reported as sexually mature at 2 years of
age [11]. Male western toads breed every year; females breed at less
regular intervals, depending on individual condition and previous years'
breeding effort [10]. Sex ratios differ according to habitat type;
males are more numerous in wet areas and females are more numerous in
dry habitats [41].

Breeding Season: Eggs are laid in open water from February to July,
with peak activity occurring in April. Timing of egg-laying activity
varies with elevation and weather conditions [20]. In Colorado,
initiation of breeding was correlated with the onset of warming weather
and initiation of snowpack melting. Eggs are usually laid in late May
or early June [41]. In western Montana, a few males were present on the
shores (of two gravel pits) by May 11, 1967, and by May 14, each pond
contained at least 30 males. Males were spaced at least 1 foot (.3 m)
apart, all facing the shore [33].

Clutch Size: Eggs are laid in gelatinous strings of 13 to 52 eggs per
inch, in masses of up to 16,500 per clutch [15,24]. Egg development
rate is partially dependent on temperature; hatching times vary [11].

Development of Young: Metamorphosis is usually completed within 3
months of egg laying. The time required for metamorphosis is given as
30 to 45 days for the boreal toad and 28 to 45 days for the California
toad [15].

Longevity: Female western toads at least 10 to 11 years of age have
been reported [10]. In Colorado, boreal toads probably attain a maximum
age of at least 9 years [41].

Ravens were significant predators on breeding toads in Oregon Cascades (Olson 1989). In Colorado, Corn (1993, Herpetol. Rev. 24:57) observed a high rate of predation on breeding adults, evidently by ravens. Crow predation on adults was observed in Idaho (Brothers, 1994, Herpetol. Rev. 25:117).

Comments: Activity varies seasonally and geographically. At low elevations, western toads are active in daylight during cool weather of late winter and spring, but most activity is at night during warmer weather. They are active day or night in summer in the mountains, depending on conditions. They remain secluded in winter in cold climates.

Maximum longevity: 11.5 years (captivity) Observations: Development depends on ambient temperature. They may lay up to 16,500 eggs (http://www.fs.fed.us/database/feis/).

The breeding period varies with local conditions; it may begin in January at low elevations but not until late spring or summer, as the winter snowpack begins to melt, in the high mountains. Females deposit an average of about 12,000 eggs/clutch, in two strands. Eggs hatch in a few days (warm temperatures) or in up to about 12 days (cold conditions). Larvae metamorphose in around 1-3 months, before the next winter; warm conditions result in the fastest larval development. Recently metamorphosed western toadlets sometimes form dense aggregations on the shores of breeding sites. Adult females may skip one or more years between successive breeding events. In northwestern Utah, single-year breeding populations at six sites ranged from a few dozen to nearly 250 individuals (Thompson 2004).

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 43 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 17
Specimens with Barcodes: 36
Species With Barcodes: 1

Information on state- and province-level protection status of animals in the
United States and Canada is available at NatureServe.

None [43]

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 1996
  Endangered

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Large range in much of the western United States and western Canada; locally common, but rapid losses and declines have occurred in many populations across the range for unknown reasons, even in relatively pristine environments.

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Moderate to broad.

Global Short Term Trend: Decline of 10-30%

Comments: This species is not threatened or declining in most of British Columbia or Alberta (see Green 1997), although Davis and Gregory (2003) documented a local extirpation at a relatively undisturbed site on southern Vancouver Island, British Columbia; they also noted an overall decline on Vancouver Island. Rocky Mountain populations in Colorado and Wyoming have undergone a drastic decline since the 1970s (Corn et al. 1989; Hammerson 1989, 1992, 1999; Carey 1993). Similarly, populations have declined greatly in the Yosemite area of the Sierra Nevada, California (Drost and Fellers 1996). Additionally, the species is apparently declining in Yellowstone National Park (Peterson et al. 1992), Montana (Reichel and Flath 1995), and locally elsewhere (Olson 1989).

Global Long Term Trend: Relatively stable to decline of 50%

Comments: Likely relatively stable in extent of occurrence, unknown degree of decline in population size, area of occupancy, and number/condition of occurrences.

This species is an explosive breeder. Females deposit thousands of eggs in long strings, usually in shallow ponds. These toads are nocturnal at low elevations and diurnal at higher elevations. During the winter, A. boreas buries itself in loose soil or uses the burrow of a small mammal (Stebbins 1985). This species tends to walk rather than hop. Both males and females lack an advertisement call (Duellman and Trueb 1986) although they are known to have a release call (Brown and Littlejohn 1971).

Population

Population Trend

Degree of Threat: Medium

Comments: The extent of threats range-wide is not known with certainty, but there appear to be multiple causes contributing to the range-wide trend.

Disease and parasites appear to be contributing factors leading to population declines. Carey (1993) hypothesized that some environmental factor or synergistic effects of more than one factor may stress toads, causing suppression of the immune system or indirectly causing immunosuppression by effecting elevated secretion of adrenal cortical hormones. Immunosuppression, coupled with the apparent effect of cold body temperatures on the ability of the immune system to fight disease, may lead to infection by Aeromonas hydrophila bacteria (which causes "red-leg") or other infectious agents and subsequently to death of individuals and extirpation of populations. Die-offs in the Southern Rockies have been associated with chytrid fungus (Batrachochytrium dendrobatidis) infections (Daszak et al. 2000), which attacks keratinized tissue and is especially detrimental to recently metamorphed toadlets. Also, toad eggs are highly susceptible to the pathogenic fungus Saprolegnia ferax (which may be introduced during fish stocking), and mortality of eggs due to this fungus has been documented in Oregon (Blaustein et al. 1994; Kiesecker and Blaustein 1997; Kiesecker et al. 2001). Kiesecker et al. (2001) observed catastrophic embryo mortality from S. ferax infection in shallow water that was protected from UV-B but not in water protected from UV-B.

Limb malformations in toads have been linked directly to trematode infections by Ribeiroia ondatrae (Johnson et al. 2001; Johnson et al 2002), although the impacts of these infections on reproduction, and the magnitude of the infections across the breeding range, require further study. Preliminary analysis suggests that limb malformations may increase mortality in larval amphibians prior to and during metamorphosis.

Some have proposed that declines are related to sensitivity of eggs to increased levels of ultraviolet radiation (Blaustein et al. 1994), but studies by Corn (1998) yielded no support for UV-B alone as the cause of declines. Also, spectral characteristics of natural waters likely shield eggs from detrimental physiological effects in all but the clearest waters (Palen et al. 2002). Corn and Muths (2002) proposed that temperature stress is as plausible a hypothesis as increased UV-B to explain episodes of high mortality observed in Oregon (Kiesecker et al. 2001).

Increased acid deposition in natural habitats is a potential threat to amphibians, but this does not appear to be a major threat to Bufo boreas. For example, declines in the Southern Rocky Mountains are not due to acidification of breeding habitats (Corn and Vertucci 1992).

In the Cascade Range of Oregon, persistent predation on adult toads by Common Ravens during the breeding season appears to have contributed significantly to declines of some populations (Olson 1992). Possible significant predation by birds also has been observed in Colorado and Idaho (Hammerson 1999).

Declines may be related at least in part to habitat destruction and degradation, water retention projects, predation by and competition with native and non-native species, fishery management activities, or other factors, but these factors have not been adequately assessed. In Idaho, several hundred toadlets were trampled when domestic sheep were herded through the dried breeding pond (Bartelt 1998).

UV-B radiation has been shown to cause reduced hatching success in Oregon (Blaustein et al. 1994), but not in Colorado, although more investigation is needed (Corn 1998). Synergistic effects between UV-B and an alga, Saprolegnia ferax , have also been shown to cause reduced hatching success in Oregon (Kiesecker and Blaustein 1995). Vertucci and Corn (1993) found that acid precipitation may not be a major cause of the decline of A. b. boreas in Colorado, but more investigation of this problem is needed (Stebbins and Cohen 1995). A. boreas tends to lay its eggs in communal masses, and such communal egg masses have been shown to be highly susceptible to infection with S. ferax (Kiesecker and Blaustein 1997).

In the southern Rocky Mountains, translocation was tried for A. b. boreas. The translocation projects failed; A. b. boreas has been declining in that area for unknown reasons, for some time (Trenham 2001).

Major Threats

More info for the terms: cover, prescribed fire

Specific information concerning prescribed fire as it affects western
toads was not available in the literature. Conservation of surface
objects used for hiding cover is important in any management decision
[10].

Reproductive success of western toads depends on amount of snowpack and
rate of snowmelt which determine the persistence of breeding pools used
by western toad populations [33].

Amphibians generally seem to be more sensitive to environmental changes
than other taxonomic groups. Western toads repeatedly use individual
stumps or logs, which may be an important consideration for conservation
and recovery programs. They are also vulnerable to mass predation by
common ravens during breeding periods when large numbers of toads
congregate at egg-laying sites. It was observed that such mass
predation did not occur when humans were in close proximity to the
toads. The authors speculated that human activity may play a role in
common raven activity pattern, and could contribute indirectly to mass
predation episodes. Since the entire breeding effort of a population is
concentrated in one location, mass predation on eggs can have severe
consequences to population recruitment. The eggs are also vulnerable to
catastrophic loss due to freezing, lowering of water levels, and other
disturbances. Human activities such as logging and/or prescribed
burning may have a negative effect on breeding congregations or on
massed eggs by reducing woody debris in and near the water, reducing
available shade, and pressuring predators to move from human activity
sites to sites where western toad breeding is occurring [10].

In northwestern California, however, western toads were slightly more
abundant in early brush/sapling stages of postharvest Douglas-fir forest
compared to later stages or undisturbed forest; they are therefore
classified as increasers after logging [28]. The water level of
breeding pools could also be affected by human activity at critical
times. The absence of nonbreeding adult females from breeding
congregations provides some protection (at the population level) from
population decline due to mass predation. More than half of females
skipped at least 1 year between breeding years at study sites in the
Oregon Cascade Range [10].

Mortality of western toads is greatest during the larval and juvenile
stages, but is slight thereafter. Most mortality can be attributed to
unseasonable weather and predation on juvenile toads. There is very
little predation on adult toads and mortality of adults is low [41].

Western toads are taken by humans for the pet trade [23].

Conservation Actions

Biological Research Needs: Further research on causes of declines is critical.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: This species occurs in many national parks, wildlife refuges, and wilderness areas, however, protection of land may not protect the species where declines may be caused by acidification, ozone depletion, disease, or other causes. In Mexico it is found within San Pedro Martir National Park.

Needs: Protection needs depend on causes of decline. At present in the Southern Rockies, efforts are being made to reduce the probability of chytrid fungus contamination of currently fingus-free breeding areas.