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Arroyo Toad (Anaxyrus (Bufo) californicus)
Arroyo Toad
(Anaxyrus (Bufo) californicus)
Legal Status
State: Species of Special Concern
Federal: Endangered
courtesy of7,
Kailash
Mozumder.
Critical Habitat: Originally designated onPhoto
February
2001
(66 FR
9414–9474); first revised April 13, 2005 (70 FR 19562–19633); proposed
revision October 13, 2009 (74 FR 52612–52664); revised February 9,
2011 (76 FR 7245–7467)
Recovery Planning: Final recovery plan, July 1999 (USFWS 1999)
Notes: Recommended listing action from Endangered to Threatened, 5Year Review, August 2009 (USFWS 2009)
Taxonomy
The arroyo toad (Anaxyrus (Bufo) californicus) is a relatively small (5 to
8.1 centimeters), stocky, blunt-nosed toad with spotted greenish gray to
tan warty skin (Stebbins 2003). A detailed description of the species’
physical characteristics can be found in Stebbins (1954). Arroyo toad is
one of three members of the southwestern toad complex (Bufo
microscaphus) in the Bufonidae. At the time it was federally listed as
endangered in 1994 (59 FR 64859–64867, arroyo toad was considered a
subspecies of southwestern toad (B. m. californicus). Based on recent
genetic studies, arroyo toad is now considered a separate species (B.
californicus) (66 FR 9414–9474). Further, the North American toads in
the genus Bufo are now assigned to the new genus Anaxyrus (Crother
2008), although many species accounts still refer to the genus as Bufo.
However, the resource agencies (e.g., California Department of Fish and
Game (CDFG) and U.S. Fish and Wildlife Services (USFWS) have
adopted the new genus Anaxyrus.
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Arroyo Toad (Anaxyrus (Bufo) californicus)
Distribution
General
The arroyo toad is endemic to the coastal plains, mountains, and desert
slopes of central and Southern California and northwestern Baja California
from near sea level to about 8,000 feet (2,400 meters). In the 5-Year
Review for the species, populations were reported to occur in the
following counties: Monterey, San Luis Obispo, Santa Barbara, Ventura,
Los Angeles, San Bernardino, Riverside, Orange, San Diego, and Imperial
(USFWS 2009) (Figure SP-R1). Since publication of the 5-year Review,
the U.S. Geological Survey (USGS) determined from unpublished data
that the putative arroyo toad populations in Imperial County are not valid
records and, as a result, Imperial County is no longer considered a part of
the species’ distribution (Fisher, pers. comm. 2012). Arroyo toads are
generally found in both perennial and intermittent rivers and streams with
shallow, sandy to gravelly pools adjacent to sand or fine gravel terraces.
Distribution and Occurrences within the Plan Area
Historical
The Plan Area falls within the Desert Recovery Unit designated in the
Recovery Plan, which includes arroyo toad populations on the northern
and eastern slopes of the San Gabriel, San Bernardino, and Peninsular
Mountain ranges in Los Angeles, San Bernardino, Riverside, San Diego,
and Imperial counties (USFWS 1999). However, as noted above, the
species is no longer considered to occur in Imperial County because the
putative arroyo toad records, including those from San Felipe, Vallecitos,
and Coyote creeks, as well as the Whitewater Canyon Basin in Riverside
County, have been determined to be invalid (Fisher, pers. comm. 2012).
Historically populations have been described from Little Rock Creek,
which flows north from the Angeles National Forest east of Palmdale in
the Antelope Valley (Figure SP-R1). However, current known populations
in Little Rock Creek are located south of the Plan Area. In addition,
populations were known from the headwaters of the Mojave River in the
San Bernardino National Forest down into the Mojave Basin. The
Independent Science Advisors (ISA) Report indicated historical
occurrences as far downstream as Afton Canyon (DRECP ISA 2010), but
the USGS indicates that the furthest downstream historical occurrence of
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Arroyo Toad (Anaxyrus (Bufo) californicus)
the arroyo toad in the Mojave River may be around Oro Grande (Fisher,
pers. comm. 2012). The recovery plan for the arroyo toad (USFWS 1999)
also shows historical occurrences extending downstream only about as far
as Oro Grande, and the basis for the ISA (2010) assertion is unknown.
Recent
Within the Plan Area, arroyo toads are known to occur on the desert slopes
of the San Bernardino Mountains. Populations of arroyo toad known
within or directly adjacent to the Plan Area include those within Subregion
9 of the Desert Slope Recovery Unit (USFWS 1999). These populations
are found in the Mojave River Basin on the very edge of the Plan Area,
potentially as far downstream as Oro Grande (Fisher, pers. comm. 2012).
There are 51 recent occurrences (i.e., since 1990) of arroyo toad recorded
in the CDFG (2011) and USFWS (2011) databases. Specific populations
in the Plan Area are known from Little Horsethief Creek, Mojave Forks
Dam, and Rancho Las Flores (USFWS 2009) (Figure SP-R1). The USGS
suggests that suitable habitat may still be present downstream of the
Mojave Forks Dam and potentially all the way to Oro Grande, but these
areas may not have been adequate surveyed in the recent past (Fisher,
pers. comm. 2012). Also, arroyo toads are located in Little Rock Creek in
the Angeles National Forest south of the Plan Area boundary.
Natural History
Habitat Requirements
The arroyo toad evolved in an ecological system that is inherently
dynamic, with marked seasonal and annual fluctuations in rainfall and
flooding. Breeding habitat requirements are highly specialized, and are the
key factors when determining habitat suitability. Specifically, arroyo toad
requires shallow, slow-moving stream and riparian habitats that are
naturally disturbed on a regular basis, primarily by flooding (USFWS
2009). Streams and washes with sandy banks free of dense vegetation with
mature willow (Salix spp.) stands, cottonwoods (Populus spp.), western
sycamore (Platanus racemosa), riparian habitats of semi-arid areas, and
small cobble streambeds provide suitable habitat for arroyo toad. In order
for breeding populations to persist, the stream system must be large
enough for regular channel scouring events to occur, but not so large that
all sands and habitat structure are lost after floods (Sweet 1992). Factors
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Arroyo Toad (Anaxyrus (Bufo) californicus)
that influence habitat suitability include stream order, elevation, and
floodplain width (Sweet 1992). Stream orders range from one to six. The
smallest channels with no tributaries are called first order streams. The
confluence of two first order streams forms a second order stream, the
confluence of two second order streams forms a third order, and so on.
Fifth and sixth order streams are usually large rivers. Looking at stream
order, arroyo toads typically are found in the upper sections of third to
sixth order streams that lack the finer silt and clay sediments but that are
not dominated by larger cobble and coarse sands. Areas of sandy or friable
(readily crumbled) soils are the most important habitat for the species, and
these soils can be interspersed with gravel or cobble deposits (70 FR
19562–19633). It is in these areas that arroyo toads typically forage,
aestivate, and reproduce. Breeding sites are typically located adjacent to
sandy terraces (59 FR 64589–64867); at or near the edge of shallow pools,
low-flow stream channels, and ox-bows; and along in-stream sand bars
with minimal current (0 to 2 kilometers (1.24 miles) per hour) and little or
no emergent vegetation. Upland non-breeding habitat used during
aestivation (described below) includes sage scrub, grassland, mixed
chaparral, oak woodland, and sagebrush.
Table 1. Habitat Associations for Arroyo Toad
Land Cover
Type
Aquatic
Land Cover
Use
Breeding,
larval/
juvenile
development
Habitat
Designation
Breeding
Friable soils of
upland
terraces
Refugia
Foraging,
aestivation
Habitat
Parameters
All life
stages occur
around
breeding
sites
Juvenile and
adult
Supporting
Information
Sweet 1992
Foraging Requirements
Larvae (tadpoles) are highly specialized feeders on loose organic material
such as detritus, interstitial algae, bacteria, and diatoms (Sweet 1992).
Subadult and adult arroyo toads are opportunistic feeders, foraging on
immediately available prey located throughout both their breeding and
upland habitats. Adults feed on a variety of invertebrates, including snails,
Jerusalem crickets, beetles, ants, caterpillars, moths, and occasionally
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Arroyo Toad (Anaxyrus (Bufo) californicus)
newly metamorphosed individuals. They usually feed at night, but may
occasionally feed during the day (Zeiner et al. 1988). Juvenile toads,
which are mostly diurnal feeders for their first 4 to 5 weeks, primary
subsist on ants (Liometopum occidentale) around the saturated areas near
breeding pools (USFWS 1999). After this period of rapid growth, they
become more nocturnal and feed mostly on ants and beetles (Sweet 1992).
Reproduction
Arroyo toad breeding period occurs from late January or February to early
July, although it can be extended in some years depending on weather
conditions (USFWS 1999). Breeding in mountainous habitats
characteristic of the Plan Area populations may commence later (May–
June) and last longer (to August) than in the coastal portion of the range.
Breeding occurs in quiet, clear backwaters of streams as waters recede
from the floods of the wet season. Adult males typically advertise at night
with a soft, high-whistled trill from suitable breeding habitat. Receptive
females seek out calling males based on the size of the male and the sound
of the call.
Although males may breed with several females in a season, females
release their entire clutch of eggs in a single breeding effort and probably
do not produce a second clutch during the season. Eggs are usually
deposited in tangled strings of 1 or 2 rows, on the bottom of shallow pools
with minimal current (0 to 2 kilometers (1.24 miles) per hour), little or no
emergent vegetation, and sand or pea gravel substrate. The eggs are
sensitive to siltation and require good water quality. Because the eggs are
laid in very shallow water and are not anchored or attached, rapid changes
in stream flow can wash them away or leave the eggs stranded to dry out.
Embryos usually hatch in 4 to 6 days; the larval period lasts approximately
65 to 85 days. The tadpoles reach a maximum length of about 1.5 inches
and are solitary and extremely cryptic, typically mottled or spotted with
blackish to brown colors.
After metamorphosis from June to August, the juveniles remain on the
bordering gravel bars until the pools no longer persist. Sexual maturity is
reached in 1 to 2 years. Outside of the breeding season, arroyo toads
burrow into the friable soils of upland terraces and are also known to seek
temporary shelter under other debris or mammal burrows. Arroyo toads
enter aestivation (a state of dormancy somewhat similar to hibernation to
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Arroyo Toad (Anaxyrus (Bufo) californicus)
prevent dehydration during hot or dry times of the year) in their burrows
during the non-breeding season, starting in the late summer from about
August and extending to about January (Ramirez 2003).
Breeding


Aestivation
________________
Source: Ramirez 2003





Dec
Nov
Oct
Sep
Aug
July
June
May
April
March
Feb
Jan
Table 2. Key Seasonal Periods for Arroyo Toad






Spatial Behavior
The extent of lateral arroyo toad movements away from the stream
channel is influenced by rainfall amounts, availability of surface water,
width of streamside terraces and floodplains, vegetative cover, and
topography (Griffin et al. 1999; Ramirez 2000). In broad, sandy
floodplains, arroyo toad often move across parallel stream channels in
search of suitable sites to lay eggs (Mitrovich et al. 2011). In their study of
arroyo toad movement patterns, Griffin et al. (1999) observed female
arroyo toad using riparian and upland habitats an average maximum
distance of 443 feet with a maximum of more than 984 feet perpendicular
to streams, while males moved an average maximum distance of 240 feet
from the streams. Within stream movement was documented up to 492
feet. The study found that both male and female arroyo toad moved more
into upland habitats after completing individual breeding activity. Female
arroyo toad become more sedentary as they mature, while males tend to
move up and downstream fairly often during the breeding season (Sweet
1993). Holland (USFWS 1999) found that arroyo toads are capable of
moving 0.3 to 1.3 miles (0.5 to 2.0 kilometers) into suitable adjacent
habitats and may not be constrained by topography. In a study using pitfall
traps, Holland and Sisk (2001) captured arroyo toads in upland habitats
averaging more than 980 and 1,640 feet from two coastal streams; one
arroyo toad was captured 3,940 feet beyond the edge of the riparian
habitat bordering the stream. Four separate studies of inland populations
by Ramirez (2002a, 2002b, 2002c, 2003) showed that arroyo toads
burrowed no farther than 1,062 feet from the edge of a stream, with an
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Arroyo Toad (Anaxyrus (Bufo) californicus)
overall average of approximately 52 feet between a burrow and the edge
of the stream. The extent of movement away from the stream channel is
influenced by climatic conditions, availability of surface water, floodplain
width, vegetative cover, and topography (Griffin et al. 1999, Ramirez
2002a). Moderate, stable temperatures and high humidity facilitate longerdistance movements into upland habitats (USFWS 1999). Juvenile arroyo
toads disperse away from their natal pools about 1 year after
metamorphosis (Sweet 1993).
During the non-breeding season (August–January), arroyo toads usually
enter aestivation to prevent dehydration during the hot and dry periods of
the year. During rainfall events and moderate temperatures (above 7°C
(45°F)), they are known to be active during all times of the year. All age
classes of post-metamorphic toads may be active on rainy nights and on
some nights of very high relative humidity (USFWS 1999).
Table 3. Movement Distances for Arroyo Toad
Type
Adult female upland
dispersal
Adult male upland
dispersal
Juvenile Dispersal
Upland aestivation
Distance
Average max 443 feet
(max 984 feet)
Average max 240 feet
Citation
Griffin 1999
0.8–1km
Average 52 feet from
stream (max 1,062 feet)
Sweet 1993
Ramirez 2002a, 2002b,
2002c, 2003
Griffin 1999
Ecological Relationships
The arroyo toad is a breeding habitat specialist (Sweet 1992). They require
shallow pools located in open sand and gravel channels, along low
gradient (typically less than 6%) reaches of medium-to-large-sized streams
(Sweet 1992). Within the 2005 USFWS critical habitat designation they
identified the Primary Constituent Elements (PCE) necessary for arroyo
toad survival and reproduction. The following are the PCEs for arroyo
toads (70 FR 19562–19633):
1. Rivers or streams with hydrologic regimes that supply water to
provide space, food, and cover needed to sustain eggs, tadpoles,
metamorphosing juveniles, and adult breeding toads. Specifically,
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the conditions necessary to allow for successful reproduction of
arroyo toads are:
a. Breeding pools with areas less than 12 inches (30 centimeters) deep;
b. Areas of flowing water with current velocities less than 1.3 feet per
second (40 centimeters per second); and
c. Surface water that lasts for a minimum length of 2 months in most
years (i.e., a sufficient wet period in the spring months to allow
arroyo toad larvae to hatch, mature, and metamorphose).
2. Low-gradient stream segments (typically less than 6% slope) with
sandy or fine gravel substrates that support the formation of
shallow pools and sparsely vegetated sand and gravel bars for
breeding and rearing of tadpoles and juveniles.
3. A natural flooding regime, or one sufficiently corresponding to a
natural regime that will periodically scour riparian vegetation,
rework stream channels and terraces, and redistribute sands and
sediments, such that breeding pools and terrace habitats with
scattered vegetation are maintained.
4. Riparian and adjacent upland habitats (e.g., alluvial scrub, coastal
sage scrub, chaparral, and oak woodlands, but particularly alluvial
streamside terraces and adjacent valley bottomlands that include
areas of loose soil where toads can burrow underground) to
provide foraging, aestivation, and living areas for subadult and
adult arroyo toads.
5. Stream channels and adjacent upland habitats allowing for
migration between foraging, burrowing, or aestivating sites,
dispersal between populations, and recolonization of areas that
contain suitable habitat. These aquatic, riparian, and upland
habitat PCEs form the bases of our critical habitat units. These
features are essential to the conservation of the arroyo toad. All
lands identified as essential and designated as critical habitat
contain one or more of the PCEs for the arroyo toad.
Introduced plants and predators have had substantial impacts on existing
populations, and may have contributed to regional extinctions of arroyo
toad. Exotic plant species (e.g., tamarisk (Tamarix spp.), giant reed
(Arundo donax), iceplant (Carpobrotus spp.), and pampas grass
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Arroyo Toad (Anaxyrus (Bufo) californicus)
(Cortaderia spp.)) may degrade arroyo toad habitat by contributing to
altered hydrology, eliminating sandbars and breeding pools, and restricting
access to and quality of upland habitats (69 FR 23253–23328). Potential
non-native predators include bullfrog (Lithobates catesbeianus), African
clawed frog (Xenopus laevis), crayfish (Procambarus spp.), and green
sunfish (Lepomis cyanellus); increases in mesopredators (e.g., common
raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) often
associated with urban development can threaten or eliminate toad
populations (69 FR 23253–23328, Jennings and Hayes 1994, USFWS
1999). Because native ants are a major food source for juveniles during
their rapid growth stage in the weeks following metamorphosis, the spread
of the non-native Argentine ant (Linepithema humile) into arroyo toad
habitat may displace native ants and other macroinvertebrates (Mitrovich
et al. 2010; Stephenson and Calcarone 1999).
Population Status and Trends
Global: Declining to Stable (USFWS 2009)
State: Declining to Stable (USFWS 2009)
Within Plan Area: Declining (USFWS 2009)
Arroyo toads have disappeared from at least 75% of their historical range
in California (USFWS 2009). They now survive primarily as small,
isolated populations, having been extirpated from much of their historical
habitat (USFWS 2009). There are known populations on private land and
other non-federal lands in the Mojave River Basin and on the desert side
of the San Gabriel Mountains. Until recently, populations were thought to
occur in San Felipe, Vallecitos, and Coyote creeks, and the Whitewater
River Basin, but these occurrences have since been determined by the
USGS to be invalid (Fisher, pers. comm. 2012). Therefore, the only
known desert populations are along the desert side of the San Gabriel
Mountains and within the Mojave River Basin, and these populations
should be the focus of the DRECP (Fisher, pers. comm. 2012).
Threats and Environmental Stressors
Historically, because arroyo toad habitats are favored sites for dams and
reservoirs, roads, mining, agriculture, livestock grazing, urbanization, and
recreational facilities, such as campgrounds and off-highway vehicle
parks, many arroyo toad populations were reduced in size or extirpated
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Arroyo Toad (Anaxyrus (Bufo) californicus)
due to extensive habitat loss that occurred from about 1920 to 1980
(USFWS 1999).
Within the Desert Recovery Unit, threats are moderate in intensity and
come primarily from non-native species, recreational activities and
development.
Arroyo toad in Little Rock Creek are threatened by non-native species,
including crayfish, bullfrogs, non-native fishes, and recreational activities
such as hiking, fishing, boating, waterplay, and occasional off-highway
vehicle use (USFWS 1999). Portions of Little Rock Creek have been
closed by the Angeles National Forest to protect the arroyo toad (USFWS
2009). As a result of dam construction and operation at Little Rock
Reservoir, arroyo toads appear to be restricted to a 3-mile (4.8-kilometer)
stretch of stream habitat above Little Rock Reservoir.
The Little Horsethief Creek population is threatened by bullfrogs, nonnative fishes, off-highway vehicles, camping, and fishing, and by gold
prospecting activities (USFWS 1999). Off-highway vehicle use in the
Mojave Forks area has been identified as a factor contributing to the near
extirpation of toads downstream from Rancho Las Flores. Roads in the
area, especially Highway 173 at the Horsethief Canyon crossing, pose a
danger to arroyo toad during movement between Rancho Las Flores and
upstream areas. In addition, arroyo toad breeding habitat has been severely
altered by beaver dams at the Rancho Las Flores site (Ramirez 1999). The
dams disrupt normal stream flow by impounding water and inundating
breeding habitat, while encouraging the growth of riparian vegetation and
favoring non-native species. The deep pools provide habitat for a number
of non-native species that are detrimental to the continued existence of the
arroyo toad (USFWS 2009).
Arroyo toads have been nearly eliminated between Victorville and the
Mojave Forks Dam, although USGS indicates that their status in the area
may be uncertain due to a lack of adequate surveys (Fisher, pers. comm.
2012). Arroyo toads were once common throughout portions of the West
Fork Mojave and the area now occupied by Silverwood Lake (USFWS
1999). Construction of the lake removed habitat where many arroyo toad
were formerly observed and collected (USFWS 1999). Until 2003, arroyo
toad had not been reported from the Cleghorn/Silverwood Lake area since
just after the lake was formed in 1972. Toads are still expected to
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Arroyo Toad (Anaxyrus (Bufo) californicus)
occasionally disperse upstream toward the reservoir; however, the dam and
reservoir pose an insurmountable barrier to further upstream movement.
Introductions of beaver (Castor canadensis) in the main Mojave River have
also eliminated shallow breeding areas (USFWS 1999).
Conservation and Management Activities
The Arroyo Toad Recovery Plan (USFWS 1999) identified the need for
the establishing three self-sustaining metapopulations or populations
within the Desert Recovery Unit. This included one population in the
Angeles National Forest (Little Rock Creek), one metapopulation in the
San Bernardino National Forest (Mojave River Basin, including West
Fork of the Mojave River; Little Horsethief Canyon; and Deep Creek) and
one population on Bureau of Land Management (BLM) land (Pinto Wash
Basin, in the Jacumba [In-Ko-Pah Mountains)] Wilderness Study Area).
However, the USGS has determined that the Jacumba population is not
valid (Fisher, pers. comm. 2012).
The U.S. Forest Service (USFS) sponsored a 3-year radiotelemetry study
in Little Rock Creek from 1999 to 2001 to characterize habitat use and
movement by arroyo toad in order to inform management of the species in
the area (Ramirez 2002a). For example, trails supporting off-highway
vehicle activity in 1999 that crossed Little Rock Creek were subsequently
closed, and pools in this area exhibited successful recruitment in 2001
(Ramirez 2002a).
The USFS has developed Land Management Plans that provide protection
for arroyo toads. Specific guidelines from the Land Management Plans
include the following: (1) Standards and guidelines with measures to
protect arroyo toad habitat that are incorporated into projects for managing
vegetation, soil, water, and riparian areas; (2) identification of the arroyo
toad as a Management Indicator Species to be used to track the health of
aquatic habitat; (3) specific requirements for monitoring and monitoring
activities that may affect arroyo toad habitat; (4) a five-step project
screening process to minimize impacts to riparian arroyo toad habitat; and
(5) guidelines for use of retardant and foams in aquatic environments to
minimize the impacts of these chemicals to the arroyo toad and its habitat
during fire suppression activities (USFWS 2009).
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Data Characterization
Recent data show that some toad occurrences in the desert previously
thought to be arroyo toads are not valid, including putative occurrences
from San Felipe, Vallecitos, and Coyote creeks (Fisher, pers. comm.
2012). The exclusion of these areas from the Plan Area leaves only the
populations on the desert side of the San Gabriel Mountains and in the
Mojave River Basin for consideration in the DRECP.
The current arroyo toad critical habitat designation concluded that the area
north of State Route 138 within the western portion of Subunit 22a does
not contain the physical or biological features essential to the conservation
of arroyo toads (i.e., the PCEs) and, therefore, does not meet the definition
of critical habitat for the arroyo toad (76 FR 7245–7467). However, the
USGS indicates that suitable arroyo toad habitat exists north of State
Route 138 and that habitat should continue to Mojave Forks Dam (Fisher,
pers. comm. 2012).
Management and Monitoring Considerations
Within the Plan Area, the USFS has developed long-term management
plans for the populations of arroyo toad within National Forests. These
plans direct USFS staff to ensure that any project activities conducted in
arroyo toad suitable habitat in the National Forests are neutral or
beneficial to arroyo toads, and any expansion of existing facilities or
development of new facilities will focus recreational use away from
arroyo toad occupied habitat (USFWS 2009). Aside from these plans,
management and monitoring of arroyo toad should be guided by the
species recovery plan (USFWS 1999). Specifically, the population on
private and other non-federal lands in the Mojave River is essential for
delisting the arroyo toad (USFWS 2009).
Predicted Species Distribution in Plan Area
Because the arroyo toad has such a restricted range in the Plan Area (i.e.,
the Mojave River Basin), an expert-based suitable habitat model was not
developed. Based on a qualitative delineation of its range along the
Mojave River, there are approximately 90,494 acres of suitable habitat for
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Arroyo Toad (Anaxyrus (Bufo) californicus)
arroyo toad in the Plan Area. Appendix B includes a figure showing the
arroyo toad’s estimated range in the Plan Area.
Appendix C provides a summary of the methods used to model DRECP
Covered Species with Maxent. For the arroyo toad, 23 occurrence points
were used to train the Maxent model and 7 occurrence points were used to
test the model’s performance. Overall, the Maxent model has excellent
statistical support. The occurrence points occur in a limited geographical
area relative to the Plan Area, increasing the predictive power of the
model. Based on a natural break in the distribution of the probability of
occurrence that Maxent estimates, all 100-meter grid cells with greater
than 0.180 probability of occurrence were defined as arroyo toad habitat.
The Maxent model predicts 14,972 acres of arroyo toad habitat, compared
with 90,494 acres qualitatively delineated within the Mojave River based
on its estimated range. The Maxent model predicts arroyo toad habitat in a
localized area around known occurrences at the head of the Mojave River
between the San Bernardino Mountains and Victorville. The qualitative
delineation of habitat along the Mojave River occurs in the same area, but
is not as dispersed as the Maxent model. The qualitative delineation also
includes arroyo toad habitat along the extent of the Mojave River where
there are no records of occurrence in the DRECP database (Dudek 2011).
Literature Cited
59 FR 64589–64867. Final rule: “Endangered and Threatened Wildlife
and Plants; Determination of Endangered Status for the Arroyo
Southwestern Toad.” December 16, 1994.
66 FR 9414–9474. Final rule: “Endangered and Threatened Wildlife and
Plants Final Designation of Critical Habitat for the Arroyo Toad.”
February 7, 2001.
69 FR 23253–23328. Proposed Rule: “Endangered and Threatened
Wildlife and Plants; Proposed Designation of Critical Habitat for
the Arroyo Toad (Bufo californicus).” April 28, 2004.
70 FR 19562–19633. Final Rule: “ETWP; Final Designation of Critical
Habitat for the Arroyo Toad (Bufo californicus).” April 13, 2005.
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Arroyo Toad (Anaxyrus (Bufo) californicus)
74 FR 52612–52664. Proposed Rule: “Revised Critical Habitat for the
Arroyo Toad (Anaxyrus californicus).” October 13, 1009.
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