General Distribution
The arroyo toad is concentrated in a small number of locations on the Los Padres National Forest.
Substantial populations exist on Piru Creek, including the lower reaches of Agua Blanca Creek; Sespe
Creek; and interconnected reaches of the upper Santa Ynez River, Mono Creek, and Indian Creek. A
smaller population occurs along the Sisquoc River. All these populations are predominantly on National
Forest System lands. The northernmost population of arroyo toads, on the San Antonio River in
Monterey County, lies just off the national forest on the Fort Hunter Liggett Military Reservation?(Stephenson and Calcarone 1999).
On the Angeles National Forest, arroyo toad populations occur along Castaic Creek; along Big Tujunga
Creek, including associated lower reaches of Mill and Alder Creeks; along Arroyo Seco Creek; and on
the desert side of the San Gabriel Mountains along Little Rock Creek. These populations lie near the
national forest boundary and, in some cases, extend beyond it (Stephenson and Calcarone 1999).
On the San Bernardino National Forest, arroyo toad populations exist on tributaries of the Mojave River
including lower Deep Creek, the West Fork of the Mojave River, and Little Horsethief Creek.
Populations also occur on lower portions of the Whitewater River, Cucamonga Creek, and Cajon Wash
(Hyde-Sato pers. comm.). The species probably still occurs on lower reaches of the San Jacinto River; a
population was recently discovered in the adjacent Bautista Creek (Stephenson and Calcarone 1999). A
new population was just discovered on Kinley Creek in 2003.
Arroyo toad populations on the Cleveland National Forest and surrounding lands are more numerous
than on the other forests, but many appear to be small. Most of the populations occur right along the
national forest boundary, with the bulk of prime breeding habitat often lying just off National Forest
System lands. This is the case at Cottonwood Creek, which includes lower reaches of Kitchen and
Morena Creeks, Potrero Creek, the Sweetwater River, the upper San Diego River, Santa Ysabel Creek
and associated lower reaches of Temescal Creek (Pamo Valley), the upper forks of the San Luis Rey
River (above Lake Henshaw) including Agua Caliente Creek, Temecula Creek including lower reaches
of Arroyo Seco Creek, San Mateo Creek, San Juan Creek, and Trabuco Creek, Cristianitos Creek,
Gabino Creek, and Talega Creek. The population along Pine Valley Creek and several of its tributaries
is predominantly on National Forest System lands (Stephenson and Calcarone 1999). Systematics
The arroyo toad is one of three members of the southwestern toad complex (Bufo microscaphus) in the
family Bufonidae. At the time it was listed, the 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) (Gergus 1998 as referenced in U.S. Fish and Wildlife Service 2001). Habitat Requirements
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).
Within these areas, arroyo toads are found in both perennial and intermittent rivers and streams with
shallow, sandy to gravelly pools adjacent to sand or fine gravel terraces. Arroyo toads have evolved in a
system that is inherently dynamic, with marked seasonal and annual fluctuations in rainfall and
flooding. Breeding habitat requirements are highly specialized. Specifically, arroyo toads require?shallow slow-moving stream and riparian habitats that are naturally disturbed on a regular basis,
primarily by flooding (U.S. Fish and Wildlife Service 2000). Reproduction
The breeding period occurs from late January or February to early July, although it can be extended in
some years depending on weather conditions. Breeding in mountainous habitats may commence later
(May–June) and last longer (to August) than in the coastal portion of the range. When water
temperatures reach 57 ° F (14 ° C), adult males advertise with a soft, high whistled trill. Receptive
females seek out calling males based on the size of the male and the sound of his 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
deposited and larvae develop in shallow pools with minimal current, little or no emergent vegetation,
and sand or pea gravel substrate. Embryos usually hatch in 4–6 days; the larval period lasts
approximately 65–85 days.
After metamorphosis from June to August, the juveniles remain on the bordering gravel bars until the
pool no longer persists. Sexual maturity is reached in 1-2 years. Little is known about movements or
other behavior in the non-breeding season (U.S. Fish and Wildlife Service 2000). Daily/Seasonal Activity
Juvenile arroyo toads spend more time exposed on terraces during the daytime than do adults, and are
thus vulnerable to diurnal predators. Once juveniles are of sufficient size to dig burrows and bury
themselves in sand, they become nocturnal. All age classes of post-metamorphic individuals tend to be
active on rainy nights with moderate temperatures (above 45 ° F [7 ° C]). Adults excavate shallow
burrows for shelter during the day when the surface is damp or for longer intervals in the dry season (U.
S. Fish and Wildlife Service 2000). Diet and Foraging
Larvae feed by inserting their heads into the substrate and ingesting loose organic material such as
detritus, interstitial algae, bacteria, and diatoms. Juveniles and adults forage for insects, especially ants
and small beetles, on sandy stream terraces (U.S. Fish and Wildlife Service 2000) or around the drip line
of oak trees (66 Federal Register 9414, U.S. Fish and Wildlife Service 2001). Predator-Prey Relations
All life stages of arroyo toad are susceptible to predation. Egg strands, which are laid in shallow water
close to shore, are extremely sensitive to disturbance and fragmentation from animals foraging or
wading in the water. There are several predators of arroyo toad larvae; these include giant water bug
(Abedus indentatus), two-striped and common garter snakes (Thamnophis hammondii and T. sirtalis),
green sunfish, and bullfrog (Rana catesbeiana). Predators of juveniles and adults include wading and
shorebirds, snakes, western pond turtle (Clemmys marmorata), raccoon (Procyon lotor), opossums
(Didelphis virginiana), and common raven (Corvus corax) (U.S. Fish and Wildlife Service 2000). Literature Cited
Gergus, E.W.A. 1998. Systematics of the Bufo microscaphus complex: Allozyme evidence.
Herpetologica 54(3): 317-325.
Jennings, M.R.; Hayes, M.P. 1994. Amphibian and reptile species of special concern in California. Final
report to the California Department of Fish and Game, Inland Fisheries Division, Rancho Cordova, CA,
under contract 8023.
Ramirez, Ruben. 2002. Arroyo toad radio telemetry habitat usage study at Little Rock Creek, Angeles N.
F. Unpublished final report.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment:
Habitat and species conservation issues. General Technical Report PSW-GTR-172. Albany, CA: Pacific
Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Sweet, S.S. 1991 Ecology and status of the arroyo toad (Bufo microscaphus californicus) on the Los
Padres National forest of southern California. Contract report to Los Padres National Forest.
U.S. Fish and Wildlife Service. 1999. Final recovery plan for the arroyo toad (Bufo microscaphus
californicus). Portland, OR.
U.S. Fish and Wildlife Service. 2000. Biological opinion on the effects of ongoing national forest
activities that may affect listed riparian species on the Cleveland National Forest, the Los Padres
National Forest, the San Bernardino National Forest and Angeles National Forest in southern
California (1-6-99-F-21).
U.S. Fish and Wildlife Service. 2001. Final designation of critical habitat for the arroyo toad, final rule.
Fed. Reg. Vol. 66, No. 26: 9414.
Information gathered from California DFG - California Interagency Wildlife Task Group
