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NATURAL HISTORY

ARROYO TOAD } Bufo californicus
FAMILY: Bufonidae

DESCRIPTION: The arroyo toad is relatively small, ranging from two to three inches in length, and has olive-green, gray, or light-brown coloration. It is plump bodied and distinctively blunt nosed with small, oval parotid glands (toxin-secreting defense organs). Arroyos are dorsally warty, having dark-spotted skin with a light-colored stripe across the head and eyelids. They are nocturnal and generally move quickly by hopping, as opposed to walking or taking large leaps.

HABITAT: Arroyos prefer shallow pools and open, sandy stream terraces with cottonwoods, oaks, or willows. Gravel or cobbles may be a part of their habitat, but fine sand is essential, since adults and juveniles burrow or overwinter on sandy terraces.

RANGE: The species lives on coastal slopes in southern California from the Salinas River Basin in Monterey and San Luis Obispo counties to Arroyo San Simón in northern Baja California, Mexico; it has also been documented in a few drainages on desert slopes of the San Gabriel and San Bernardino mountain ranges. Current distribution is highly fragmented.

MIGRATION: Arroyo toads do not technically migrate, but during breeding season, males may travel one to 2.5 miles along stream corridors calling out for potential mates; only the largest males will remain at one breeding pool for the duration of the season. Females are more sedentary and tend to stay within 50 yards of stream corridors or breeding pools.

BREEDING: Breeding sites are typically located among gravel and sand deposits within quiet margins of open streams. The breeding season runs from February or March through July. Females select a calling male, and after mating, the female lays strings of eggs into calm waters roughly 3.5 inches deep on fine sediments.

LIFE CYCLE: Eggs hatch within four to six days of deposit, and tadpoles develop over an extended period of 65 to 85 days. For three to five weeks, juvenile arroyo toads remain within a few feet of their breeding pool and forage during the day. Adults are nocturnal, often burrowing during the day and emerging at night to feed. Most males reach sexual maturity in their second year, while females generally first breed at age three; the average life span is five years. Adult toads hibernate from August or September until February or March by burrowing into the ground or in the stream channel itself.

FEEDING: Arroyos eat a wide variety of invertebrates, though juveniles and adults predominantly feed on ants.

THREATS: The arroyo toad is in danger from habitat degradation due to water projects, development, and urban sprawl. It is also vulnerable because of invasive species predation and small population size.

POPULATION TREND: The arroyo toad has been extirpated from an estimated 65 percent of its former range. Currently, only six of the 22 extant populations south of Ventura, California, are known to contain more than a dozen adults.

Photo © Jason Jones