Pseudacris cadaverina (Cope, 1866[a])
Edward L. Ervin1
This account is
dedicated to the memory of the late Dr. Boris I. Kuperman, my friend and mentor.
1. Historical versus Current Distribution. The geographic distribution of
California treefrogs (Pseudacris cadaverina) extends from coastal
southern California, to Baja Norte, Baja California, Mexico. Within the United
States, California treefrogs are restricted to California, ranging southward along the
Coast Ranges from San Luis Obispo County, to and across the Transverse Ranges, extending
east to Joshua Tree National Park, and south along the Peninsular Ranges to the Mexican
border. California treefrogs occur from near sea level to around 2,290 m (7,500
ft). They have a discontinuous distribution within their range but are often
locally abundant (Gaudin, 1979; Stebbins, 1985). A previous report of an isolated
population of California treefrogs occurring in the Granite Mountains, Granite Mountains
Preserve in the East Mojave Desert (Greene and Luke, 1996), is unconfirmed and considered
questionable (G. Stewart, personal communication).
2. Historical versus Current Abundance. Jennings and Hayes (1994a) reviewed the
data on 80 amphibian and reptile species native to California to assess the possible need
for special listing and/or protection. Data were assembled from individuals having
experience with each species, the scientific literature, museum collections, unpublished
field notes, field reconnaissance, and archival records. Jennings and Hayes
concluded that California treefrogs did not warrant any state-level status or legal
protection. Since that time, no information or findings have become available that
would suggest the overall status of this species has changed. However, California
treefrogs are difficult to find in presumably high-quality habitat along stream segments
where populations of non-native predatory fish (i.e., green sunfish [Lepomis
cyanellus]) have become established, suggesting that some populations may be
experiencing declines (R. Fisher, unpublished data; personal observations).
3. Life History Features.
Reproduction is aquatic.
i. Breeding migrations. Unknown.
ii. Breeding habitat. Oviposition takes place in pools of still or slow moving
water usually surrounded by large water-worn rocks and boulders (Storer, 1925; Stebbins,
1951). California treefrogs and Pacific treefrogs are often syntopic, with
California treefrogs generally calling from banks and islands and rarely from the water;
Pacific treefrogs call from shallow water, often in contact with emergent vegetation
(Littlejohn, 1971; personal observations).
B. Eggs. The
mean measurement of 15 eggs preserved on 5% formalin was 1.95 mm (vitellus; range
1.83–2.10) and 4.39 (envelope; range 4.14–4.68; Storer, 1925).
i. Egg deposition sites. Eggs are deposited in the quiet pools of intermittent and
perennial streams. Egg capsules are surrounded by a colorless gelatinous envelope
with adhesive properties that secures most to stationary debris on or near the bottom of
the pool (Storer, 1925; Stebbins, 1951; Gaudin, 1965). Eggs are exuded singly and
have a tendency to adhere together. Breeding and eggs deposition occur from early
February to early October (Stebbins, 1985), after high flows from seasonal storms have
begun to subside. During rainfall events and the subsequent increase in stream
flow, eggs that dropped into interstitial pockets of the substrate are less susceptible
to displacement. A photograph showing eggs attached singly to a sycamore leaf
appears in Storer (1925, plate 13, fig. 39).
Anzalone et al.
(1998) conducted experiments investigating the effects of solar UV-B on the survivorship
and hatching success of California treefrog embryos. The study demonstrated that
the groups of embryos shielded from UV-B displayed a significant increased survival rate,
while embryos directly exposed to solar UV-B had a decreased survival rate. Laying
eggs individually lower in the water column, as opposed to egg masses or strings close to
the surface, provides protection from the deleterious effects of direct solar radiation
and the unpredictable hydrologic conditions of lotic environments of the
ii. Clutch size. Unknown.
i. Length of larval stage. The larval period ranges from 40–75 d (Stebbins,
ii. Larval requirements. Larvae are found in pools of still or slow-moving water
usually surrounded by large water-worn rocks and boulders (Storer, 1925; Stebbins,
1951). As a result of rainfall and the subsequent increased velocity of water,
tadpoles are occasionally redistributed downstream. Tadpoles are most abundant in
fishless pools and stream reaches (Hemphill and Cooper, 1984; personal
a. Food. California treefrog larvae are classified as generalists and typically
feed on detritus, periphyton from algal crusts and mats, and from the surface of
submerged objects such as leaves, sticks, and rocks (Duellman and Trueb, 1986; Stebbins
and Cohen, 1995).
b. Cover. When not actively foraging, tadpoles often seek out the warmer water
found along shallow pool margins. When disturbed or threatened, they quickly
retreat to deeper waters and seek cover among algae mats, submergent vegetation, leaf
litter, or gaps between cobble stones. Tadpoles possess robust tail musculature that
reaches almost to the tail tip and are consequently strong swimmers (Cunningham, 1964;
Gaudin, 1964; personal observations).
iii. Larval polymorphisms. None reported.
iv. Features of metamorphosis. Metamorphosis has been observed in California from
June–August (Stebbins, 1951).
v. Post metamorphic migrations. Cunningham (1964) wrote: "Immediately after
metamorphosing, juveniles are extremely common, sometimes numbering several individuals
per square yard for distances of 6.1 m (20 ft) or more surrounding the pond from which
they emerged. In mid August, however, in such sites as along the Mojave River,
juveniles suddenly become quite uncommon. Mortality may be high or the toads [sic]
may simply change their habitats and become difficult to find."
Habitat. Recently metamorphosed individuals are often found aggregated under and
between small rocks and cobble and at the base of annual plants growing along the margins
of breeding pools. Newly metamorphosed animals show average daily movements of 1 m
(range 0.5–2 m) and move from refugia in pursuit of prey (Harris, 1975). One
exceptional juvenile was discovered beneath damp leaves in a small depression 46 m (150
ft) from water (Cunningham, 1964).
Habitat. During active periods, adults most commonly are found in close proximity
to and along stream channels. During the daytime, individuals seek refuge in
cavities or small depressions on the surfaces of the boulders lining streams, often fully
exposed to direct sunlight. These perches are usually within a few jumps from the
nearest pool. Stebbins (1951) writes: "Typical habitat includes clean rock
surfaces, crevices, shade, and during the breeding season, quiet, clean
water." Lillywhite and Light (1975) discovered that while California treefrogs
bask in direct sunlight, they discharge a clear, non-viscous fluid onto their integument
to prevent the underlying epithelium from drying. Minimal loss of water from the
whole animal nevertheless occurs by evaporation and renewal of the mucous film.
Outside the breeding season, these treefrogs spend little time in the water.
discovered occasionally in upland habitats far from the drainage during the autumn and
winter (S. Sweet, personal communication). In April, two individuals were observed
approximately 46 m (50 yd) almost vertically from a small stream; in mid June, an
individual was discovered in a rodent burrow located in dry soil approximately 46 m (50
yd) from a small stream (Cunningham, 1964). As cited in Stebbins (1951),
"Klauber has found it on granite boulders to about 100 feet horizontally and 50 feet
vertically from the nearest stream (Storer ms.)." No male/female differences in
habitat characteristics or utilization have been reported.
F. Home Range
Size. California treefrogs occupy relatively small portions of the streamside
habitat available to them during the spring and summer (Dole, 1974; Harris, 1975).
Adult treefrogs move an average distance of 3 m (1–5 m)/d while juveniles move
less, an average of 1 m (0.5–2 m)/d. Adult movements are associated with
foraging and breeding, while juvenile activities are primarily in pursuit of prey
(Harris, 1975). Dole (1974) showed that adults rarely moved > 3–4 m in
higher quality habitat.
Five females that
Dole (1974) studied were recaptured in the same area that each had occupied the previous
year. Two of them were recaptured in the same location while three others were
within 2 m of their original locations. One treefrog was captured six times over a
593-d period spanning two winters. This individual was always found to be within 2
m of her original capture location. Movements of the four other females captured
in both years were greater. One of these females, originally captured in July, was
recaptured 80 m downstream the following March, but by June she had returned to her
previous spot. The three others had moved downstream. By the following
summer all three had returned 91–218 m upstream to where they had been observed
Of the male
treefrogs recaptured during both years of the study, the first moved 13 m, the second
moved 6 m in 8 mo, and the third moved 75 m upstream. Diminishing levels of pooled
water and available moisture were suspected to be the reason some adults made extensive
downstream movements to an area containing deeper pools and a greater tree canopy.
will move long distances (Kay, 1989). These movements tend to occur between areas
of favorable habitat characteristics such as boulders and pooled water and are not
thought to be related to population density (Kay, 1989).
Territories. The first report of a California treefrog encounter call (sensu
McDiarmid and Adler, 1974) appeared in Littlejohn (1971), although no details were
provided. Male California treefrogs have been reported to warn male intruders and
maintain territories with encounter calls, and if necessary, defend their calling sites
with male–male aggressive encounters (F.T. Awbrey, cited in Wells, 1977a; Fellers,
observations are noteworthy in that they serve as examples of site-specific
territoriality for California treefrogs. Male aggressiveness has been observed in
the field on two separate occasions with both encounters being similar in nature
(personal observations). On the evening of 18 May 1999 (1725 hr) in Hot Springs
Canyon (Orange County, California), a vocal response was elicited from a vocalizing male
California treefrog by imitating his advertisement call. While this in itself is
not unique, this individual also reoriented toward the call and hopped up onto a
partially buried, 50 cm high, granite boulder. While slowly being approached from 3
m away, imitation calls were again presented to him. He quickly responded by
hoping about 20 cm in a single leap to the highest point of the rock, remained trained on
the "intruder," and began to return calls with greater intensity. The
second encounter occurred on the afternoon of 21 March 2000 (1310 hr) in Tenaja Canyon
(Riverside County, California). A male California treefrog responded to the
imitation calls in much the same manner. However, this individual approached from
the water's edge with a series of hops across the bedrock towards the observer.
This treefrog traveled approximately 2 m to within 30 cm of the observer while continuing
to respond to the imitation calls, also with increased intensity. The vocalizations
reported here have been interpreted as encounter calls because they were accompanied by
territorial behavior (i.e., approaching the intruder) and were acoustically distinct from
the typical advertisement call (i.e., greater intensity).
suggest that the drive to defend a preferred site or territory can be strong. Most
likely, this aggressive behavior is restricted to the breeding season. At this
time, no one has analyzed or described the entire call repertoire of California
Aestivation/Avoiding Dessication. The distribution of California treefrogs
suggests that they have adapted to a variety of weather conditions. Desert
populations must aestivate in late summer and early autumn to avoid the hot dry
conditions, and high elevation populations must hibernate in the winter months to avoid
freezing temperatures (Miller and Stebbins, 1964; Ball and Jameson, 1970; also see
"Torpor [Hibernation]" below).
Migrations. Seasonal habitat usage patterns can be summarized from Harris (1975) as
follows. During spring (mid March to mid June) and summer (mid June to mid
September), individuals aggregate on granitic boulders along stream and river courses
associated with pools of water. In the fall (mid September to November) and winter
(December to mid March), individuals move to crevices located on higher ground bordering
the drainages. The migration from summer habitats to winter habitats appears to
function in avoiding desiccation, predation, and high water from unpredictable and
occasional heavy rains during the winter season (Dole, 1974). During the
transition from late winter to early spring (i.e., March–April), individuals begin
to reappear along the stream and river courses in greater numbers.
(Hibernation). By late fall (mid November) the great majority of California
treefrogs have moved to higher ground. From December to mid March, California
treefrogs are seldom encountered (Harris, 1975; unpublished data). Adults seek deep
moist crevice microhabitats located on hillsides (Cunningham, 1964; Harris, 1975) and
occasionally in damp portions of mine adits (R. Fisher, D. Stokes, personal
communication). High concentrations of urea accumulate in the body fluids (140 mM)
during dehydration or periods of reduced water turnover. This increases the body
water potential to levels where net cutaneous water uptake is possible and reduces the
gradient for the net loss of water to the environment (Jones, 1982).
Associations/Exclusions. California treefrogs occur across a wide elevational range
and therefore are associated with a diverse herpetofauna. For example, riparian
woodlands along lower gradient stream segments, whether in valley bottoms or at the foot
of mountainous terrain, support species such as Coast Range newts (Taricha t.
torosa), California toads (Bufo boreas halophilus),
arroyo toads (B. californicus), Pacific treefrogs (Pseudacris
regilla), California red-legged frogs (Rana draytonii),
foothill yellow-legged frogs (R. boylii), two-striped gartersnakes
(Thamnophis hammondii), and southwestern pond turtles (Emmys
marmorata pallida). Co-existence with these species often occurs
in ecotones, or transitional zone habitats that include stream reaches bordered by rocks
and boulders that are favored by California treefrogs (Schoenherr, 1976; DeLisle et al.,
1986; personal observations).
The channel of
steeper gradient streams in the mountains and foothills are characterized by a stair-step
watercourse forming a series of riffles, runs, and still to slow-flowing pools, often
confined to rocky canyons. Coast Range newts, mountain yellow-legged frogs
(Rana muscosa), two-striped garter snakes, and southwestern pond
turtles are found in these habitat conditions. Where the distributional ranges of
these species overlap with California treefrogs, they often co-occur (Schoenherr, 1976;
DeLisle, 1985; Anzalone et al., 1998). Red-spotted toads (Bufo
punctatus) and California treefrogs co-occur in wetlands, including canyons,
springs and oases, of desert regions (Miller and Stebbins, 1964; Glaser, 1970).
are known to share the same stream reaches and macrohabitats with several native fish
species including rainbow trout (Oncorhynchus mykiss, freshwater form), southern
steelhead (Oncorhynchus mykiss, sea-run form), threespine stickleback
(Gasterosteus aculeatus), Santa Ana sucker (Catostomus
santaanae), arroyo chub (Gila orcutti), and speckled dace
(Rhinichthys osculus; R. Fisher, unpublished data; personal
observations). These associations are possible because these fish are thought to
feed primarily on invertebrates and aquatic vegetation and are presumably less reliant on
amphibian eggs or larva (Moyle, 1976, 2000; McGinnis, 1984). However, California
treefrogs are often most abundant in streams lacking fish fauna (Hemphill and Cooper,
1984; Cooper et al., 1986; personal observations). Strategic placement of eggs and
the availability of refugia and structurally complex tadpole foraging areas may be
important factors determining these interspecific associations with California
A variety of
introduced species are well established in the aquatic habitats utilized by California
treefrogs. The most widespread of these are red swamp crayfish
(Procambarus clarkii), African clawed-frogs (Xenopus
laevis), American bullfrogs (Rana catesbeiana), black bullheads
(Ameiurus melas), mosquitofish (Gambusia affinis),
hatchery stock rainbow trout, largemouth bass (Micropterus salmoides),
bluegill (Lepomis macrochirus), green sunfish (Lepomis
cyanellus), and European carp (Cyprinus carpio; Gamradt and
Kats, 1996; Stephenson and Calcarone, 1999; R. Fisher, unpublished data; personal
observations). The relative impact of introduced aquatic species on California
treefrog populations has not been determined. Interspecific exclusions are currently
adult hybrids between California treefrogs and Pacific treefrogs have been reported
(Brattstrom and Warren, 1955; Gorman, 1960). However, attempts to hybridize these
species in the laboratory have resulted in the production of inviable crosses that failed
at the earliest stages of development (Maxon and Jameson, 1968; Ball and Jameson, 1970;
L. Age/Size at
Reproductive Maturity. Storer (1925) concluded that California treefrogs reach
their adult size and breed when 2 yr old. This interpretation is based on finding no
more than two size classes among metamorphosed individuals.
N. Feeding. A
stomach content analysis of 15 adult California treefrogs recovered the following prey
types: grasshoppers (Orthoptera), spiders (Arachnida), ants (Hymenoptera), beetles
(Coleoptera), moths (Lepidoptera), sowbugs (Isopoda), true bugs (Hemiptera), and
lacewings (Neuroptera; Cunningham, 1964).
Cooper et al (1986) conducted field experiments to investigate predation by rainbow trout
and demonstrated that they have the capacity to completely eliminate California treefrog
larvae from stream pools. Introduced non-native green sunfish have been shown to
prey on adult California treefrogs (Ervin et al., 2001a). Established populations
of this predatory fish occur in many coastal southern California drainages that
currently support California treefrog populations (Stephenson and Calcarone, 1999;
personal observations). Highly aquatic two-striped garter snakes, which have a
geographic distribution similar to California treefrogs (Rossman et al., 1996), prey on
larvae and metamorphosed individuals (Cunningham, 1959; Schoenherr, 1976; personal
Mechanisms. The pigmentation patterns of the California treefrog larva, ranging
from light to dark brown and with varying amounts of gold flecking (Gaudin, 1965),
closely resembles the appearance of the sand and rocky stream substrates. This
cryptic coloration, in combination with the tendency of larvae to seek refuge in the
presence of trout, would likely reduce or delay predation (Cooper, 1988).
Juvenile and adult
California treefrogs possess coloration and marking patterns on the dorsum that resemble
those of the rocks and boulders they inhabit (Storer, 1925; Stebbins, 1951). Their
ability to remain undetected is enhanced by the tendency to remain virtually still when
approached (Storer, 1925; Stebbins, 1951; Cunningham, 1964). Most diurnal perches
are within 1 m from water's edge, enabling a rapid escape requiring one or two jumps to
the nearest still pool or, occasionally, a swift current (Storer, 1925; Stebbins, 1951;
Cunningham, 1964). Noxious and or toxic properties in eggs, larvae, and adults are
Unknown. There is a single record of a California treefrog exhibiting gross
morphological abnormalities associated with limbs, and it is one of the few reports to
document an extra-legged frog from lotic habitat (E.L.E. and P.T.J. Johnson, unpublished
data). This specimen possessed three normal extremities with two malformed
hindlimbs on the right side. The primary limb, the femur and surrounding
musculature were greatly reduced and the tibiofibula folded back upon itself to form a
distinct bony triangle (taumelia). The foot extended anteriorly and exhibited only
one clearly defined digit (ectrodactyly). The supernumerary right limb (polymelia),
which was independent of and ventral to the primary limb, was also poorly developed with
a truncated femur and only three digits. Trematode metacercariae, which have been
shown to cause developmental abnormalities in the rear limbs of other species of frogs,
were not found in this specimen.
The larval stage of chiggers (Hannemania hylae; Acarina: Trombiculidae)
has been shown to embed in the skin of adult California treefrogs (Welbourn and Loomis,
1975). Approximately 98.9% of the treefrogs in this study had a mean of 21.4
chiggers/treefrog. While Welbourn and Loomis (1975) determined that one life cycle
is completed each year, unengorged larvae were found on treefrogs throughout the summer.
Goldberg and Bursey
(2001) examined the helminth communities in California treefrogs and found the trematode
Langeronia burseyi and metacercariae of Alaria sp., Fibricola
sp., and Gorgoderina sp.; the cestode Distoichometra bufonis; and two
species of nematodes (Rhabdias ranae and larvae of Physaloptera
sp.). They also provided a breakdown of the infection site, number of helminths,
prevalence, and mean intensity for helminths from California treefrogs from three
counties in southern California.
California treefrogs from Cedar Creek (San Diego County, California) were examined and
found to be infected by three groups of parasites. Hannemania
hylae were located in the abdominal skin and the bottom surface of the front and
rear feet. Prevalence was 100%, while mean intensity was 28 (range
4–57). Ribeiroia sp. (Trematoda) metacercariae were found encysted
and excysted in the musculature of the rear feet and pelvic area with 87% prevalence and
a mean intensity of 34 (range 7–92). Finally, two protozoans were found in
the intestines, the flagellate Opalina sp. and the ciliate Balantidium
sp., with a prevalence of 60% and 37%, respectively (B. Kuperman and V. Matey,
4. Conservation. While Jennings and Hayes (1994a) concluded that California
treefrogs did not warrant any state-level status and/or legal protection, California
treefrogs are difficult to find in presumably high-quality habitat where populations of
non-native predatory fish have become established, suggesting that some populations may
be experiencing declines (R. Fisher, personal communication; personal observations).
1Edward L. Ervin
U.S. Geological Survey
Biological Resource Discipline
Western Ecological Research Center
San Diego Field Station
5745 Kearny Mesa Road, Suite M
San Diego, California 92123
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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