California Treefrog, Pseudacris cadaverina (Cope, 1866)

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AMPHIBIAN
DECLINES
THE
CONSERVATION
STATUS
OF
UNITED
STATES
SPECIES
Edited by
MICHAEL
LANNOO
UNIVERSITY
OF
CALIFORNIA·
PRESS
Berkeley
Los Angeles London

Pseudacris cadaverina (Cope, 1666[a])
CALIFORNIA
TREEFROG
Edward1. Ervin
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
south-
ward 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
Mexi-
can
border. California treefrogs occur
from
near
sea level to
around
2,290 m
(7,500 ft). They
have
a
discontinuous
dis-
tribution
within
their
range
but
are
often
locally
abundant
(Gaudin, 1979; Stebbins,
1985). A previous
report
of
an
isolated
population
of
California treefrogs occur-
ring in
the
Granite
Mountains,
Granite
Mountains
Preserve in
the
East Mojave
Desert (Greene
and
Luke, 1996), is
un-
confirmed
and
considered
questionable
(G. Stewart,
personal
communication).
2.Historicalversus 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unpublished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 reconnais-
sance,
and
archival records.
Jennings
and
Hayes
concluded
that
California treefrogs
did
not
warrant
any state-level status or
legal
protection.
Since
that
time,
no
in-
formation
or
findings
have
become
available
that
would
suggest
the
overall
status of
this
species has changed. How-
ever, California treefrogs are difficult to
find
in
presumably
high-quality
habitat
along
stream
segments
where
popula-
tions
of
non-native
predatory
fish (i.e.,
green
sunfish
(Lepomis cyanellusJ)
have
become
established, suggesting
that
some
populations
may
be experiencing
declines
(R. Fisher,
unpublished
data;
personal
observations).
3. LifeHistory Features.
A.Breeding. 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 (P. regil/a) are
often
syn-
topic, with California treefrogs generally
calling from banks
and
islands
and
rarely
from
the
water; Pacific treefrogs call from
shallow water, often in contact with emer-
gent
vegetation
(Littlejohn, 1971; per-
sonalobservations).
California
Treefrog
(Pseudacris cadaverina)
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. Eggsare deposited
in the quiet pools of intermittent and
perennial streams. Egg capsules are sur-
rounded 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). Eggsare exuded singly and
have a tendency to adhere together. Breed-
ing 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 dis-
placement. A photograph showing eggs at-
tached singly to a sycamore leaf appears in
Storer (1925, plate 13, fig. 39).
Anzalone et al. (1998)conducted exper-
iments investigating the effectsof 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 di-
rectly exposed to solar
UV-B
had a decreased
survival rate. Laying eggsindividually lower
in the water column, as opposed to egg
masses or strings close to the surface, pro-
vides protection from
the
deleterious ef-
fects of direct solar radiation
and
the
unpredictable hydrologic conditions of lone
environments of
the
southwest.
ii.Clutchsize. Unknown.
C.Larvae/Metamorphosis.
i.
Length
of
larval
stage. The larval period
ranges from
4()"'75
d (Stebbins, 1951).
ii.
Larval
requirements.
Larvae are found
in pools of still or slow-moving water usu-
ally surrounded by large water-worn rocks
and
boulders (Storer, 1925; Stebbins,
1951). Asa result of rainfall and the subse-
quent
increased velocity of water, tadpoles
are occasionally redistributed downstream.
Tadpoles are
most
abundant
in fishless
pools
and
stream reaches (Hemphill and
Cooper, 1984; personal observations).
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 sub-
merged objects such as leaves, sticks, and
rocks (Duellman and Trueb, 1986; Steb-
bins
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 re-
treat to deeper waters
and
seek cover
among
algae mats, submergent vegeta-
tion, leaf litter, or gaps between cobble
stones. Tadpoles possess robust tail mus-
culature
that
reaches almost to the tail tip
and
are
consequently
strong swimmers
HYLIDAE
467

(Cunningham, 1964; Gaudin, 1964; per-
sonal observations).
iii.
Larval
polymorph
isms. None reported.
iv.
Featuresof metamorphosis. Metamor-
phosis has been observed in California
from
june-August
(Stebbins, 1951).
v.
Post-metamorphic
migrations.
Cunning-
ham
(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
qulte
uncommon.
Mortality may be high
or the toads
[sic]
may simply change their
habitats
and
become difficult to find."
D.Juvenile Habitat. Recently metamor-
phosed individuals are often found aggre-
gated
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 excep-
tional juvenile was discovered
beneath
damp
leaves in a small depression 46 m
(150 ft) from water
(Cunningham,
1964).
E.AdultHabitat. 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 sun-
light. These perches are usually within a
few jumps from the nearest pool. Stebbins
(1951) writes: "Typical
habitat
includes
clean rock surfaces, crevices, shade, and
dunng
the
breeding season, quiet, clean
water." Lillywhite
and
Light (1975) dis-
covered
that
while California treefrogs
bask in direct sunlight,
they
discharge a
clear, non-viscous fluid
onto
their integu-
ment
to
prevent
the
underlying
epithe-
lium 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.
Individuals are discovered occasion-
ally in
upland
habitats far from
the
drainage during the
autumn
and
winter (S.
Sweet, personal communication). In April,
two individuals were observed approxi-
mately 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 rns.)." No
male/female differences in habitat charac-
teristics or utilization have been reported.
F.Home RangeSize. California treefrogs
occupy relatively small
portions
of
the
468
HYLIDAE
streamside habitat availableto them during
the spring and summer (Dole, 1974; Har-
ris, 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 for-
aging and breeding, while juvenile activi-
ties 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 loca-
tion 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 orig-
inal capture location. Movements of the
four other females captured in both years
were greater. One of these females, origi-
nally 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 down-
stream. By
the
following
summer
all three
had returned 91-218 m upstream to
where they
had
been observed originally.
Of the male treefrogs recaptured dur-
ing 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. Dimin-
ishing 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.
California treefrogs 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).
G. Territories. The first report of a Cali-
fornia treefrog encounter call (sensu Mc-
Diarmid
and
Adler, 1974) appeared in
Littlejohn (1971),
although
no details
were provided. Male California treefrogs
have been reported to warn male intrud-
ers
and
maintain
territories
with
en-
counter calls,
and
if necessary, defend
their calling sites
with
male-male aggres-
sive encounters
(F.
T. Awbrey, cited in
Wells, 1977a; Fellers, 1979a).
The following observations are note-
worthy in
that
they
serve as examples of
site-specific territoriality for California
treefrogs. Male aggressiveness has been
observed in
the
field on two separate occa-
sions with
both
encounters being similar
in nature (personal observations). On the
evening of 18 May 1999 (1725 hr) in Hot
Springs Canyon (Orange County, Califor-
nia), a vocal response was elicited from a
vocalizing male California treefrog by im-
itating 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 em high, gran-
ite boulder. While slowly being ap-
proached from 3 m away, imitation calls
were again presented to him. He quickly
responded by
hoping
about 20 em in a
single leap to
the
highest
point
of the
rock, remained trained on the "intruder,"
and began to return calls with greater in-
tensity. The second encounter occurred
on the afternoon of 21 March 2000 (1310
hr) in Tenaja Canyon (Riverside County,
California). A male California treefrog re-
sponded to the imitation calls in much
the same manner. However, this indiVid-
ual approached from the water's edge with
a seriesof hops across
the
bedrock towards
the observer. This treefrog traveled ap-
proximately 2 m to within 30 em of the
observer while continuing
to
respond to
the
imitation calls, also with increased in-
tensity. The vocalizations reported here
have been interpreted as encounter calls
because
they
were accompanied by terri-
torial behavior (i.e., approaching
the
in-
truder)
and
were acoustically distinct
from the typical advertisement call (i.e.,
greater intensity).
These observations suggest
that
the
drive to defend a preferred site or territory
can be strong. Most likely, this aggressive
behavior is restricted to the breeding sea-
son. At this time, no one has analyzed or
described the entire call repertoire of Cali-
fornia treefrogs.
H.
Aestivation/Avoiding
Desiccation. The
distribution of California tree frogs sug-
gests
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 hi-
bernate in
the
winter
months
to avoid
freezmg temperatures (Miller
and
Steb-
bins, 1964; Ball and jameson, 1970; also
see "Torpor [Hibernation)" below).
I. Seasonal
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, preda-
tion, 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.
J. Torpor (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 encoun-
tered (Harris,
1975;
unpublished
data).
Adults seek deep moist crevice microhabi-
tats 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 lev-
els where net
cutaneous
water uptake is
possible
and
reduces
the
gradient for the
net
loss of
water
to the
environment
(Jones,
1982).
K.Interspecific Associations/Exclusions.
California treefrogs occur across a wide el-
evational range
and
therefore are associ-
ated
with
a diverse herpetofauna. For
example, riparian
woodlands
along lower
gradient stream segments,
whether
in val-
ley
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.
califomicus),
Pacific treefrogs
(P. regilla),
California
red-legged frogs
(Rana draytonii), foothill yellow-legged
frogs (R. boylii), two-striped gartersnakes
(Thamnophis
hammondii),
and
southern
Pacific
pond
turtles (Clemmys 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 (Schoen-
herr,
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, moun-
tain yellow-legged frogs (R.
rnuscosa),
two-
striped garter snakes,
and
southern
Pacific
pond
turtles are
found
in these habitat
conditions.
Where
the
distributional
ranges of these species overlap
with
Cali-
fornia treefrogs,
they
often
co-occur
(Schoenherr,
1976;
Delisle,
1985;
Anza-
lone
et al.,
1998).
Red-spotted toads (B.
punctatus)
and
California tree frogs co-
occur in wetlands,
including
canyons,
springs
and
oases, of desert regions (Miller
and
Stebbins,
1964;
Glaser,
1970).
California treefrogs are
known
to
share
the
same stream reaches
and
macro-
habitats
with
several native fish species in-
cluding
rainbow
trout
(Oncorhynchus
mykiss, freshwater form),
southern
steel-
head
(0.
mykiss,
sea-run
form), three-
spine stickleback (Gasterosteus aculeatus),
Santa Ana sucker (Catostomus santaanae),
arroyo
chub
(Gila
orcutti)
,
and
speckled
dace (Rhinichthys osculus; R. Fisher, un-
published
data;
personal
observations).
These associations are possible because
these fish are
though
t to feed primarilyon
invertebrates
and
aquatic vegetation and
are presumably less reliant on amphibian
eggs or larva (Moyle,
1976,
2000;
McGin-
nis, 1984). However, California treefrogs
are often most
abundant
in streams lack-
ing fish fauna (Hemphill
and
Cooper,
1984; Cooper et al.,
1986;
personal obser-
vations). Strategic placement of eggs
and
the availability of
refugiaand
structurally
complex tadpole foraging areas may be
important
factors
determining
these in-
terspecific associations
with
California
treefrogs.
Avariety of introduced species are well
established in
the
aquatic habitats utilized
by California treefrogs. The most wide-
spread of these are red swamp crayfish
(Procambarus clarkii), African clawed-frogs
(Xenopus laevis), American bullfrogs (R.
catesbeiana), black bullheads (Ameiurus
melas}, mosquitofish (Gambusia affinis),
hatchery stock rainbow trout, largemouth
bass (Micropterus salmoides), bluegill (Lep-
omis macrochirus), green sunfish (L. cyanel-
Ius), 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
unknown.
Probable
natural
adult
hybrids be-
tween California treefrogs
and
Pacific
treefrogs have been reported (Brattstrom
and Warren,
1955;
Gorman, 1960). How-
ever, attempts to hybridize these species
in the laboratory have resulted in the pro-
duction of inviable crosses
that
failed at
the earliest stages of development (Maxon
and
Jameson,
1968;
Ball
and
Jameson,
1970; Gaudin,
1979).
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.
M.Longevity.
Unknown.
N.Feeding. Astomach
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).
O. Predators. Cooper et al (1986) con-
ducted field experiments to investigate
predation by rainbow
trout
and
demon-
strated
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
cur-
rently support California treefrog popula-
tions (Stephenson
and
Calcarone,
1~99;
personal observations). Highly aquatic
two-striped garter snakes,
which
have a
geographic distribution similar to Califor-
nia treefrogs (Rossman et al., 1996), prey
on larvae and metamorphosed individu-
als (Cunningham, 1959; Schoenherr, 1976;
personal observations).
P. Anti-Predator Mechanisms. The pig-
mentation
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 lar-
vae 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 re-
main undetected is enhanced by the ten-
dency 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 currently unknown.
Q.
Diseases.
Unknown. There is a sin-
gle record of a California treefrog exhibit-
ing 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 speci-
men
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 supernu-
merary 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 ab-
normalities in
the
rear limbs of
other
species of frogs, were
not
found in this
specimen.
R. Parasites. The larval stage of chig-
gers (Hannemania hylae; Acarina: Trombi-
culidae) has
been
shown to embed in the
skin of adult California treefrogs (Wel-
bourn
and
Loomis, 1975). Approximately
98.9%
of
the
treefrogs in this study had a
mean of
21.4
chiggers/treefrog.While
Weibourn
and
Loomis (1975) determined
that
one life cycle is completed each year,
unengorged larvae were found on treefrogs
throughout
the
summer.
HYLIDAE
469

Goldberg and Bursey (2001) examined
the
helminth
communities in California
treefrogs
and
found the trematode
Langero-
nia
burseyi
and metacercariae of Alariasp.,
Fibricola
sp., and
Gorgoderina
sp.; the ces-
tode
Distoichometra
buionis;
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.
Fifteen adult California treefrogs from
Cedar Creek (San Diego County, Califor-
nia) were examined
and
found
to be in-
fected by three groups of parasites.
Hannemania hylaewere located in
the
ab-
dominal
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) metacer-
cariae 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
intes-
tines, the flagellate Opalina sp.
and
the
cil-
iate Balantidium sp.,
with
a prevalence of
60% and 37%, respectively (B. Kuperman
and V.Matey, unpublished data).
4. Conservation.
While
Jennings
and
Hayes (1994a) con-
cluded
that
California tree frogs did
not
warrant
any
state-level status
and/or
legal
protection,
California treefrogs are diffi-
cult
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).

Recommended citation: Ervin, E.L. 2005. California Treefrog Pseudacris cadaverina. 467-470.
In: Amphibian Declines: The Conservation Status of United States Species. Lannoo, M. J. (Ed.)
University of California Press, Berkeley, CA. pp. 1115.
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