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Eleutherodactylus (= Syrrhophus) marnockii (Cope, 1878a)
Cliff Chirping Frog
J. Eric Wallace1
The genus
Syrrhophus was synonomized with the genus Eleutherodactylus and
considered a subgenus (including the genus Tomodactylus) by Hedges (1989).
But Dixon (2000) notes that this synonomy does not consider behavior, morphology, or
genetic characters and so maintains Syrrhophus at the generic level.
1. Historical versus Current Distribution. The type locality of cliff chirping
frogs (Eleutherodactylus marnockii) is “near San Antonio”
(Cope, 1878a). This is further restricted to Helotes, Bexar County, Texas, by
Strecker (1933). Cliff chirping frogs are common in rocky areas of central Texas
on the Edwards Plateau west to the Stockton Plateau (Jameson, 1955; Dixon, 2000).
Currently, most gaps in the distribution of cliff chirping frogs are likely from lack of
survey effort. Searches in appropriate habitats throughout their range will likely
continue to increase our knowledge of their distribution (Husak, 1998; Malone, 1998) and
are especially needed along the western edge of their known range—the possible
contact zone with spotted chirping frogs (E. guttilatus; see taxonomic
discussion under E. guttilatus account). Fossil records exist from
Edwards, Foard, Knox, and Kerr counties, Texas (Parmley, 1988a,b; Dixon, 2000) suggesting
a Pleistocene distribution approximately 320 km to the north of present day populations.
Jameson (1955)
presents the only comprehensive study on the ecology of cliff chirping frogs. His
work on the population dynamics of cliff chirping frogs combines extensive field
observations, intensive experimental field manipulations, and laboratory work. Much
of the information in this species account is extracted directly from there. Dixon
(2000) provides a current, comprehensive bibliography of cliff chirping frogs with notes
on taxonomy. Popular accounts in field guide format may be found in Cochran and
Goin (1970), Smith and Barlow (1978), Garrett and Barker (1987), Behler and King (1989),
Conant and Collins (1998), and Bartlett and Bartlett (1999a).
For discussions of
the historical and current biogeography of the subgenus (= Syrrhophus; Hedges,
1989) and for the species marnockii, see Smith and Buechner (1947), Blair
(1950), Milstead et al. (1950), Morafka (1977), Duellman and Sweet (1999), and Hedges
(1999).
2. Historical versus Current Abundance. Jameson (1955) conducted population
studies at 12 sites in the vicinity of Austin, Texas, and estimated population densities
of cliff chirping frogs from 1.2–8.9 frogs/ac. He attributed variation in
local densities to availability and structure of rocky substrate and moisture (as
evidenced by amount of vegetation). Areas with more moisture and vegetation and
greater rock structure (e.g., talus slopes and rock piles) supported denser
populations. During his research, he noted reductions in frog densities at two of
his study sites and suggested disturbance by fire to be the cause in one case and road
construction in the other.
3. Life History Features.
A. Breeding.
Reproduction is terrestrial. Breeding occurs primarily from April–May with a
second pulse during September–October; both peaks are coincident with rain events
(Jameson, 1955). Based on observations of gravid females, he suggests that breeding
may take place from late February to early December. Calling is most pronounced
during the early evening following dusk and tends to diminish throughout the night;
during the height of the breeding season(s), calls may be heard until dawn. Cliff
chirping frogs exhibit complex mating behaviors including preamplectic courtship and
mating-specific vocalizations (Jameson, 1954). Amplexus is axillary. He noted
what appeared to be a call hierarchy in which groups of 3–4 individuals followed
the lead of a dominant male. Fouquette (1960) provides descriptions of two types of
calls produced by cliff chirping frogs. Jameson (1955) comments on the extreme
difficulty of sexing frogs in the field. The only means was the presence of eggs
observable through the stomach wall in gravid females and the vocalizations of
males. He notes that while males may mate several times/year, females may mate
from 1–3 times/year. Jameson (1955) provides additional, detailed information
on breeding behaviors and general activity patterns under various environmental
conditions.
i. Breeding migrations. This highly terrestrial frog does not form breeding
migrations or aggregations.
ii. Breeding habitat. Little is known regarding cliff chirping frog breeding
microhabitats. Frogs have been observed in amplexus twice in the wild, once on an
exposed rock substrate and once in a rock crack above dry soil. In neither case was
there any moist soil nearby. Chirping frogs in the wild continue to vocalize while
in amplexus. Jameson (1955) suggests this may be an attempt to lead the female to
moist soil for egg deposition or may be necessary to instigate egg laying and/or to
ensure proper fertilization. In captivity, mating occurred only when males called
females to a site with moist soil after which males did not continue to call while in
amplexus. All eggs laid in captivity were sterile (Jameson, 1955).
B. Eggs.
i. Egg deposition sites. Egg deposition sites in nature are unknown despite
considerable effort to locate them (Jameson, 1955).
ii. Clutch size. In captivity, 8–20 sterile eggs were laid in trenches dug in
moist soil by the female and covered by both frogs with their legs as they moved
forward.
C. Direct
Development. Larvae undergo direct development within the egg capsule and hatch as
froglets into the terrestrial environment (Jameson, 1955; Lynch, 1971). Specific
information on timing and duration of development is lacking. The incubation period
for the closely related Rio Grand chirping frog (E. cystignathoides
campi) under captive and experimental conditions was 14–16 d (Hayes-Odum,
1990).
i. Brood sites. Unknown.
ii. Parental care. Parental care occurs in some Eleutherodactylus and has
been suggested to occur in barking frogs (E. augusti; Jameson,
1950b). Because barking frogs co-occur with cliff chirping frogs in the same
habitats and environmental conditions, parental care in chirping frogs requires further
investigation.
D. Juvenile
Habitat. Juvenile habitat is likely similar to adults, i.e., they require a similar
physiography in the form of rocky and vegetative structure providing for cover and moist
refugia. In Jameson’s (1955) intensive study, juveniles were observed in all
but the driest and coldest months (December, January) of the year, with peak activity
similar to that noted for adults and coincident with moist periods.
During a field
manipulation study on dispersing juveniles, Jameson (1955) recorded an average dispersal
distance of 211.4 ± 25.6 m (231 ± 28 yd) for those individuals that
apparently recruited into the resident population. He found that most juveniles
dispersed parallel to available habitat (in these cases, rocky exposures) and considered
time of dispersal dependent on availability of moisture and time of breeding and
hatching.
E. Adult
Habitat. Cliff chirping frogs are saxicolous and to some extent cavernicolous in
nature and are primarily found in the juniper-oak association of the Balconian Province
of Blair (1950). They are always found in association with rocks and may be found
underneath and in crevices in rocks occurring along limestone ledges and bluffs, on talus
slides, in ravines, and near streams (Smith and Buechner, 1947; Wright and Wright, 1949;
Jameson, 1955). Caves often support large populations (Jameson, 1955). These
frogs are primarily nocturnal with most activity recorded in the hours following dusk,
especially following spring and fall rains (Wright and Wright, 1949; Jameson,
1955). During the height of breeding season(s), individuals remain active
throughout the night and males may continue to vocalize during daylight hours (Jameson,
1955). During the day, these frogs can be found under cover objects (Wright and
Wright, 1949; Jameson, 1955). On a few occasions, Jameson (1955) observed
individuals on arboreal perches from 1.2–2.4 m (4–8 ft) above the ground.
Jameson (1955)
showed that these highly terrestrial frogs are relatively incapable of swimming, as
demonstrated by individuals that drowned within 2 hr of being placed in a jar of water,
and attributes their inactivity during intense rainfall events to this inability.
F. Home Range
Size. Jameson (1955) estimated average home ranges of cliff chirping frogs during
the breeding season from four distinct types of habitat. Average home ranges by
type ranged between 0.052–0.139 ac. Size of home ranges were significantly
correlated with the unique physiography of each type of site (i.e., the more structurally
diverse the habitat, the smaller the home range). Home ranges tended to be
occupied throughout their lifespan (Jameson, 1955).
G.
Territories. Unknown.
H.
Aestivation/Avoiding Dessication. Cliff chirping frogs may be found at nearly any
time during the year if environmental conditions are appropriate. Activity during
hot, dry summer periods is generally minimal. Jameson (1955) observed frogs at
temperatures as high as about 32 ˚C (90 ˚F) but does not elaborate on
activities.
I. Seasonal
Migrations. Chirping frogs do not undertake seasonal migrations per se, however,
through experimental field manipulations, Jameson (1955) showed that cliff chirping frogs
will move into areas of decreased population density from areas of high population
density.
J. Torpor
(Hibernation). Activity during cold wet winter periods is generally minimal.
Jameson (1955) found that during cold, moist periods individuals could be observed in the
same crevice over the course of several days. He has observed frogs at
temperatures as low as 1 ˚C (34 ˚F), but does not elaborate on their
activities.
K. Interspecific
Associations/Exclusions. Cliff chirping frogs are sympatric with barking frogs
(Eleutherodactylus augusti) throughout much of their range in Texas and
often share the same rocky microhabitats (Jameson, 1954; Dixon, 2000). Cliff
chirping frogs have also been found associated with Gulf Coast toads (Bufo
valliceps [now considered to be Coastal-Plain toads, B.
nebulifer; see Mulcahy and Mendelson, 2000; Mendelson, this
volume), red-spotted toads (B. punctatus), and western slimy
salamanders (Plethodon albagula; McAlister, 1954; Jameson, 1955; Hubbs
and Martin, 1967). Jameson (1955) lists several vertebrates and invertebrates that
co-occur with cliff chirping frogs and might compete for prey.
L. Age/Size at
Reproductive Maturity. Based on measurements of gravid females and calling males,
frogs reach sexual maturity at 19–22 mm and 18–22 mm, respectively (Jameson,
1955). Lynch (1970) measured 103 museum specimens and found adult males and
females ranging between 18.4–28.9 and 20.4–35.4 mm, respectively. They
attain a maximum length of 38 mm (Cope, 1889). The period of fastest growth occurs
during the spring and summer (Jameson, 1952, fig. 4), and growth rates decrease as frogs
become larger.
M. Longevity.
Jameson (1955) suggests cliff chirping frogs may live ≤ 3 yr in the wild.
N. Feeding
Behavior. Documented prey of wild cliff chirping frogs include ants, small beetles,
camel crickets, termites, and small spiders (see Jameson, 1952, for more detailed
information). Captive animals also feed on a variety of insects (Jameson,
1955). Jameson (1952) noted the interesting behavior of chirping frogs
"robbing" insects entrapped in the webs of orbit web spiders (Argiopidae).
O. Predators.
Known predators of cliff chirping frogs include western diamond-backed rattlesnakes
(Crotalus atrox), mottled rock rattlesnakes (C.
lepidus), copperheads (Agkistrodon contortrix), black-necked
garter snakes (Thamnophis cyrtopsis), and large wolf spiders (Milstead
et al., 1950; Fouquette, 1954; Jameson, 1955). Jameson (1955) observed predation
in the laboratory by barking frogs (E. augusti), Coastal-Plain toads,
and tarantulas.
P. Anti-Predator
Mechanisms. To avoid capture, cliff chirping frogs are capable of quick movements
and will hop or run for the nearest cover, usually in the form of rock cracks or crevices
(Jameson, 1955).
Q. Diseases.
Unknown.
R. Parasites.
Mites of the genus Hannemania are known ectoparasites of cliff chirping frogs
(Jameson, 1952; Lynch, 1970).
4. Conservation. Cliff chirping frogs have no federal or state conservation
status. Based on Jameson’s (1955) findings, cliff chirping frogs were common
and relatively abundant in several urban areas in Austin, Texas. This suggests an
ability to cope with at least certain types of human-mediated habitat disturbance.
They are still found in city parks today (Bartlett and Bartlett, 1999a). Resurveys
at Jameson’s urban sites would provide insight into the long-term ability of this
frog to persist in urban settings.
The recent
introduction of Rio Grande chirping frogs through the potted plant trade into some urban
areas (e.g., San Antonio, Texas; Dixon, 2000) may place introduced frogs in direct
contact with resident populations of cliff chirping frogs. The repercussions of this
interaction are unknown, but detrimental effects could include introduction of novel
disease pathogens, competition, and/or hybridization. Measures should be
instituted to decrease the likelihood of further introductions.
1J. Eric Wallace
School of Renewable Natural Resources
University of Arizona
Tucson, Arizona 85721
batrachia@yahoo.com
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Apr 2024.
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