Spotted Chirping Frog
© 2011 Timothy Burkhardt (1 of 3)
Country distribution from AmphibiaWeb's database: Mexico, United States
Eleutherodactylus (= Syrrhophus) guttilatus (Cope, 1879)
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 this author maintains Syrrhophus at the generic level.
1. Historical versus Current Distribution. The type locality of spotted chirping frogs (Eleutherodactylus guttilatus) is Guanajuato, Mexico (Cope, 1879). In the United States, spotted chirping frogs are known from the Big Bend Region of West Texas in Brewster, Presidio, and Pecos counties (Dixon, 2000). Most survey work has focused on the southwestern portion of the region. More survey work is needed in northern Brewster, Jeff Davis, and Terrell counties, the possible contact zone with cliff chirping frogs (E. marnockii). The taxonomy of chirping frogs in this region has had a dynamic and controversial history that is necessary to discuss in order to interpret the available literature.
Chirping frogs from the Chisos Mountains, Brewster County, Texas, were described as a distinct species (Syrrhophus gaigeae) based on slight differences in color pattern and morphometrics, but primarily on the supposed geographic separation of approximately 400 km (250 mi) from cliff chirping frog (S. marnockii) populations to the east (Schmidt and Smith, 1944). Subsequently, Milstead et al. (1950) looked at frogs of both regions and compared them with animals from an area that fell between the two ranges. They were unable to discern the differences described by the previous authors and considered the two species conspecific. These results were in turn supported by the detailed morphological analysis of S. marnockii conducted by Jameson (1955). Lynch (1970), in the most recent taxonomic revision of the genus, recognized Big Bend frogs as unique from central Texas frogs based on color pattern and their allopatric distribution, but synonomized S. gaigeae with S. guttilatus of Mexico. This is the current taxonomy, yet others contend that most chirping frogs from the Edwards Plateau to the Trans-Pecos region of Texas are of the same species (Morafka, 1977; Dixon, 2000).
References to the distribution of spotted chirping frogs in Mexico can be found in Lynch (1970), Conant (1983), and Flores-Villela (1993). For discussions of the historical and current biogeography of the subgenus Syrrhophus and the species guttilatus, see Blair (1950), Milstead et al. (1950), Morafka (1977), Campbell (1999), and Duellman and Sweet (1999).
Little research, beyond field surveys, has been conducted on this frog in this region, and the reader is largely referred to the information in the cliff chirping frog (E. marnockii ) account. Dixon (2000) provides a current and comprehensive bibliography of this species with notes on taxonomy (see his Syrrhophus marnockii account). Popular accounts in field guide format may be found in Smith and Barlowe (1978), Garrett and Barker (1987), Behler and King (1998), Conant and Collins (1998), and Bartlett and Bartlett (1999a).
2. Historical versus Current Abundance. Based on collecting trips in 1957–'58, Milstead (1960) states “that the population [of chirping frogs] is still quite strong” in Big Bend National Park. During surveys in the Park a few years earlier (i.e., 1955), Minton (1959) and his field party were unable to locate individuals of this species and attributed this to drought conditions. Surveys during the wet summer of 1999 confirmed this frog as common and widespread throughout the Park (unpublished data).
3. Life History Features.
A. Breeding. Reproduction is terrestrial. Little is known on the breeding behavior of spotted chirping frogs. Breeding activity (i.e., calling males) begins in earnest with the onset of summer (June–July) rains continuing for about 2 wk and tapering off over the next about 1.5 mo (S. Droege, unpublished data; unpublished data). Males tend to vocalize from rock cracks and crevices that are 0.2–1.3 m above the ground (unpublished data). An audio-spectrogram of a call from an individual from Durango, Mexico, is provided in Conant (1983).
i. Breeding migrations. This highly terrestrial frog does not undertake breeding migrations or form breeding aggregations. Similar to cliff chirping frogs (E. marnockii), they probably maintain a home range.
ii. Breeding habitat. Unknown.
i. Egg deposition sites. Unknown.
ii. Clutch size. One female collected in July contained five unpigmented eggs, each about 4 mm in diameter (Gaige, 1931). Garrett and Barker (1987) state that females deposit fewer than 15 eggs and Bartlett and Bartlett (1999a) note clutches of 5–12 eggs, yet no reference as to the origin of these data are given.
C. Direct Development. Development in spotted chirping frogs occurs within the egg; young hatch as froglets (Conant and Collins, 1998).
i. Brood sites. Unknown.
ii. Parental care. Unknown.
D. Juvenile Habitat. Unknown, but probably similar to adult habitat characteristics.
E. Adult Habitat. Spotted chirping frogs are found in a variety of habitats in the Chichuhuan Biotic Province (Blair, 1950). In the mountains, they inhabit rocky outcrops in ravines, along bluffs, and manmade rock walls in the oak-juniper woodland. At lower elevations they have been found in mines, along road cuts, and along limestone bluffs on the Rio Grande (Scudday, 1996; J.F. Scudday, personal communication; unpublished data). Spotted chirping frogs are nocturnal,and may be found by day under rocks, leaf litter, and debris (Bartlett and Bartlett, 1999a).
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Periods of drought may severely inhibit the activity of this frog (Minton, 1959; J.F. Scudday, personal communication).
I. Seasonal Migrations. Spotted chirping frogs are not known to make seasonal migrations and probably maintain a home range similar to cliff chirping frogs.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. No other saxicolous amphibians are known to co-occur with spotted chirping frogs. Red-spotted toads (Bufo punctatus) and Canyon treefrogs (Hyla arenicolor) have been observed in the same canyons as spotted chirping frogs (unpublished data).
L. Age/Size at Reproductive Maturity. In a study of preserved material from the United States and Mexico, adult male and female spotted chirping frogs ranged from 20.6–29.0 mm SVL and 25.7–31.0 mm, respectively (Lynch, 1970). Adult, calling males from the Chisos Mountains, Texas, were 30–33 mm (n = 6) and weighed 1.8–2 g (n = 3; unpublished data).
M. Longevity. Unknown.
N. Feeding Behavior. Gaige (1931) found ants, beetles, a termite, and an isopod in the stomach of one female from the Chisos Mountains. While releasing an individual during daylight I observed it capture and eat a winged termite. The peak of activity in summer 1999 coincided with a large flight of termites (unpublished data), suggesting that they constitute an important and abundant prey source during this period. It is suspected that spotted chirping frogs feed on other small insects and invertebrates, including spiders and small crustaceans (Garrett and Barker, 1987).
O. Predators. Unknown.
P. Anti-Predator Mechanisms. Spotted chirping frogs are quick to jump to cover when disturbed (unpublished data). Although Conant and Collins (1998) state that spotted chirping frogs will run when disturbed, rather than leaping or hopping.
Q. Diseases. Unknown.
R. Parasites. Larval mites (Hannemania hylae) are known parasites of spotted chirping frogs (Gaige, 1931; Lynch, 1970; Jung et al., 2001).
4. Conservation. Spotted chirping frogs have no federal or state conservation status. They are common and relatively abundant in several areas of Big Bend National Park (unpublished data). There is little large-scale development in the Park and in those places where there is (e.g., the Basin), spotted chirping frogs are still found. In fact, on several occasions, attempts to locate random individuals in remote areas resulted in observing frogs in manmade rock walls (trail retaining walls, erosion control barriers) despite the availability of more natural habitat nearby. Like their other generic counterparts in the United States, spotted chirping frogs seem to thrive with certain types of human-mediated habitat disturbance. Due to the remote nature of much of the spotted chirping frogs' native habitat, they are most likely under no immediate population threats.
Acknowledgments. Funding for work in Big Bend National Park was provided by PRIMENet (Park Research and Intensive Monitoring of Ecosystems Network), an interagency effort of the Environmental Protection Agency and National Park Service. I thank Raymond Skiles, wildlife biologist at Big Bend National Park, for making available his vast knowledge of the area, and James Dixon and James F. Scudday, both long-time Texas herpetologists, who provided me with their expertise regarding this species in the region. I also thank Robin Jung and Sam Droege of the USGS Patuxent Wildlife Research Center, who provided support during my time of study.
1J. Eric Wallace
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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