Eleutherodactylus (= Syrrhophus) cystignathoides (Cope,
Rio Grande Chirping
J. Eric Wallace1
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
1. Historical versus Current Distribution. The type locality of Rio Grande
chirping frogs (Eleutherodactylus cystignathoides) is Potrero, near
Cordoba, Veracruz, Mexico (Cope, 1877). The type locality of the subspecies found in
the United States (E. c. campi) is Brownsville, Cameron
County, Texas (Stejneger, 1915). In the United States, Rio Grande chirping frogs
are native to extreme south Texas along the lower Rio Grande Valley in Cameron and
Hildago counties. They have been introduced, probably by way of the potted plant
trade, into Corpus Christi, Dallas, Houston, Kingsville, Tyler, San Antonio, Huntsville,
and the vicinity of LaGrange, Texas (Dixon, 2000). Some of these introduced
populations have become established in the natural environment (McGown et al., 1994;
Lutterschmidt and Thies, 1999).
regarding this species in Mexico, see Martin (1958), Lynch (1970), and Flores-Villela
(1993). Dixon (2000) provides a current, comprehensive bibliography of Rio Grande
chirping frogs. Popular accounts in field guide format may be found in Cochran and
Goin (1970), Smith and Barlowe (1978), Garrett and Barker (1987), Behler and King (1998),
Conant and Collins (1998), and Bartlett and Bartlett (1999a).
For discussions of
the historical and current biogeography of the subgenus Syrrhophus (Hedges,
1989) and the species cystignathoides, see Blair (1950), Morafka (1977), and
Duellman and Sweet (1999).
2. Historical versus Current Abundance. Rio Grande chirping frogs are abundant
and thrive in the presence of humans (Wright and Wright, 1949; Conant and Collins,
1998). Brach (1992) suggests that these semi-tropical frogs are able to persist
north of their native range by seeking cover under ornamental rockwork that retains heat
3. Life History Features.
Reproduction is terrestrial.
i. Breeding migrations. Rio Grande chirping frogs do not form breeding
aggregations and, as with cliff chirping frogs (E. marnockii), may
maintain territories (Hayes-Odum, 1990). Breeding occurs from April–May, when
males may be heard both night and day (Wright and Wright, 1949). Hayes-Odum (1990)
found that adults called actively when the relative humidity was above 82% and when air
and substrate temperatures were 16–29 ˚C. In an introduced population in
Houston, Texas, males called on rainy nights from April–July (Hayes-Odum,
1990). Courtship behavior was observed in captivity and amplexus was axillary
(Hayes-Odum, 1990). Wright and Wright (1949) noted inguinal amplexus with captive
cliff chirping frogs.
ii. Breeding habitat. See "Adult Habitat" below.
i. Egg deposition sites. Eggs were laid just under the soil surface in the
laboratory (Hayes-Odum, 1990).
ii. Clutch size. Eggs are laid in clutches consisting of 5–13 large eggs
(3–3.5 mm in diameter; Wright and Wright, 1949; Hayes-Odum, 1990).
Development. Complete metamorphosis occurs within the egg; young hatch as froglets,
ranging in size from approximately 5–8.5 mm (Wright and Wright, 1949; Hayes-Odum,
1990). In a laboratory setting, eggs hatched after 14–16 d of artificial
incubation (Hayes-Odum, 1990).
i. Brood sites. Brooding has not been observed (see "Parental care"
ii. Parental care. In a laboratory setting, Hayes-Odum (1990) observed one female
leave her eggs shortly after laying them.
Habitat. Hayes-Odum (1990) reported that hatchlings were found on wet nights.
General juvenile habitat characteristics are likely similar to adult characteristics.
Habitat. Rio Grande chirping frogs inhabit low elevation coastal plains in the
Tamaulipan Province (Blair, 1950). Most published accounts of these frogs in the
United States (including introduced populations) consist of observations in urban
settings. Rio Grande chirping frogs are often associated with debris piles and
watered lawns and gardens (Stejneger, 1915; Wright and Wright, 1949; Hayes-Odum, 1990;
Brach, 1992). More natural environments include dense vegetation along riparian
areas and the edges of lotic, semi-permanent waters (Martin, 1958; Conant and Collins,
1998). Rio Grande chirping frogs can be found under cover objects during the day
(Wright and Wright, 1949). Brach (1992) suggests that these semi-tropical frogs are
able to persist well north of their native range (e.g., Tyler, Texas) by seeking cover
under ornamental rockwork that retains heat and moisture. They are known to
utilize arboreal perches 0.2–1.5 m above the ground (Martin, 1958; Hayes-Odum,
1990; Brach, 1992).
F. Home Range
Territories. Hayes-Odum (1990) observed several instances of one frog moving toward
another stationary frog, resulting in the displacement of the stationary frog.
From these observations, she suggested that Rio Grande chirping frogs may be
Aestivation/Avoiding Dessication. As with other members of the genus, activity
diminishes with dry conditions.
Associations/Exclusions. Unknown, but may include (as inferred from microhabitat
similarities) white-lipped frogs (Leptodactylus fragilis), marine toads
(Bufo marinus), Gulf Coast toads (B. nebulifer),
sheep frogs (Hypopachus variolosus), and western narrow-mouthed toads
(Gastrophryne olivacea; Blair, 1950; Conant and Collins, 1998).
L. Age/Size at
Reproductive Maturity. Rio Grande chirping frogs range in size from 15–25.5
mm SVL (Wright and Wright, 1949). Measurements of preserved material from animals
throughout their range (both subspecies) were 16.0–23.5 mm for males and
16.0–25.8 mm for females (Lynch, 1970). The largest individual observed by
Wright and Wright (1949) was a female; females tend to be larger (Hayes-Odum,
1990). In reproductively mature females, eggs may be visible through the thin skin
of their abdomen (Hayes-Odum, 1990).
Behavior. Generally unknown, but one individual regurgitated cockroach eggs during
capture (Wright and Wright, 1949).
Mechanisms. To avoid capture, Rio Grande chirping frogs are quick to leap to
shelter in crevices or under cover objects (Wright and Wright, 1949).
Larval forms of Abbreviata sp. have been found in Houston populations
(introduced) of Rio Grande chirping frogs (McAllister and Freed, 1992).
4. Conservation. Rio Grande chirping frogs have no federal or state
conservation status. They are common and relatively abundant in a number of
different urban settings and have been since their early discovery (e.g., Wright and
Wright, 1949). They obviously can cope with at least certain types of
human-mediated habitat disturbance. This is further evidenced by their ability to
acclimate to novel habitats into which they are introduced, some very different from
their native environment (e.g., Brach, 1992).
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 (E. marnockii)
and other amphibians. 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
1J. Eric Wallace
School of Renewable Natural Resources
University of Arizona
Tucson, Arizona 85721
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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