Spotted Chorus Frog
© 2019 Nicholus Ledbetter (1 of 3)
Country distribution from AmphibiaWeb's database: Mexico, United States
Pseudacris clarkii (Baird, 1854[b])
Michael J. Sredl1
1. Historical versus Current Distribution. Spotted chorus frogs (Pseudacris clarkii) are distributed from extreme northeast Tamaulipas through central Texas and north through central Oklahoma and into central Kansas (Wright and Wright, 1949; Conant, 1975; Pierce and Whitehurst, 1990). A single adult male spotted chorus frog collected in McLean County, Illinois, was likely introduced as a tadpole during fish stocking (Shepard and Burdett, 2000). A population in Chouteau County, Montana, is also likely introduced (Conant, 1975). The report of spotted chorus frogs from New Mexico (Painter and Burkett, 1991) is based on a misidentification of an upland chorus frog (Pseudacris triseriata; Stuart, 1992), although spotted chorus frogs have been reported within 32.2 km of New Mexico (Tinkle and Knopf, 1964). Spotted chorus frogs may readily expand their range in dry years (Bragg, 1960b). No assessment of current range of this species has been done.
2. Historical versus Current Abundance. Little is known of historical abundance of spotted chorus frogs, and comments on historical abundance are few and largely anecdotal. Strecker (1902, in Wright and Wright, 1949) characterizes them as “an abundant species, especially so in the vicinity of marshes.” Similarly, Cope (1894, in Wright and Wright, 1949) noted them to be “abundant and noisy in pools near the Cimmaron River, at Tucker, Oklahoma.” No comprehensive studies of recent abundance have been conducted.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Spotted chorus frogs breed from January to early June, occasionally in summer to early October; breeding usually follows rains (Bragg, 1943a; Livezey and Wright, 1947; Wright and Wright, 1949; Smith, 1950; Kennedy, 1958; Blair, 1961a; Wiest, 1982). Olfactory cues may be important in locating natal ponds. Grubb (1973c) found that male and female spotted chorus frogs moved toward the odor of water from their home ponds in preference to that from foreign ponds that were sometimes only a few meters distant from the home pond. As male spotted chorus frogs approach the breeding pond, they will produce a call that differs from their typical breeding call (Bragg, 1943a). This call has been characterized as having a “pensive” or “pleading” quality to it. Bragg (1943a) speculated that this call may function to attract other males to appropriate breeding ponds. Large choruses quickly form after heavy rains in late winter, spring, late summer, and early fall (Blair, 1961a). Winter rains may induce a few males to call briefly. Spotted chorus frogs may delay breeding if spring is dry (Smith, 1950). Late breeding congresses may compensate partially for lack of breeding following spring droughts (Kennedy, 1958).
ii. Breeding habitat. Spotted chorus frogs breed in temporary and semi-permanent ponds, and in marshes, shallow water-lily ponds, roadside ditches, grassy ponds, mesquite ponds, buffalo wallows, flooded fields, and other transient pools (Burt, 1936; Bragg, 1943a; Wright and Wright, 1949; Jameson, 1956a; Kennedy, 1958). The water level of these ponds is usually high during the winter, so the fringe of grassland is included in the area covered by water (Burt, 1936). Jameson (1950a) noted a depth of 0.6–1.2 m in breeding ponds in Texas. Spotted frogs never breed in permanent water in Texas (Lord and Davis, 1956). In Oklahoma, they were observed to avoid deep water (Bragg, 1943a). Similarly, Smith (1950) stated that in Kansas, breeding “occurs in temporary, shallow pools, never in deep pools.” They also seem to avoid muddier, less protected livestock ponds where spadefoot toads (Scaphiopus sp.) and true toads (Bufo sp.) breed (Smith, 1934). Site fidelity may be high. In central Texas, spotted chorus frogs returned to the same breeding pond 2 yr in a row (Jameson, 1956a).
After breeding congresses form, males call from the grassy edges of the pond, while hidden (Wright and Wright, 1949). Males call while immersed in water to the level of the throat, with only the head exposed to the air (Bellis, 1957). Most calling is done at night (Wright and Wright, 1949; Blair, 1961a), but at the peak of breeding, males call day and night (Bragg, 1943a; Blair, 1961a). Air temperatures of a pond in Texas where males were observed calling ranged between 3.0 and 23.2 ˚C, averaging 14.5 ˚C in 1973 (Wiest, 1982). There may be “a considerable influence of one individual on the other” in the induction of vocalization or “leader effect” (Bragg, 1950d). The call has been described as “a loud, medium pitched, and rapidly repeated ‘whank, whank, whank’” (Bragg, 1943a). At temperatures below 12 ˚C, the call is a slow grinding note. Bellis (1957) found a positive correlation between water temperature and call frequency. Amplexus is axillary, and may last as long as 24 h (Smith, 1950d). The pair move about, chiefly through the efforts of the female.
i. Egg deposition sites. Eggs are deposited here and there in loose, irregular masses attached to plant stems (Livezey and Wright, 1947; Eaton and Imagawa, 1948; Wright and Wright, 1949), never > 75 mm from the surface of the water (Bragg, 1943a). In Oklahoma, typical oviposition sites were upright sedges or grasses, never twigs. Oviposition sites were never slanting vegetation, as is the habit of chorus frogs (P. "triseriata," Bragg, 1943b).
ii. Clutch size. Approximately 1,000 eggs are laid in masses ranging from 3–50 (Bragg, 1943a,b; Livezey and Wright, 1947; Wright and Wright, 1949; Smith, 1950d). Females likely lay > 1 clutch of eggs/year, but this has not been verified (Blair, 1961a).
Blair (1961a) reported an air temperature range of 8.3–27.2 ˚C, and a median air temperature of 17.2 ˚C during breeding. In 1973, air temperatures of a pond in Texas where spotted chorus frogs were ovipositing ranged from 11.8–21.3 ˚C, averaging 17.8 ˚C (Wiest, 1982). These frogs have been reported to breed at air temperatures as low as 5.5 ˚C (Bragg, 1943a). Laboratory experiments indicate that the lower lethal temperature limit of developing larvae is between 5.5–11.3 ˚C, while the upper lethal temperature limit is between 35.0–39.0 ˚C (Ballinger and McKinney, 1966). Eggs hatch in 2.5–3 d (Bragg, 1943a).
C. Larvae/Metamorphosis. Altig et al. (1998) describe the tadpoles of spotted chorus frogs. Bragg (1957) noted that color of larvae varies greatly, depending on the environment. Tadpoles collected from clear, stained waters were darker than tadpoles collected from a muddy ditch. Those collected from the muddy ditch were characteristic of the original description (Bragg, 1957). Tadpoles reach a maximum body length of 30 mm (Wright and Wright, 1949).
i. Length of larval stage. Spotted chorus frog larvae metamorphose in 30–45 d at a SUL between 8.0–13.0 mm in Texas (Wright and Wright, 1949; Blair, 1961a), while those in Kansas have been reported to reach between 13.5–17.0 mm (Smith, 1934). In laboratory experiments, length of larval period had a weak inverse correlation with multilocus heterozygosity (Whitehurst and Pierce, 1991).
ii. Larval requirements. Larval requirements are poorly understood. Rosenberg and Pierce (1995) found that growth of spotted chorus frog tadpoles was depressed in acidic conditions. Although a prairie species, they occur in east Texas, a region where acidic conditions potentially can be found (Pierce and Whitehurst, 1995).
a. Food. No detailed study of tadpole diet has been conducted.
b. Cover. No detailed study of tadpole habitat needs has been conducted.
iii. Larval polymorphisms. None reported.
iv. Features of metamorphosis. Recently metamorphosed spotted chorus frogs are diurnal (except when it is extremely hot and dry), agile, and difficult to catch. Wright and Wright (1949) noted that they have very delicate skin. They remain at the pond for a few weeks, then scatter widely (Bragg, 1943b).
v. Post-metamorphic migrations. Except that they disperse widely, little is known of post-metamorphic migrations.
D. Juvenile Habitat. No detailed study of the habitat characteristics of juvenile spotted chorus frogs has been conducted.
E. Adult Habitat. Very little is known about adult habitat characteristics. Spotted chorus frogs principally are found in prairies and prairie islands in savannas (Bragg, 1943b; Conant, 1975; Pierce and Whitehurst, 1990). After emerging from hibernacula, adults are thought to range through pastures and fields while foraging; they do not frequent stream margins or pools except to breed (Bragg, 1943a).
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Aestivation is not reported, but spotted chorus frogs have been noted to have periods of inactivity during hot, dry weather (Bragg, 1943a).
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Burt (1936) observed that an adult spotted chorus frog found in mid March under a rock may have hollowed out earthen tunnels where it may have undergone at least temporary hibernation. Little else is known about hibernation.
K. Interspecific Associations/Exclusions. Spotted chorus frogs have been reported to occur with numerous temporary and semi-permanent pond breeding amphibians, including plains spadefoot toads (Spea bombifrons), Couch’s spadefoot toads (Scaphiopus couchii), eastern spadefoot toads (Scaphiopus holbrookii), Great Plains toads (B. cognatus), Texas toads (B. speciosus), southern toads (B. terrestris), Gulf Coast toads (B. nebulifer), Woodhouse’s toads (B. woodhousii), northern cricket frogs (Acris crepitans), eastern gray treefrogs (H. versicolor), spring peepers (Pseudacris crucifer), Strecker’s chorus frogs (P. streckeri), upland chorus frogs (P. feriarum), Rio Grande leopard frogs (R. berlandieri), American bullfrogs (R. catesbeiana), southern leopard frogs (R. sphenocephala), and western narrow-mouthed toads (Gastrophryne olivacea; Burt, 1936; Bragg, 1943a; Wright and Wright, 1949; Jameson, 1950a, 1956a; Blair, 1961a; Wiest, 1982; Altig et al., 1998).
Interactions of spotted chorus frogs and the Pseudacris nigrita complex (P. nigrita, P. clarkii, P. triseriata, P. brachyphona, P. brimleyi) have been of great interest to biologists studying speciation (Mecham, 1958; W.F. Blair, 1964a). Call, habitat differences, and time of breeding are thought to be important isolating mechanisms. Michaud (1962) demonstrated that female spotted and upland chorus frogs can resolve calls of their own species. Time of breeding in the overlap zone of these two species in Texas and Oklahoma is less clear. In some areas, the breeding peak of the spotted chorus frog comes later than that of the upland chorus frog (Lindsay, 1958, in Mecham, 1958), while in other areas breeding of these two species peaks about the same time (Lord and Davis, 1956). Lord and Davis (1956) observed that in pools where spotted chorus frogs abounded, upland chorus frogs were not common. However, in pools where upland chorus frogs were abundant, spotted chorus frogs were just as abundant. Bragg (1960b) studied populations of spotted and upland chorus frogs in a prairie-savanna ecotone between 1935–'59. In wet years, upland chorus frogs (savanna dwelling) expanded their range westward into more prairie-like habitat, while in dry years spotted chorus frogs (prairie dwelling) expanded their range eastward into more savanna-like habitat (Bragg, 1960b). Although these two species often co-occur in the same breeding ponds, there have been few reports of natural hybrids or observation of interamplexion (Lord and Davis, 1956; W.F. Blair, 1964a).
The range of spotted chorus frogs also overlaps with Strecker’s chorus frogs. Although spotted chorus frogs breed a little later than Strecker’s chorus frogs, there is overlap, and time of breeding does not appear to be as important an isolating mechanism as differences in calls (Blair, 1961a).
L. Age/Size at Reproductive Maturity. Wright and Wright (1949) report breeding sizes of males to be between 20–29 mm; females, 21–31 mm SUL. Age at reproductive maturity and growth rates have not been investigated.
M. Longevity. In the wild, spotted chorus frogs live at least 2 yr (Jameson, 1956a).
N. Feeding Behavior. Adults are thought to forage in pastures and fields, but little else on feeding behavior or diet has been reported.
O. Predators. Predators of spotted chorus frogs are not well known. Western ribbon snakes (Thamnophis proximus; Clark, 1974) are known predators of spotted chorus frogs. Other garter snakes (Thamnophis spp.) and water snakes (Nerodia spp.) are likely important predators.
P. Anti-Predator Mechanisms. Spotted chorus frogs are wary: upon slight disturbance spotted chorus frogs duck beneath the water’s surface (Burt, 1936). Other anti-predator mechanisms have not been reported.
Q. Diseases. None reported.
R. Parasites. Spotted chorus frogs have been found to be infected with protozoans (Hexamita intestinalis, Tritrichomonas augusta, Opalina sp., Nyctotherus cordiformis, and Myxidium serotinum), nematodes (Cosmocercoides variabilis), cestodes (Cylindrotaenia americana), and larval intradermal mites (Hannemania sp.; McAllister and Upton, 1987a; McAllister, 1991).
4. Conservation. Spotted chorus frogs are not protected by any state or by the U.S. Federal Government. Little is known of their historical abundance, and what is known is largely anecdotal. Similarly, no assessment of their current range has been done. Spotted chorus frogs are known to naturally expand their range in dry years (Bragg, 1960b). At least one, human-mediated, introduced population has been established in Chouteau County, Montana. According to Levell (1997), in Kansas, spotted chorus frogs can be commercially collected for sale as bait.
1Michael J. Sredl
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 9 Jul 2020.
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