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Chihuahuan Green Toad

Anaxyrus debilis (Girard, 1854)

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Overview
The Chihuahuan Green Toad (Anaxyrus debilis) is characterized by dry skin, a rounded snout, and enlarged parotoid glands—either kidney-shaped or elongate—positioned posterior to each eye. Unlike many congeners, it lacks cranial crests. Dorsal coloration is typically green to yellow-green with black spots or streaks, often forming a reticulate pattern. The venter is yellowish, variably marked with dark pigment. Males exhibit dark throats; females have yellowish throats and are generally larger.
The labial tooth row formula in tadpoles is 2/2, a unique and derived (apomorphic) trait within the genus, shared only with close relatives A. kelloggi (western Mexico) and A. retiformis (Arizona and Sonora).
Adults typically range from 32–50 mm (1¼–2 inches) in snout–vent length. The largest known Kansas specimen is a 44 mm (1¾ inch) female (KU 5652) from Morton County, collected by T.E. White and E.H. Taylor on 15 August 1928. The maximum recorded size across the species’ range is 54 mm (2⅛ inches) (Powell et al. 2016).

Distribution
The Chihuahuan Green Toad (Anaxyrus debilis) is currently restricted to rangeland and canyon systems above the Smoky Hill River and Ladder Creek drainages in Greeley, Logan, Wallace, and Wichita counties, Kansas. Historically, its range likely extended continuously (excluding the sandy alluvial valley of the Arkansas River) from Logan and Wallace/Sherman counties southward to populations in northwestern Oklahoma, northern Texas, northeastern New Mexico, and southeastern Colorado. Prior to widespread habitat alteration in the mid-19th century, the region consisted primarily of short-grass prairie interspersed with playa wetlands—habitats no longer suitable for A. debilis due to intensive cultivation and hydrological modification.
All records from Morton County (Cragin 1894; Taylor 1929; Hill 1931; KU 5643–54; MVZ 43326) predate the Dust Bowl era of the 1930s. Additional unvouchered or poorly localized reports include specimens from Grant County (KU 5642; Kellogg 1932), Hamilton County (Cragin 1894; see Remarks), and Barber County (Cragin 1894).

Reproduction
Burkhart (1984) and Taggart (1992) studied Anaxyrus debilis in western Kansas, providing foundational data on its ecology and life history. This species inhabits rugged upland topography within open grassland systems at elevations ≥2,500 ft, in regions receiving <20 inches of annual precipitation. Preferred microhabitats include intermittently moist areas along drainages, cattle tanks, and small pond dams. The species is highly secretive and primarily nocturnal.
Cragin (1894) described the species as abundant during September rainfall along the Cimarron River in Morton County. Taylor (1929) reported hail-killed specimens in a temporary pool on 8 August and observed individuals sheltering under rocks on the bluffs north of the river. Roth and Collins (1979) documented diurnal activity in Wallace County on 10 June, where a female was found on a south-facing slope of a dry ravine with rocky, sandy soils.
Anaxyrus debilis often shelters beneath rocks or in mammal burrows. Remaining populations persist in uncultivated native prairie and canyon systems; much former habitat has been lost to agricultural development. Breeding is opportunistic and tied to precipitation events from late May through early September (Sullivan 1984; Degenhardt et al. 1996; Taggart 1997). Reproductive sites include flooded fields, roadside ditches, cattle tanks, and other ephemeral pools. Eggs are typically deposited singly or in short clumped strings, loosely attached to aquatic vegetation.
Reproductive observations include:
Taylor (1929): Chorusing on 8 August in Morton County.
Roth (pers. comm. 1980; in Collins 1993): Day and night chorusing from 17–18 June in Wallace County; ~100–120 males observed in a canyon system, with one amplexed pair on land.
Burkhart (1984): Chorusing in Logan County from 26 June to 1 July in flooded grassy areas near creeks and arroyos.
Taggart (1992, 1997): Chorusing recorded 12 June to 2 September; egg-to-toadlet metamorphosis observed in 8 days under optimal conditions.
Egg counts from females in Wallace County were 975 and 1,610 (Irwin, pers. comm.; Collins 1993). One clutch contained 1,287 non-adhesive eggs deposited singly; ova averaged 0.98–1.15 mm in diameter. Metamorphosis occurs at ~19 mm SVL (3/4 in). Larval duration varies: Strecker (1926) suggested <3 weeks, Burkhart (1984) estimated >25 days, and Taggart (1997) observed development completed in 8 days.
Toadlets often utilize deep fissures in clay substrates of drying pools for shelter and moisture retention (Seymour 1972; Creusere & Whitford 1976; Taggart 1997). Juveniles may remain at hatching sites for up to 55 days, using vegetation and soil cracks for cover.
Taggart (1992) reported juvenile A. debilis feeding on brown ants, small moths, beetles, and grasshoppers.

Remarks
The Chihuahuan Green Toad was first reported in Kansas by Cragin (1894), based on individuals he observed on 4 September 1886 in Morton and southern Hamilton counties. He also mentioned a specimen from western Barber County; however, A. debilis is not known to occur there. The earliest extant Kansas specimen is KU 5642, collected in 1911.
Historically, A. debilis was more widespread in west-central Kansas, likely forming a continuous distribution (excluding the Arkansas River sand prairies) with populations in northwestern Oklahoma, northern Texas, northeastern New Mexico, and southeastern Colorado. Habitat conversion to dryland agriculture and hydrological modification, particularly during and after the Dust Bowl of the 1930s, resulted in widespread habitat loss.
A disjunct northern population was rediscovered by Roth and Collins (1979) in Wallace County (UMMZ 67442, collected in 1929). Subsequent work by Burkhart (1984) and Taggart (1997) documented populations in Logan, Greeley, and Wichita counties, particularly along the Smoky Hill River and Ladder Creek drainages. These represent the only known extant populations in Kansas and are geographically and ecologically isolated from other parts of the species’ range.
Within these northern populations, A. debilis is most frequently encountered on chalk flats, Ogallala outcrops, and associated breaks. Records from Morton, Grant, Hamilton, and Barber counties are questionable or unverifiable. Cragin’s 1886 reference to Hamilton County likely refers to present-day Stanton County, which was not established until 1887. The Hamilton County specimens cited by Taggart (1997) were in fact from Greeley County. Kellogg (1932) reported one specimen from Greeley County (9 mi NE of Tribune, KU) and six from Logan County (KSC 50–55), though the latter are now lost. The Barber County record (Cragin 1884) lacks a voucher and lies over 225 km from other known populations.
In response to presumed extirpation in southwestern Kansas, the Kansas Department of Wildlife and Parks initiated reintroduction efforts from 1991 to 1993 at multiple sites in the Cimarron National Grassland. Despite annual surveys since 2001, no A. debilis have been detected at release sites.
The closest extralimital populations occur along the Cimarron River in Oklahoma (~43 km west of Morton County) and the Arkansas River in Colorado (~101 km west of Hamilton County). Future survey efforts should target Stanton, Sherman, Morton, Hamilton, and Grant counties.
A population genetics study is currently underway to compare these northern populations with others across the species’ range, which may clarify taxonomic status and historical biogeography. The Kansas populations are hypothesized to have been isolated by the Arkansas River sand prairies for as long as 10 million years.
Where it persists in Kansas, A. debilis is locally abundant and often the most frequently encountered Anaxyrus species under suitable conditions. Rundquist (1979) previously questioned the validity of records from Barber, Hamilton, and Greeley counties available at that time.
The species was listed as Threatened in Kansas in 1987. No formal recovery plan has been completed. Under Kansas Administrative Regulations, critical habitat is defined as any site with a self-sustaining population of a threatened or endangered species, or areas deemed essential for conservation.
Designated critical habitat for A. debilis includes:
All native prairie lands and waters bounded by a line beginning at the SE corner of Sec. 36, T15S, R37W (Logan–Wichita Co. line), extending due north to the Smoky Hill River (Sec. 24, T13S, R37W), west along the river to the K-27 crossing (Sec. 27, T13S, R40W, Wallace County), then south along K-27 to the SW corner of Sec. 35, T15S, R40W, and east along the county lines back to the point of origin. This includes suitable habitat in Logan and Wallace counties.
All appropriate habitats within the Cimarron National Grassland, Morton County.
Burkhart (1984) expressed concern over habitat degradation from groundwater depletion and feedlot pollution. Collins and Collins (1991) noted the absence of this species at historical localities in Morton County and concluded it was extirpated from the area by the late 1920s. Taggart (1992) observed predation of A. debilis larvae by Plains Garter Snakes (Thamnophis radix).
Based on a captive individual, Snider and Bowler (1992) reported a maximum longevity of five years and three months.

References

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Cragin, Francis W. 1894. Herpetological notes from Kansas and Texas. Colorado College Studies Fifth Annual Publication:37-39.

Taylor, Edward H. 1929. List of reptiles and batrachians of Morton County, Kansas, reporting species new to the state fauna. University of Kansas Science Bulletin 19(6):63-65.

Hill, J. Eric. 1931. An addition to the herpetological fauna of Kansas. Science 74(1926):547-548.

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THE CENTER FOR NORTH AMERICAN HERPETOLOGY — Accessed: Tuesday 09 June 2026 13:10 CT