© 2009 Andreas & Christel Nöllert (1 of 6)
Country distribution from AmphibiaWeb's database: Mexico, United States
Bufo speciosus Girard, 1854
Gage H. Dayton1
1. Historical versus Current Distribution. In the United States, Texas toads (Bufo speciosus) are distributed throughout the western 2/3 of Texas, west into southeastern New Mexico, and north into western Oklahoma, including the panhandle (McAllister and Trauth, 1993; Killebrew et al., 1995; Dixon, 2000). The distribution of Texas toads has not changed as dramatically as other Bufo species throughout the United States (J. Dixon, personal communication).
2. Historical versus Current Abundance. Brown (B.C., 1950) reported that Texas toads are one of Texas’ most abundant toads. However, data on changes in abundance of Texas toads over their entire range do not exist. Dixon (2000) reports that populations of Texas toads in the Rio Grande Valley, Texas, are declining due to the heavy use of pesticides and herbicides on agricultural lands. The decline of Texas toads in the Rio Grande Valley is somewhat alarming, as Texas toads represent one of the most abundant toads in the region (Thorton, 1977). Population trends of Texas toads in southeast New Mexico appear stable (C.W.P., personal observations).
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Adults aggregate at temporary pools within a few hours after a rain event. Breeding males call any time of day for up to 4 d after a rain event, calling most intensely at night (Moore, 1976; G.H.D., unpublished data). Males call while clinging to partially submerged vegetation or in the shallow regions of the breeding site. Their call consists of a continuous series of explosive trills, each lasting approximately 1.5 s, given at intervals of about 1 s (Stebbins, 1985). Axtell (1958) reported that calling males were “passive in their relationship with the females until they approached and made body contact.” Axtell (1958) also reported that females preferred the loudest calling male (also the largest) over smaller individuals in the vicinity.
ii. Breeding habitat. Texas toads breed in temporary rain pools in open areas near streams, in pools in creek valleys, and in irrigation ditches, cattle tanks, and temporary desert pools (Bragg and Smith, 1943; Wright and Wright, 1949; Moore, 1976; Dayton and Fitzgerald, 2001). Breeding season is from April–September following heavy rains (Bragg and Smith, 1943; Moore, 1976).
i. Egg deposition sites. Eggs are typically deposited around the base of submerged vegetation. Multiple pairs will deposit eggs around the same clump of grass.
ii. Clutch size. Eggs are brown and yellow, crowded (14–20 eggs/30 mm), about 1.4 mm in diameter, and hatch in 2 d (Wright and Wright, 1949). There are no data on clutch size for Texas toads. However, the clutch of an average sized Great Plains toad (Bufo cognatus), closely related to Texas toads, is about 11,000 eggs (Krupa, 1994); this number could be used as an estimate until data on Texas toads are available.
i. Length of larval stage. The tadpole stage lasts from as few as 18 d (Moore, 1976) to approximately 60 d (Wright and Wright, 1949).
ii. Larval requirements.
a. Food. Tadpoles scrape algae off of submerged vegetation and substrate. There are no data on the specific dietary preference of Texas toad tadpoles.
b. Cover. Cover may be aquatic vegetation or rocky substrate, although this may vary from site to site. When startled, tadpoles will often retreat to deeper areas within the pool.
iii. Larval polymorphisms. Have not been documented.
iv. Features of metamorphosis. Studies have reported time to metamorphosis from 18 d–60 d (Wright and Wright, 1949; Moore, 1976). Thus, timing and duration of metamorphosis varies depending upon site characteristics (i.e., water temperature, presence of predators, densities, and resource availability).
v. Post-metamorphic migrations. Recently metamorphosed toadlets usually remain near the natal pool until the pool has dried (Degenhardt et al., 1996). No data are available on migration distance; however, dispersal is likely correlated to the proximity of suitable adult habitat. Moore (1976) monitored the growth of recently metamorphosed toads for 7 mo in southern Texas. He calculated a growth rate of approximately 10 mm/mo, which indicates that toads born early in the breeding season would reach sexual maturity in time to breed the following year. Toadlets will burrow into the soil, take refuge in mud cracks, or retreat beneath vegetation and other cover to prevent desiccation.
D. Juvenile Habitat. Although Texas toads burrow, they also utilize habitat beneath rocks and in mud cracks and gopher burrows (Wilks, 1963; G.H.D., personal observation). The critical habitat characteristics for juvenile Texas toads are likely similar to those of the adults, i.e., high water retention in soils and/or relatively high humidity in refuge sites.
E. Adult Habitat. Texas toads are a desert species found in association with permanent streams, irrigation ditches, watering tanks, and ephemeral pools (Jameson and Flury, 1949; Wright and Wright, 1949; Dayton, 2000a). They are found in grassland, open woodland, and mesquite-savanna habitats. Texas toads prefer sandy soils, where they burrow. However, they are associated with soils that are frequently inundated and have a relatively high percentage of clay (Dayton, 2000a). Habitat characteristics for adults are likely similar to those of juveniles. It is crucial for adults to take refuge in sites with relatively high humidity and/or water holding capacity to prevent desiccation during dry periods that can last for several months.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Texas toads burrow in mud, inhabit gopher burrows, and take refuge beneath rocks and in mud cracks to avoid desiccation (Wright and Wright, 1949; Wilks, 1963; G.H.D., personal observation).
I. Seasonal Migrations. During the breeding season, migrations to breeding sites occur. Distance traveled by the toads is unknown and undoubtedly varies depending upon suitable habitat surrounding each breeding site.
J. Torpor (Hibernation). During dry periods, toads remain dormant in refuge sites.
K. Interspecific Associations/Exclusions. Texas toads breed in sites also occupied by Gulf Coast toads (B. nebulifer), green toads (B. debilis), western narrow-mouthed toads (Gastrophryne olivacea) and Couch's spadefoot toads (Scaphiopus couchii, Wright and Wright, 1949; Bragg, 1955a; G.H.D., personal observation). They will also breed and hybridize with Woodhouse's toads (Bufo woodhousii) and Great Plains toads (Blair, 1961b; Ballinger, 1966; Rogers, 1973a,b).
L. Age/Size at Reproductive Maturity. Males 52–78 mm; females 54–91 mm (Wright and Wright, 1949).
M. Longevity. The life span of Texas toads in the wild is unknown. However, a wild-caught specimen was kept in the Philadelphia Zoo for 4 yr, 3 mo. Sex and age at the time of capture of this individual was unknown (Bowler, 1977).
N. Feeding Behavior. Texas toads are opportunistic feeders that take a diverse array of terrestrial and flying arthropods (Degenhardt et al., 1996). The stomach contents from one individual included hemipterans, coleopterans, and hymenopterans (Malone, 1999).
O. Predators. Grackles (Quiscalus quiscala), beetle larvae (Dytiscidae, Hydrophilidae), and yellow mud turtles (Kinosternon flavescens) will feed on tadpoles in drying pools (Wright and Wright, 1949; Dayton and Fitzgerald, 2001). Garter snakes (Thamnophis sp.) also likely prey upon all life stages.
P. Anti-Predator Mechanisms. Texas toads secrete toxic substances to deter predators. Tissue samples from 13 specimens from two localities in Texas revealed the presence of 5-hydroxytryptamine, N-methyl-5-hydroxytryptamine, and dehydrobufotenine (Cei et al., 1968).
Q. Diseases. No disease outbreaks have been reported in Texas toad populations.
R. Parasites. The gall bladder myxosporean Myxidium serotinum has been found in Texas toads (McAllister and Trauth, 1995; McAllister et al., 1995a). Kuntz (1941) reported the nematotaeniid tapeworm, Distoichometra bufonis, from Texas toads from Oklahoma.
4. Conservation. Although historical data on the abundance and distribution of Texas toads over their entire range do not exist, population and abundance trends throughout the majority of their range appear to be stable (J. Dixon, personal communication; C.W.P. personal observations). Declines have been observed in agricultural areas in southern Texas where pesticide and herbicide use is heavy (Dixon, 2000). Texas toads can be locally abundant and do not seem to be undergoing the dramatic declines that are being observed for some of the other amphibian species in North America.
1Gage H. Dayton
2Charles W. Painter
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Jul 2019.
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