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Xenopus laevis   (Daudin, 1802)

Common Name: African Clawed Frog

Synonyms and Other Names: common platanna

Taxonomy: available through

Identification: Xenopus laevis is a flattened frog with a small head and a SVL (snout-vent length) of 50-over 130 mm (2-over 5 in) (Passmore and Carruthers, 1995; Kobel et al., 1996; Channing, 2001; Stebbins, 2003). The small, lidless eyes are located dorsally and turned upward (Stebbins, 2003). There is no visible tympanum (Channing, 2001). The forefeet have slender, unwebbed fingers (Channing, 2001; Stebbins, 2003), which are generally held pointed in a forward direction. In mature adults, the hindfeet are large, fully webbed, and have sharp black claws on the three innermost toes (Channing, 2001; Stebbins, 2003). These frogs have no tongue (Stebbins, 2003), and a minute tentacle is located beneath each eye (Passmore and Carruthers, 1995; Channing, 2001; Stebbins, 2003). The skin is very smooth except where the lateral line sensory system gives it a "stitched" appearance (Stebbins, 2002). The dorsal coloration of X. laevis is olive to brown, often with blotches, spots, or mottling (Passmore and Carruthers, 1995; Kobel et al., 1996; Channing, 2001; Stebbins, 2003). The African clawed frog does not hold its legs beneath itself to raise its body above the substrate when on land. No other frog in North America looks like this representative from the family Pipidae. The underwater calls, which are vocalized by both sexes, consist of long, rapid, high trills that slow down to a rattling "riitrriirrr…" (Kobel et al., 1996; Stebbins, 2003). The unique tadpole is translucent, has a tentacle on each side of its mouth, and a slender tail ending in a filament (St. Amant and Hoover, 1973; Thompson and Franks, 1978, 1979; Channing, 2001; Stebbins, 2003).

Xenopus laevis has been illustrated by a variety of authors (St. Amant and Hoover, 1973; von Filek, 1973; Deucher, 1975; Thompson and Franks, 1978, 1979; Stebbins, 1985, 2003; Videler and Jorna, 1985; Wever, 1985; Alderton, 1986; Mattison, 1987; Bartlett, 1989; Nieuwkoop and Faber, 1994; Passmore and Carruthers, 1995; Davies and Davies, 1997; Bernardini, 1999; Sire et al., 2000; Channing, 2001; Arnold and Ovenden, 2003).

Size: snout-vent length from 50 to over 130 mm

Native Range: The indigenous range of X. laevis is in sub-Saharan Africa including the countries of Namibia, South Africa, Lesotho, Swaziland, Botswana, Mozambique, Zimbabwe, the Congo, southwestern Kenya, eastern Nigeria, Zambia, Angola, Malawi, Tanzania, Sudan, Burundi, Rwanda, Uganda, Cameroon, and Gabon (Kobel et al., 1996; Tinsley et al., 1996; Poynton, 1999; Channing, 2001).

Alaska	Hawaii	Caribbean

Interactive maps: Continental US, Alaska, Hawaii, Caribbean

Nonindigenous Occurrences:

Arizona: Xenopus laevis were intentionally introduced into man-made ponds in Arthur Park Golf Course, Tucson, Pima County, Arizona, in the 1960s (Tinsley and McCoid, 1996). Other X. laevis were released into man-made bodies of water in southern Arizona by the same individual (Tinsley and McCoid, 1996). D. Swann (personal communication 1997) also has recently observed X. laevis in golf course ponds in Tucson.

California: In California, X. laevis were first collected from several localities in Orange County (Westminster, East Garden Grove-Winterburg Channel, Slater Lake, Fountain Valley [Ocean View Channel and an associated lake], and Greenfield-Banning Channel southeast of the Santa Ana River) in the late 1960s through the early 1970s (Lenaker, 1972; St. Amant and Hoover, 1973; Bury and Luckenbach, 1976; Tinsley and McCoid, 1996). Additional specimens were collected in Irvine, Orange County, in 1989 (Tinsley and McCoid, 1996). Since it was first introduced to California, X. laevis has been found in the following counties: San Bernardino County (Prado Basin, Chino Hills State Park) (Stebbins, 2003), San Diego County (Sweetwater [west Mt. Helix area], San Diego, Otay, and Tijuana Rivers, Tecolote Creek, and Spring Valley) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Santa Barbara County (Goleta Slough) (Stebbins, 2003), Los Angeles County (Santa Clara River, Munz Lake, Palmdale, Upper Rio Hondo, Compton Creek, Vasquez Rocks County Park, Edwards Air Force Base [Piute Ponds], and ponds and streams in Soledad, Agua Dulce and Placerita Canyons) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Riverside County (Arroyo Seco Creek and surrounding ponds, Santa Margarita River drainage, Vail Lake, and Riverside city) (McCoid and Fritts, 1980, 1989; Stebbins, 1985, 2003; Tinsley and McCoid, 1996), Imperial County (irrigation canals) (Stebbins, 1985), Ventura County (Santa Clara River and estuary, and Vern Freeman Diversion at Saticoy), Kern County (Edwards Air Force Base) (Stebbins, 2003), (Lafferty and Page, 1997; output from California Academy of Sciences), and Yolo County (University of California Davis campus) (Tinsley and McCoid, 1996; Stebbins, 2003).

Since it was first introduced to California, X. laevis has been found in the following counties:  San Bernardino County (Prado Basin, Chino Hills State Park) (Stebbins, 2003), San Diego County (Sweetwater [west Mt. Helix area], San Diego, Otay, Rancho Jamul, and Tijuana Rivers, Tecolote and Dulzura Creeks, and Spring Valley) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Kuperman et al., 2004; output from California Academy of Sciences), Santa Barbara County (Goleta Slough) (Stebbins, 2003), Los Angeles County (Santa Clara River, Munz Lake, Palmdale, Upper Rio Hondo, Compton Creek, Vasquez Rocks County Park, Edwards Air Force Base [Piute Ponds], and ponds and streams in Soledad, Agua Dulce and Placerita Canyons) (Bury and Luckenbach, 1976; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; output from California Academy of Sciences), Riverside County (Arroyo Seco Creek and surrounding ponds, Santa Margarita River drainage, Santa Ana River, Vail Lake, and Riverside city) (McCoid and Fritts, 1980, 1989; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Kuperman et al., 2004), Imperial County (irrigation canals) (Stebbins, 1985), Kern County (Edwards Air Force Base) (Stebbins, 2003), San Francisco County (Lily Pond in Golden Gate Park, San Francisco) (E. Mills in Lagos, 2004), Ventura County (Santa Clara River and estuary, and Vern Freeman Diversion at Saticoy) (Lafferty and Page, 1997; output from California Academy of Sciences), and Yolo County (University of California Davis campus) (Tinsley and McCoid, 1996; Stebbins, 2003).

Colorado: In June 1990, a single X. laevis was found under a submerged log in a relic beaver pond associated with the North Fork of the Snake River, Summit County, Colorado (Bacchus et al., 1993; Tinsley and McCoid, 1996; Livo et al., 1998). The water was partially frozen and slushy (Bacchus et al., 1993).

Florida: In 1964, 200 African clawed frogs were released into Hialeah (Red Road) Canal, Hialeah, Dade County, Florida, by an animal importer (King and Krakauer, 1966). An additional Florida record includes a single X. laevis found near Tampa, Hillsborough County, with no date of collection recorded (Tinsley and McCoid, 1996).

Massachusetts: Newly transformed X. laevis were collected from a small pond at the Acton Arboretum, Acton, Middlesex County, Massachusetts, in 1993 (Cardoza et al., 1993).

North Carolina: A population of X. laevis existed in fish hatchery ponds at an unknown locality in North Carolina during an unspecified period of time (Tinsley and McCoid, 1996). This is probably the same population cited by McCoid (in McCoid and Kleberg, 1995).

Virginia: A nonindigenous population of X. laevis was first observed in an artificial pond in a nature preserve (unnamed) in Virginia, "south of Washington, D.C.," in 1982 and sampled by R. Tinsley in 1987 (Tinsley and McCoid, 1996). Afterwards, local conservation personnel systematically collected hundreds of adults and juveniles (Tinsley and McCoid, 1996). Ernst et al. (1997) mention 30 recently transformed X. laevis collected from a pond at the Gulf Branch Nature Center, Arlington, Fairfax County, between 15 May and 30 June 1984 (C. Ernst, personal communication 1997). These probably represent the same population mentioned by Tinsley and McCoid (1996).

Wisconsin: In 1972, a "large number" of late-stage larval X. laevis were collected from an artificial pond in Greenfield Park, Milwaukee, Milwaukee County, Wisconsin (Tinsley and McCoid, 1996).

Other U. S. western states: African clawed frogs are "rumored" to occur in Nevada, New Mexico, Utah, and Wyoming (Smith and Kohler, 1978). Perhaps these are the other unnamed states vaguely alluded to by Tinsley and McCoid (1996).

Mexico: Nonindigenous X. laevis seem to have spread into Baja California, Mexico, through the Tijuana River and intersecting irrigation canals from California (Tinsley and McCoid, 1996).

Chile:  Nonindigenous African clawed frogs were first reported in Chile in 1985 (Tinsley and McCoid, 1996), although their original introduction may have taken place as early as 1973 (Jaksic, 1998). Additional specimens were captured on land with Sherman traps, in the Santiago area, in 2001 (Lobos and Garín, 2002).  Xenopus laevis has since spread into IV Region (Limari River Basin), VI Region, and throughout Metropolitan Region, and V Region (Lobos and Jaksic, 2005).

Atlantic: Nonindigenous X. laevis were collected from Ascension Island in the southern Atlantic, in 1944 and 1958, near the summit of Green Mountain (Loveridge, 1959). Additional X. laevis were observed in a mountaintop pond (probably from the same aforementioned population) in the early 1980s (Tinsley and McCoid, 1996).

Europe: Xenopus laevis specimens have been collected in the Hamburg area, Germany, and Gorichem and Utrecht, the Netherlands (Tinsley and McCoid, 1996). In the United Kingdom, populations of X. laevis have been found on the Isle of Wight, southern Wales, London, Kent, and various southwestern waterways in England (Arnold, 1995; Tinsley and McCoid, 1996; Arnold and Ovenden, 2002).

Means of Introduction: In most cases of nonindigenous occurrences the exact means of introduction is not clearly known. However, X. laevis has long been used in laboratory research, for studies in genetics, physiology, biochemistry, developmental biology, human pregnancy diagnosis (Deuchar, 1975; Thompson and Franks, 1978, 1979; Stebbins, 1985, 2003; Tinsley and McCoid, 1996), and they became established in many laboratory aquaria throughout the world in the 1950s and 1960s (Tinsley and McCoid, 1996). Earliest reports of established nonindigenous populations of X. laevis worldwide are coincident with the end of their use in human pregnancy diagnosis (Tinsley and McCoid, 1996). Loveridge (1959) claims that the established nonindigenous population of X. laevis on Ascension Island, in the southern Atlantic, was caused by the use of this species in diagnostic testing on that island during the World War II years. Moreover, X. laevis are popular aquarium pets, known for being nondemanding, unusual pets (von Filek, 1973; Alderton, 1986; Bartlett, 1989; Tinsley and McCoid, 1996; Davies and Davies, 1997). Because these frogs live relatively long lives (see below) they are often simply dumped into nearby waters due to loss of interest, the end of an experiment, or misguided ethics (Tinsley and McCoid, 1996). The release of 200 African clawed frogs into a canal in Dade County, Florida, was simply due to an animal importer carelessly dumping unwanted stock (King and Krakauer, 1966). The release of X. laevis into the Tucson area and nearby areas of southern Arizona was intentionally caused by a single individual (Tinsley and McCoid, 1996) – simple curiosity?

Status:

Massachusetts: The status of X. laevis remains unclear in Massachusetts, as the collection of newly transformed frogs (Cardoza et al., 1993) suggests a breeding population that may spread.

Virginia: Large numbers of X. laevis were removed from the artificial pond in Virginia through 1987 up to 1988; this may have eliminated them from this immediate vicinity, but it is not known if any frogs migrated to nearby habitat before this time (Tinsley and McCoid, 1996).

North Carolina: Xenopus laevis were eliminated from the fish hatchery ponds in North Carolina by draining the ponds (Tinsley and McCoid, 1996).

Florida: Currently there is no clear evidence for any established population of X. laevis in Florida (King and Krakauer, 1966; Tinsley and McCoid, 1996).

Wisconsin: No further X. laevis were collected from the artificial pond in Milwaukee, Wisconsin, in subsequent years after 1972, indicating they are not established (Tinsley and McCoid, 1996).

Colorado: Further collecting at the nonindigenous site in Summit County, Colorado, in June 1991 revealed no more African clawed frogs (Bacchus et al., 1993); thus, they are not established.

Arizona: The only established population of X. laevis in Arizona is in the golf course ponds in Tucson, Pima County (Stebbins, 1985, 2003; Tinsley and McCoid, 1996; D. Swann, personal communication 1997). It is probably this population that caused Howland (1996) to consider them established but not widespread in Arizona. African clawed frogs are unlikely to spread from the Tucson area, due to the surrounding desert habitat.

California:  African clawed frogs are well established in California (Stebbins, 1985, 2003; Laudenslayer et al., 1991; McCoid and Kleberg, 1995; Tinsley and McCoid, 1996).  Those populations of X. laevis in Orange, San Bernardino, San Diego, Los Angeles, Santa Barbara, San Francisco, Riverside, Imperial, Kern, and Ventura Counties are clearly established and invasive (Lenaker, 1972; St. Amant and Hoover, 1973; Bury and Luckenbach, 1976; McCoid and Fritts, 1980, 1989; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Lafferty and Page, 1997; Kuperman et al., 2004).  The population of X. laevis at the University of California Davis campus, Davis, Yolo County, was successfully eradicated through poisoning by the California Department of Fish and Game, and as of 1992 was no longer present (Tinsley and McCoid, 1996; Stebbins, 2003). Efforts are underway to eradicate the X. laevis in Golden Gate Park, San Francisco (Lagos, 2004). In southern California, X. laevis will continue to spread, assisted by the presence of numerous irrigation canals and ditches that are seasonally or anthropogenically flooded with water.

Other U.S. western states: The rumors of X. laevis existing in Nevada, New Mexico, Utah, and Wyoming have never been verified (Smith and Kohler, 1978).

Mexico: Xenopus laevis is established in Baja California, Mexico (Flores-Villela, 1993; Smith and Smith, 1993; Stebbins, 2003). These populations need to be monitored to determine their invasiveness and impact. Other worldwide localities: African clawed frogs are established in the United Kingdom and Ascension Island (Arnold, 1995; Tinsley and McCoid, 1996; Measey, 1998a, 2001; Measey and Tinsley, 1998; Arnold and Ovenden, 2002), and in Chile they are an established, highly invasive species (Tinsley and McCoid, 1996; Lobos and Garín, 2002; Lobos and Measey, 2002). The status of X. laevis in Germany and the Netherlands remains unknown (Tinsley and McCoid, 1996).

Other worldwide localities:  African clawed frogs are established in the United Kingdom and Ascension Island (Arnold, 1995; Tinsley and McCoid, 1996; Measey, 1998a, 2001; Measey and Tinsley, 1998; Arnold and Ovenden, 2002), and in Chile they are an established, highly invasive species (Tinsley and McCoid, 1996; Jaksic, 1998; Lobos and Garín, 2002; Lobos and Measey, 2002; Lobos and Jaksic, 2005).  The status of X. laevis in Germany and the Netherlands remains unknown (Tinsley and McCoid, 1996).

Impact of Introduction:

In many parts of its indigenous and nonindigenous range, X. laevis is regarded a pest (Rundquist, 1978; Channing, 2001).  In South Africa, mass migrations lead to large numbers of clawed frogs invading houses and clogging up irrigation pipes (Tinsley et al., 1996).  Migrating individuals in Africa also invade fish farms, consuming both fish and fish food, and are difficult to keep out (Channing, 2001).

In Riverside and San Diego Counties, California, X. laevis consumes native invertebrates, the eggs, tadpoles and adults of native frogs, and the nonindigenous western mosquito fish, Gambusia affinis (McCoid and Fritts, 1980; Stebbins, 2003).  Nonindigenous X. laevis inhabiting the Santa Clara River estuary in Ventura County, California, includes the endangered tidewater goby, Eucyclogobius newberryi, in its diet (Lafferty and Page, 1997).  Additional native Californian vertebrates consumed by X. laevis include western toads (Bufo boreas), arroyo chubs (Gila orcutti), and locally endangered threespine stickleback (Gasterosteus aculeatus) (Stebbins, 2003).   It in turn is prey for indigenous garter snakes, Thamnophis couchi hammondi, fish, and the nonindigenous bullfrog, Rana catesbeiana (Lafferty and Page, 1997).  African clawed frogs also carry a rather diverse parasite load (Prudhoe and Bray, 1982; Tinsley, 1996; Lafferty and Page, 1997) and individuals from nonindigenous populations in California harbor a variety of parasites (Kuperman et al., 2004); however, there are no studies to verify if these parasites pose a direct threat to nonindigenous ecosystems. In Chile, nonindigenous X. laevis are consumed by several species of native birds (Lobos and Jaksic, 2005). Overall, the impact of these hardy, adaptable, invasive frogs requires further study throughout its nonindigenous range.

Remarks:

The taxonomy and nomenclature of X. laevis has been summarized or reviewed by Frost (1985, 2000), Kobel et al. (1996), and Collins and Taggart (2002).  Channing (2001) lists a variety of vernacular names for African clawed frogs.  Several authors have summarized by the biology and natural history of X. laevis (von Filek, 1973; Deuchar, 1975; Thompson and Franks, 1978, 1979; McCoid and Fritts, 1980, 1989; Wever, 1985; Nieuwkoop and Faber, 1994; Passmore and Carruthers, 1995; Tinsley et al., 1996; Lafferty and Page, 1997; Bernardini et al., 1999; Sire et al., 2000; Channing, 2001; Stebbins, 2003; and various contributions compiled by Tinsley and Kobel, 1996).

Stebbins (1985) and Frost (2000) discuss the possibility that nonindigenous X. laevis may represent a composite of different undescribed species; thus, the actual identity of frogs in the United States may be unclear.  However, Kobel et al. (1996), in listing the six tentatively identified subspecies of X. laevis in Africa, suggest that several could be full species.  Since all reports of nonindigenous and aquarium-raised X. laevis are typically of the nominate subspecies, X. laevis laevis from the Cape region of South Africa (Tinsley and McCoid, 1996), the question of species identity could be rendered moot if X. l. laevis acheives specific status.  Future studies are required to verify this.

Xenopus laevis is a primarily aquatic, highly adaptable frog that can inhabit almost any body of water, natural or man-made, and tolerates sewage and relatively saline (up to 40%) waters (Passmore and Carruthers, 1995; Tinsley et al., 1996; Lafferty and Page, 1997; Channing, 2001).  They can survive fairly cold, temperate climates and can easily disperse overland in order to exploit new habitats, particularly newly created man-made habitats (Tinsley et al., 1996; Channing, 2001; Lobos and Garín, 2002; Lobos and Jaksic, 2005).  In Africa and Chile, X. laevis often migrates over land in swarms containing hundreds or thousands of individuals (Tinsley yet al., 1996; Channing, 2001; Lobos and Jaksic, 2005).  Some of these mass migrations are stimulated by droughts (Tinsley et al., 1996; Tinsley and McCoid, 1996; Channing, 2001; Lobos and Jaksic, 2005).  Nocturnal overland excursions may be quite common (Tinsley et al., 1996; Lobos and Garín, 2002).  In Chile they are spreading at a rate of 3.1-3.9 km/year through both overland migration and the use of irrigation canals in agricultural areas (Lobos and Jaksic, 2005).  African clawed frogs can survive droughts by burrowing into the substrate (Tinsley et al., 1996; Channing, 2001).  Their unique sliding pelvis apparatus allows them to avoid predators by diving backwards from the water surface (Videler and Jorna, 1985).  Moreover, powerful toxins in the skin can deter some predators (Tinsley et al., 1996; Channing, 2001).  These carnivores mostly consume aquatic invertebrates, but also include small vertebrates, including other X. laevis, in their diet (McCoid and Fritts, 1980; Tinsley et al., 1996; Lafferty and Page, 1997; Measey, 1998a; Channing, 2001; Lobos and Jaksic, 2005).  Additionally, they are capable of capturing terrestrial prey (Measey, 1998b).  Xenopus laevis can survive starvation conditions for at least 12 months and can rapidly regain lost weight when food is once again available (Tinsley et al., 1996).  The hardy adults live up to 12 years, with a record of over 30 years (McCoid and Fritts, 1989; Tinsley and McCoid, 1996; Channing, 2001).  African clawed frogs are highly fecund and mate underwater; the amplectant male fertilizing as many as 1000 eggs as the female oviposits (von Filek, 1973; Channing, 2001).  Mating may be stimulated by a sudden increase in water level or nutrient levels, including sewage outflows (Tinsley et al., 1996; Channing, 2001).  The tadpoles feed on planktonic organisms while suspended upside-down in the water (Channing, 2001; Stebbins, 2003).

The possession or importation of X. laevis is prohibited or regulated in the states of Arizona, California, Hawaii, Nevada, Oregon, Utah, Virginia (Levell, 1997; Stebbins, 2003) and New Jersey. Black market sales of this species in the aquarium hobbyist trade continued at least into the 1980s (Stebbins, 1985). Lobos and Jaksic (2005) have proposed that the pet trade of X. laevis be banned in Chile.

References

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Other Resources:

Xenopus laevis (African clawed frog) (Global Invasive Species Program)

Exotic and Nongame Species Requiring a Permit (New Jersey Division of Fish and Wildlife)

Author: Louis A. Somma

Revision Date: 3/24/2005

Citation for this information:
Louis A. Somma. 2009. Xenopus laevis. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=67> Revision Date: 3/24/2005

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