Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: African Clawed Frog

Synonyms and Other Names: Common Platanna.

Channing (2001) lists a variety of vernacular names for African clawed frogs.

Taxonomy: available through www.itis.gov

Identification: Xenopus laevis is a dorsoventrally flattened frog with a relatively small head and a SVL (snout-vent length) of 50-over 140 mm (2-over 5 in) (Passmore and Carruthers, 1995; Kobel et al., 1996; Channing, 2001; Stebbins, 2003; Elliott et al., 2009; Stebbins and McGinnis, 2012). The small, lidless eyes are located dorsally and turned upward (Stebbins, 2003; Stebbins and McGinnis, 2012). There is no visible tympanum (Channing, 2001; Dodd, 2013). The forefeet have slender, unwebbed fingers (Channing, 2001; Stebbins, 2003; Stebbins and McGinnis, 2012; Dodd, 2013), 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; Powell et al., 2012; Stebbins and McGinnis, 2012; Dodd, 2013), hence the comman name African Clawed Frog. 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, 2003; Stebbins and McGinnis, 2012; Dodd, 2013). 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; Stebbins and McGinnis, 2012; Dodd, 2013). It 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. Its 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; Elliott et al., 2009); a recording is available on a CD (Elliott et al., 2009). 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; Lemm, 2006; Stebbins and McGinnis, 2012; Dodd, 2013).

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; Fouquet, 2001; Arnold and Ovenden, 2003; Reed, 2005; Brennan and Holycross, 2006; Lemm, 2006; Anonymous, 2007; Elliott et al., 2009; Krysko et al., 2011: MorphoBank Project No. p536, www.morphobank.com; Powell et al., 2012; Stebbins and McGinnis, 2012; Dodd, 2013).

Size: SVL (snout-vent length) of 50-over 140 mm (2-over 5 in).

Native Range: Xenopus laevis, as currently defined, is indigenous to much of southern and sub-Saharan Africa including Namibia, South Africa, Swaziland, Lesotho, Botswana, Zambia, Mozambique, Zimbabwe, Malawi, Democratic Republic of the Congo, and probably Angola (Poynton 1999, Channing 2001, Measey and Channing 2003). It is unclear if populations of Xenopus in African countries further to the northeast and northwest of this range are actually conspecific, and more research is required to delineate this species’ full indigenous range (Measey and Channing 2003), although Channing and Howell (2006) exclude them from eastern Africa.

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: 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 14%; or 40% seawater) waters (Passmore and Carruthers, 1995; Tinsley et al., 1996; Lafferty and Page, 1997; Channing, 2001; Elliott et al., 2009; Dodd, 2013). It can survive fairly cold, temperate climates and can easily disperse overland in order to exploit new habitats, particularly newly created man-made habitats (McCoid and Fritts, 1993; Tinsley et al., 1996; Channing, 2001; Lobos and Garín, 2002; Crayon, 2005; Lobos and Jaksic, 2005; Faraone et al., 2008; Measey et al., 2012; Dodd, 2013). In Africa and Chile, X. laevis often migrates over land in swarms containing hundreds or thousands of individuals (Tinsley et 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; Dodd, 2013). Nocturnal overland excursions may be quite common (Tinsley et al., 1996; Lobos and Garín, 2002). In Chile, it is 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; Dodd, 2013). 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 (McCoid and Fritts, 1993; 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, 1993; Tinsley et al., 1996; Lafferty and Page, 1997; Measey, 1998a; Channing, 2001; Crayon, 2005; Lobos and Jaksic, 2005; Dodd, 2013). Additionally, it is 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; Tinsley et al., 2012).

African Clawed Frogs are highly fecund and mate underwater; the amplectant male fertilizing thousands of eggs as the female oviposits (von Filek, 1973; McCoid and Fritts, 1993; Channing, 2001; Crayon, 2005; Brennan and Holycross, 2006; Lemm, 2006; Stebbins and McGinnis, 2012; Dodd, 2013). Mating may be stimulated by a sudden increase in water 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 and can occur in such numbers that they can almost sterilize the immediate waters (Channing, 2001; Stebbins, 2003; Lemm, 2006; Stebbins and McGinnis, 2012).

 

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 (Shapiro and Zwarenstein, 1934; Deuchar, 1975; Thompson and Franks, 1978, 1979; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Fouquet, 2001; Reed, 2005; Anonymous, 2007; Evans et al., 2008; Elliott et al., 2009; Kraus, 2009; Stebbins and McGinnis, 2012; Dodd, 2013), and it became established in many laboratory aquaria throughout the world during the 1950s and 1960s (Tinsley and McCoid, 1996; Stebbins and McGinnis, 2012; Dodd, 2013; Vredenburg et al., 2013). 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; Measey et al., 2012). 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. Lillo et al. (2013) demonstrated that X. laevis in Sicily were probably derived from laboratory animals of South African stock. 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; Elliott et al., 2009; Dodd, 2013). Because these frogs live relatively long lives (see below) they are often simply dumped into nearby waters due to loss of interest or the end of an experiment (Tinsley and McCoid, 1996). The release of 200 X. laevis into a canal in Miami-Dade County, Florida, was simply due to an animal importer dumping unwanted stock (King and Krakauer, 1966). The X. laevis collected in Brevard County, Florida, was likely an escaped or released pet (Krysko et al., 2011). 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).

Status: Massachusetts: The status of X. laevis at first remained unclear in Massachusetts, as the collection of newly transformed frogs (Cardoza et al., 1993) suggested that a breeding population could have spread; however, they are not established at this time (Kraus, 2009).

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 (Tinsley and McCoid, 1996). They are not established (Ernst et al., 1997; Kraus, 2009).

North Carolina: Xenopus laevis was eliminated from the fish hatchery ponds in North Carolina by draining the ponds (Tinsley and McCoid, 1996; Kraus, 2009).

Florida: Dodd (2013) speculates the individual X. laevis from Brevard County could be indicative of a population, and more recent collections (December 2013-January 2014) indicate African Clawed Frogs are established in Riverview, near Tampa, Hillsborough County. These Riverview frogs are from a population inhabiting a surrounding complex of aquaculture ponds (many abandoned) and could have been established since the 1970s. It is not known if African Clawed Frogs are currently established in Miami-Dade County.

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; Kraus, 2009).

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 (Kraus, 2009).

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; Crayon, 2005; Brennan and Holycross, 2006; Kraus, 2008, 2009, 2012; Elliott et al., 2009; Measey et al., 2012; Powell et al., 2012; Dodd, 2013). 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 (Brennan and Holycross, 2006).

California: African Clawed Frogs are well established in California (Stebbins, 1985, 2003; Laudenslayer et al., 1991; McCoid and Fritts, 1993; McCoid and Kleberg, 1995; Tinsley and McCoid, 1996; Lemm, 2006; Kraus, 2008, 2009, 2012; Elliott et al., 2009; Measey et al., 2012; Powell et al., 2012; Dodd, 2013). Those populations of X. laevis in Orange, San Bernardino, San Diego, Los Angeles, Santa Barbara, Riverside, Imperial, Kern, and Ventura Counties are clearly established (Lenaker, 1972; St. Amant and Hoover, 1973; Bury and Luckenbach, 1976; McCoid and Fritts, 1980, 1989, 1993; Stebbins, 1985, 2003; Tinsley and McCoid, 1996; Lafferty and Page, 1997; Kuperman et al., 2004; Crayon, 2005; Measey et al., 2012; Stebbins and McGinnis, 2012; Dodd, 2013). 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; Measey et al., 2012; Stebbins and McGinnis, 2012). Efforts to eradicate X. laevis in Golden Gate Park, San Francisco (Lagos, 2004) appear successful as of 2011 (Measey et al., 2012). In southern California, X. laevis has opportunity 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). Although collected in Texas, they are not established (Dixon, 2013).

Mexico: Xenopus laevis was considered established in Baja California, Mexico (Murphy, 1983; Flores-Villela, 1993; Smith and Smith, 1993; Mahrdt et al., 2003; Stebbins, 2003; Kraus, 2009). Although these populations need to be monitored to determine their current status (Measey et al., 2012), another established population in Baja California has been verified (Peralta-García et al., 2014).

Other worldwide localities: African Clawed Frogs are established in the United Kingdom but might be extirpated on Ascension Island (Arnold, 1995; Tinsley and McCoid, 1996; Measey, 1998a, 2001; Measey and Tinsley, 1998; Arnold and Ovenden, 2002; Kraus, 2009; Measey et al., 2012; Tinsley et al., 2011a, 2011b, 2012), 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; Kraus, 2009; Measey et al., 2012). The status of X. laevis in Germany, Sweden, the Netherlands, and Israel remains unknown (Tinsley and McCoid, 1996; Kraus, 2009; Measey et al., 2012; Rabitsch et al., 2013). African Clawed Frogs were eradicated from Spain (Measey et al., 2012). This pipid is established in France, Italy (Sicily), Portugal, and Japan (Fouquet, 2001; Lillo et al., 2005, 2011, 2013; Eggert and Fouquet, 2006; Fouquet and Measey, 2006; Faraone et al., 2008; Kraus, 2009; Rebelo et al., 2010; Measey et al., 2012).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic

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). Additional native Californian vertebrates consumed by X. laevis include Western Toads (Anaxyrus boreas), Arroyo Chubs (Gila orcutti), and locally endangered Three-spined Stickleback (Gasterosteus aculeatus) (Tinsley and McCoid, 1996; Stebbins, 2003; Stebbins and McGinnis, 2012; Dodd, 2013). Xenopus laevis also preys on native species elsewhere in its introduced range (e.g., Measey, 1998; Lobos and Jaksic, 2005; Lillo et al., 2011, Courant et al. 2018), where they may also trigger trophic cascades due to predation on zoobenthos and zooplankton (Courant et al. 2018). In turn, X. laevis are preyed upon by species such as for indigenous Two-striped Garter Snakes (Thamnophis hammondii), fish, and the nonindigenous Bullfrog (Lithobates Catesbeianus) in California (Lafferty and Page, 1997) and several species of native birds in Chile (Lobos and Jaksic, 2005).

As a potential asymptomatic vector for Ranaviruses and Batrachochytrium dendrobatidis (chytrid) fungus, they have the potential to devastate native amphibians (Kraus, 2009; Stebbins and McGinnis, 2012; Vredenburg et al., 2013). Additionally, African Clawed Frogs harbor at least 25 genera of parasites, many of which are host-specific (Prudhoe and Bray, 1982; Tinsley, 1996; Lafferty and Page, 1997; Crayon, 2005; Tinsley et al., 2011a, 2011b, 2012; Dodd, 2013), and individuals from nonindigenous populations in California harbor at least 10 species of parasites (Kuperman et al., 2004).

In Southern Africa, migrations of X. laevis have been implicated in obstructing irrigation pipes and invading houses (Tinsley et al., 1996), and invading aquaculture facilities where they consume both fish and fish food (McCoid and Fritts, 1993; Channing, 2001).

Remarks: The taxonomy and nomenclature of X. laevis have been summarized or reviewed by Frost (1985, 2000, 2015), Kobel et al. (1996), Collins and Taggart (2002, 2009), Measey and Channing (2003), Frost et al. (2006), Evans et al. (2008), and Kraus (2008, 2012), and Fouquette and Dubois (2014). Numerous authors have summarized the biology and natural history of X. laevis (von Filek, 1973; Deuchar, 1975; Thompson and Franks, 1978, 1979; McCoid and Fritts, 1980, 1989, 1993; 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; Brennan and Holycross, 2006; Lemm, 2006; Elliott et al., 2009; Stebbins and McGinnis, 2012; Tinsley et al., 2012; Dodd, 2013; and various contributions compiled by Tinsley and Kobel, 1996).

Stebbins (1985) and Frost (2000) discussed 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 is rendered moot if X. l. laevis is treated with full specific status, and the origin of captive populations continues to be the Cape of South Africa (Measey and Channing, 2003).

The possession or importation of X. laevis is prohibited or regulated in the states of Arizona, California, Hawaii, Nevada, Oregon, Washington, Utah, Louisiana, Kentucky, Virginia, North Carlolina, and New Jersey (Levell, 1997; Stebbins, 2003; Lemm, 2006; Elliott et al., 2009; Stebbins and McGinnis, 2012). 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: (click for full 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)

US Fish and Wildlife Service Ecological Risk Screening Summary for Xenopus laevis

Author: Somma, L.A. and J.A. Freedman

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.