Thirty years after their introduction to California, some patterns of distribution and dispersal of clawed frogs emerge: (1) populations are derived from independent introduction events in five of the counties they now inhabit (San Bernardino and Ventura counties were colonized from neighboring counties); (2) lotic (flowing water) systems are susceptible to complete colonization, including into their brackish interface with tidal waters (e.g., Santa Clara and Sweetwater rivers); (3) some climatic and biological barriers seem to prevent or retard their spread (discussed below); clawed frogs are not present in all apparently suitable habitats (e.g., Santa Barbara and Southern Riverside counties); (4) desert wetlands can sustain clawed frog populations (e.g., Piute Ponds on Edwards Air Force Base); (5) if human-aided introductions continue, there are few freshwater aquatic habitats in California that are not at risk for colonization. Waters that flow either rapidly all year or freeze over completely are among the few systems likely to remain free from invasion.
A passage from Tinsley et al. (1996, p. 44) concerning feeding ability is illuminating: "Xenopus represents a much more formidable predator than most anurans, which rely on the tongue for selective capture of rather small prey items. In Xenopus, prey capture employs a combination of toothed jaws that improve the grip on the prey, forelimbs that are used to fork the prey into the mouth, and the strong hindlimbs that can be used to rake the prey with the sharp claws. This shredding action enables Xenopus to tackle larger food items than could otherwise be ingested whole; indeed, groups of Xenopus may attack the same prey and can tear the body into fragments that can then be ingested. This method of feeding is particularly useful for scavenging."
Lotic body pack WAV
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In bodies of water where there are limited prey, adults will cannibalize young (Buxton, 1936; McCoid and Fritts, 1993; Picker, 1994). Larvae may act as collectors of nutrients such as seasonal single-celled algal blooms, which are unavailable to adults. Adults that cannibalize these larvae can thus rely indirectly on this phytoplankton food base (Savage, 1963; Picker, 1994; Tinsley et al., 1996). Cannibalism allows clawed frogs to colonize a body of water that does not offer a large prey base for the adults or to stay in a body of water that has been depleted of prey. 2ff7e9595c
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