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Lithobates onca

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AMPHIBIA ANURA RANIDAE

Scientific Name: Lithobates onca
Species Authority: (Cope, 1875)
Common Name(s):
English Relict Leopard Frog
Synonym(s):
Rana onca Cope, 1875
Taxonomic Notes: There has been historical confusion and controversy regarding the taxonomic status of various leopard frog populations in the region occupied by Lithobates onca (Jaeger et al. 2001). Some authors have identified extinct populations of leopard frogs in the Las Vegas Valley as L. onca while others consider these populations to have been a separate species, L. fisheri, the Vegas Valley leopard frog (see Jennings (1988)). The systematic relationship of the extinct Las Vegas populations remains unresolved (although see the unpublished report by Jennings, Riddle and Bradford (1995)). Some leopard frog populations along the Virgin River have been identified as L. yavapaiensis (see distributions in Stebbins 2003), but this perspective has been rejected (Jaeger et al. 2001).

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(v); C2a(i) ver 3.1
Year Published: 2004
Date Assessed: 2004-04-30
Assessor(s): Jef Jaeger, David Bradford, Geoffrey Hammerson
Reviewer(s): Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)
Justification:
Listed as Endangered because its Area of Occupancy is less than 500km2, with all individuals in fewer than five locations, and the number of mature individuals in Arizona, Nevada and Utah is declining; and because its population size is estimated to number fewer than 2,500 mature individuals, there is an observed continuing decline in the number of mature individuals, and no subpopulation contains more than 250 mature individuals.
History:
1996 Vulnerable

Geographic Range [top]

Range Description: This species occurs on the border region of Arizona, Nevada, and Utah, USA, mostly below 1,000m asl. It was known from the Virgin and Muddy River drainages and along the Colorado River drainage downstream of its confluence with the Virgin River to Black Canyon below Lake Mead (Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005). In the late 1990s, the species could be found at seven sites in three general areas: a spring near Littlefield, Arizona, on the Virgin River; several springs along the Nevada side of the Overton Arm of Lake Mead; and within several springs in the Black Canyon along the Nevada side of the Colorado River (Jaeger et al. 2001; Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005). By 2001, two of these populations, including the one near Littlefield, had gone extinct (Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005).
Countries:
Native:
United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: As of 2001, there were five known sites in two general areas containing reproducing populations of leopard frogs (Jaeger et al. 2001; Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005). A rough estimate of the total population size (combining all sites) was approximately 1,100 adults (range 693-1,833), most of which were at a single spring (Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: It occurs and reproduces in springs and outlet creeks, typically in or within a few meters of water, year round (Bradford, Jaeger and Jennings 2004, Bradford, Jennings and Jaeger 2005). It does not tolerate habitat disturbance.
Systems: Freshwater

Threats [top]

Major Threat(s): The causes of the decline of this species are not entirely clear, but the loss of habitat to agriculture and water development were likely causes, as was the introduction of American bullfrogs (Rana catesbeiana), crayfish, and exotic predatory fish (Jennings 1988). These factors remain active threats. Vegetation encroachment, of both exotic and native vegetation, has been suspected of causing recent declines (Bradford, Jaeger and Jennings 2004).

Conservation Actions [top]

Conservation Actions: Remaining populations occur within the Lake Mead National Recreation area. A range-wide conservation assessment and strategy is currently being developed by a working group consisting of representatives from federal, state, and local governmental agencies, as well as specialist representatives. Current conservation measures include the re-introduction of this frog to suitable, unoccupied locations, and in 2002 frogs were released at two unoccupied natural spring sites.

Citation: Jef Jaeger, David Bradford, Geoffrey Hammerson 2004. Lithobates onca. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 December 2014.
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