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Historically, Cienega Creek, within the current boundaries of the Las Cienegas Natural Conservation Area (LCNCA), was habitat for two species of native leopard frogs: Chiricahua leopard frog and lowland leopard frog. Large reproductive populations of both species occurred in the creek at such high numbers that movement and splashes from frogs jumping into the creek would spook cowboy's horses trying to drink from the cool waters of stream. Populations of both frog species in the creek began to crash in the 1980's following a state-wide trend of leopard frog decline. These declines became so alarming that the Chiricahua leopard Frog was listed as a threatened species by U.S. Fish and Wildlife Service in 2002 and both species were declared "Species of Concern" by the Arizona Game and Fish Department in the 1990's. The last recorded Chiricahua leopard frog in Cienega Creek was seen in the creek in 2004 while the last lowland leopard frog was seen in 2007.
Two causal factors are likely responsible for the demise of the native leopard frogs in Cienega Creek; the invasion of Cienega Creek by the American bullfrog and the exotic fungal disease chytridiomycosis, caused by the chytrid fungus pathogen Batrachochytrium dendrobatidis (Bd). Bullfrogs are voracious predators that have been documented to eat practically any animal they can catch and swallow, including insects, fish, birds, small mammals, frogs, snakes and turtles. In Arizona native frog declines have been well documented as the result of bullfrog invasion. Bullfrogs are resistant to Bd infection yet have been found to be vectors for the disease thereby giving a lethal one-two punch of disease and predation to native frog populations. Bullfrogs were first observed in the creek in 1987 and were well established by 1997. During this same period the numbers of native leopard frogs declined so that by the 2000's they were effectively eradicated in the creek on the LCNCA.
Bullfrog eradication efforts began in 2002 by University of Arizona and Bureau of Land Management (BLM) but were hampered by the large scale of the problem and a lack in funding. This changed in 2010 when the Cienega Watershed Project received funding from National Fish and Wildlife Foundation to create the FROG Project. The FROG Project is a group of conservationists/biologists lead by ecologist Philip Rosen (PhD) and anthropologist Netzin Stelkis (PhD candidate) along with conservationist/naturalist Dennis Caldwell and ecologist David Hall (MSc). The primary goal of the FROG project is to eradicate nonnative aquatic species and restoration of aquatic habitats throughout the region. Emphasis was also placed on increasing public awareness and interest through outreach and education
With cooperation and support from BLM, FROG project field workers began surveys and eradication of bullfrog populations in the periphery of Cienega Creek in 2010. These surveys identified possible satellite bullfrog and nonnative fish populations that threatened Cienega Creek with possible recolonization, and by the end of 2010 these populations were eradicated. Initial eradication efforts within Cienega Creek began in 2010, but intense eradication efforts began in spring of 2011, and, as a result, bullfrog reproduction was prevented in the creek. By 2013, over 1,800 bullfrogs have been removed; the last bullfrog seen, and removed, was in mid-June of this year. Current evidence suggests eradication of bullfrogs throughout the LCNCA. This is believed to be the first successful landscape-scale bullfrog eradication involving a complex cienega-creek system.
The successful bullfrog eradication allowed Chiricahua leopard frog reintroductions to begin as early as the fall of 2011. The FROG Project, together with the BLM, designed enhanced warm water habitats to maximize longevity and mitigate disease. To date, two reproductive populations of Chiricahua leopard frogs have been established within Cienega Creek. In addition, six populations within enhanced-satellite habitats have been established, four of which are now highly productive. At least two more introductions of frogs to enhanced habitats are being planned for 2014 with the goal of producing a metapopulation of Chiricahua leopard frogs on the LCNCA, helping to insure the species long-term persistence within the LCNCA.
Unexpectedly, lowland leopard frogs have appeared this year within the lower section of Cienega Creek below the confluence of Pump Canyon. Over 26 lowland leopard frogs were observed, and the presence of recently metamorphosed frogs, along with adults, suggest that this population is breeding successfully in this stream reach. This is remarkable as surveys throughout the area from 2010-2012 detected no frogs. Lowland leopard frogs have been known from this area in the past and may have been there during these surveys in undetectable numbers. Immigration from nearby populations downstream in the Pima County Cienega Creek Natural Preserve or in Wakefield canyon is also a possibility.
This short summary of leopard frog status on the LCNCA has necessarily omitted many aspects of the FROG Project. A comprehensive report of the FROG Project goals and accomplishments is available for download at:
https://sites.google.com/site/frogspotsprogram/home/final-report.
Many people and agencies helped to make the FROG Project a success and their contributions are outlined and acknowledged in the above report.
This article by Dave Hall first appeared in TECH TALK, Newsletter for Biological Planning, December 6, 2013.
Thanks Dave for the article and for your work!
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