Short Term Occupancy And Abundance Dynamics Of The Oregon Spotted Frog Rana Pretiosa Across Its Core Range
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Short-term Occupancy and Abundance Dynamics of the Oregon Spotted Frog (Rana Pretiosa) Across Its Core Range
The Oregon spotted frog (Rana pretiosa) occupies only a fraction of its original range and is listed as Threatened under the Endangered Species Act. We surveyed 93 sites in a rotating frame design (2010-13) in the Klamath and Deschutes Basins, Oregon, which encompass most of the species' core extant range. Oregon spotted frogs are declining in abundance and probability of site occupancy. We did not find an association between the probability that Oregon spotted frogs disappear from a site (local extinction) and any of the variables hypothesized to affect Oregon spotted frog occupancy. This 4-year study provides baseline data, but the 4-year period was too short to draw firm conclusions. Further study is essential to understand how habitat changes and management practices relate to the status and trends of this species.
Frogs of the United States and Canada
The most thorough, updated guide to frogs and toads in the United States and Canada available. A stunning diversity of frog species can be found from coastal swamps to lofty mountain peaks, and from the Florida Keys to the Arctic Ocean. They live in subtropical lowlands, grassland prairies, deserts, and alpine-tundra habitats. Some species have restricted habitat requirements, whereas others occur contiguously from the arid plains or humid southeastern forests to the high tundra. In this new edition of Frogs of the United States and Canada, C. Kenneth Dodd Jr. tours the reader through the marvelous world of North American frogs. Covering 114 native and introduced species from all US states and Canadian provinces, this comprehensive reference on the biology, behavior, and conservation of the Order Anura includes detailed and updated information on • past and present distribution • life history and demography • reproduction and diet • landscape ecology and evolution • diseases, parasites, and threats from toxic substances • conservation and management Hundreds of occurrence maps, line drawings, and new color photographs of frogs and their habitats enhance the text. The most thorough treatment of the life histories, distribution, and status of North American frogs ever produced, Frogs of the United States and Canada has been the go-to reference for naturalists, scientists, and resource managers in their efforts to understand and conserve frogs, their habitats, and biodiversity for over a decade. Based on a meticulously updated examination of more than 8,000 references current through 2021, this second edition ensures Dodd's master work will remain an unparalleled resource for years to come.
Quantifying the Impacts of a Novel Predator
The decline of the Oregon Spotted Frog (Rana pretiosa), a Pacific Northwest endemic now federally listed as threatened, has been attributed to several aspects of ecosystem alteration, primarily habitat degradation and loss. The introduced American Bullfrog (Rana (Aquarana) catesbeiana) has been widely implicated in those declines, but the basis of that contention has been difficult to characterize. The bullfrog occurring at every site of recent Oregon Spotted Frog extirpation has focused concern about its impact. Here, I present a suite of interconnected studies that examine the behavioral ecology of both species to better understand the potential for bullfrog-mediated Oregon Spotted Frog extirpation. I quantified Oregon Spotted Frog anti-predator behavior from the only known population successfully co-occurring with bullfrogs (Conboy Lake) and a population devoid of bullfrog impact (Big Marsh), and compared these behaviors to the predatory traits of the bullfrog. The initial study revealed that captive-reared individuals from the Oregon Spotted Frog population that has successfully co-occurred with bullfrogs respond faster to a predatory stimulus (measured as latency to response) than Oregon Spotted Frogs from a population not to exposed to bullfrogs. Subsequent field investigations of the approach distance allowed by a predator stimulus before taking evasive action (termed the flight initiation distance: FID) conducted with the Oregon Spotted Frog population co-occurring with bullfrogs first demonstrated that FID of recently metamorphosed bullfrogs is consistently greater than that of recently metamorphosed Oregon Spotted Frogs. Further, examination of FID across all post-metamorphic age classes of Oregon Spotted Frogs revealed that older frogs do not allow as close approach as recently metamorphosed Oregon Spotted Frogs. This age class shift in FID did not occur in the Oregon Spotted Frog population not exposed to bullfrogs. In the latter population, FID did not differ among age classes. Since the bullfrog might be driving this age-based change in anti-predator behavior, I explored the variation in strike distance of bullfrogs from the site of co-occurrence in both the field and laboratory to determine the extent of overlap with Oregon Spotted Frog FID. I found that the bullfrog strike distance significantly overlaps the FID of all ages of Oregon Spotted Frogs from the bullfrog-free site but only that of youngest (recently metamorphosed) frogs at the site of co-occurrence. Older Oregon Spotted Frogs from the site of co-occurrence generally escaped at distances greater than the strike distance of bullfrogs. Collectively, these studies strongly suggest that bullfrogs have altered the escape behavior of Oregon Spotted Frogs at Conboy Lake and that most adult Oregon Spotted Frogs at Conboy may have a size-based release from predation by bullfrogs. Implicit in this finding is that bullfrogs may pose a real threat via predation to other Oregon Spotted Frog populations with which they might come into contact where the distribution of bullfrog body sizes differ substantially from that at Conboy Lake.