The History and Current Status and Distribution of Beavers in Yellowstone National Park

Smith, Douglas W.; Tyers, Daniel B.

doi:10.3955/046.086.0404

Cited by 25 publications

(28 citation statements)

References 23 publications

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“…The strong association between beaver and amphibians suggests recent increases in beaver colonies in GRYN have likely benefited amphibians at least at local spatial scales (Smith and Tyers, 2012). For example, ponds that beaver constructed in two areas in Grand Teton NP during summer 2011 were colonized and used for breeding by A. boreas in 2012, even though we had not detected A. boreas breeding in that area since monitoring began in 2005.…”

Section: Discussionmentioning

confidence: 86%

Trends in Rocky Mountain amphibians and the role of beaver as a keystone species

Hossack

Gould

Patla³

et al. 2015

Biological Conservation

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a b s t r a c tDespite prevalent awareness of global amphibian declines, there is still little information on trends for many widespread species. To inform land managers of trends on protected landscapes and identify potential conservation strategies, we collected occurrence data for five wetland-breeding amphibian species in four national parks in the U.S. Rocky Mountains during 2002-2011. We used explicit dynamics models to estimate variation in annual occupancy, extinction, and colonization of wetlands according to summer drought and several biophysical characteristics (e.g., wetland size, elevation), including the influence of North American beaver (Castor canadensis). We found more declines in occupancy than increases, especially in Yellowstone and Grand Teton national parks (NP), where three of four species declined since 2002. However, most species in Rocky Mountain NP were too rare to include in our analysis, which likely reflects significant historical declines. Although beaver were uncommon, their creation or modification of wetlands was associated with higher colonization rates for 4 of 5 amphibian species, producing a 34% increase in occupancy in beaver-influenced wetlands compared to wetlands without beaver influence. Also, colonization rates and occupancy of boreal toads (Anaxyrus boreas) and Columbia spotted frogs (Rana luteiventris) were P2 times higher in beaver-influenced wetlands. These strong relationships suggest management for beaver that fosters amphibian recovery could counter declines in some areas. Our data reinforce reports of widespread declines of formerly and currently common species, even in areas assumed to be protected from most forms of human disturbance, and demonstrate the close ecological association between beaver and wetland-dependent species.Published by Elsevier Ltd.

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Section: Discussionmentioning

confidence: 86%

Trends in Rocky Mountain amphibians and the role of beaver as a keystone species

Hossack

Gould

Patla³

et al. 2015

Biological Conservation

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“…Beaver have not recolonized any of the sites that were active complexes in the 1920s [27,32]. Seventeen years after restoration of wolves, heights of willows in our control plots (figure 2) and at similar sites across the northern range (figure 4) remain far below the 2 m threshold needed for restoration.…”

Section: Discussionmentioning

confidence: 99%

Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction

2013

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Efforts to restore ecosystems often focus on reintroducing apex predators to re-establish coevolved relationships among predators, herbivores and plants. The preponderance of evidence for indirect effects of predators on terrestrial plant communities comes from ecosystems where predators have been removed. Far less is known about the consequences of their restoration. The effects of removal and restoration are unlikely to be symmetrical because removing predators can create feedbacks that reinforce the effects of predator loss. Observational studies have suggested that the reintroduction of wolves to Yellowstone National Park initiated dramatic restoration of riparian ecosystems by releasing willows from excessive browsing by elk. Here, we present results from a decade-long experiment in Yellowstone showing that moderating browsing alone was not sufficient to restore riparian zones along small streams. Instead, restoration of willow communities depended on removing browsing and restoring hydrological conditions that prevailed before the removal of wolves. The 70-year absence of predators from the ecosystem changed the disturbance regime in a way that was not reversed by predator reintroduction. We conclude that predator restoration may not quickly repair effects of predator removal in ecosystems.

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“…After wolf reintroduction and decreases in the elk population on the northern range, both beaver ( Caster canadensis ) and bison ( Bison bison ) numbers increased, possibly due, in part, to the increase in available woody plants and herbaceous forage resulting from less competition with elk (Ripple & Beschta ; Smith & Tyers ). Because of the large body size of bison, their populations have been little affected by wolf predation in the park.…”

Section: Introductionmentioning

confidence: 99%

Trophic cascades from wolves to grizzly bears in Yellowstone

Ripple

Beschta

Fortin

et al. 2013

Journal of Animal Ecology

115

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Summary1. We explored multiple linkages among grey wolves (Canis lupus), elk (Cervus elaphus), berry-producing shrubs and grizzly bears (Ursus arctos) in Yellowstone National Park. 2. We hypothesized competition between elk and grizzly bears whereby, in the absence of wolves, increases in elk numbers would increase browsing on berry-producing shrubs and decrease fruit availability to grizzly bears. After wolves were reintroduced and with a reduced elk population, we hypothesized there would be an increase in the establishment of berry-producing shrubs, such as serviceberry (Amelanchier alnifolia), which is a major berry-producing plant. We also hypothesized that the percentage fruit in the grizzly bear diet would be greater after than before wolf reintroduction. 3. We compared the frequency of fruit in grizzly bear scats to elk densities prior to wolf reintroduction during a time of increasing elk densities (1968)(1969)(1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987). For a period after wolf reintroduction, we calculated the percentage fruit in grizzly bear scat by month based on scats collected in 2007-2009 (n = 778 scats) and compared these results to scat data collected before wolf reintroduction. Additionally, we developed an age structure for serviceberry showing the origination year of stems in a northern range study area. 4. We found that over a 19-year period, the percentage frequency of fruit in the grizzly diet (6231 scats) was inversely correlated (P < 0Á001) with elk population size. The average percentage fruit in grizzly bear scats was higher after wolf reintroduction in July (0Á3% vs. 5Á9%) and August (7Á8% vs. 14Á6%) than before. All measured serviceberry stems accessible to ungulates originated since wolf reintroduction, while protected serviceberry growing in a nearby ungulate exclosure originated both before and after wolf reintroduction. Moreover, in recent years, browsing of serviceberry outside of the exclosure decreased while their heights increased. 5. Overall, these results are consistent with a trophic cascade involving increased predation by wolves and other large carnivores on elk, a reduced and redistributed elk population, decreased herbivory and increased production of plant-based foods that may aid threatened grizzly bears.

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The History and Current Status and Distribution of Beavers in Yellowstone National Park

Cited by 25 publications

References 23 publications

Trends in Rocky Mountain amphibians and the role of beaver as a keystone species

Trends in Rocky Mountain amphibians and the role of beaver as a keystone species

Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction

Trophic cascades from wolves to grizzly bears in Yellowstone

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