These projects are linked to ARMI by funding source or partnership. Lead scientists may be recipients of additional ARMI support through competitive funding, or participating in collaborations with other scientists. Projects focus on the goals of ARMI, to determine causes of decline, understand the scope and severity of amphibian declines, and provide essential scientific information to support effective management actions to reverse or halt declines.
A complete understanding of disease and its role in amphibian declines is lacking (Daszak et al. 1999). In the western U.S., the amphibian chytrid fungus (Batrachochytrium dendrobatidis) has features of an introduced, lethal infectious disease to which amphibian populations have no resistance and which has been associated with population declines in several species. Information on the distribution of chytrid, the susceptibility of populations to chytridiomycosis, and the role of chytrid in amphibian population declines is critically needed.
Amphibian declines have occurred in the western U.S. at a disproportionate rate. Studies in the eastern U.S. show that forest succession and closure of canopy over breeding ponds can lead to the decline of some species. The relationship between forest structure and lentic amphibians has not been investigated in the western U.S.
Recent evidence from Glacier National Park has linked B. boreas with wildfire. We documented increases in the number of breeding sites after wildfires in 2001 and 2003. Following the 2001 Moose Fire, 10 of 43 wetlands that had been surveyed or were dry prior to the fire were colonized. Toads had not previously been found breeding in the area during 1999-2001, and no wetlands outside of the burned area were colonized in 2002. Toads also colonized several (> 20) previously-vacant wetlands after they were burned by additional fires 2003. B. boreas is often associated with disturbed habitats, and wildfire is a landscape-scale disturbance that creates habitat conditions that are seemingly preferred.
In conjunction with our ARMI monitoring work, we are currently conducting a study of the distribution of amphibian populations across a chronosequence of fires on the west side of Glacier National Park. However, monitoring alone will not provide explanations as to why adult toads seem to quickly colonize burned habitats or what characteristics of burned areas make them attractive to toads. We use a combination of adult habitat use and thermal modeling of the terrestrial environment, to compare characteristics of burned and unburned wetlands, as well as continue broad-scale surveys to further our understanding of the response of amphibians to wildfire. These data may also be important to understand the potential implication of fire suppression and alteration of the natural fire regime and stand structure (where that has occurred) on amphibian communities.
The goal of the project is to understand how fire in upland and riparian forests influences stream communities and determine whether prescription burning mimics the ecological function of fire in a watershed. The project has two components: Wildland Fire Effects, documenting the range of biotic and abiotic responses to wildland fires, by comparing stream communities and habitat conditions in watersheds that burned, at varying intensities, to streams in unburned forests, and Prescribed fire effects, determining whether prescription burning restores the “ecological integrity” of forests, by monitoring stream communities and habitat conditions before and after prescription burn treatments and comparing observed responses to unburned reference streams during the same time
periods.
The boreal toad (Bufo boreas) is listed as an endangered species in Colorado and a protected species of special concern in Wyoming. Three of the other four native amphibians to Rocky Mountain National Park and Grand Teton National Park, the Columbia spotted frog, Rana luteiventris; boreal chorus frog, Pseudacris maculata; and northern leopard frog, R. pipiens, are also of conservation concern in both states. All of these species are susceptible, or likely susceptible, to Batrachochytrium dendrobatidis (Bd). Monitoring of boreal toad populations at the Black Rock apex site near Grand Teton National Park has revealed high annual incidence (25–50%) of Bd, but this population has not undergone the declines seen in boreal toads in the southern Rockies. However, the potential for Bd to affect amphibian populations in the Greater Yellowstone Ecosystem led to the funding of three research projects: a pilot study in Grand Teton National Park funded by ARMI and the Rocky Mountains Cooperative Ecosystem Studies Unit and two studies funded through the USGS Park Oriented Biological Support program.
This study documented high incidence of Bd among boreal toads and Columbia spotted frogs at two sites along the Snake River in Grand Teton National Park and the Rockefeller Parkway. Radio telemetry revealed few differences in behavior between toads with and without Bd at Schwabacher Landing in Grand Teton National Park, but the four toads that tested positive for presence of Bd when radios were attached in July all survived and tested negative for Bd when radios were removed in September.
Results from this study (Murphy et al. in press) indicate that Bd is common in and around Grand Teton National Park. Bd was detected on adult toads from all 10 breeding populations that were surveyed at a mean incidence of 67%. Bd was successfully isolated and cultured from a toad collected at the Black Rock apex site. In laboratory experiments, this Bd isolate caused lethal disease within 35 days in all toadlets reared from tadpoles collected at Black Rock or obtained from the Colorado Division of Wildlife Native Aquatic Species Restoration Facility. Survival time was longer in toadlets from Wyoming than Colorado and in toadlets spending more time in dry sites. In a second trial involving Colorado toadlets exposed to fewer Bd zoospores, infection did not result in lethal chytridiomycosis in any treatment. However, Bd infection intensity was higher in more humid aquaria and in aquaria without dry refuges available. Toads from Grand Teton National Park may escape chytridiomycosis from a slight advantage in innate resistance, or because their native habitat hinders Bd growth or provides more opportunities for reducing pathogen loads through behavior.
The high prevalence of Bd across boreal toad populations in both Grand Teton National Park and Rocky Mountain National Park argues that a deeper understanding of the dynamics of this disease has both ecological and management implications. Because different effects of Bd on toads have been observed in these two parks, these populations make an excellent model system in which to identify factors—both environmental and evolutionary—that may alter disease dynamics. Furthermore, a better understanding of how environmental factors affect the manifestation of chytridiomycosis may enable appropriate management of amphibian habitat to reduce the likelihood of disease. Objectives: 1. quantify and compare habitat selection, intensity of Bd infection, and skin microflora of boreal toads; 2. quantify and compare the physiological 'operative' environment for toads with physical models; 3. quantify and compare the amount of Bd in aquatic environments used by toads over the season; and 4. determine whether the pathogenicity of Bd strains, and the susceptibility of boreal toads, vary according to origin.
Rocky Mountain National Park is reintroducing boreal toads (larvae) at a site near to a historical locality for boreal toads in hopes of establishing a population of these amphibians. The goal of this reintroduction is to use hatchery-reared offspring from wild-caught boreal toads from Rocky Mountain National Park. One portion of this effort is the simultaneous release of a small number of adult boreal toads. These animals are to provide information on several aspects of reintroduction. First, they are serving as disease sentinels and are being tested weekly for the presence of the amphibian chytrid fungus Batrachochytrium dendrobatidis; second, we are collecting data on their movements, temperature and habitat choices, in collaboration with researchers at Idaho State University (see project above) and third, there is the possibility that these animals will breed, laying eggs in the reintroduction site. We are using radiotelemetry, weekly assessments of disease status in the sentinel adults, and intensive environmental sampling.
Research on the effects of fire on amphibians in western forests has occurred primarily in wilderness areas and other protected lands (Pilliod et al. 2003, Hossack et al. 2006, Hossack and Corn 2007). But the effects of wildfire on amphibians are likely magnified in managed landscapes, where populations may already be depressed. I plan to use measures of vigor (body size and condition, egg size) and physiological stress to quantify sublethal effects of wildfire and logging on the long-toed salamander (Ambystoma macrodactylum) and the Rocky Mountain tailed frog (Ascaphus montanus). These are the two widespread species in our region that are most likely to be negatively affected by disturbance (Naughton et al. 2000, Hossack et al. 2006).
Most disturbance-related declines of amphibians are likely the result of a suite of correlated sublethal effects, including reduced growth and body size (Todd and Rothermel 2006, Cummer and Painter 2007), body condition (Karraker and Welsh 2006), and increased physiological stress that may compromise immunity (Hopkins et al. 1997, Carey et al. 1999, Homan et al. 2003). All of these effects are linked with survival, reproduction, and dispersal—factors that are critical to population persistence—yet sublethal responses have only recently been adopted as measures of the effects of disturbance on amphibian populations. I expect these measures will be informative for assessing long-term consequences of disturbance on amphibian populations.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.fort.usgs.gov/RARMI/rarmi_research.asp
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