Though a third of amphibian species worldwide are thought to be imperiled, existing assessments simply categorize extinction risk, providing little information on the rate of population losses. We conducted the first analysis of the rate of change in the probability that amphibians occupy ponds and other comparable habitat features across the United States. We found that overall occupancy by amphibians declined 3.7% annually from 2002 to 2011. Species that are Red-listed by the International Union for Conservation of Nature (IUCN) declined an average of 11.6% annually. All subsets of data examined had a declining trend including species in the IUCN Least Concern category. This analysis suggests that amphibian declines may be more widespread and severe than previously realized.
The state of amphibians in the United States
Muths, E., M.J. Adams, E.H.C. Grant, D. Miller, P.S. Corn, and L.C. Ball
More than 25 years ago, scientists began to identify unexplained declines in amphibian populations around the world. Much has been learned since then, but amphibian declines have not abated and the interactions among the various threats to amphibians are not clear. Amphibian decline is a problem of local, national, and international scope that can affect ecosystem function, biodiversity, and commerce. This fact sheet provides a snapshot of the state of the amphibians and introduces examples to illustrate the range of issues in the United States.
The importance of local and landscape-scale processes to the occupancy of wetlands by pond-breeding amphibians
Variation in the distribution and abundance of species across landscapes has traditionally been attributed to processes operating at fine spatial scales (i.e., environmental conditions at the scale of the sampling unit), but processes that operate across larger spatial scales such as seasonal migration or dispersal are also important. To determine the relative importance of these processes, we evaluated hypothesized relationships between the probability of occupancy in wetlands by two amphibians [wood frogs (Lithobates sylvaticus) and boreal chorus frogs (Pseudacris maculata)] and attributes of the landscape measured at three spatial scales in Rocky Mountain National Park, Colorado. We used cost-based buffers and least-cost distances to derive estimates of landscape attributes that may affect occupancy patterns from the broader spatial scales. The most highly ranked models provide strong support for a positive relationship between occupancy by breeding wood frogs and the amount of streamside habitat adjacent to a wetland. The model selection results for boreal chorus frogs are highly uncertain, though several of the most highly ranked models indicate a positive association between occupancy and the number of neighboring, occupied wetlands. We found little evidence that occupancy of either species was correlated with local-scale attributes measured at the scale of individual wetlands, suggesting that processes operating at broader scales may be more important in influencing occupancy patterns in amphibian populations.
Long-Term Observations of Boreal Toads at an ARMI Apex Site
Corn, P.S., E. Muths, and D.S. Pilliod
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Questioning Greater Yellowstone’s Future: Climate, Land Use, and Invasive Species. Proceedings of the 10th Biennial Scientific Conference on the Greater Yellowstone Ecosystem. October 11–13, 2010, Yellowstone National Park, WY, and Laramie, WY
The U.S. Geological Survey’s Amphibian Research and Monitoring Initiative (ARMI) is a national project with goals to monitor the status and trends of amphibians, conduct research on causes of declines, and provide information and support to management agencies for conservation of amphibian populations. ARMI activities are organized around extensive inventories and place-based monitoring (such as collaboration with the Greater Yellowstone Inventory and Monitoring Network), and intensive population studies and research at selected locations (apex sites). One such site is an oxbow pond on the Buffalo Fork near the Black Rock Ranger Station east of Grand Teton National Park. We have been conducting mark-recapture of boreal toads (Anaxyrus boreas) at Black Rock since 2002. In concert with studies of other toad populations in the Rocky Mountains, we have documented a high rate of incidence of the chytrid fungus Batrachochytrium dendrobatidis (Bd) and a negative rate of growth of the toad population, but not the population crash or extinction observed in other populations with high prevalence of Bd...
Amphibian Research and Monitoring Initiative: Rocky Mountain Region
The Department of Interior's Amphibian Research and Monitoring Initiative (ARMI) is designed to determine where populations of amphibians are present; to monitor specific sentinel populations and to investigate potential causes of decline and deformity. The Rocky Mountain Region of ARMI encompasses Montana, Wyoming, Colorado, and New Mexico. Two USGS-Biological Resource Division Centers initiate and develop ARMI projects in this region.
Status of amphibians on the Continental Divide: surveys on a transect from Montana to Colorado, USA
Corn, P.S., B.R. Hossack, E. Muths, D.A. Patla, C.R. Peterson, and A.L. Gallant
The Rocky Mountain Region of the United States Geological Survey’s Amphibian Research and Monitoring Initiative is conducting monitoring of the status of amphibians on a transect that extends along the Continental Divide from Canada to Colorado and comprises four National Parks. Monitoring uses visual encounter surveys to determine site occupancy, with multiple visits to a subset of sites to estimate detection probabilities for each species. Detection probabilities were generally high (above 0.65) among species. There was a gradient in site occupancy, with most species scarce in the south and relatively common in the north. For example, Bufo boreas is close to extinction in Rocky Mountain National Park, was found at fewer then 5% of sites in Yellowstone and Grand Teton National Parks in the middle of the transect, but occurs at approximately 10% of sites in Glacier National Park. The salamander Ambystoma tigrinum was rare in Rocky Mountain and occurred at less than 25% of sites at Yellowstone and Grand Teton, but A. macrodactylum occurred at more than 50% of site in Glacier. There are numerous differences among parks, such as latitude, climate, numbers of visitors, and human population density in the surrounding landscape. The degree to which these factors have influenced the current distribution and abundance of amphibians is unknown but should be a focus of additional research.
The United States Geological Survey's Amphibian Research and Monitoring Initiative
Corn, P.S., E. Muths, M.J. Adams, and C.K. Dodd, Jr
Amphibian decline achieved recognition as a global issue after the meeting of the Firest World Congress of Herpetology in England in 1989. During the ensuing decade, considerable progress was made in documenting the status of populations and in understanding the causes of some of the declines. However, significant gaps in our knowledge remained, including basic information on status and life history. Additionally, the occurrence of large numbers of malformations in some locations in North America in the mid-1990s increased the urgency to critically examine the status of anuran populations…
Fort Collins Science Center: Species and Habitats of Federal Interest
Ecosystem changes directly affect a wide variety of plant and animal species, floral and faunal communities, and groups of species such as amphibians and grassland birds. Appropriate management of public lands plays a crucial role in the conservation and recovery of endangered species and can be a key element in preventing a species from being listed under the Endangered Species Act. The Species and Habitats of Federal Interest Branch of the Fort Collins Science Center (FORT) conducts research on the ecology, habitat requirements, distribution and abundance, population dynamics, and genetics and systematics of many species facing threatened or endangered status or of special concern to resource management agencies. FORT scientists develop reintroduction and restoration techniques, technologies for monitoring populations, and novel methods to analyze data on population trends and habitat requirements. FORT expertise encompasses both traditional and specialized natural resource disciplines within wildlife biology, including population dynamics, animal behavior, plant and community ecology, inventory and monitoring, statistics and computer applications, conservation genetics, stable isotope analysis, and curatorial expertise.