Current Focus Area - Designing a national monitoring program for animals whose life histories and habitats are as varied as those of amphibians is very challenging. Some species have entirely aquatic lifestyles, and other species spend much of their time on land or in burrows. Some species are vocal; others are silent. Some species are associated with simple population structure, others with metapopulation structure. Some species are sedentary, whereas others may migrate several kilometers. Because of this diversity it is difficult to identify monitoring variables that are meaningful in all regions and it is infeasible to implement nationally uniform methods for measuring such variables. Considerable effort is being invested by ARMI to determine what kinds variables might provide value at a national level and how these variables might be implemented in a regionally meaningful, but nationally interpretable, fashion.

National Metrics - The most promising national variable to date is one based on species presence . Documenting shifts in species presence through time will provide important data for assessing changes in amphibian status. The "proportion of area occupied" (PAO) by an amphibian species has been identified by ARMI as the only metric that so far meets the Program criteria for being nationally interpretable and regionally adaptable.

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Sample Frame - The ARMI monitoring program design must address two major sources of variation and uncertainty in amphibian sampling: spatial variation and detectability. Because amphibians are not uniformly distributed across the landscape and investigators are unable to survey the entire landscape, scientists must design a sampling framework that provides an acceptable level of geospatial representation of amphibians. And because it is rarely possible to detect all animals present in sites that are surveyed, it is important to estimate what percentage of a population has been detected.

ARMI wildlife biologists are currently testing different sample frame approaches tailored to the types of species and environmental challenges that occur in different areas of the nation. For example, wildlife biologists in the Northwestern and Rocky Mountain ARMI regions are focusing their surveys on ponds, which dot the landscape throughout the federal lands being surveyed. In those regions, the geographic area of inference has been stratified by drainage basins, and a random selection of basins is being implemented within which to survey ponds [read about an example]. In the Southeast ARMI region, wildlife biologists are faced with environmental conditions that are not conducive to the same approach. There, extensive wetlands, such as the Okefenokee Swamp, make it impossible to completely survey an entire waterbody. Southeastern biologists are therefore developing a habitat stratification that can be used to select portions of extensive wetlands for surveying amphibians.

While a geospatial stratification can help to address how well we represent the spatial variation in amphibians, it does not assist in the matter of detectability, which refers to the nearly universal problem in animal surveys of it being rarely possible to detect all individuals present at a site. While we use stratification to determine what sites to survey, we incorporate particular field protocols once we get there to provide the data needed to estimate or remove the effects of detectability. We want to make certain that apparent changes in animal abundance reflect true changes and not just differences due to changes in the detection rate (such as from seasonal or local weather effects, sub-optimal timing of field visits relative to species' breeding cycles, or differing abilities among field observers).

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Field Methods - A robust initial inventory of species is key to establishing the ARMI monitoring program. Field efforts at survey sites center around determining the species present at a site, as well as noting the species not detected (but expected). Multiple sampling techniques (e.g., visual surveys, auditory surveys, pvc pipes, cover boards) are being employed to maximize detection of species, as no single method is appropriate for all species or habitats. Research to determine the best combination of field techniques per region of the country has been underway since the 2001 field season.

Particular field efforts are also implemented to collect data to estimate rates of species detectability. To estimate detectability, it is desirable to sample sites (ponds, quadrats, caves, etc.) at least two times during a field season in order to compare differences in the types and numbers of amphibians detected each time. Such repeated measures can be incorporated into the PAO metric to more accurately estimate true changes in site occupancy.

Also being tested at the field level are improved means for recording and uploading data in order to improve time efficiency and reduce transcription effors. A good description of these efforts is provided on the Rocky Mountain ARMI region web site.

Field efforts at a small subset of sites throughout the nation will be much more intensive, focusing on collecting data for a wider array of variables in order to address specific questions about species/population-habitat-stressors interactions. Results from these studies will be posted on our "Products" page in the form of publication citations, downloadable PDF files, or pointers to associated web sites.

As ARMI field protocols become better defined for each region, we will post descriptions on our “Products” page so that ARMI cooperators and others interested in adopting the procedures can access the necessary documentation.

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Habitat & Stressors - ARMI scientists record a variety of variables at each site in order to support analyses of relations between amphibian species and habitats or potential stressors. While some of these relations have been documented in previous studies, most have not, and few previous studies have addressed how the relations might change spatially or temporally. Because of its multiscale approach to monitoring, the ARMI Program provides an opportunity to gain this perspective

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Variables -Along with amphibian species data, ARMI scientists collect detailed information about amphibian habitat at every site. Subsequent statistical analyses help illuminate associations between species and vegetation cover (e.g., community type, ground/canopy cover, duff layer), land use, terrestrial settings (e.g., elevation, aspect, slope, substrate), and weather conditions (e.g., air temperature, wind speed, precipitation). Data from aquatic habitats include water chemistry (e.g., hardness, conductivity, pH), physical parameters (e.g., size and depth of water body, flow rates, substrate), and aquatic vegetation (e.g., species, density, height above water). [Visit the USGS Water Resources Division ARMI web site for more information on water quality investigations for ARMI.]

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Malformations & Disease - Multiple limbs, missing limbs, and facial abnormalities are the striking hallmarks of developmental malformations seen in frogs. The broad geographic distribution of malformations, now reported from most states, and the high percentage of malformations in some frog populations (up to 50% malformed individuals in some locations) warrant attention. The USGS National Wildlife Health Center is collaborating with ARMI regional herpetologists, as well as with biologists from other agencies, to conduct integrated studies to determine the causes for these malformations. USGS scientists have modified and expanded their diagnostic capabilities and field investigation methods to accommodate the unique life histories and habitats of amphibians. These new capabilities are particularly important in determining whether infectious agents play a role in causing the observed malformations. The National Wildlife Health Center has developed a Field Guide to Malformations of Frogs and Toads to assist field biologists in appropriately identifying and describing observed malformations. Download Adobe Acrobat Reader