Background

Amphibian malformations and diseases, changes in historical ranges, and declines of amphibians at the population level have been noted globally, though the extent of these declines are not well understood, and robust long-term data quantifying amphibian declines are lacking. The life histories, dispersal abilities and physiological tolerances of amphibians make them potentially more susceptible to environmental change and the introduction of multiple, synergistic stressors at many life history stages. Because of these characteristics, amphibians may be good indicators of local and regional ecosystem change and perturbation.

Amphibian responses to anthropogenic landscape change are well documented, and in a rapidly urbanizing region, such as Washington, D. C., the potential for multiple, synergistic stressors is significant. Amphibians in an urban landscape are vulnerable to alteration or loss of habitat, increased exposure to disease and predation and the impacts stemming from human infrastructure such as road networks, trail networks and changes in water quality and quantity. To abate the loss of species or the change in distribution requires long-term monitoring of populations and habitats to gain a better understanding of the stressors present and their effects. This information can then feed into park level management strategies.

Objectives

• Determine changes in species richness over time within the NCRN.
• Determine if the proportion of habitats occupied by amphibian species is changing over time; and, if so, how are the changes related to landscape variables including surrounding land use, road density or distance to nearest road, and proximity to or density of other potential breeding sites.
• Determine if the proportion of habitats occupied by amphibian species is related to water quality variables, other biotic and abiotic variables, hydroperiod, or climatic conditions.
• Identify priority areas within individual Parks for amphibian habitat management and protection.
• Identify and evaluate management actions to reverse declining trends or to increase the occupancy of potential habitats.
• Document the occurrence of amphibian malformations and disease outbreaks and establish SOPs for collection and vouchering of infected, dying or dead specimens.

Measures

Recently, the proportion of area occupied (PAO) metric has been developed to aid the U.S. Geological Survey's Amphibian Research and Monitoring Initiative (ARMI) in the collection of large-scale data on amphibians in the United States. This approach focuses on the proportion of habitat (or area) occupied by 1 or more target species, rather than focusing on true abundance or population size. Still, it is rare that target species are always detected at occupied sites, and the occupancy estimation methods are robust to variation in detectability due to species, habitats, and other biotic and abiotic variables. In addition, the methods allow the incorporation of covariates to test specific hypotheses about factors influencing the distribution of amphibians by providing methods to estimate occupancy despite missed observations at a site.

Status

Monitoring is done through a cooperative agreement with the United States Geological Survey, Patuxent Wildlife Research Center. They began monitoring in 2005 in streams and wetland habitats at Chesapeake & Ohio Canal National Historical Park and Rock Creek Park and have continued this monitoring every year up to 2010. They also monitored streams in Prince William Forest Park in 2006, 2008, and 2009.

Manassas National Battlefield Park wetlands have been monitored continuously from 2007 to 2010 by NCRN staff.

Contacts
Patrick Campbell, NCRN Network Coordinator
202.342.1443 ext. 229

Dr. Evan Grant, Coordinator for Northeast Ampibian Research Monitoring Initiative,
USGS Patuxent Wildlife Research Center
301.497.5842

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