Susan Walls, Ph.D.
Biography
RESEARCH
Susan Walls is a research wildlife biologist who serves as the coordinator and lead scientist for the southeastern region of the Amphibian Research and Monitoring Initiative (ARMI). ARMI is a national program for which funding was appropriated by Congress in 2000 in response to mounting evidence and concern for declines of amphibians in the U.S. and worldwide. Susan's research group establishes and implements long-term monitoring of amphibians at key sites within the southeastern U.S. (AL, GA, FL, SC, NC and TN) and conducts research on potential causes of declines. The team focuses on model-based monitoring to assess the impacts of climate change, emerging diseases, habitat restoration, and invasive species on amphibian communities.
Science and Products
Monitoring of Amphibians at St. Marks National Wildlife Refuge in Northwest Florida
Freshwater wetlands provide critical habitat for a diverse array of organisms, including many amphibians. Yet, under the threat of climate change, these habitats are among the most imperiled ecosystems on Earth.
Population Demography and Food Web Analysis of Large Aquatic Salamanders (Siren and Amphiuma) in North Florida
Understanding amphibian's life-histories can help predict how they may persist in aquatic habitats in the face of droughts and other climate change-associated events.
Adaptive Habitat Conservation for Flatwoods Salamanders
USGS scientists investigate adaptive habitat conservation for Flatwoods salamanders.
Evaluating the Prevalence of the Amphibian Chytrid Fungus, Batrachochytrium dendrobatidis, in the Southeastern U.S.: Any Evidence of Disease-Related Population Declines?
Pathogens and infectious disease play a role in some recent species extinctions and are likely to impact biodiversity in the future. Environmental DNA - eDNA - is coupled with traditional amphibian sampling methods to determine the distribution and prevalence of the amphibian chytrid fungus, also known as Bd, in the southeastern US.
A Decision Support Tool for Repatriation of Aquatic Fauna: A Case Study Involving the Striped Newt (Notophthalmus perstriatus) at St. Marks National Wildlife Refuge, Florida
The Striped Newt is a small salamander found in xeric habitats (e.g., scrub, sandhill, dry flatwoods) of the lower coastal plain and northern peninsular Florida. Though once considered "common," they are currently a candidate species for federal listing.
Use of Amphibian Communities as Indicators of Restoration Success in the Greater Everglades
Habitat alteration and climate, when combined, are serious threats to amphibians and other wildlife. Habitat suitability models are being used to predict the responses of an amphibian community to hydrological and habitat restoration in the Greater Everglades Ecosystem.
Coping with Invasive Alien Species and Environmental Stressors: Linking Behavioral Studies with Management for Anuran Amphibians
Climate change and invasive species are two key drivers of biodiversity loss. Knowing how amphibians respond to climate change and invasive species can greatly improve predictions of species' persistence in the face of these factors and can help guide resource managers and conservation biologists in developing strategies to manage for these encroaching disturbances.
A new framework for analysing automated acoustic species-detection data: occupancy estimation and optimization of recordings post-processing
The development and use of automated species-detection technologies, such as acoustic recorders, for monitoring wildlife are rapidly expanding. Automated classification algorithms provide a cost- and time-effective means to process information-rich data, but often at the cost of additional detection errors. Appropriate methods are necessary to...
Chambert, Thierry A.; Waddle, J. Hardin; Miller, David A.W.; Walls, Susan C.; Nichols, James D. Identifying small depressional wetlands and using a topographic position index to infer hydroperiod regimes for pond-breeding amphibians
Small, seasonal pools and temporary ponds (<4.0 ha) are the most numerous and biologically diverse wetlands in many natural landscapes. Thus, accurate determination of their numbers and spatial characteristics is beneficial for conservation and management of biodiversity associated with these freshwater systems. We examined the utility of a...
Riley, Jeffrey W.; Calhoun, Daniel L.; Barichivich, William J.; Walls, Susan C. Structured decision making as a conservation tool for recovery planning of two endangered salamanders
At least one-third of all amphibian species face the threat of extinction, and current amphibian extinction rates are four orders of magnitude greater than background rates. Preventing extirpation often requires both ex situ (i.e., conservation breeding programs) and in situ strategies (i.e., protecting natural habitats). Flatwoods salamanders (...
O'Donnell, Katherine; Messerman, Arianne F; Barichivich, William J.; Semlitsch, Raymond D.; Gorman, Thomas A.; Mitchell, Harold G; Allan, Nathan; Fenolio, Dante B.; Green, Adam; Johnson, Fred A.; Keever, Allison; Mandica, Mark; Martin, Julien; Mott, Jana; Peacock, Terry; Reinman, Joseph; Romañach, Stephanie; Titus, Greg; McGowan, Conor P.; Walls, Susan C. Species interactions and the effects of climate variability on a wetland amphibian metacommunity
Disentangling the role that multiple interacting factors have on species responses to shifting climate poses a significant challenge. However, our ability to do so is of utmost importance to predict the effects of climate change on species distributions. We examined how populations of three species of wetland-breeding amphibians, which varied in...
Davis, Courtney L.; Miller, David A.W.; Walls, Susan C.; Barichivich, William J.; Riley, Jeffrey W.; Brown, Mary E. Life history plasticity does not confer resilience to environmental change in the mole salamander (Ambystoma talpoideum)
Plasticity in life history strategies can be advantageous for species that occupy spatially or temporally variable environments. We examined how phenotypic plasticity influences responses of the mole salamander, Ambystoma talpoideum, to disturbance events at the St. Marks National Wildlife Refuge (SMNWR), FL, USA from 2009 to 2014. We observed...
Courtney L. Davis; David A.W. Miller; Walls, Susan C.; Barichivich, William J.; Riley, Jeffrey W.; Brown, Mary E. Extinction debt as a driver of amphibian declines: An example with imperiled flatwoods salamanders
A comprehensive view of population declines and their underlying causes is necessary to reverse species loss. Historically, in many cases, a narrow view may have allowed species declines to continue, virtually undetected, for long periods of time (perhaps even decades). We suggest that extinction debt is likely responsible for numerous (perhaps...
Semiltsch, Raymond D; Walls, Susan C.; Barichivich, William J.; O'Donnell, Katherine Overcoming challenges to the recovery of declining amphibian populations in the United States
The US Endangered Species Act of 1973 (ESA) affords many potential benefits to species threatened with extinction. However, most at-risk amphibians—one of the most imperiled vertebrate groups—remain unlisted under the provisions of the ESA, and many impediments to recovery exist for those species that have been listed. Of the 35 US amphibian...
Walls, Susan C.; Ball, Lianne C.; Barichivich, William J.; Dodd, Kenneth; Enge, Kevin M; Gorman, Thomas A.; O'Donnell, Katherine; Palis, John G; Semlitsch, Raymond D. Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines
Since amphibian declines were first proposed as a global phenomenon over a quarter century ago, the conservation community has made little progress in halting or reversing these trends. The early search for a “smoking gun” was replaced with the expectation that declines are caused by multiple drivers. While field observations and...
Grant, Evan H. Campbell; Miller, David A. W.; Schmidt, Benedikt R.; Adams, M.J.; Amburgey, Staci M.; Chambert, Thierry A.; Cruickshank, Sam S.; Fisher, Robert N.; Green, David M.; Hossack, Blake R.; Johnson, Pieter T.J.; Joseph, Maxwell B.; Rittenhouse, Tracy A. G.; Ryan, Maureen E.; Waddle, J. Hardin; Walls, Susan C.; Bailey, Larissa L.; Fellers, Gary M.; Gorman, Thomas A.; Ray, Andrew M.; Pilliod, David S.; Price, Steven J.; Saenz, Daniel; Sadinski, Walt; Muths, Erin L. Do geographically isolated wetlands influence landscape functions?
Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North...
Cohen, Matthew J.; Creed, Irena F.; Alexander, Laurie C.; Basu, Nandita; Calhoun, Aram J.K.; Craft, Christopher; D’Amico, Ellen; DeKeyser, Edward S.; Fowler, Laurie; Golden, Heather E.; Jawitz, James W.; Kalla, Peter; Kirkman, L. Katherine; Lane, Charles R.; Lang, Megan; Leibowitz, Scott G.; Lewis, David Bruce; Marton, John; McLaughlin, Daniel L.; Mushet, David M.; Raanan-Kiperwas, Hadas; Rains, Mark C.; Smith, Lora; Walls, Susan C. Geographically isolated wetlands: Rethinking a misnomer
We explore the category “geographically isolated wetlands” (GIWs; i.e., wetlands completely surrounded by uplands at the local scale) as used in the wetland sciences. As currently used, the GIW category (1) hampers scientific efforts by obscuring important hydrological and ecological differences among multiple wetland functional types...
Mushet, David M.; Calhoun, Aram J.K.; Alexander, Laurie C.; Cohen, Matthew J.; DeKeyser, Edward S.; Fowler, Laurie G.; Lane, Charles R.; Lang, Megan W.; Rains, Mark C.; Walls, Susan C. Anuran site occupancy and species richness as tools for evaluating restoration of a hydrologically-modified landscape
A fundamental goal of wetland restoration is to reinstate pre-disturbance hydrological conditions to degraded landscapes, facilitating recolonization by native species and the production of resilient, functional ecosystems. To evaluate restoration success, baseline conditions need to be determined and a reference target needs to be established...
Walls, Susan C.; Waddle, J. Hardin; Barichivich, William J.; Bartoszek, Ian A.; Brown, Mary E.; Hefner, J. M.; Schuman, Melinda J. Identifying monitoring gaps for amphibian populations in a North American biodiversity hotspot, the southeastern USA
I review the primary literature to ascertain the status of amphibian monitoring efforts in the southeastern USA, a “hotspot” for biodiversity in North America. This effort revealed taxonomic, geographic and ecological disparities in studies of amphibian populations in this region. Of the species of anurans and caudates known to occur...
Walls, Susan C.
A Unified Research Strategy for Disease Management
As wildlife diseases increase globally, an understanding of host-pathogen relationships can elucidate avenues for management and improve conservation efficacy. Amphibians are among the most threatened groups of wildlife, and disease is a major factor in global amphibian declines.
Large-scale Review of Amphibian Species and Community Response to Climate Change
Amphibian species and community richness has been declining in North America and climate change may play a role in these declines. Global climate change has led to a range shift of many wildlife species and thus understanding how these changes in species distribution can be used to predict amphibian community responses that may improve conservation efforts.