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Vernal Pool Ecology and Conservation and Amphibian Metapopulation Dynamics in Southern New England

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Welcome to our vernal pool studies website. The purpose of this website is to facilitate dissemination of information pertaining to studies conducted under the auspices of this research program; specifically, to briefly describe each study, list the investigators and publications resulting from this project, and make available data and documents. vernal pool image

About the Investigators

The vernal pool ecology and conservation program involves a team of scientists at the University of Massachusetts, Department of Environmental Conservation, Landscape Ecology Lab:

Principal Investigators:

  • Dr. Kevin McGarigal --Associate professor and Director of the Landscape Ecology Lab, UMass, Amherst..
  • Scott Jackson -- Director the Natural Resources and Environmental Conservation (NREC) Extenion Program, UMass, Amherst.

Research Associates and Graduate Assistants:

  • Brad Compton -- Research associate; investigator on the kernel pools connectivity project, marbled salamander metapopulation dynamics project, and metapopulation viability modeling project.
  • Chris Jenkins -- Former graduate assistant; investigator on the marbled salamander metapopulation dynamics project.
  • Lloyd Gamble -- Former graduate assistant; investigator on the marbled salamander metapopulation dynamics project, kernel pools connectivity project and metapopulation viability modeling project.
  • Brad Timm -- Graduate assistant; investigator on the eastern spadefoot toad project and marbled salamander metapopulation dynamics project.
  • Ethan Plunkett -- Former graduate assistant; investigator on the metapopulation viability modeling project and the marbled salamander metapopulation dynamics project.
  • Megan Chesser -- Graduate assistant; investigator on the marbled salamander metapopulation dynamics project.

Marbled salamander metapopulation dynamics project

Project Description

In the context of increasingly fragmented natural habitats and global declines in biodiversity, there is an urgent need to better understand the spatial complexities of rare wildlife populations and the scales at which they operate. The marbled salamander is rare in Massachusetts at the northern edge of its range and offers an excellent opportunity to examine its spatial ecology and conservation.

marbled salamander image
Metapopulation theory, originally based on a binary view of habitat patches in a non-habitat matrix, provides one conceptual framework which has been widely accepted for its potential relevance to fragmented populations. A large body of theoretical work has followed in this arena, but remains largely unsubstantiated by empirical studies of real populations. The theory is easily expanded to accommodate spatial heterogeneous landscapes such as exists in southern New England. vernal pool cluster image

We are addressing this problem with an unprecedented landscape-level investigation into the population dynamics of marbled salamanders (Ambystoma opacum) among clusters of vernal pools in western Massachusetts. In the preliminary phase of this study (1998-2001), we identified optimal study locations, built an extensive field infrastructure, and compiled baseline data on amphibian populations at these sites (see this brochure for description of the origin of this project and preliminary findings). In a continuation of this work (2002 to present), we are building and analyzing a multi-year data set for several "breeding populations" in order to address the following objectives:

1) Characterize the range of demographic variation and temporal synchrony among local marbled salamander populations.

2) Quantify dispersal rates among breeding sites and subsequently, the degree of effective isolation or interaction among these sub-populations.

3) Build spatially-explicit and empirically-parameterized population models to generate informed hypotheses about the scale(s) at which marbled salamander populations operate and the significance of sub-population interactions to overall population viability.


Toward these objectives, we are continuously monitoring drift fence arrays which completely encircle 14 breeding ponds in a 1-km-radius study area. Amphibians are captured, recorded, and released as they enter or leave pond basins during breeding migrations and post-metamorphosis emergence. Photographic-recapture methodsare being used (in collaboration with Dr. Sai Ravela at MIT) to uniquely identify all adult marbled salamanders and mark-recapture methods associate metamorph salamanders with their natal ponds. A range of vital rates and demographics are being calculated from capture-recapture data and skeletochronology analyses, including local population sizes, sex ratios, age at maturity, reproductive success, and longevity.

We hope to greatly augment our understanding of local dynamics in amphibian populations and to provide data to rigorously quantify dispersal rates in marbled salamanders. In addition, this work will provide a thoroughly documented empirical example of how amphibian populations operate at a landscape-scale, offering to assess the relevance of metapopulation theory to pond-breeding amphibians and potentially to provide alternative conceptual frameworks. To the conservation and natural resource policy communities, this work will provide insights regarding the potential effectiveness or shortfalls of existing regulations targeting ephemeral wetlands and will provide much-needed contextual information to better direct conservation strategies for vernal pool amphibians. While most current efforts remain centered on individual breeding sites and surrounding "buffer zones", this work may provide compelling evidence that larger-scale conservation planning is requisite to ensure the persistence of spatially dynamic populations.


dorsal pattern recognition image


Gamble, L.R., K. McGarigal, D.B. Sigourney, and B.C. Timm. 2009. Survival and breeding frequency in Marbled Salamanders (Ambystoma opacum): implications for spatio-temporal population dynamics. Copeia 2:394-407. (pdf)

Gamble, L. R., S. Ravela, and K. McGarigal. 2008. Multi-scale features for identifying individuals in large biological databases: an application of pattern recognition technology to the marbled salamander Ambystoma opacum. Journal of Applied Ecology 45:170–180. (pdf)

Gamble, L.R., K. McGarigal, and B.W. Compton. 2007. Fidelity and dispersal in the pond-breeding amphibian, Ambystoma opacum: Implications for spatio-temporal population dynamics and conservation. Biological Conservation 139:247-257. (pdf)

Timm, B. C., K. McGarigal, and B. W. Compton. 2007a. Timing of large movement events of pond-breeding amphibians in western Massachusetts, USA. Biological Conservation 136:442-454. (pdf)

Timm, B. C., K. McGarigal, and L. R. Gamble. 2007b. Emigration timing of juvenile pond-breeding amphibians in western Massachusetts. Journal of Herpetology 41(2):243-250. (pdf)

Timm, B.C., K. McGarigal, and C.L. Jenkins. 2007c. Emigration orientation of juvenile pond-breeding amphibians in western Massachusetts. Copeia 3:685–698. (pdf)

Jenkins, C. L., K. McGarigal, and B. C. Timm. 2006. Orientation of movements and habitat selection in a spatially-structured population of marbled salamanders (Ambystoma opacum). J. of Herpetology 40(2):240-248. (pdf)

Gamble, L. R., K. McGarigal, C. L. Jenkins, and B. C. Timm. 2006. Limitations of regulated “buffer zones” for the conservation of marbled salamanders. Wetlands 26(2):298-306. (pdf)

Jenkins, C. L., K. McGarigal, and L. Gamble. 2003. Comparative effectiveness of two trapping techniques for surveying the abundance and diversity of forest floor vertebrates along drift fence arrays. Herpetological Review 34:39-42. (pdf)

Jenkins, C. L., K. McGarigal, and L. Gamble. 2002. A comparison of aquatic surveying techniques used to sample Ambystoma opacum Larvae. Herpetological Review 33:33-35. (pdf)

Kernal pools connectivity project

Project Description

Vernal pool-breeding amphibian populations operate at multiple scales, from the individual pool, to the pool and its surrounding upland habitat, to clusters of pools connected by periodic dispersal of individuals, to broader regional clusters of pools connected via gene flow. To understand and conserve these populations, we must adopt a multi-scale perspective.

vernal pool connectivity image

When metapopulation dynamics play a role in long-term viability, conservation efforts limited to the protection of individual pools or even pools with associated upland habitat may be ineffective over the long term if connectivity among pools is not maintained. Connectivity becomes especially important and difficult to assess in regions where suburban sprawl is rapidly increasing land development, road density, and traffic rates. In this project, we developed a model of connectivity among vernal pools for the four ambystomatid salamanders that occur in Massachusetts and applied it to the nearly 30,000 potential ephemeral wetlands across the state. This model is based on a modification of the kernel estimator (a density estimator commonly used in home-range studies) that takes landscape resistance into account. The model was parameterized with empirical migration distances for spotted salamanders (Ambystoma maculatum), dispersal distances for marbled salamanders (A. opacum), and expert-derived estimates of landscape resistance. The model ranked vernal pools in Massachusetts by local, neighborhood, and regional connectivity and by an integrated measure of connectivity, both statewide and within ecoregions. The most functionally connected pool complexes occurred in southeastern and northeastern Massachusetts, areas with rapidly increasing suburban development. A sensitivity analysis showed that estimates of pool connectivity were relatively insensitive to uncertainty in parameter estimates, especially at the local and neighborhood scales. Our connectivity model could be used to prioritize conservation efforts for vernal-pool amphibian populations at broader scales than traditional pool-based approaches.


Compton, B.W., K. McGarigal, S.A. Cushman, and L.R. Gamble. 2007. A resistant-kernel model of connectivity for amphibians that breed in vernal pools. Conservation Biology 21(3):788-799. (pdf)


A model of vernal pool connectivity for amphibians in western Massachusetts (Compton, Cushman, and McGarigal). Presented at the 10th Annual Meeting of The Wildlife Society, Burlington, Vermont, USA, September 6-10, 2003


The data provided here contains the results of the kernel pools model for Massachusetts (Compton et al. 2007). The data is provided in two formats: ascii text and ArcGIS shapefile, as described in the readme.text file.

  • readme.txt - ascii text file (read this first!)
  • - zip file containing model results in ascii text format
  • - zip file containing model results in shape file format
  • - zip file (40 mb) containing model results of the neighbor kernel surface (i.e., neighborhood connectivity surface)

Metapopulation viability modeling project

Project Description

In conjunction with the marbled salamander metapopulation dynamics study (see description above), this project, initiated in 2005, was being conducted under the auspices of a larger USDA National Research Initiative project led by the University of Rhode Island entitled: Validating Best Forest Management Practices around Vernal Pools: Amphibian Metapopulations, Opportunity Costs, Public Values and Harvester Compliance (PI is Stephen Swallow). Briefly, the larger project integrated conservation biologists and economists, and included four primary areas of inquiry pertaining to the measurement of amphibian response to forest harvesting around vernal pools. One of the overall study objectives was to test the degree to which amphibian metapopulations react to forest harvesting around vernal pools through field experiments in working forests of New England. This work focused on the degree to which dispersal of amphibians is inhibited by various levels of harvesting (and canopy closure) in varying buffer zones from the margin of a vernal pool out to several hundred meters. A component of this work involved an effort to develop and parameterize a model of amphibian metapopulations in a working forest with multiple vernal pools over which subpopulations disperse and interbreed to sustain the metapopulations of vernal pool species. We developed a spatially explict metapopulation viability model for this purpose. Using detailed demographic and movement data collected on marbled salamanders during our long-term field study to help parameterize the model, we assesed the population viability under a range of hypothetical land use scenarios. This simulation unites ecological theory with empirical data to create a better understanding of how specific land use decisions might effect vernal pool breeding amphibians, and hopefully will allow land managers and policy makers to make more informed decisions. In particular, we hope that our results will assist investigators and managers in identifying configurations of forest harvesting practices that may sustain similar levels of amphibian metapopulations.


Manuscripts describing this work are in review and will be posted here at a later date.

Marbled salamander conservation plan

Project Description

In conjunction with the marbled salamander metapopulation dynamics project, kernel pools connectivity project and metapopulation viability modeling projects, we have developed a strategic conservation plan for marbled salamanders in the state of Massachusetts. This plan is based on ten years of intensive field work in western Massachusetts and extensive computer modeling, as described in the projects above. This plan is a work in progress and as new findings become available either through our own work or the work of others, we will update the plan.


McGarigal, K. 2008. Marbled Salamander (Ambystoma opacum) Conservation Plan for Massachusetts. University of Massachusetts publication. (pdf)

Eastern spadefoot toad project

Project Description

The Eastern spadefoot toad (Scaphiopus h. holbrooki) is a unique member of the amphibian fauna in the northeastern United States, belonging to a family of toads (the spadefoots: Pelobatidae) that are adapted to desert environments. Of the 7 species of spadefoot toads found in North America, the Eastern spadefoot is the only species found east of the Mississippi River, and lies at the northernmost extent of its range in Massachusetts.

eastern spadefoot toad image

While this species is relatively abundant throughout the southern portion of its range (Florida and the southeastern coastal plain), here in New England the Eastern spadefoot is among our rarest amphibians. This species is listed as either state threatened or endangered in the three New England states in which it is known to occur (MA, CT, and RI), and populations are few and far between throughout, with exception to Cape Cod.

Recent work at Cape Cod National Seashore has documented significant populations of spadefoot toads throughout the Park, likely comprising the greatest concentration of this species in the Northeast. However, to date, there has been limited research conducted with respect to spadefoot toads at the Park as well throughout the remainder of the Northeast, and much of the information known at the current time has been obtained via incidental observations.

In order to provide for more effective management of this species at Cape Cod, as well as rangewide, a greater understanding of life history and population ecology attributes must be gained. Our reseach project, initiated in 2005, is focused on: 1) Identifying and characterizing breeding/non-breeding sites at Cape Cod National Seashore; 2) assessing the terrestrial movement ecology of this species via radio-telemetry; 3) identifying specific meteorological and environmental conditions stimulating movement events; and 4) predicting impacts of increased groundwater withdrawal rates on populations of this species.

In addition, impacts of road mortality on populations of pond-breeding amphibians is a concern that is gaining more attention both publicly and scientifically over recent years, and likely has a significant negative impact on populations in increasingly developed areas. Data collected over recent years during nocturnal roadway surveys at Cape Cod National Seashore has documented significant road mortality of spadefoot toads during movement events, and it is unknown whether the current rates of road mortality are sustainable over the long-term. Using nocturnal roadway surveys and a combination of other methods, we are quantifying road mortality of spadefoot toads and assessing impacts this may be having on local and regional populations.


The projects describe here were funded by the following organizations: University of Massachusetts, Amherst; Natural Heritage & Endangered Species Program of the Massachusetts Division of Fisheries and Wildlife; Cape Cod National Seashore and the National Park Service, Sweet Water Trust (Boston, MA), U.S. Geological Survey Amphibian Research and Monitoring Initiative (ARMI), the Silvio Conte National Wildlife Refuge (Challenge Grant #50181-1-J045A), Massachusetts Environmental Trust (Boston, MA), and the Robert & Patricia Switzer Foundation. This work would not have been possible with the contributions of numerous field technicians and volunteers, and we are eternally grateful for their contributions.

For more information, please contact:
Dr. Kevin McGarigal
Department of Environmental Conservation
University of Massachusetts
304 Holdsworth Natural Resources Center
Box 34210, Amherst, MA 01003
Fax: (413) 545-4358; Phone: (413) 577-0655

Copyright 2000 University of Massachusetts Amherst, Massachusetts, 01003. (413) 545-0111. This is an official page of the University of Massachusetts Amherst campus. All material in this website is made available according to the Fair Use Statute of the U.S. Copyright Act