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Declining Amphibians in Western North America: Historical and Current Perspectives

1R. Bruce Bury and 2Donald J. Major

1,2Biological Resources Division
US Geological Survey
3080 SE Clearwater Dr.
Corvallis, OR 97333

Losses of amphibian populations appear greater in western North America than in the East (Corn 1994; Bury et al. 1995). The West has great diversity of habitats and ecosystems, often changing over relatively short distances. Many amphibian species occur as endemics (small geographic ranges) or occur in isolated wetlands or on mountain peaks. The ranges of most endemics in the West are dispersed across the landscape compared to endemics in the East that tend to be clustered in centers of endemism (see Bury et al. 1995 attached). The Pacific Northwest has large expanses of wet forests where several species, genera and families evolved and are now restricted geographically. For example, there are ancient lineages tied to cool-stream habitats: tailed frogs, torrent salamanders and giant salamanders. Overall, there are few shared species of amphibians in the West and the East. Eastern species that enter parts of the West include the tiger salamander, Woodhouse's toad and painted turtle. However, the West's herpetofauna is distinct from the East.

Sampling of western amphibians requires a set of techniques for each major region (e.g., Northwest forests to arid lands) and varied habitat types (stream, pond and terrestrial). Some methods proposed elsewhere do not work in the West. For example, calling surveys are of limited or no value in most of the West because few species vocalize (only heard if right near the animal). Exceptions are spadefoot toads in the arid southwest and Pacific treefrogs. The later species is widespread and ubiquitous. There is less need to survey it compared to other species (e.g., native ranid frogs) that appear to be declining in many parts of their ranges throughout the West.

The western situation is driven by legal and agency mandates (e.g., the President's Forest Plan for the Pacific Northwest) to maintain biodiversity, endangered species, and sensitive species. The West has high proportion (40-95%) of public lands. Major lands include the National Forests (U.S. Forest Service: USFS), Bureau of Land management (BLM), National Wildlife Refuges (U.S. Fish & Wildlife Service: USFWS), and National Parks (National Park Service: NPS). State agencies play a major role in managing wildlife and have their own laws and guidelines to list animals as sensitive, protected or endangered species. Also, State Forestry Practices Acts and other regulations can greatly effect amphibian populations. Industry biologists and conservation groups add vital support to protection and management of resident herpetofauna.

Volunteer programs on amphibians in the West seem minor or less effective than elsewhere in North America. In part, this reflects the dominance of agency and other groups (above). Also, the vastness of the West tends to concentrate volunteer efforts in or around larger cities. It is more difficult to organize surveys in undeveloped areas, which are often great distances from the urban centers. Whatever the reasons, agency and related efforts have highly motivated biologists who do most of the survey efforts in the West.

Scope and Objectives
The scope of this paper is declining amphibians in western North America. We only mention monitoring because this component is just being developed. Most current work is in fact inventory surveys. To us, monitoring is defined as reliably sampling amphibian populations over long periods, and this requires accurate population estimates that are not obtainable at this time.

We focus on the Pacific Northwest or specific cases in the West, but we attempt to discuss issues of broad interest and to present a model of a survey system that works regionally. Our objectives are to review relevant historical developments (set the stage), compare efforts by organizations (DAPTF, agencies, etc.), and review sampling techniques suited to the West.

Declines in populations are not unique to amphibians in the West as other aquatic organisms (e.g., fishes) have also experienced drastic losses. Amphibians appear to be suffering many of the same fates as associated fish populations: decreased number of populations and smaller population sizes.

Too often, the declining amphibian issue is considered a problem that happened a year or so ago. However, the situation has been under study for some time. There is a big difference in effort today compared to earlier because of the attention to the "amphibian crisis" by the press, public and biologists. The overall effect is highly beneficial and the issue of declining amphibians is now a major conservation effort.

Concern for western amphibians has occurred for decades with many of the early battles on protection of threatened and endangered species. One of the first was the listing of the Santa Cruz long-toed salamanders in central California. It was added to the Endangered Species list in the early 1970s. Many similar efforts lead to listing and protecting other endemic species of amphibians.

Losses of species with widespread distributions became an issue in the late 1970s and into the 1980s. There were apparent major declines in western toads and tiger salamanders in the Rocky Mountains in Colorado and southern Wyoming, and other studies have shown losses in montane habitats of California (reviewed by Corn 1994). In response to these reports, we earlier attempted a regional program on declining amphibians (Appendix 1: Study Proposal excerpts). However, it was not funded and no strategy exists today to inventory and "monitor" amphibians of the West. Still, agency biologists have been concerned and involved with amphibian issues for decades, and were among the first to push for action.

Biologists in different regions of the West are in constant contact and exchange information on many issues. We now assess the relative importance of various groups working in the West. First, we want to clearly state that the situation changes fast and the evaluations are our own. To us, the organizations and group efforts fall into several categories.

The Declining Amphibian Population Task Force (DAPTF) was established in the early 1990s. Today, DAPCAN (DAPTF - Canada) is a leader in North America because they have already finished six national meetings and have prepared a publication on sampling methodologies.

In the United States, regional groups DAPTF cover the continent. The California-Nevada and Southwest groups are active with many projects. The Pacific Northwest DAPTF had a strong start but appears to have lost stream lately as it is generally inactive today.

NAAMP seems to have low influence in the West. In part, NAAMP is a new program. Also, the situation "out West" differs from needs in the East (e.g., calling surveys and volunteer efforts are of lesser importance). Also, the West is a vast region with a tradition of independent efforts as the norm.

In 1994, a new group developed and called itself the Pacific Northwest Amphibian & Reptile Consortium (PNARC). It is now attached to the Society of Northwest Vertebrate Biologists (SNVB), which has a 77 year history. PNARC has become a regional powerhouse for training and publications.. Many PNARC members participated in a training session in 1989 in Roseburg, Oregon, that attracted 125 people, primarily to discuss forest amphibian issues. In March 1996, PNARC offered Amphibian Training to 225 participants in Corvallis, Oregon. Topics covered stream, pond and some terrestrial species. Terrestrial amphibian and general reptile sessions are planned for March 1997 in Yakima, WA (annual meeting of SNVB).

PNARC plans to release a handbook on Sampling Amphibians in Lentic Habitats in 1997 (see Table). This may be followed by handbooks on streams and, perhaps, terrestrial amphibians. They are aimed at the Pacific Northwest, but likely are broad in scope. Techniques were field tested prior to being recommended.

2. Sampling Techniques:

Many sampling protocols for forest amphibians resulted from the Old-growth Wildlife Habitat Program, funded by the U.S. Forest Service and Bureau of Land Management. This major effort sampled forest wildlife in three states (WA, OR, no. CA) comparing young, mature and old growth stands (all naturally regenerated) and a few managed (clearcut) sites. Sampling protocols were developed for terrestrial (Corn and Bury 1990) and stream (Bury and Corn 1991) amphibians. However, these were field tested in 1982-83 and employed regionally in 1984-85. Stream techniques were modified by Welsh and Lind (1991) to sample three 5-m lengths.

Current Surveys. (To be a summary only)

Streams.---Habitat-based sampling (Welsh et al. in prep.). Habitat-type stream, and then 0.6 m belts sampled in proportion to percent occurrence. Sampling with Random Draws (Bury and Major in prep.). We examine 100-m stretches of streams and habitat-type the area; then, 10 1-m belts are randomly placed for sampling. Details of methods will be published in 1997.

Terrestrial.---There is high variation within forest stands, which confounds sampling designs. Also, "edge" effects may exist when adjacent stands have different successional stages (e.g., a clearcut adjacent to a mature forest) and the influence of the open habitat on the forest stand are currently unknown. There is clearly a need to incorporate greater use on of random sampling in forests, and closer attention to substrate (especially talus) and cover objects. We predict that it will be many years before we develop an effective, repeatable sampling scheme for forest-floor amphibians.

Table 1. Handbooks on Sampling Techniques

Sampling Amphibians in Lentic Habitats, edited by Deanna H. Olson, William P. Leonard and R. Bruce Bury. Out for review. Proposed handbook for Northwest Fauna (published by the Society of Northwest Vertebrate Biologists). Target Date for Release: Spring 1997.

Table of Contents (tentative):

Appendix 1. Study Proposal excerpts
Appendix 2. Copy of publication on declining amphibians.

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U.S. Geological Survey
Patuxent Wildlife Research Center
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Last Modified: June 2002