INVENTORY AND MONITORING OF AMPHIBIANS AND ... - …

INVENTORY AND MONITORING OF AMPHIBIANS AND REPTILES IN THE POWDER RIVER BASIN AREA OF WYOMING

FINAL REPORT 2010

Prepared by: Wendy Estes-Zumpf, Zoologist

Hannah Griscom, Zoologist Doug Keinath, Senior Zoologist Wyoming Natural Diversity Database

University of Wyoming 1000 E. University Ave // Department 3381

Laramie, Wyoming 82071

Prepared for: Bill Ostheimer & the Aquatic Task Group

BLM Buffalo Field Office 1425 Fort Street

Buffalo, Wyoming 82834 February 2011

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TABLE OF CONTENTS

EXECUTIVE SUMMARY......................................................................................................................4 INTRODUCTION .................................................................................................................................6

Objectives ...................................................................................................................................6 METHODS .........................................................................................................................................7

Study Area ..................................................................................................................................7 Selection of Monitoring Sites ....................................................................................................8 Survey Protocols ........................................................................................................................8 Monitoring Pathogens .............................................................................................................11 RESULTS & DISCUSSION .................................................................................................................12 Monitoring Sites ......................................................................................................................12 2010 Survey Results .................................................................................................................12 Species Distributions ...............................................................................................................15 BLM Special Area Results .......................................................................................................16 Tiger Salamander Mortality ....................................................................................................17 Chytrid Analyses ......................................................................................................................18 RECOMMENDATIONS .......................................................................................................................18 ACKNOWLEDGEMENTS ....................................................................................................................20 LITERATURE CITED.........................................................................................................................21 TABLES AND FIGURES .....................................................................................................................23

Table 1. Species of amphibians and reptiles expected to occur in the Powder River Basin of Wyoming ..........23 Table 2. List of acronyms for species names used in tables and figures.............................................................24 Table 3. Locations of proposed monitoring sites for long-term monitoring of amphibian and reptile populations in the Powder River Basin, Wyoming. ................................................................................................................. 24 Table 4. Occupancy estimates for amphibians detected during nocturnal call surveys in 2010. ........................ 25 Table 5. Occupancy estimates for amphibians detected during visual encounter surveys in 2010. .................. 26 Table 6. Occupancy estimates for reptiles detected during visual encounter surveys in 2010 ........................... 26 Table 7. Comparison between vehicle mortality rates documented for the same 1-mile stretches of road surveyed by WYNDD in 2009 & 2010 ................................................................................................................ 27 Table 8. Results of amphibian and reptile surveys in key areas of the Powder River Basin .............................. 28 Figure 1. Map of the Powder River Basin and Welch Management Area where amphibian and reptile surveys were conducted by WYNDD from 2008 to2010. ................................................................................................. 30

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Figure 2. Location of proposed monitoring sites for amphibians and reptiles in the Powder River Basin and surrounding area ................................................................................................................................................... 31

Figure 3. Location of amphibian and reptile surveys conducted in the Powder River Basin in 2010. ............. 32

Figure 4. Relative diversity of species detected at survey locations from 2008 to 2010 during WYNDD field work in the Powder River Basin...........................................................................................................................33

Figure 5. Locations of occurrences for Northern Leopard Frogs and Boreal Chorus Frogs detected 2008-2010 during WYNDD field surveys in the Powder River Basin. .................................................................................. 34

Figure 6. Locations of occurrences for Woodhouses Toads detected 2008-2010 during WYNDD field surveys in the Powder River Basin. ................................................................................................................................... 35

Figure 7. Locations of occurrences for Tiger Salamanders detected 2008-2010 during WYNDD field surveys in the Powder River Basin .................................................................................................................................... 36

Figure 8. Locations of occurrences for Plains Spadefoot Toads and Great Plains Toads detected 2008-2010 during WYNDD field surveys in the Powder River Basin ................................................................................... 37

Figure 9. Locations of occurrences for Bullsnakes detected 2008-2010 during WYNDD field surveys in the Powder River Basin .............................................................................................................................................. 38

Figure 10. Locations of occurrences for Prairie Rattlenakes detected 2008-2010 during WYNDD field surveys in the Powder River Basin .................................................................................................................................... 39

Figure 11. Locations of occurrences for gartersnakes detected 2008-2010 during WYNDD field surveys in the Powder River Basin .............................................................................................................................................. 40

Figure 12. Locations of occurrences for less common snakes detected 2008-2010 during WYNDD field surveys in the Powder River Basin ....................................................................................................................... 41

Figure 13. Locations of occurrences for Northern Sagebrush Lizard and Greater Short-horned Lizards detected 2008-2010 during WYNDD field surveys in the Powder River Basin ................................................................. 42

Figure 14. Locations of occurrences for turtles detected 2008-2010 during WYNDD field surveys in the Powder River Basin .............................................................................................................................................. 43

Figure 15. Locations of areas identified by the BLM as areas of interest for amphibian and reptile surveys .... 44

Figure 16. Locations of amphibian in the Powder River Basin area that tested positive for chytrid fungus from 2008 to 2010. ........................................................................................................................................................ 45

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EXECUTIVE SUMMARY

Coal Bed Natural Gas (CBNG) development in the Powder River Basin (PRB), Wyoming, continues to expand. The effect of CBNG development on local amphibians and reptiles is largely unknown, but possible impacts could result from changes in water quality, changes in water flow regimes, and increases in road densities and traffic volume. The Aquatic Task Group (ATG) is an inter-agency working group focused on studying and mitigating impacts of CBNG development in northeastern Wyoming and southeastern Montana. The Wyoming Natural Diversity Database (WYNDD) has been working with the Buffalo Field Office of the BLM, a member of the ATG, since 2008 to conduct an inventory and develop a monitoring plan for amphibians and reptiles in the PRB. The goal of this project is to determine the current status of amphibians and reptiles in the PRB so that future monitoring can detect changes, if any, in species composition, reproductive success, and occupancy rates due to CBNG development. We conducted several types of surveys to inventory amphibians and reptiles from 2008-2010 and to began monitoring efforts in 2010. Survey methods included visual encounter surveys of water bodies, roadkill/basking surveys, nocturnal call surveys, and visual encounter surveys of rock outcrops. We also measured water quality and/or habitat characteristics at all sites.

Over the course of the project, we have documented 19 (6 amphibian, 13 reptile) of the 21 species thought to possibly occur in the PRB, with species detection varying by survey method. The only species not confirmed that might occur in the PRB are the Bullfrog, an invasive species in Wyoming, and the Northern Prairie Lizard. In 2010, we detected 2 Pale Milksnakes, a species for which confirmed observations previously were lacking in the PRB. Tiger Salamanders and Boreal Chorus Frogs were the most common amphibian species detected, but Northern Leopard Frogs were also estimated to occupy 42% of water bodies. Bullsnake and Prairie Rattlesnakes were the most common snakes detected on roads and at rock outcroppings. Gartersnakes were typically found during VES surveys along water bodies. Northern Sagebrush Lizards were detected throughout the PRB at most rock outcrops surveyed.

We recorded road mortality along set routes at previously identified "roadkill hotspots" as well as incidental findings of amphibian and reptiles killed by vehicles. Bullsnakes and Prairie rattlesnakes were most frequently found dead on roads and average roadkill rate was 3.2 mortalities/mile at the 5 "hotspots". However, 88% of mortalities were documented on 2 stretches of SR338 next to the Welch Management Area.

We continued to collect data on known amphibian pathogens in the PRB. Large numbers of dead Tiger Salamanders have been observed in the PRB since surveys began in 2008. In 2009, diagnostic tests confirmed that salamanders sent for testing had died of a ranavirus infection. Tiger Salamander mortality was documented at 50% of lentic (standing water) sites in 2010, including the Fortification Creek area and near Ice Cave west of Kaycee. Chytrid fungus was also detected in amphibians in 2010, however, the infection rate in 2010 (7.7%) was much less than in 2009 (23%). The decreased infection rate could indicate a decrease in the prevalence of the fungus in the PRB or could result from annual variation in site selection or local weather patterns. Continued monitoring of chytrid infection rates is necessary to assess the nature of the observed trend.

In addition to monitoring efforts, we also conducted inventories for amphibians and reptiles at 10 areas of special interest to the BLM. Of these, the Fortification Creek area and the Welch

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Management area contained the most species detected. We identified 8 species at Fortification Creek in 2010 and 11 species in the Welch Management Area across 2009 and 2010 field seasons.

At the conclusion of the report, we provide locations of potential long-term monitoring sites. We recommend that the BLM and ATG to review sites to make sure they meet the needs of the group. We also recommend survey protocols for the different types of surveys proposed for long-term monitoring, including recommended modifications to improve the ability to assess trends in populations and reproductive success using occupancy modeling.

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INTRODUCTION

The Powder River Basin (PRB) in northeastern Wyoming is a surprisingly complex landscape marked by plains and large forested escarpments in the north and highly eroded ridges and breaks along the river to the south. The PRB encompasses sagebrush and grassland dominated vegetation types and is part of the Great Plains. The complex topography and sedimentary soils support a diverse array of plant and animal species. The PRB also is an important area for the extraction of coal bed natural gas (CBNG). Currently, over 18,000 CBNG wells exist in the PRB and numerous additional leases are pending. CBNG development entails establishment of new roads, construction of wells and other infrastructure related to the extraction of CBNG, and the release of groundwater extracted from coal seams into surface streams, rivers, or holding ponds. In 2003, the Buffalo Field Office (BFO) of the Bureau of Land Management (BLM) prepared an Environmental Impact Statement (EIS) for CBNG development in Wyoming and Montana which outlines potential impacts to hydrology, wildlife, and other natural resources in the Powder River Basin (BFO BLM 2003). The EIS identified 2 primary areas of concern with respect to amphibians and reptiles; (1) changes in water quality and timing due to release of CBNG product waters into surface waters, and (2) road mortalities from increased vehicular traffic.

The Aquatic Task Group (ATG) was formed in response to the lack of knowledge regarding how CBNG could impact local natural resources. The ATG is an inter-agency and inter-state working group focused on studying and mitigating impacts of energy development on aquatic ecosystems in northeastern Wyoming and southeastern Montana. In 2008, the Wyoming Natural Diversity Database (WYNDD) began a 3-year study of amphibians and reptiles in the PRB under the guidance of the ATG. The purpose of the study was to conduct an inventory of reptiles and amphibians in the PRB and design a monitoring program to track population trends as CBNG development continues to increase in the region. The majority of funding for this work was provided by the Buffalo Field Office of the BLM with some matching funds from WYNDD.

In 2008 and 2009, WYNDD conducted inventories for reptiles and amphibians across the PRB to determine the presence and relative abundance of species in the region. In 2010, our objectives focused on establishing a feasible monitoring plan with standardized survey protocols and collecting the first year of data under this plan. Because new long-term riparian monitoring reaches along the Powder River were in the process of being established, WYNDD was instructed to exclude riparian monitoring until sites were agreed upon. Thus, monitoring in 2010 focused on upland and lentic (pond) sites, with additional inventories in areas of particular interest to the Buffalo Field Office of the BLM.

Objectives

This project had 4 overall objectives:

1. Complete a literature review of impacts to amphibians and reptiles from vehicular traffic and changes in water quality.

2. Determine the general distribution and characterize the status and habitat of all amphibians and reptiles occurring in the PRB below 1,370 m.

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To do this, locations of all herptofauna observations will be combined with data from the WGFD (Turner, 2007) and WYNDDs database to produce a distribution map for each species. Overall site occupancy measures and current literature will be used to categorize species into general groups such as ,,common in PRB, ,,moderately abundant in PRB, and ,,rare in PRB. Qualitative descriptions of habitat by species will be produced by combining standardized variables collected at survey sites (including water quality) and those presented in the literature.

3. Identify potential current and long-term impacts of CBNG activities on amphibians and reptiles and suggest possible mitigation measures. This will be achieved by measuring road mortality rates and water quality tolerance levels.

Note: The impact of CBNG activities on amphibians and reptiles can only be roughly estimated within the framework of this project.

4. Establish a long-term, repeatable monitoring protocol that can be used to track population trends and impacts from CBNG activities in the future.

The literature review (Objective 1) was completed in 2008, and surveys to determine the distribution and habitat use of amphibians and reptiles in the PRB were conducted in 2008 and 2009 (Objective 2 & 3; Estes-Zumpf et al. 2010). Draft distribution maps for each species were provided in the Year 2 progress report (Estes-Zumpf et al. 2010) and final distribution maps are available free of charge upon request from WYNDD (). This report details the first year of formal monitoring efforts (site choice, protocols, etc.) as well as additional inventories at key sites identified by the BLM.

METHODS

Study Area

The Powder River watershed is located in northeastern Wyoming (Figure 1) and has an area of approximately 25,000 km2. The main stem of the river flows north into Montana where it joins the Yellowstone River. Within Wyoming, tributary streams that originate in the Bighorn Mountains to the west generally have perennial flow fed by snowmelt, whereas ephemeral tributaries originating in the plains to the south and east are characterized by short duration flows from rainstorms (Davis et al., 2006). The majority of CBNG development in the PRB is below 1,370 m elevation and, thus, defines the study area for this project. Topography is complex and includes floodplains, escarpments, upland plains, and highly eroded breaks. The climate is semiarid and land cover is dominated by two ecological systems; Inter-mountain Basins Big Sagebrush Steppe and Northwestern Great Plains Mixed-grass Prairie. Riparian vegetation along rivers and streams is usually composed of willows and tall grasses with cottonwood forests restricted to the larger rivers, but there are very few natural lentic (standing water) wetlands in the Basin. Twenty-one species of reptiles and amphibians potentially occur in the Powder River Basin of Wyoming (Table 1). Most of these species belong to the suite of Great Plains species

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whose far western range occurs in northeastern Wyoming. See Table 2 for a list of acronyms for species names used in this document.

Over 50% of land ownership in the PRB is private, limiting efforts to establish long-term monitoring sites on accessible public lands. Livestock grazing dominates land use with irrigated agriculture restricted to areas immediately adjacent to perennial rivers (Davis et al. 2006). CBNG production has increased greatly on both public and private lands in the last 10 years, especially in the eastern half of the PRB where natural gas is most easily recoverable. Gas field development often entails building and maintaining extensive road networks to serve well pads, pipelines, and compression stations. Deep aquifer water is pumped to the surface and discharged into ephemeral drainages or reservoirs in order to release natural gas trapped in coal seams. The aquifer water is usually colder than surface water and often has higher concentrations of sodium bicarbonate and other salts (Davis et al. 2006). For more background information about the potential impacts of water quality and road network changes on amphibians and reptiles, see Griscom et al. (2009; Appendix A).

Selection of Monitoring Sites

Selection of monitoring sites was guided by the following criteria.

1. Sites should be on accessible public lands to ensure access for future surveys.

2. Sites should be located in or near habitat for sensitive reptile and amphibian species (water bodies and/or rock outcrops).

3. Sites should be selected in areas of high and low potential CBNG impact.

4. Sites are known to contain one or more sensitive amphibian and/or reptile species.

It is important to note that much of the PRB is private land and was excluded in most cases from our monitoring plan. Limitations due to access issues and presence of habitat (especially water) further restricted site selection. As a result, sites selected for long-term monitoring were strategically chosen rather than randomly selected and much of the PRB was not sampled. Therefore, inferences about changes in amphibian and reptile populations from this monitoring plan are limited to changes observed at monitoring sites and should not be extrapolated to the entire PRB.

Surveys Protocols

Nocturnal Call Surveys

Nocturnal call surveys can be an efficient and effective way to survey for anurans (frogs and toads), especially in areas where to habitat is restricted. Males of all anuran species in the PRB vocalize under suitable weather conditions to attract females to breeding sites. Calls can be used to identify individuals to species and, depending on environmental conditions, can be heard up to an estimated 2 km away. Road-based nocturnal call surveys are an effective way of detecting species presence across relatively large distances without requiring physical access to adjacent land.

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