Mapping Amphibian Occurrence on the Road System at Mount Rainier National Park

Mount Rainier Science Brief

Anthony S. Anderson*, Mount Rainier National Park; Darin D. Swinney, Mount Rainier National Park; Rebecca A. Lofgren, Mount Rainier National Park

Coastal Tailed Frog (Ascaphus truei)

NPS/ A.S. Anderson Photo

Summary

We set out to map amphibian presence along several roads at Mount Rainier National Park to help mitigate road-related impacts to amphibians. These impacts include vehicle collisions, annual road maintenance activities, and Federal Highways restoration projects. We conducted night road surveys from 2014 to 2016 following rain events in the spring through fall months on 42 miles of road. Our objectives were to (1) detect all amphibians present on the road during our surveys, and (2) identify amphibian hot spots. We conducted most surveys by vehicle at speeds averaging 5 mph which enabled us to detect juvenile frogs and small plethodontid salamanders. Amphibians encountered were identified to species, measured, locations recorded, and road-killed individuals collected. We detected 1243 amphibians between 2014 and 2016 with 52 % of those encountered road-killed. Twelve of 14 species known to occur at Mount Rainier were found on park roads during these surveys including 2 species of concern (Plethodon larselli and P. vandykei). The most common species detected were Coastal Tailed Frogs (Ascaphus truei), which accounted for 63.8 % of all amphibian species encountered (793 total, 55.3% road-killed). We identified several amphibian hotspots associated with wetland features. The mapping project has served as a resource for park management to mitigate impacts of road rehabilitation projects on amphibians, and to evaluate site specific options at known amphibian hotspots to mitigate impacts of road-associated maintenance operations.

Larch Mountain Salamander (Plethodon larselli)

NPS/ A.S. Anderson Photo

Introduction

Mount Rainier National Park is located in west-central Washington, on the western slope of the Cascade Range. Encompassing over 236,000 acres, the park is 97% designated wilderness with a road system that makes up 0.13% of the total area. Visitation at MORA exceeds 1 million visitors annually with peak visitation during the summer months.

We set out to map amphibian presence along several roads at Mount Rainier National Park to help mitigate road-related impacts to amphibians. These impacts include vehicle road kill, annual road maintenance activities, and Federal Highways restoration projects. Our objectives were to (1) detect all amphibians present on the road during our surveys, and (2) identify amphibian hot spots.

Map of Mount Rainier National Park with the Project Area roads highlighted on the south side of the park. The roads in the study are the Paradise Road, Paradise Valley Road, Stevens Canyon Road, and Highway 123.

NPS Graphic

Methods

Site Characteristics
The four roads (Table 1) surveyed occur on the south side of Mount Rainier and essentially form a continuous transect spanning the west and east sides of the park with an elevation range from 1720 to 5400 feet and a total length of 41.6 miles. These 4 roads span several vegetation zones, bisect several major glacial rivers, and are adjacent to numerous aquatic habitats and upland features important to amphibians.

Table 1. Roads surveys with their total lengths and elevation ranges. We surveyed the entire length of three roads and a small section of Highway 123*.

Road Name	Length (miles)	Elevation Range (feet)
Nisqually-Paradise Road	17.7	2000-5400
Paradise Valley Road	2.1	5360-4800
Stevens Canyon Road	19.0	4880-2160
Highway 123	2.8* (16.3)	2160-1720

Ensatina (Ensatina eschscholtzii)

NPS/ A.S. Anderson Photo

Survey Methods
We conducted night road surveys April through November, following or during a rain event when the road surface was predominantly wet and temperatures were above freezing (4.5-19 C). Surveys were done by vehicle at speeds averaging 5 mph with occasional forays on foot when we encountered heavy leaf litter or other debris on pavement. We used the vehicles low beams and fog lights to illuminate the road surface under typically rainy conditions. We also used led flashlights (116 lumens) to spot check for potential amphibians from the vehicle window or on foot. Searches were done by either 1 or 2 surveyors from the front of vehicle. A third surveyor recorded data from the back seat and helped with logistics on 1 night. Surveys were started no earlier than 1 hour after sunset and we tried to finish 1 hour before sunrise. Roads were typically surveyed in sections and not in their entirety on a given night, based on weather conditions and availability of surveyors. Additionally, we recorded opportunistic observations made while in route to and from surveyed road sections. We recorded search effort hours as time spent actively searching multiplied by the number of surveyors. For opportunistic observations we recorded search effort hours only when traveling close to 5 mph. Amphibians encountered were identified to species, measured, locations recorded, and road-killed individuals collected. Live amphibians were placed off the road on the side the individual was facing or if direction of travel was uncertain then the nearest side to where the amphibian was located.

Van Dyke's Salamander (Plethodon vandykei)

NPS/ A.S. Anderson Photo

Results

Total survey effort for 2014-16 was 24 survey nights representing 59.9 search effort hours and 138.6 miles surveyed on 41.6 miles of road (Table 2). We detected 1243 amphibians between 2014 and 2016 with 52 % of those encountered road-killed (Table 3). Twelve of 14 species known to occur at Mount Rainier were found on park roads during these surveys including 2 species of concern (Plethodon larselli and P. vandykei). The most common species detected were Coastal Tailed Frogs (Ascaphus truei), which accounted for 63.8 % of all amphibian species encountered. The next most common species detected were Northwestern Salamanders (Ambystoma gracile, 6.8%) followed by Ensatinas (Ensatina eschscholtzii, 6.6%) and Cascade Frogs (Rana Cascadae, 6.2%). The two roads with the greatest elevational range also had the greatest diversity of amphibians with 11 species each. Coastal Tailed Frogs were found on all four roads with high concentrations on all but Hwy 123. The majority of hot spots on the map reflect Tailed Frog numbers with the exception of the lower Paradise road where several pond breeding amphibians occur and the road bisects wetland and upland habitat.

Table 2. Number of miles surveyed by year on each of the four roads including total miles surveyed by year and total search effort hours by year. Parentheses indicate additional miles searched opportunistically at much lower search effort.

	Miles surveyed by year
Road	2014	2015	2016
Nisqually-Paradise	(13)	26.2 (11.1)	44.3 (24.9)
Paradise Valley	2.1	4.2	2.1
Stevens Canyon	7.3	29 (19)	15 (14.5)
Hwy 123	-	(2.8)	5.6
Total Miles	9.4 (13)	62.2 (32.9)	67 (39.4)
Total Search Effort Hours	6.52	24.1	29.3

Table 3. Total amphibian observations on 4 roads (Paradise Rd, Valley Rd, Stevens Canyon Rd, and a 2.8 mi. section of Hwy 123) totaling approximately 42 miles, between 2014-16, representing 24 survey nights (2014: 6 nights, 2015: 7 nights, and 2016: 11 nights) and 59.9 search effort hours. Parentheses indicate number of total observations made during 3 surveys (Stevens Canyon 2015-16, Valley Road 2014) in which the road was closed to traffic.

Species	Total Observations	Road Kill	% Road Kill
Ascaphus truei	793 (114)	376	55.3
Ambystoma gracile	85	30	35.2
Ensatina eschscholtzii	82 (7)	13	17.3
Rana cascadae	77 (7)	45 (1)	62.8
Pseudacris regilla	45	24	53.3
Rana aurora	41	34	82.9
Plethodon larselli	37 (6)	8	25.8
Taricha granulosa	35	27	77.1
Ambystoma macrodactylum	14 (2)	4	33.3
Rana species	10	7	70
Dicamptodon tenebrosus	8	1	25
Anura species	8	5	62.5
Plethodon vehiculum	4	1	25
Plethodon vandykei	3	1	33.3
Dicamptodon species	1	1	100
Grand Total	1243 (136)	577 (1)	52

Discussion

The relatively large number of Ascaphus truei observed during surveys was unexpected. Based on our observations, it appears that Ascaphus are attracted to wet pavement much like snakes are attracted to warm pavement. Their typical response on being approached either by vehicle or on foot was to crouch, lying prone upon the road. This response may in part account for the 55% mortality rate we observed. We hope to expand on this work in the future with a more rigorous survey methodology, but as it stands the mapping project has served as a resource for park management to mitigate impacts of road rehabilitation projects on amphibians, and to evaluate site specific options at known amphibian hotspots to mitigate impacts of road-associated maintenance operations.

Acknowledgements

We would like to thank the following people for their assistance and support for this project: Kirsten Anderson, Kate Baustian, Andrew Bennett, Robin Cloughley, Jeff Antonelis-Lapp, Colleen Parker, Christine Phelan, Barbara Samora. Courtney Thomas, and Annie Tran.