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Meet Our Yellowstone Guides

We love Yellowstone! 

All our Yellowstone guides have many years experience in assisting participants of every age and background in place-based, science-based learning in the world's first National Park. We are adept at helping you feel Yellowstone's essence, not just see it. Our knowledge, experience, passion, and storytelling will leave you with memories of an unrivaled experience and a deeper appreciation for living on a moving, breathing planet!

Ashea Mills
Ashea Mills,

Naturalist Guide

Ashea has spent twenty-five years exploring and sharing the Greater Yellowstone Ecosystem, helping people connect to a wild landscape and to themselves. After obtaining a degree in English Writing Arts and Theater, she found herself in Yellowstone, working seasonally and falling in love with one of the most dynamic landscapes on earth. She has led all ages and interests through the park as a Yellowstone guide, including children’s programming, driving snow coaches, skiing and hiking deep into the backcountry, geyser gazing and road-based wildlife watching. Since 2020, she has become an expert in Virtual Touring, offering her Yellowstone interpretation in increasingly modern ways while the world adapted.

She is a certified Leave No Trace Trainer and Wilderness First Responder. She lives in Gardiner, MT with her husband Mike, an ecologist, and young daughter. Immersing in Yellowstone's wildness and the surrounding public lands on skis and foot is where they find nourishment.

Barbara Ulrich
Barbara Ulrich, M.S.
Naturalist Guide

Barbara is a geologist who has been exploring and studying the Yellowstone ecosystem for the past 25 years. Originally from Connecticut, she moved to Gardiner, Montana after retiring from her career as an environmental geologist with the State of Colorado. Her passion for Yellowstone originated from her interest in wolf reintroduction.

Barbara has been an instructor for Yellowstone Association, a guide for Xanterra, driving snow coaches and historic yellow buses, and for the past 15 years, a private guide. While in the field, Barbara loves focusing on Yellowstone’s unique geology and its influence on the ecosystem. In 2020, she earned a second master’s degree from Montana State University, where she specialized in paleoecology.

When not working in Yellowstone, Barbara enjoys traveling and has visited the Brazilian Amazon, the Galapagos, Africa, the Arctic, Greenland, and Iceland. France is her favorite destination.

Barbara received her B.A. in geology from Vassar College and her first M.S. in geology from Rutgers University.

Barbara is a Certified Interpretive Guide with the National Association for Interpretation. She lives on the Yellowstone River with her dog, Beau.

Rhiana Peck
Rhiana Peck
Naturalist Guide

Rhiana grew up on the northern edge of Yellowstone Park, where she thrived on being an active outdoors woman with the mountains and rivers of the Greater Yellowstone Ecosystem as a backdrop.
For the past decade, she has studied and lived abroad in India and Turkey, earning a degree in Sociology and Anthropology from Earlham College in Indiana. Her interest in history and the human experience lends to sharing the unique story Yellowstone tells with visitors from around the world.
After relocating back to the northern edge of the park in 2020, Rhiana is excited for the opportunity to immerse herself in her home dirt, and share her voice connecting the human story to a wild landscape. Winter finds her driving a snowcoach in Yellowstone’s interior based at Old Faithful, interpreting the landscape for a wide variety of travelers. Summer finds her based in Gardiner with the Walking Shadow Ecology team, presenting the stories of Yellowstone through the lens of geology, wildlife, and the human connection.
Rhiana is a Certified Interpretive Guide (CIG) with the National Association for Interpretation (NAI) and is a Wilderness First Responder. 

Virginia Miller
Virginia Miller
Naturalist Guide

Virginia comes to work as one of our Yellowstone guides from a long history in outdoor education and the Girl Scouts. She first worked in the park in 2012, thinking it would be just a fun one- summer job. But after falling in love with the animals, Yellowstone's thermal features, and even the lodgepole pines, she never left! Virginia has worked for 8 years with the Yellowstone Association and Yellowstone Forever Institute as a Naturalist, working with families, teacher workshops, school groups and everyone in between. In the Girl Scouts, she has worked as a summer camp counselor and Leadership Director, and as an international volunteer and Leadership Seminar facilitator. Virginia is a Certified Interpretive Guide, a Leave No Trace Trainer, and a Wilderness First Responder. After the initial shock of her first -30° Yellowstone winter days, this California girl now thrives in the winter and lives for summer hikes and paddle trips. She uses her degree in theater to make science and the outdoors come alive for students of all ages!

Dr. Mike Tercek
Mike Tercek, PhD

Mike first visited Yellowstone with his parents in 1982, and 2024 is his 34th consecutive year working in the park. His research projects have included rare (endemic) plants in Yellowstone's geothermal areas, trophic cascades (wolf - ungulate - willow interactions) on the northern range, adaptations of plants to high carbon dioxide environments, and various number-crunching / big data analyses. For the last 10 years, he has focused mostly on climate change and its effects on protected lands. He likes to dabble in repairing or modifying electronic equipment, especially for scientific data collection.  Most of his work is aimed at producing practical results that will improve land management decisions. Through his consulting company (, he works on a wide variety of ecological and climate-related projects throughout the western US. He also manages, a tool for land use managers across the country. His work provides our Yellowstone guides with the most up-to-date information on Yellowstone ecology and climate science.

My life has been changed by this incredible experience. I have a deeper awareness of the awesomeness of nature.

Reggie D.

Our Yellowstone Guides

Thank you for a most sincere, and now deeper, appreciation for the journey, wildlife, the living Earth, and what brings us home to ourselves.

Leon A.

Our Yellowstone Guides

Walking Shadow is a business devoted to advancing knowledge of Yellowstone National park through highly experienced guides.
Christine D.

Our Yellowstone Guides

"I can’t stop thinking about Yellowstone and how important it is that we care for our Earth."

Carly, age 8

Our Yellowstone Guides
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