Mammal Tracks, 2nd ed. and the Elusive House Mouse

North American deermouse. Yosemite National Park, CA. Photograph by Mark Elbroch

Many animal signs have eluded me and caused me concern over the years. House mouse (Mus musculus) footprints were one such sign—I expected I’d seen them, but wasn’t certain. Certainly house mice are supposed to be widespread in some environments, but I’d never actually seen one in the northern woodlands that have for the most part characterized my homes over the last 30+ years.

The answer was to gather footprints from captive mice, and work backwards I figured. With the help of Andy Stratton, we did just that. Their footprints, thank goodness, have some distinctive features and therefore I can be fairly certain that I’ve not often mistaken deermice or harvest mice footprints for those of house mice. With the exception of one important occasion, unfortunately—I misidentified house mouse tracks in the 1st edition of Mammal Tracks and Sign.

It ends up that house mice are well established in reserves and parks bordering San Francisco Bay, where they compete with listed salt water harvest mice. And this is exactly where I’d taken the photograph found on page 593 in the second edition of Mammal Tracks and Sign: A Guide to North American Species, written with Casey McFarland. I’d called them harvest mouse tracks in the first edition, but upon inspection, they clearly aren’t. One quick and easy distinguishing feature useful in their identification is that whereas harvest mice front and hind tracks are of similar dimensions, the hind footprints of house mice are distinctly larger than those of front tracks.

I’m thrilled to finally feel I’ve made some progress with this elusive critter. One box checked, hundreds more to go!


Page 593 in the new edition of Mammal Tracks and Sign where I confess my mistake in the first edition–these are footprints of house mice not harvest mice.

Read Mammal Tracks and Sign, 2nd edition for additional details about house mouse tracks, and countless other tidbits to refine one’s observations in the natural world. The book is slightly taller and wider than the previous edition, but more slender. It feels better in the hand I think. Its just slightly more than 2.8 lbs, or weighs nothing at all as a Kindle file.

It’s dense. The designers really packed it in there, trying to save space everywhere possible to reduce the length of the book. Many images are smaller than I would have liked, but that’s just because I think tracks and sign are beautiful. Educationally, they should suffice.

The contributions of so many other people really elevated this edition to another level. Thank you everyone. Chris Hass shared so much about coatimundis, Preston Taylor and Matt Nelson shared amazing things about wild pigs, and numerous biologists contributed amazing images to expand the chapter on interpreting prey remains. And my CyberTracker evaluator and Specialist colleagues, Jonah Evans, George Leoniak, Dave Moskowitz, Kim Cabrera, Michelle Peziol, and Connor O’Malley contributed so much as well. And that’s just for starters… so many others contributed as well. Thank you all.

Link to the book on Amazon

Link to book on Barnes and Noble

Reflection on Tracker Evaluations in North America

Male mountain lion tracks. Mark Elbroch

Jonah Evans, CyberTracker Evaluator and host of, sent me an audio file of a talk I gave on the CyberTracker Tracker Evaluation system, at the International Society of Professional Trackers in 2005 (I think) in Texas, just before we gave the first tracker evaluation to Texas Parks and Wildlife Department employees responsible for river otter surveys in the eastern portions of the state. It was a historic moment, and tremendous fun to boot. Since then, we’ve evaluated and trained about 90 staff of Texas Parks and Wildlife. They were brave enough to let us assess their staff, and it was the perfect launch to North American tracker evaluations–working with people who utilize tracking skills in their everyday work and lives. I wouldn’t have had it any other way.

Moose trail, Grand Teton NP, Wyoming. Mark Elbroch

Its a long talk (link below), just to warn you, but mostly anecdotal and hopefully entertaining. Its fun to look back and consider how far the system has grown in this country over the last 14ish years. If we include those in training, we’ve about a dozen evaluators working across North America now, spreading the system created by Louis Liebenberg so many years ago in South Africa. Numerous countries have hosted evaluations around the globe, ranging from Spain to Denmark to Vietnam to Botswana to Canada. The system continues to grow.

Thank you everyone who has contributed to its success.

Link to the talk.

The Olympic Cougar Project


M16, a male puma being followed as part of the new Olympic Cougar Project. Photograph by Mark Elbroch

Panthera’s Puma Program has been silent for awhile, but we’ve not been idle. We’ve been changing and growing, and we’re launching new projects in both North and South America. Here, we introduce the Olympic Cougar Project. It is a large-scale, multi-national collaborative effort, in which we’re assessing mountain lion (or cougars as they are locally called in the Pacific northwest) connectivity in western Washington State.

Previous research on the genetic diversity of mountain lions in Washington State highlighted that cats on the Olympic Peninsula west and south of Seattle may already be in trouble. They are genetically less diverse than those on the mainland, likely because the Peninsula’s mountain lions are isolated from mainland populations. Without doubt, the situation is getting worse.

The Olympic Peninsula is fast becoming an island. The Interstate-5 (I-5) highway corridor south of Seattle is one of the fastest developing regions on the west coast, and is increasingly severing wildlife connectivity in western Washington.

Location of the Olympic Cougar Project. The red arrow denotes connectivity between the Peninsula and the mainland across the I-5 corridor. 1=Makah Tribe, 2=Lower Elwha Klallam Tribe, 3=Jamestown S’Klallam Tribe, 4=Quinault Tribe, 5=Skokomish Tribe

South of the peninsula lies the massive Columbia River, forming a considerable barrier for mountain lions traveling that direction. Discharging more water than any other river in the northwest, a mountain lion would need to swim about 6 miles to cross the mouth of the river. Mountain lions that wind their way eastward, closer to I-5, can shrink that crossing to a feasible swim as short as 2/3 of a mile. There are stories of mountain lions swimming across water bodies up to a mile wide, but much of the river south of the Olympic Peninsula is 2-6 miles wide.

West of the peninsula lies the Pacific Ocean, and to the north the Strait of Juan de Fuca which, at its narrowest point, offers a 15-mile swim to Vancouver Island across shipping lanes full of massive ships and hungry orcas. The bustling Puget Sound sits to the east. Navy shipyards, ferry traffic between Seattle and offshore islands, and poisonous trace metals from old industry seeping into the estuary make this area treacherous for any wildlife, pumas included.

Looking at all the options, the south and the east are still the best possibilities for pumas to immigrate and emigrate from the Peninsula. However, this means traveling through increasingly developed areas along the I-5 corridor from Tacoma, WA southward to the Oregon border. Certainly to the south, closer to Oregon, that path is much less developed and much easier, but with time the highway will widen and infrastructure and communities will grow to create a wider developed corridor, and a noose for wildlife like mountain lions, that require large connected landscapes to maintain their health over time.

F6, an adult female mountain lion (or cougar) being followed by our new Olympic Cougar project. Photograph by Mark Elbroch

Ultimately, our goal is to map mountain lion connectivity, identify bottlenecks and blockages in wildlife corridors, and work with state developers to ensure I-5 is modified to aid wildlife on the Olympic Peninsula for generations to come. Within this umbrella, we’re also studying mountain lion dispersal, assessing competition between mountain lions and bobcats, and working with an incredible array of talented scientists to analyze movement and genetic data collected from mountain lions throughout western Washington.

Our core team is composed of people working for the Lower Elwha Klallam Tribe (LEKT), and Panthera scientists. LEKT received funds from the Administration for Native Americans to study mountain lions and predation as part of building their Seventh Generation Wildlife Management Plan, to guide the Tribe in the sustainable use of natural resources. Kim Sager-Fradkin, Wildlife Program Manager, leads the LEKT team, and I lead the Panthera team. Cameron Macias is the first LEKT tribal member to attend graduate school to study natural resource management, and is analyzing mountain lion and bobcat genetic samples collected in our study, with support from a Panthera Kaplan Graduate Grant. Together, LEKT and Panthera are forging alliances with additional tribal partners and the Washington Department of Fish and Wildlife Department to share existing data sets and strategically gather additional data to fill knowledge gaps on the Peninsula’s wild cats.

An intimate video of M16 as he investigates his first encounter with one of our motion-triggered video cameras.

With the Olympic Cougar Project, we’re attempting something bold, something big, and something swift to protect key routes that will maintain and increase connectivity among pumas in western Washington. In the face of industrial development, urban sprawl and natural hazards, it’s a colossal undertaking, but the results will be rewarding beyond belief. If we succeed, and we will, our work may save untold thousands of cats and other animals long into the future. Join us to support the effort. And stay tuned, there is so much more to come from the Olympic Cougar Project.

We’re also on Facebook!

Two Washington Talks on Mountain Lion Social Behaviors in February

For anyone interested in mountain lion social behaviors, please join me on February 1st in Port Angeles, Washington or February 24th in Duvall, Washington.

Feb 1 at Studium Generale in the Little Theater, Peninsula College:

1502 E. Lauridsen Blvd./Port Angeles, Wa. 98362.

Here is a link for directions:

Additional directions: The “Little Theater” is centrally located in the Pirate Union Building (“The PUB”), which is directly above (south of) the main parking area. If you walk between the library and the clock tower building, you will come right to it.


Feb 24 at Wilderness Awareness School, Duvall WA.

Contact: Marcus Reynerson <>

I don’t actually know exactly where the presentation will occur–contact Marcus for details.
The office of WAS is at 26425 NE Allen St, Ste 203, Duvall, WA 98019. Their main campus is Linne Doran and directions are found here:
Thank you for your interest.


Do Mountain Lions Target Bulls and Bucks?

F47, an adult female mountain lion, turns back to look at the camera. Photograph by Steve Winter / National Geographic.


I’m often told that mountain lions target adult male deer and elk, called bucks and bulls by many people. Its become a point of contention among deer and elk hunters, and has fueled persecution of mountain lions. We just published a paper in which we tested this assumption in two areas of the Rocky Mountains.

I share a longer blog about our results on National Geographic’s CatWatch. But in short, we found that mountain lions went out of their way to target the youngest age classes of deer and elk, not the adult males.

The full article published in Wildlife Research can be found here. If you’d like a copy, please send a message through our project Facebook page.  Thank you for your interest.

Scientists Warning to Humanity

In 1992, the Union of Concerned Scientists and >1700 scientists wrote the “World Scientists’ Warning to Humanity”. They warned of environmental destruction and warned, “a great change in our stewardship of the Earth and the life on it is required, if vast human misery is to be avoided.”

Twenty five years later, scientists make the same plea. I signed the #ScientistsWarningtoHumanity.

Read the paper published in BioScience, spread the news.

Caption for the image adapted and shortened from that published in the paper by Ripple et al. (2017.) in BioScience:

Panel (a) shows emissions of halogen source gases, which deplete stratospheric ozone, assuming a constant natural emission rate of 0.11 Mt CFC-11-equivalent per year. In panel (c), marine catch has been going down since the mid-1990s, but at the same time, fishing effort has been going up. Panel (f) illustrates vertebrate animal abundance between 1970 and 2012– vertebrates declined by 58 percent. Five-year means are shown in panel (h). In panel (i), are increasing abundance of humans and ruminant livestock (domestic cattle, sheep, goats, and buffaloes).


Welcome, a Fresh Start

Well, it is exciting to finally have a website again. Its been more than 2 years since I gave up wildlifetrackers dot com, which was promptly hacked and still displays my name while now selling outdoor products. Please do not support the site. Have a look around and please let me know your feedback. Thanks.

There’s a lot happening in the mountain lion world right now, and I hope to write a few blogs about current issues. Stay tuned. Much more to come.

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