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How to Make a Plaster Track Cast

As the creeks and streams subside, now is a good time to walk the river to look for tracks. Plus when it’s hot, Koda loves it too.  I put on my water sandals and shorts, stash my backpack with all the items I need to cast prints, and head for Sunlight Creek.

Where I found the tracks.

Where I found the tracks.

This time of year one might find resident animal tracks, like badger or mink.  Moose and deer are always around the creek.  In the fall grizzlies come down to investigate hay fields, berries, and gut piles from  hunter kills.  They’ll walk the river as a corridor.

Some of the best areas for small animals are the creek sides.  Larger wildlife course the entire stream. I cross the river over and over, checking in the wet sand and mud for tracks and finally find a set I want to cast.

I found some tracks that are interesting enough to cast

I found some tracks that are interesting enough to cast

The first order of business is to set up my casting materials.  You need to bring Plaster of Paris, a larger cup for mixing (I suggest 2), something to hold water to pour into your mixing cup, and a sturdy spatula.  I bring a garbage bag as a table to prevent the plaster from getting everywhere.  Keeping the stream area clean and free of plaster is important.

Simple tools you need for your cast

Simple tools you need for your cast

On the left you see my large tub of plaster.  I bring a lot in case I want to make several casts.  On the right is my 16oz. plastic cup with the plaster.

Around the tracks you want to cast, make a circular dam with the surrounding sand.  This will be the edges of your cast and prevents the plaster from just flowing everywhere.

Now fill your cup with plaster and add water a little at a time.  You want the consistency to be like cake batter.  Mix well with the spatula.  If it’s too runny then it won’t set correctly or will just take way to long to set. Too hard and you won’t be able to pour it.  Make sure all the lumps and dry plaster are gone and mixed well.

The plaster is setting.  Takes about 15-20 minutes depending upon weather and sun exposure

The plaster is setting. Takes about 15-20 minutes depending upon weather and sun exposure

Today I was having a hard time because it was so hot the plaster was setting up quickly in the cup before I had a chance to pour it.

Pour gently into your tracks and the mold area.  You want to be certain that the plaster gets into the tracks and there are no bubbles.  Once the mixture fills the casting area, you can lightly tap and smooth with your spatula to get rid of any air pockets.  Don’t make the cast too thin or it will be fragile when dry.

The best thing to do while waiting is to look for more tracks.  Work one direction as you cast prints, then backtrack to retrieve your casts.  It takes, depending upon the weather and wetness of your site, about 15 to 20 minutes to set fully.

Once hard, pull up gently.  You can wash the sand and dirt off in the river, but don’t scrub it at this point.  The plaster will not set up full until thoroughly dry, probably the next day.  Be gentle with these new casts as they can break easily.

Cast removed from track.  Still fragile

Cast removed from track. Still fragile.  You are seeing dirt and sand

Once dry, you can wash the cast outside and rub more dirt off.  Don’t rub it too clean as the dirt provides contrast enough so you can see the track more clearly.

Cast on right is dry and finished. Left is today's cast.  It's dry enough to wash but not to completely clean.

Cast on right is dry and finished. Left is today’s cast. It’s dry enough to wash but not to completely clean. Same animal, different days.

Use a permanent marker on the back of the cast to date it and put the location where you found the track.

Now all that’s left is to identify your track.  Anyone have ideas what this animal was?

Weasel video

Here’s another type of weasel. I’m pretty sure this one is a long-tailed weasel because it’s tracks were about the right size. It’s hard to tell an ermine from a long-tail from the video. The quality was compromised because of the snow.I tried to enhance it a bit.

I was trying to catch a mink. I baited with sardines and fish and set the box on an ice bar right along the river. But instead I caught this guy.  Notice the white fur with the black tip.  Both ermines and long tail weasels change their coat color to white in winter.  Watch the other video and you will see that Martens keep their coat color.   This box is about similar size to the Marten box because minks are about Marten size.  That will give you a size difference.

I’ll keep trying for that Mink!


There are plenty of weasels this year after a plentiful squirrel population. Here is a marten exploring a box with fat I made for him.

Tracking small mammals

With warm temperatures and little snow in my mountain lion tracking areas, I’ve turned to tracking small mammals above my house.  I’m not sure if I am just becoming aware of what these tracks look like, or if I am actually noticing an explosion of long-tailed weasels this year.

During last summer, we had a lot of reports in the neighborhood of weasels.  One neighbor told me her indoor cat killed a baby weasel and left it in the living room.  Obviously, some weasel had gotten into her house and had a litter.  Because weasels kill a tremendous amount of mice, she wasn’t too happy with her cat.  I personally watched a weasel take three baby bluebirds from their nest that were about to fledge.   I attribute all these sighting to an explosion of Unita ground squirrels this summer.

The weasel family has a distinct gait, especially in snow, called a 2×2.

you can see the 2x2 gait where the back feet land in the front feet tracks.

you can see the 2×2 gait where the back feet land in the front feet tracks.

These are really clear weasel tracks on the porch

These are really clear weasel tracks on the porch.  My shoe for size.

The only way I could figure out what kind of weasel I was seeing was to take measurements of the track width.  After taking lots of measurements, I found I’m seeing long-tailed weasels, not ermines.  From my observations, it appears that weasels hardly ever backtrack, unlike squirrels who make a deep trails back and forth between their caches and trees.  They wander from one rock or juniper to the next looking for mice and voles.  The reason you rarely see backtracking is because, unlike squirrels, they don’t have permanent dens.  Instead they go out looking for prey, make a kill, then take over their prey’s nests.  They might use these nests for a few days only.

Vole tracks on snow

Vole tracks on snow close up

Vole bound.  You can see it's tail drag

Vole bound. You can see it’s tail drag.  My shoe is for size.


Mouse tracks in snow

Mouse tracks in snow

I’ve found these weasel tracks in fairly predictable areas–forested areas encircling small to medium sized meadows.  This would make sense considering their prey consists mainly of voles and mice.

I followed a weasel track into the trees and came across Marten tracks.  Martens, like weasels, are mustelids and have that characteristic 2×2 in snow except much bigger.  Where weasels have a trail width of 1″-3″ depending upon which weasel, martens have a trail width of 2 3/4″ to 4 1/2″ and a much bigger foot.  Once you start to recognize these tracks, they will be easy to distinguish from rodents and from each other.

Scale shows width of track

Scale shows width of track

Ruler shows trail width

Ruler shows trail width

The Martens, unlike the weasels, like to travel in heavy timber for protection.  They also eat voles, but take squirrels, carrion, berries,fruit, chipmunks and birds.  Martens climb trees whereas weasels rarely do.  They prefer old growth forests.  James Lowery says that ‘logging that removes old growth trees and forest management practices that result in islands of forest separated by open space do not provide good habitat for marten and, some would say, destroy the health of the forest as well.”    Lowery’s comments makes me wonder about the logging that is going on this winter in the Sunlight area.

I walked up Little Sunlight Campground the other day which has been extensively logged.  Loggers have created huge slash piles.  They took all the largest trees and left islands of narrow girthed conifers in groups with large meadows in between.  When I walked the logging road, I saw almost no tracks except deer and a few elk, but no squirrels or smaller critters.  Are these the best forest practices in a wild place like the GYE?  Many people I talk to say we need this for fire protection, or we need the lumber.  But control burns are better for the habitat as they suppress invasives that come up after logging, and encourage fire adapted plant materials that fix nitrogen to sprout.  This kind of logging will be good for large browsers, but not for martens and other animals that depend on old growth forests and dense cover.

You can see the slash pile beyond Koda.  This was a heavily forested area before logging

You can see the slash pile beyond Koda. This was a heavily forested area before logging

Weasels and birds

A pair of bluebirds has been nesting here for over a month.  They laid a clutch around May 25 which didn’t hatch until several weeks ago (unless perhaps, when I go to inspect the box, they built a nest on top of the old unhatched eggs).  From what I’ve seen and read, bluebird eggs should hatch within about two weeks so this was very unusual.  I had been checking the 5 eggs every few days, till finally, on June 25, they hatched.

The father is an especially watchful and concerned dad.  He is always checking on the hatchlings, and he was always checking on the eggs too.  Three eggs hatched and lately, as they’ve been growing, the parents have been busy feeding those hungry youngsters.

Concerned dad

Long-Tailed weasel

I just returned from a Bioblitz over the weekend in the Pryors.  I headed out to check my trail camera in the woods and upon my return the bluebirds were really upset, making a big racket right outside their box.  I stood watching fairly close, wondering what the fuss was about.  Then I saw.  A head popped out of their house, and suddenly a long-tailed weasel emerged.  He ran off into a ground squirrel hole quick as a flash. Then I went to check on the babies.  One had fledged and was alive in the grass, but the other two were dead in the box.  If only I’d been a bit quicker I might have scared that weasel off.

I watched the birds for the next several hours.  The weasel returned for his prizes and carried them back into the hole, while the fledgling made his way through the grass uphill into deeper cover.  While the upset parents kept an eye out for the weasel, they also fed and protected their only baby that was left.

fledging hiding in bushes, making it’s way farther from the nest box

Meanwhile a menagerie of other bird species were coming around, interested.  Juncos, a female bluebird, and especially a pair of chipping sparrows wondered what the fuss was about, sometimes helping to scare off the intruder.  One of the most fascinating things was to watch the response of all the neighboring birds over the course of the several hours the bluebirds were upset.

That weasel, or its offspring, may have been the one that ate my pika two years back.  Oddly, he seemed to know exactly when to make his move for the birds–when they were just about to fledge, still helpless yet nice and plump.

mom still feeding the one chick left in the bushes

I rarely see weasels although I know they are around.  But being opportunistic carnivores, they have impeccable hunting skills.  Since I’ve watched this pair of bluebirds year after year, I feel a kinship with them and wanted to drive off that weasel.  I even tried to get my dog to flush him out.  Maybe the fact that the dog and I were gone for 3 days gave this weasel his bold chance.   Yet nature has it’s own ways and my human interference, well-intentioned though it may be, is probably more of the problem than a solution.

Otters (video footage), connectivity, and Bison

Today I went back to Abbott’s Lagoon to do some tracking on my own.  I arrived late, around 11, and by then at least a dozen people, kids and adults, had tracked around the dunes.  Being vacation week, there were more people than usual during the weekday.  But I managed to find a lot of tracks regardless.

The first thing I came upon were four otters playing right under the bridge.  No other people were around so I took the opportunity to stay quiet and watch them with my camera.  They swam in and among the vegetation, then three of them got up on the sandy bank and rolled around.  Here’s a link to my YouTube video of them rolling.  From watching them, it appears they were cleaning and drying themselves with all that rolling, helping to maintain the insulative quality of their fur.

Otter print

Otter fresh scat (you see the otter leaving it in the video link)

Despite all the human prints, there were lots of pristine areas on the dunes with only animal activity, and boy was there a lot of it.  Bobcat, coyote, rodent, raccoon, and skunk as well as birds and these otters were visible.  Black-tail deer hang in the fields on the hike in.   The dunes are alive at night when the people are gone.  Its amazing to think all these animals are living and thriving so close to humans.

Every morning I walk the five minutes to Muir Beach and run the dog.  This morning the weekend crowds were gone and I was the only person out there at 8am.  On the way back to the parking lot, I noticed some fresh scat, left while I was at the beach, by a bobcat.

Marin County, which is part of the North Bay, is a fairly unique area being so close to the city.  Just across the Golden Gate bridge, it has tremendous amounts of open space.  Besides the Golden Gate National Recreation area, Muir Woods National Monument, Mount Tamalpais State Park, Point Reyes National Seashore, and Samuel P. Taylor State Park, all in one county, Marin has protected its watersheds.  Unlike San Francisco which imports its water from Hetch Hetchy in the Sierras, Marin supplies its own water from rainfall, with some imports from the Russian River in Sonoma County.  Mount Tamalpais is the weather-keeper mountain in the county.  Fog and rain patterns are determined by the mountain and all of its surrounding lands are part of Marin Municipal Water District.  The drainages providing the water runoff feeds into several lakes and reservoirs on the mountain slopes.  These are all protected lands, never to be developed.  In addition, Marin topography is a series of valley and hills.  The hills, in general, are protected Open Space, while the valleys are populated.  There are few connecting roads between the valleys over these hills.  Throw into the mix Marin Agricultural Land Trust, a trust formed by the large ranches patchworked around Point Reyes, and you have a lot of open space.

What makes this unique is that animals have a chance to move; there is a corridor of connectivity of open, protected lands that allows movement of animals all the way to the next county north.  Marin provides a template of how we can protect land in urban highly populated areas that allows for wildlife as well.  Cougars even live here and there has never been any incidents with people or dogs.  Even an occasional black bear has been sited here and probably there will be more in the future.  These are not wild lands, but urban lands with connective open space for humans and wildlife to live side by side.

The other night I was having dinner with some friends.  They indulged me for 10 minutes and listened to my impassioned spiel on how important our last remaining wild lands are, for our soul, for our grand children, and for the great megafauna of North America.  I can get lost in these passions.  At the end of it, my friend asked me “If you could suggest one thing I could do, what would it be?”  What a great question.  At that moment I had no answer.  I told her that I’ve racked my brain thinking about that myself.  I didn’t think what she wanted to hear was ‘Donate to such-and-such an organization’.  What she wanted to hear was what the one thing she could do to make a difference, despite the fact that it’s not her main passion and she lives in a city.

So today, at the beach, I thought about one main thing.  Its the one main thing I have for today.  Tomorrow I could change it.  I suggest the one main thing would be to visit Yellowstone and see the bison.  As you see the bison, read a one or two page article summarizing their complicated situation and plight.  Sure, everyone knows something about the wolves and their plight.  But the bison situation really tells the story about everything that is constipated and locked up right now with megafauna.  They are managed not as wildlife, but as livestock under the completely wrong federal agency.  They are not allowed room to roam.  And all the reasons why, the issues between the Cattlemen’s Association and bison advocacy groups, the culling that goes on by the Park, the difficulty acquiring winter habitat outside the park with connectivity, and the fact that bison are America’s iconic animal, one that was almost slaughtered to extinction…I think the plight of today’s bison should be the one thing every person in the United States should learn about.  The story of the bison might communicate to even a person living in New York why we must advocate for connectivity, wildlands, and room to roam.

The Iconic Bison

What I’m doing this winter

My animal interest is not discriminating; I have a fascination with all species.  But I do notice the rhythm of my encounters goes in waves.  And as the encounters go, so does my fascination with that particular species.  I’ve had my wolf and bear periods, now I’m into my bobcat and marten epoch.

Last winter, walking to my mailbox at dusk, I caught a glimpse of something low in a nearby tree watching me.  The light was dim, I couldn’t see well, only a vague outline.  At first I thought it was an owl, a large one, maybe a Great Horned.  But then, something told me I was missing the mark.  I looked again.  It was a bobcat, watching Koda and I peacefully.  It’s repose came from its certainty of the dim light hiding its form, its’ knowingness that humans have bad night vision and that a canine can be fooled by staying still.   I’ve caught that guy on my camera, but the camera wasn’t working right, the photo was blurred, and this winter I’m determined to get some good photos and track him further.  Bobcats have become my new favorite animal.

My only bobcat photo which is terrible. That's a track plate apparatus a la Jim Halfpenny in the background

People trap bobcats up there.  Last year their pelts were going for over $500.  What a crime!  If I see a trap, although by law I could be fined, or jailed, for damaging it in any way, including putting a suffering animal out of its misery, there is no crime for peeing around the trap.  I pee around every trap I see.  That tells the animals “This is my territory so don’t go here.”  Save an animal by urinating.

This year my other fascination is martens.  There are plenty of martens around here.  I hadn’t learned their tracks last year, but now I know it.  I followed some trappers last year to understand how to find them. Although I don’t agree with trapping, I admit that trappers have to know their animals well.  So after asking them some questions of where to look, now I know.  I’ll set up a photography trap, one with bait that only takes pictures, not kills animals.  I’m looking to figure out those martens.

This is a marten

Another in the weasel family is the elusive mink.  We have mink in the river.  This summer I tracked them, as well as cast their tracks.  I got a ‘bead’ on where they’re hanging out and I want a good trail camera video of them.  They don’t hibernate, so I’m hoping to get some winter footage.

Hard to see but these are mink prints

Two other animals pose a great attraction for me this winter.  Snowshoe hares and lynx.  They are connected to each other too, one the food for the other.  The more snowshoe hares, the greater the chance of seeing lynx.  A recent study in Yellowstone found that before the introduction of wolves, the booming coyote population feasted on snowshoe hares.  As their population dropped so did the lynx.  Lynx decline had been thought to be related to climate change, but now that the hare is recovering (‘Amazing alert’:  wolves do what no humans can do–reduce coyote populations!), lynx are coming back there too.

I know there are a few lynx here, but I’ve never seen them.  A few summers ago the forest service even did a vegetation study in the valley to determine food sources for snowshoe hare.  Really it was a lynx study.  A friend of mine who hunts the hares in the Big Horns said he saw zillions of tracks in an area that will be closed in the winter to traffic.  Its high up on a series of reefs.  I can easily snowshoe the road in winter and check out the tracks.

tracks of the snowshoe hare

 The last on the list would be another in the weasel family.  This is an animal I’ve longed to see my entire life, ever since I was seventeen, backpacking in the Tetons, when I heard that the only animal that will take on a grizzly is a wolverine.  Yes, I’d love to see a wolverine.  They are essentially endangered, though not yet listed.  Several years ago an intensive study was done in the GYE, including Sunlight valley and the Beartooths.  No wolverines were found here during that study.  They used a variety of methods, including winter traps that look like miniature log cabins and regular fly overs during the winter months, the best time to see tracks.  Wolverines have incredibly large territories.  Glacier National Park, one of the few places in the lower 48 to boast a population of wolverines, can only support 6 or 7 males territory-wise.

Although these mountains are prime wolverine territory, the study found wolverines only in the southern Absarokas, and none in these more northern parts of that range. They also found wolverines in the Wind River Mountains.   I still like to think there’s some wandering around out here though.  If you see their tracks this winter,  report them.  Doug Chadwick wants to know about it.  A movie that has fabulous footage of wolverines is called Running Free.  Essentially targeted for middle school age kids, the movie isn’t half bad but worth the watch just to see all the footage of wolverines.