Studying Pressure releases in the tracking sandbox – July 6th and 7th, 2019

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Studying Pressure Releases can be very difficult, especially if you are doing it on your own, or perhaps having only one or two resources to work from, so it made for a lovely weekend up at Earth Tracks headquarters to study Pressure Releases with a motivated, curious and fun group of folks, despite the heat and humidity.

Pressure Releases (“PR” from here on) are sign written within or without the track of an animal created by pressure against the substrate the animal has moved over. This could be some dirt thrown up by a boot coming down on a muddy path, or a tiny sand ridge created by the pressure of a frogs hind leg as the frog lands in a sandbox (more on this example later…).  They are created in the substrate by a bodies weight, by the shifting of that weight, and through the motion generating pressures and then how the substrate reacts to those specific pressures.

Tom Brown Jr's book "The Science and Art of Tracking"

Tom Brown Jr’s book “The Science and Art of Tracking”

There are many examples of PR, all of which we learned about this past weekend can be found in Tom Brown Jr.’s book “The Science and Art of Tracking”. We really studied three causal qualities of PRs actually

  • 1) Pressure Against The Wall, which can teach us about turn a body in motion has made, sudden stops and even the eventual position of the next track by observing the increasing intensity of pressure required to create different possible PRs in the previous track. With names like “ridge”, “crest”, and “cave”, these PRs are like microcosms of the greater landscape though they are sign written by a foot (or other part of a body in motion) putting pressure on the substrate.
  • 2) Changing Or Maintaining Forward Motion, which teaches us about how much energy was required to, you guessed it, change or maintain forward motion. This might include speeding up from a slow jog to a fast jog, to a fast run for a human, or in the coyote counterpart, trot, bound, and gallop, all the while only looking at one track instead of requiring a set of tracks to determine a gait pattern.
  • 3) Roll and Head Position, which could mean looking at the depth of toes or the heels to determine if the animal, human or not, was looking up or down.

Tom Brown covers many more PRs with seemingly endless variability for each depending on a wide variety of influences and outcomes. I would be helpful to find his book and study it while working in a tracking sandbox.

Alexis explained the PRs, using diagrams written on a flip chart to help elaborate, and then demonstrated by moving through the tracking sandbox. He asked us to imagine an hour hand of a clock protruding from his chest and facing 12:00 and then he turned his torso very slightly so he would be facing 12:15 on the clock, and then 12:30, and then 1:00, with each turn taking a new step to create a new set of tracks. Each track would show slight variations in the pressure in the wall of the track highlighting the turns Alexis was making. These could be read by turning our heads so we could see the horizon of the sand and noting the peaks in the displaced sand which now stood atop the wall of the track, or by the way a toe seemed to dig into the floor of the track creating a small indentation or “cave” where the floor of the track met the wall.
This is just one small example of a PR.

The day went on, and we all took turns stepping into the sandbox moving in small ways, or big ways and then after stepping out of our tracks examining the PRs which remained.


Disk – light intensity


Disk-fissure – more intensity


Dish-crumble – even more intensity


We took a break on our first day to drive a little ways to a nearby woodland, but then got back in the sand the next morning. We began with the 3rd study, Roll and Head Position, where Alexis stood in the box and demonstrated head turns and the resulting PRs.

Examining the PR created in the track by looking over the Left Shoulder. Note the longer shadowed area on the left side of the left track denoting the greater depth to which the left foot sank due to the shift in weight.

A highlight of the morning was being visited by a Northern Leopard Frog (Lithobates pipiens) which was quickly placed in the tracking box so we could observe their movements and the PRs left behind as they hopped out and made their way back to the pond.

Lithobates pipiens

Note increased depth in the print of the hind leg on left side denoting more pressure from this foot created by pushing out of the sitting position while hopping out of the sand.










Later still, we tried another activity in the box. While everyone else was looking away, a student moved through the box with variying speed and actions while being filmed. When the student was done and camera stopped, everyone returned to the box to try and decipher what had just taken place. We used our bourgening knowledge to explore the PRs and movements highlighted in the tracks to figure out what had just happened, and after a few minutes of discussion and comparing ideas, we reviewed the video to confirm or challenge what we thought had happened. What excitement it was to be right! What joy to be wrong! It was so much fun to see where there was a forward bend with head facing the left, when we thought the head was straight and the fissures and crumbles were created by increased speed. This activity was certainly a hit.

First, try and decipher the tracks… then watch the video.

Studying PRs is a lifelong commitment. Perhaps many lifetimes of work is required to truly master and understand all the possible interpretations which lie in a track.

I am in deep gratitude to Tom Brown Jr, Alexis Burnett, and all the other teachers who take the time to pass on these skills to others so that we can hopefully build on this great moving body of knowledge even more, and explore, decipher and celebrate the mysteries we encounter, in the sandbox or the woods.


  • Kaya

    What a wonderful coverage of the experience

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