How to Tell How Old Animal Tracks Are in Snow and Mud

Use the last event that actually changed this patch

Start with the surface the animal stepped on. A snowfall, a freeze or a rise in the water can change that surface. If you can see which came first, you have something firmer than a judgement about the shape of the print. The Diavik wolverine survey in the Northwest Territories records whether sign comes before or after a snowfall or a local wind event. Its field sheet also records the weather and the condition of the snow. The procedure uses a wind threshold for its own survey, where the crew has a reason to expect snow to move under particular conditions. Diavik wolverine survey protocol and field sheet.

Look for the same layer just outside the track. If the foot cut through a distinct cover of new snow, the impression was made after at least that much snow had landed. It might have been made while the storm was still going. If snow sits in the hollow, ask whether it is the same deposit you see across the rest of the patch. A uniform layer that continues over the rim and into the hollow is better evidence of later deposition than a few loose grains at the bottom. Those grains could have fallen from a branch or blown in long after the storm.

In your notes, write down exactly what the evidence puts on either side of the event. “Made after this layer accumulated” is useful even when you cannot time the layer to the hour. “The print was already there when this drift formed” can be useful even if the drift formed well after the last snowfall. Both statements depend on recognizing the layer at the print. If you cannot tell which deposit you are looking at, leave the order open.

When a clock time helps

A photograph that clearly shows the same surface empty on one visit and the impression present on the next can bound when the visible mark appeared. Compare fixed features, frame coverage and light. Check whether the surface stayed intact between visits. A mark that becomes visible as a thin cover melts may predate the earlier photograph, even if the earlier view looks empty.

A nearby station records conditions at its own instruments. A shaded path at a different elevation can hold snow while the station reports rain. Check whether the reported event left a recognizable change at the print. Some stations also lack hourly precipitation or other fields you might want to use. ECCC historical weather data and data availability and station notes.

Read the crust, then compare snow in the same exposure

A snow track takes its shape from the snow that was there when the foot landed. In loose powder the walls can fall in almost at once. On a firm surface the foot may leave only a faint impression or break the crust into chips. Even tracks from one crossing can look different where a packed trail meets deeper powder. Use the prints on the same surface to compare edges. A clear print in one patch and a faint one in another say little about which foot passed first.

Snow can change after the track is made even if no new snow falls. Its grains change as water vapour moves through the snowpack. Warming can melt part of the surface, and a later freeze can harden it again. Sun-facing slopes and sheltered shade receive different amounts of solar heating. You may see a rounded depression on the sunny stretch and a more angular one under spruce along the same line. Check whether you can see the connecting steps before treating the contrast as two visits. WSL’s snow-grain research and how exposure affects snow.

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Inspect where a crust meets the rim. A break through a layer that you can trace across the adjacent surface puts the impression after that crust formed. A thin, continuous glaze coating the wall or floor of an existing hollow can suggest that freezing happened after the impression, if you can establish how that glaze formed. A shiny floor by itself is weak evidence. It could be compacted snow, ice the foot exposed or ice formed from water that pooled later. Without a recognizable layer, record the shine or hardness and leave its timing open.

Watch for snow that moved sideways

Wind can scour one patch and deposit snow in the next. Look at the exposed ground and sheltered hollows nearby. Is there a drift against one side of a stump? Is the same pale powder piled against the downwind walls of several prints? That pattern can help you recognize transported snow even when the forecast showed no fresh fall. A track that cuts the drift was made after the part it cut accumulated. Where wind stripped snow away, a print may become more visible as it gets older. Where the snow settled, a recently made track can lose its shape. Avalanche Canada’s explanation of wind transport and snow exposure.

Look for the clearest surviving section of the same trackway before deciding the sign is missing. A bare gap could mean that the animal crossed packed ground without leaving much of a mark, or that weather removed that section. It does not tell you the animal turned there. For timing, keep your inference attached to the patch with the evidence.

Separate the condition of the mud from the time of the step

Compare the impression with nearby ground of the same material and moisture. Damp clay can hold a raised rim and fine detail. A foot in very wet mud can leave walls that slump almost as soon as the weight lifts. Firm ground may register only part of a foot. In a study recreating the conditions that produced ancient human footprints on the British Columbia coast, the researchers made clear impressions in a damp clay mixture. Their result helps explain why two patches register different shapes. It cannot assign an age to a print on a riverbank today. B.C. coastal footprint experiment.

A wet floor can mean water collected in an older depression. A dry raised rim can mean only that the exposed mud dried faster than the bottom. Check for seepage, a thin film on nearby ground, cracks that continue across the patch and any recent change in the waterline. There is no dependable hours-old reading from one of those signs alone. Controlled emu experiments recorded mud collapsing and flowing after the foot came out. In a separate coastal field experiment, some human footprints hardened while others were gradually reshaped by currents and burrowing. Both studies show ways the shape can change. Neither tested a general timetable for Canadian wildlife tracks. Emu track experiments and coastal footprint experiments.

If you think a shower left pits across the surface, inspect the track at an angle and compare its floor with the rim and ground beside it. Pits on the floor can support rain after the impression formed if you can tie them to that shower. A footprint that clearly cuts a pitted surface is younger than the pitted layer. A few marks around a single print may come from drops under branches, local splash or an earlier shower. If you have no way to separate those possibilities, “possible rain marks on the floor” is an observation worth keeping without adding a time.

Use similar care along a shore. Water that demonstrably deposited a thin layer across the inside of a print arrived after the print. A nearby waterline only shows where water reached at some point. It may not tell you what happened at the exact patch, and seepage can fill a hollow without the whole bank flooding. Read the patch from a stable position on an open route.

Use intersections to put two passes in order

Where two trackways cross, locate the point where the edges meet. Look for a rim that continues across the other impression or a wall that visibly cuts an earlier rim. Follow each line across several prints so you can tell which edge belongs to which pass. If both walls have slumped, or you cannot trace either line through the crossing, leave the order unresolved. The deeper print could come from a heavier animal or softer footing, and its depth alone adds nothing to the order.

• Photograph the crossing and enough of both lines to show where they continue. Take a closer view of the contact if you can do so without stepping into either line.
• Write which edge was cut and which line continues. If the evidence is clear at only one crossing, say where you saw it. If a second crossing suggests the opposite order, check whether you paired the right tracks.
• Record the result as relative order until you have independent timing. “The second line crosses over the first” gives the sequence. It does not say how long the gap was.

Keep age and detectability separate when comparing visits. Fresh snow can hide older sign and leave very little time for a new pass to register. In an original Canada lynx snow-track study conducted in Montana and Wyoming, the researchers’ simulations found that detection varied with the number of days since snowfall and the number of survey visits. The work concerns the chance of finding a track on their survey routes. An empty patch after a storm can mean that the surface was reset or you saw only part of the route. It cannot establish that an animal has stopped using the area. Canada lynx snow-track study and survey simulations.

Check what the weather record can tell you

Start with what happened at the print. If you saw flakes settling on an undisturbed trail at 08:40, write down the time and which patch they covered. If you only heard that it snowed overnight, keep that as a report to check. A regional snowfall can leave a continuous layer on an open path and little change under nearby conifers. Look for the layer at the actual print before using it in your estimate.

When you get back, open Environment and Climate Change Canada’s historical data search for the date you visited. Search by station name, province or territory, or proximity to the site. Use the station map to see where the instruments sit. A station down in a valley may be closer in kilometres than one on a comparable slope. Save the station name and the distance or difference in elevation when either matters to your interpretation. ECCC’s historical data search · ECCC’s station map

1. Open hourly observations if the station has them. Look for a change that could have altered the surface, such as rain followed by cooling or a shift to stronger winds. Check which fields the station actually reports. A daily snowfall total alone gives you no start or end time for snow at the print. ECCC’s explanation of hourly and daily records
2. Put your notes and the station readings on the same time basis. Read the time label on the report before matching an hour to a photograph. Local Standard Time is used in Canadian weather archives and can differ from the daylight time on a device. If the time basis of an old photograph is unknown, keep its clock time provisional. ECCC’s climate data glossary
3. Write the station reading alongside what you saw. Rain at a station suggests a possible change at the trail, but the amount can differ considerably across the same region. ECCC’s radar archive can show when a band moved through the area. Neither a radar frame nor a station reading establishes when drops hit the particular patch of mud you photographed. ECCC’s notes on local precipitation differences · ECCC’s historical radar guide (PDF)

Check whether you can identify a particular event at all. If you know there were two showers, both could have left pits in the mud. If you were there when a new layer formed, record what covered the ground, whether the layer reached your observation point and whether you revisited the same patch. A record of snow at the trailhead and a print farther up the trail are two separate observations.

Practise on four Canadian field examples

These cases are fictional. The places are real, but the prints, dates and weather observations are invented to show how a defensible window changes with the evidence. Check the park’s current routes and notices before a visit.

Banff, Alberta. A hoofprint breaks a known boot mark

You take a photograph at 09:10 of a boot mark you made on a designated winter trail. A split in the heel tread gives you a detail to match on the way back. The ground beside the heel is visible in the photograph and has no hoofprint. At 11:25, you find two hoof impressions across the trail. One cuts the ridge at the edge of the heel mark and presses part of that ridge into its own floor. The second hoof impression lies clear of the boot mark.

Use the place where the two marks actually touch. Their paths happen to cross, but the compressed heel ridge is the part that puts one event after the other. The boot mark was already there at 09:10 and the hoofprint was there by 11:25. Those are your bounds for the overlapping hoofprint, assuming the heel pattern matches the earlier photograph. Check whether other visible prints belong to the same line before giving them the same window.

Your note can say “after the 09:10 boot mark and present by 11:25, local time.” Two hours and fifteen minutes is the width of the observation window. The animal could have crossed just after the photograph or just before your return. Photograph the overlap from the trail if you can do so safely. Banff’s winter guidance advises visitors who see tracks to avoid following them toward the animal. Parks Canada’s Banff winter guidance

Algonquin, Ontario. One line looks different in sun and shade

From a trail beside a lake, you see an apparent line of hoofprints through powder in the shade, then onto snow that has softened beside the open shoreline. The shaded walls are steep. The impressions in the exposed patch are wider, with rounded rims. Looking at one print from each surface in isolation, you might call them two visits. From where you stand, the spacing and direction look continuous, though you lose sight of two steps behind a rise.

Record the possible connection, then judge each patch against the snow immediately beside it. The differences can be explained by the surfaces, so they give you little basis for putting the two sections in time order. If you saw no relevant event before your arrival at 14:40, write “present by 14:40, earliest time unknown.” Keep the sequence tentative where you could not see the steps.

If you come back along the same path later, use the same tree or bend to find the section again. Compare any additional print with your first image. A shift in light can reveal an older depression. If the snow in that exact spot was clearly smooth at 14:40, you can place the additional print after that check.

If the impressions appear to go onto the lake, end the comparison there. An animal’s crossing gives you no basis for judging what the ice will support now. Ontario Parks advises avoiding travel on ice whenever possible, since conditions vary and springs or currents can affect them. Take your notes from the land route. Ontario Parks winter safety guidance

Kejimkujik, Nova Scotia. Rain at the station and rain at the print

You find a broad print on exposed mud at 16:10. A station 24 kilometres away reports rain in the late morning. From the maintained trail, you can see small pits in the print floor and around its edge. The surface beneath an overhanging branch nearby is smooth. On the photo alone, you can describe the pitting and say it may have happened after the print formed. You cannot tell which shower caused it, or even whether drops falling from the canopy made some of the pits.

Now add an earlier observation of the exact patch. At 13:05, someone in your group photographed the same unmarked surface with a distinct pebble at the edge. If the photo clearly shows the place, the passage falls between 13:05 and 16:10. Keep the station rain before 13:05 and the pitting in the print as separate observations.

If the first picture only shows the path several steps away, keep the later observation and leave the earliest time open. Skip the bank if water has cut across the route. Parks Canada’s Kejimkujik hiking guidance notes that spring water can flood low sections of trails and asks visitors to use designated routes. Kejimkujik hiking guidance

Grasslands, Saskatchewan. Wind leaves an order without a clock

On an open trail, you see a shallow groove filled with windblown snow. The thin drift continues over the lip and onto the surrounding ground. In a second line, several prints break the drift and expose the darker layer beneath it. You can see both relationships at one crossing, where the rim of the second line cuts the surface of the drift inside the first impression.

Describe the events in order. The first impression was there before that fill was deposited. The second broke the deposited layer. You have an order at the crossing if the fill and the adjacent drift are the same continuous layer. A station wind report cannot tell you exactly when that pocket filled. If the lines only appear to meet and you cannot make out the break, leave the order open as well.

Write “first impression, wind fill, second impression” with the visit time. The prints may look almost equally faint after the next gust. There is no need to walk into the exposed area to find a better example. Check the park’s trail conditions before setting out and follow any access directions you meet on the route. Grasslands National Park trail conditions

If the station lists several windy periods between your visits, retain them in the weather notes. The crossing still gives you three events in sequence, but it cannot identify which gust or day left the drift. A photograph of the already filled print taken on an earlier visit would give a date by which the first two events had happened. It would leave the first impression’s earliest possible time unknown.

Keep the record if you have to leave the print

Note where you were standing, the time, what was visible and which part you could not check. If you can safely take two photographs from the permitted route, start with the surface and nearby reference feature, then frame the overlap closer. Leave the print and its edge undisturbed. Treat a closing animal distance, a closed trail or uncertain footing as the end of the inspection. A short note with one reliable clue is enough to preserve what you learned. Parks Canada’s guidance on giving wildlife space and respecting closures

Record the print, the patch and the time evidence

Start with a wide frame that shows where the print sits. A bend in a trail, the base of a distinct tree or a patch of exposed gravel can help you find it again. Then take a photo that shows the crossing pattern and a closer one that shows the edge, the floor and the surface outside the print.

1. Keep the scale in the same plane. If you can place a ruler beside the print without changing the surface, keep it level with the part you want to compare. If that would damage a fragile edge, photograph from the permitted route and leave the measurement approximate.
2. Repeat the angle and viewpoint. A low angle shows shadow and relief. A view from above shows shape and spacing. Use the same angle for repeat photos where possible and note when a different light direction changes how the rim appears.
3. Save the date and time zone. Write down when you saw the track, when you saw the surface without it and when a dated weather event reached the patch. A photo timestamp can help when its clock and time zone are known.
4. Write the narrowest claim you can defend. Keep the raw observations beside the timing inference. If another observer can read what you saw and come to the same conclusion, the note will still be useful when the track disappears.

Guide’s log · A fictional practice session

In this exercise I make two shoe impressions on snow in a private yard with permission. One sits on a shaded patch beside the fence and one gets sun through an opening. I photograph both from above just after making them and write down the time. My first impression of the sunny print is that its heel looks shallower, even though I made it at the same time. The snow under it was different from the start.

When I look again after lunch, the sunny rim has softened. The shady one still shows the tread. I check the original photos before labelling the changes. A photograph of just the two final prints would give me no way to tell when I made them. With the originals I can see which parts of each shape were there at the start.

I write down the change in shade, the surface and the time of each photo. For the next exercise I choose two nearby patches of similar snow and keep the time and shoe constant. I keep the original photos so I can compare the new session with the first one.

For an animal trackway, keep species, timing and behaviour as separate notes. The predator and prey track guide can help with identification clues. The behaviour guide explains what a sequence can support after you have described the sign itself.