Measuring tracks: print size, trail width, stride and groups

The size and spacing of prints depend on three things: how big the animal is, which gait it uses (walking, trotting, bounding, galloping) and how fast it is. A bigger animal has bigger feet and longer legs; a faster animal places its feet further apart. Because these influences overlap, you need several measurements to narrow down an animal.

Trail width is particularly useful: the distance across the direction of travel from the outer edge of the left prints to the outer edge of the right prints. It depends mainly on how broadly the animal is built and stays more stable than stride length at changing speeds. That is why it is often the most reliable value, especially in snow, where individual prints are blurred.

In animals that bound or gallop, several feet often land close together and form a group. Then you measure the length of such a group and the distance from one group to the next. For walking or trotting animals, you measure the distance between consecutive prints.

It sounds petty but it is crucial: field guides define terms differently. Some measure the length of a print with claws, others without. Some understand “stride” as the distance to the next print, others as the distance to the next print of the same foot – which is then roughly twice as much. Anyone who compares measurements from one book with the measuring method of another book will reach wrong conclusions.

So decide on one field guide before measuring and write the definitions in your notebook. In “Mammal Tracks & Sign”, Elbroch describes a consistent approach and measurement ranges for North American species; European species have their own field guides, some with different definitions. What matters is not which method you choose but that you always use the same one.

Always measure the print at its greatest length and width, and on the clearest print of the trail. Front and hind feet differ in size in many animals; if you can tell them apart, measure them separately.

Find a trail with several consecutive prints, for example in snow, damp sand or on a farm track after rain. If needed, mark prints with small sticks so you do not lose count. Then measure at least five values in a row: print length and width, trail width and spacing.

Do not write down only an average but the smallest and largest value, plus substrate, gait, date and weather. Also take photos: one straight down with the tape in the image plane, and an overview showing several prints of the trail. That way you can check later what you measured.

A good start is to measure known animals: your own dog, the neighbour's cat in a tracking plot, or your own shoes when walking slowly and quickly. That shows you how much spacing changes with speed, while trail width changes less.

Measuring is worthwhile when you want to identify a track with a field guide, when you keep a tracking journal or take part in a monitoring or citizen-science project. Measurements make your observations traceable for others and comparable over years.

With single, blurred prints or thawed snow tracks, by contrast, measuring achieves little – the values would be distorted. And even good measurements are only an aid, not proof: the ranges of different species often overlap. Only the overall picture of print, trail, habitat and other signs leads to a reliable identification.

When measuring you look down for a long time and easily forget your surroundings. So do not work at roadsides, on bank edges or on ice. At dusk it is better to stay on paths, because you see obstacles less well and others see you less well.

If a trail leads into rough terrain, let it end where it is safe for you. An incomplete series of measurements is better than a sprained ankle or wet feet in the cold.