A Field Guide to Animal Tracks

1. What they did

Olaus Murie, a naturalist and artist who spent his life in wild country, wrote this field guide to help amateur naturalists, professional wildlife workers and biologists identify animals from the signs they leave, even when the animals themselves are never seen. As the series editor, Roger Tory Peterson, puts it, the book is a bridge between the art of identification and the science of ecology.

The guide covers every North American mammal, from the Arctic to Mexico and Central America, for which Murie had obtained tracks. It also includes over thirty birds, some amphibians and reptiles, and a few insects and other invertebrates, with sections on twigs and limbs and on bone and horn chewing. For each animal there is a short account of the animal and its sign, line drawings of tracks and trail patterns with measurements and often the place, date and ground or snow conditions, drawings of scats with their variations, and a pen and ink drawing of the animal in its habitat. Most drawings were made in the field from his own plaster casts and sketches.

The introduction, “What Has Happened Here?”, explains how to read signs and how to preserve tracks and scats. The book opens with a key to tracks and closes with a bibliography and index.

2. What they found

Reading the sign

Reading tracks is not easy. The same animal leaves different tracks in mud, dust and snow, and snow tracks enlarge and distort as the sun warms them. Tracks are often incomplete, and they vary with the animal’s age and sex. Front and hind tracks usually differ in toe number, shape and size.

Droppings vary too: a half-grown coyote’s may resemble a full-grown fox’s, and the same animal’s droppings are larger after bulky food with fur or feathers and smaller on lean rations. Elk droppings that are flattened or formless show summer range and green forage; hard pellets show winter or autumn food.

For these reasons Murie asks readers to use the book as a guide rather than a rigid key.

Examples from the field

Tracks in Wyoming snow showed a jackrabbit dodging one coyote, until a second coyote came down the hill and closed in; a few drops of blood and the two coyote trails leaving together finished the story.

White spots on cliffs revealed woodrats from a passing car, and long streaks of “whitewash” revealed a raven nest.

Plaster casts showed a finer “fingerprint” pattern under the toes of sandhill cranes than of wild turkeys.

Reindeer in Alaska were seen chewing the antlers off each other’s heads; elk chew antler tips with their grinding teeth, while rodents carve antlers, horns and bones neatly with their gnawing teeth.

Limits of identification

Some signs cannot be told apart. The droppings of the dog family overlap so much in size that identification is sometimes uncertain. Murie found no way to distinguish the footprints or droppings of the three kinds of deer, and badger and opossum scats are not distinctive.

Bird pellets vary so much with the food eaten that individual pellets cannot be identified without a known nest or perch.

Murie repeatedly advises looking for accompanying signs and keeping in mind which animals are known to live in the area.

Preserving tracks and scats

Plaster of paris casts: how thick to mix the plaster, how to cast whole track groups with reinforcing sticks, and how to lift and clean the cast. Paraffin, and water putty mixed with sand, as alternatives. For snow, chill the mix with snow, dust in dry plaster first, or spray the track with very cold water to form an ice lining.

Scats kept as reference specimens should be identified by tracks at the spot or collected where only one kind of animal of that type lives, and can be coated against insects.

3. What they concluded

Familiarity with mammal signs (tracks, droppings, gnawings, scratchings, rubbings, dams, nests and burrows) opens up a delightful field for anyone outdoors, and the serious field biologist needs skill in reading them.

People have lost the power of tracking by scent, but can read a more complex story in footprints than identification and direction of travel. Murie notes that Indigenous peoples of North America and the Arctic and experienced woodsmen read imperfect track records with remarkable skill.

Beginners gradually develop a knack for reading signs, yet even professionals are sometimes stumped. Murie offers the guide “with humility” and points out the gaps in knowledge where they occur.

A collection of well-identified scats could be useful to palaeontologists studying fossil droppings (coprolites).

4. How tracking was or was not used

Tracking is the subject of the book. Murie identified tracks and signs of mammals, birds, reptiles, amphibians and invertebrates in mud, sand, dust and snow, recorded trail patterns, strides and straddles, and interpreted scats, feeding signs, chewed bone and antler, burrows and mounds. His examples include following trails to read what happened, such as the coyotes and jackrabbit, and a wolf trail followed with a hound that tracked by scent.

5. Tracker or observer certification

Reported but not validated. The book rests on the author’s own experience as a field biologist (with the United States Fish and Wildlife Service, in Alaska, Hudson Bay and Wyoming), described by the editor as an eminent naturalist and accomplished woodsman. No test of his tracking skill is given, which is expected for a field guide of this kind.

6. Other technologies, skills or innovations

Plaster of paris casting of tracks, with practical tips; paraffin and water putty (with sand) as alternatives, and methods for casting tracks in snow and dust.

Preparing smooth ground, sometimes with bait, to record tracks under controlled conditions (“stage setting”, after Ernest Thompson Seton).

Field drawing of tracks to scale with a tape measure, noting strides and print sizes.

Preserving scats as reference specimens.

A pictorial key to tracks with general distribution areas.

7. Implications for conservation (from the paper)

Murie suggests that preparing ground to record tracks has possibilities for the field biologist working on population studies and ecology, and that signs such as elk droppings help build up the facts of an animal’s life story, useful to the scientist as well as the amateur. The editor notes Murie’s lifelong dedication to wilderness preservation.