Following Fox Trails

1. What they did

Adolph Murie wanted to know what a pair of red foxes actually ate and how they hunted, by studying one place and a few animals closely over time rather than collecting stomachs from many places. He worked on the Edwin S. George Reserve in southern Michigan from January to August 1934.

He used two methods:

• Following fox trails in the snow. After each snowfall he followed the foxes’ tracks, reading what they had done: where they turned aside, pounced, chased rabbits, killed, ate, cached food, left scent and rested. He also returned to the caches later to see what happened to them.
• Collecting fox droppings. He gathered 768 droppings (535 along trails and 233 at the den) and had their contents identified, then compared the results with the kills he found on the trails.

He also found and watched the den, and noted the foxes’ range.

2. What they found

Hunting and caching (from the trails)

• He found 60 food items along the trails, plus 20 places where a fox had pounced in the grass, usually leaving no sign of whether it caught anything.
• 26 items had been cached: 12 rabbits, 1 muskrat, 4 lemming-voles, 2 meadow mice, 4 short-tailed shrews, 1 garter snake and 2 prairie deer-mice. Most food not needed straight away was cached, often just under the snow, apparently pushed in with the nose and covered while hardly breaking stride.
• The foxes killed more than they ate. On one night at least six rabbits were killed; on 1 April he knew of ten cached rabbits still untouched.
• To his knowledge the foxes returned to 16 food items, sometimes eating part of a rabbit, or galloping about with it in play before caching it again.
• Of 16 caches he watched, 9 vanished without sign of what took them. Seven caches and four uncached items fed other animals: crows, a marsh hawk, a skunk, and hawks or owls (probably great horned owls).
• Most rabbit chases he followed on the snow ended in a kill. Twice a rabbit was caught right at a hole it was trying to escape into.
• Of 21 shrews and moles found on the trails, only 4 (all short-tailed shrews) had been cached; most were left lying uneaten.
• The trails also showed scent marking at grass tufts, stakes and old bones, visits to many burrows, a fox stepping in a badger’s tracks for a quarter of a mile, and a fox chasing a weasel away from a freshly killed rabbit.

Diet (from the droppings, Table I)

• Cottontail rabbit was the main food: in 70.8% of trail droppings and 85.8% of den droppings.
• Lemming-voles (23.7% of trail droppings) and meadow mice (20.3%) came next. Both were much rarer in den droppings.
• Beetles, mainly June beetles, became a staple in May and June: in 23% of May droppings, 42% of June droppings and 64.8% of den droppings. Murie suggests the pups caught many beetles themselves.
• Birds were in 12.3% of trail droppings and 4.2% of den droppings, and were most frequent in March and least frequent in May and June, the nesting season.
• Shrews and moles, deer-mice, fox squirrels, woodchucks, muskrats (5.8% of all droppings), deer and sheep (both thought to be carrion), turtles, snakes, nuts, corn and fruit seeds made up the rest. No sign of harm to deer fawns or to farm poultry was found.
• Field observations and dropping analysis agreed well, for example on the importance of rabbits and mice and the low value of shrews.

Den and range

• The first den was found on 4 May. Around 25 May the family moved about 400 yards to a second den, where at least four young were seen; it was empty by 13 June.
• Most hunting was inside the 1,200-acre reserve, but the foxes regularly went in and out under the fence.

3. What they concluded

• The main foods of the red fox here were cottontail rabbit, lemming-vole, meadow mouse and beetles.
• Bird predation was highest in March and lowest in the nesting season.
• Foxes capture more food than they can eat and cache the surplus; skunks, crows, marsh hawks and owls use these caches, so the extra kills still feed other animals.
• Shrews and moles are often caught but seldom eaten or cached.
• Food at the den differed from food elsewhere: more rabbit and insects, fewer mice.
• What a fox eats depends largely on what is easy to catch; prey such as deer-mice and fox squirrels that live with good cover or are active by day were taken less.
• The fox’s economic effect is both harmful and beneficial. Murie argues it should be allowed to live in fair numbers, controlled mainly by hunting and trapping, and values the “touch of wildness” a fox gives to farm country.

4. How tracking was or was not used

Tracking was the main field method. Murie followed fox trails in fresh snow after each snowfall and read the hunting story from tracks and signs: sharp turns and pounces, chases with rabbit and fox jump lengths, blood spots, fur, caches (marked by disturbed snow), beds, nose marks in the snow, scent (urine) marks, droppings and gait changes from trot to gallop. He used track size to tell the larger male’s trail from the female’s, and track spacing to describe trotting (generally 11 to 16 inches; nine to eleven inches for one fox he watched). He also read other animals’ tracks and signs at caches and carcasses (skunk, crow, hawk and owl whitewash, down feathers) and followed deer tracks for a parallel deer study. He calls tracking “practically equivalent to observing an animal for a long period of time under natural conditions; the trail is a sign language which only needs a certain amount of interpretation to be understood.” Snow was limited in southern Michigan, so tracking days were few, and he could follow only part of each night’s trails. Droppings were collected from trails and burrow mounds; he discusses how hard it is to tell fox droppings from those of badgers, opossums, coyotes and skunks, and explains why he thought few of his were from other species.

5. Tracker or observer certification

Not reported. Murie did all the tracking himself; no tracking qualification or test is described.

6. Other technologies, skills or innovations

• Comparing two independent methods, kills read from trails and food remains in droppings, to check each other.
• Revisiting caches to find out which other animals used them.
• Hand drawings of trail stories (pounces, shrew capture and caching, a rabbit chase and cache) and photographs of caches, dens and prey habitat.

7. Implications for conservation (from the paper)

• Close study of one area and a few animals over time gives more exact knowledge of food habits, which is needed to make sound decisions about carnivores.
• In spite of heavy fox predation, rabbits stayed abundant, showing that fox and rabbit can live together in one place.
• Predator surplus kills feed other species and fit into a “scheme of natural balances”.
• The fox should be allowed its “rightful niche”, with land managed for both economic and aesthetic interests rather than for small minority groups.