A Thousand Miles of Fox Trails in Michigan’s Ruffed Grouse Range

1. What they did

Michigan Department of Conservation biologists had long used snow tracking to study the winter habits of wolves, coyotes, bobcats and red foxes. Arnold (1956) had trailed foxes for a thousand miles in the farmland of southern Michigan. This study asked a different question: what effect do red foxes have on ruffed grouse in winter in the northern “wild land” of the state?

Over three winters (December 1955 to April 1958), biologists and student aides employed as “fox trailers” followed fox trails in the snow, mostly on two state-owned areas in the northern Lower Peninsula: the Gladwin Field Trial Area and the Rifle River Area. Grouse populations there were also being studied by other biologists.

• Following the trails. They recorded what the foxes did, what they killed, what they ate and which cover types they used, on a standard tracking record form at the end of each day. Distances were measured by counting paces with pocket counters (“tally-whackers”).
• Scats. They collected fox scats along the trails and analysed them, because mice and shrews were much easier to identify in scats than from the trail itself.
• Food available. They recorded grouse, snowshoe hare and cottontail sign along the trails, and used grouse census figures from other biologists. Because deer carcasses turned out to be the main winter food, they also measured how many deer were shot illegally and left in the woods.
• Daily range and cover. For foxes followed until they were jumped from their daytime beds, they measured the trail distance and straight-line distance, and compared the distance foxes travelled in each cover type with how much of each area that type covered.

2. What they found

Food habits

• Deer shot and left by hunters in the November season were the bulk of the foxes’ winter food. Along 1,109 miles of trail, foxes visited 203 deer carcasses (one for every 5.5 miles) and deer entrails 121 times. Early in winter, viscera from field-dressed deer were important.
• Mice, shrews, porcupines and cottontails were also prominent. Porcupines found along the trails were probably shot by hunters.
• Foxes spent a lot of time hunting mice and shrews, but success was hard to judge: often a drop of blood on the snow was the only sign of a kill. 123 fresh kills of mice and shrews were recorded.
• In 138 scats, deer occurred in 68.1%, cottontail in 23.2%, meadow vole in 21.7% and deer mouse in 18.8%. Ruffed grouse occurred in 3.6%.

Effect on game

• Fox predation on game was negligible. The only game killed by the foxes followed were five cottontails, two bobwhites and one snowshoe hare.
• None of the 19 dead grouse found along the trails were killed by the foxes being followed. Hawks or owls had killed at least four; some of the others might have been killed earlier by foxes.

Food availability

• Grouse and snowshoe hares were near the low point of their 10-year cycles. Even so, fresh grouse sign was found along 67% of fox trails, and the trackers flushed 223 grouse (one bird per 5 miles walked). Snowshoe hare tracks were along 55% of the trails and cottontail sign along 39%.
• Winter grouse density was two to four birds per 100 acres, down from 5 to 10 in the “high” years of 1950 to 1952.
• In the 1956 and 1957 deer seasons, biologists marked 41 illegally shot deer. Fox trackers later found 27 of them plus 34 unmarked carcasses. A Lincoln index estimate gave an annual waste of slightly over four deer per square mile, over 400 pounds of potential food per section. The author notes foxes there had practically no competition from other scavengers in winter.

Daily range

• 84 foxes were jumped from their daytime beds. On average they had travelled 3.64 miles from where the trail was picked up to the bed; the straight-line distance averaged 0.94 mile.
• Assuming the trail is picked up, on average, at the midpoint of a night’s hunting, this gives a nightly hunting area of about 2.8 square miles, twice the 1.4 square miles estimated for southern Michigan foxes.

Cover types

• Foxes seemed to slightly prefer lowland brush on both areas (Gladwin: 3.8% of trail distance against 0.4% of the area; Rifle River: 15.8% against 9.0%), and used oak a little more than expected at Rifle River.
• White birch, marsh and conifer swamp were avoided at Gladwin, and swamp hardwoods at Rifle River.

3. What they concluded

• Red foxes had a negligible effect on game, including ruffed grouse, in northern Michigan in winter.
• Their main winter food was illegally killed deer left from the fall hunting season. This amount of venison will support a high fox population during this critical period. Foxes still hunted mice extensively.
• Northern foxes hunted about 2.8 square miles a night and apparently ranged farther than southern Michigan foxes. They showed a slight preference for lowland brush.
• The author recognises that the trackers’ habits introduced some bias; for example, biologists were distinctly reluctant to follow fox trails across the ice on beaver floodings.

4. How tracking was or was not used

Tracking was the main method. The team trailed red foxes in snow for 1,109 miles, interpreting from the tracks and signs what the foxes did: kills and food items visited (carcasses, entrails, blood on the snow), scats, and daytime beds where foxes were jumped. They also recorded tracks and signs of grouse, snowshoe hares and cottontails along the trails, and fox trackers found marked and unmarked deer carcasses used in the Lincoln index estimate. The author quotes Murie (1936) that following a trail “is practically equivalent to observing an animal for a long period of time under natural conditions”, and notes that Michigan’s snow from late November to early April solves the method’s most serious limitation. Unlike an earlier study in Iowa (Scott 1943), they had fairly good success staying on individual fox trails, so they could measure distance in each cover type.

5. Tracker or observer certification

Not reported. The trailing was done by biologists of the Michigan Department of Conservation’s Game Division and by student aides employed as fox trailers. Nothing is said about their tracking experience or any test of their skill. The author notes that the trackers’ own habits introduced some bias into the cover type results.

6. Other technologies, skills or innovations

• A standard tracking record form, filled in at the end of each day afield.
• Distances measured by counting paces with pocket “tally-whackers” (Veedor counters).
• Scat analysis to identify small mammals that could not be told apart on the trail.
• Marked carcasses and a Lincoln index to estimate how many illegally shot deer were left in the woods.

7. Implications for conservation (from the paper)

• Red foxes were not a significant predator of ruffed grouse or other game in winter on these areas.
• Deer wasted by hunters, slightly over four per square mile a year, provided foxes with a large winter food supply that can support a high fox population.