Nature Notes From Crater Lake
Volume 25, 1994
On the Trail of Winter Animals
By Polly Dubbel and Anton Briefer
Winter at Crater Lake is a time of deep
snow cover. Many animals avoid these difficult living conditions either
by migrating or hibernating. Yet quite a few animal species found in the
park remain active throughout the winter. Many of these animals spend at
least some of their time on the surface of the snow, leaving tracks that
are not easily observed in other seasons. In fact, winter is the best
time to see evidence of some less commonly observed species such as pine
martens, martes americana.
Where and When to
Find Tracks
The abundance of wildlife here makes
finding interesting tracks especially easy. Tracks can be found just
about anywhere in the park, even in the sparse vegetation and harsh
conditions on exposed peaks and ridges. Most people who visit Crater
Lake in winter stop et Rim Village, where large numbers of pine marten
and squirrel tracks can be seen. Park Headquarters, an area with less
severe weather conditions and more diverse forest has a wider variety of
tracks.
The best times to look for winter
tracks are the first few days after snowstorms. During storms, animals
are generally less active and any tracks will be quickly covered by new
snow. The older a track is, the more likely it will be obscured or
erased by drifting, melting, or drippings from trees. Some of the older
windswept tracks may still be partly visible, however, as a raised
pattern above the surrounding snow. These marks remain because the snow
which had compressed to form the track is less susceptible to drifting.
Identifying Animals
by Tracks
Almost all animal tracks have
distinguishing characteristics which allow identification of their
maker. Some of these tell-tale features are: appearance of individual
prints (size, shape, presence of claws, number of toes), distance
between sets of prints, distance between left and right feet, and the
general pattern of the track. The appearance of a single print is the
least useful means of identifying tracks because the clarity of a print
varies depending on the snow conditions, the age of the print, the
typical walking gait of the animal, and what the animal was doing when
it left the print. The most useful pieces of information for identifying
an animal by its track are the general pattern of the track, determined
by the animal's gait and the spacing of the prints. In snow, even
weathered tracks usually provide this much information.
Animal tracks are easily divided into
three groupings. The groups are: an alternating track, the two-print
bound, and the four-print bound. These divisions usually relate more to
the appearance of the track pattern rather than the animal's gait. Most
animals have some variations in their track patterns, but if the track
is followed any distance, it will usually revert to one of the main
groups.
The alternating track, common to all
dogs and cats, is generally made with a walking or trotting gait. It is
characterized by legs moving diagonally together, with the hind feet
placed in or near the prints of the front feet. An alternating track can
also result from side to side stepping, such as in the porcupine's
waddle.
The two-print bound is most commonly
seen in members of the weasel family. It occurs when the animal leaps
and lands on the two front feet, then lifts the front feet for the next
bound as the rear feet land in the prints of the front feet.
The four-print bound is a signature of
the common rabbit hop. This pattern is created when the front feet land
first after the leap, followed by the hind feet landing on the outside
and ahead of the front feet.
These three groups encompass tracks
from very small animals, such as mice, to the largest mammals active in
winter. To narrow the animal identification, two measurements are
useful. One is the straddle of the track, which measures the width of
the track between the outside edges of the prints. The other is stride,
or the distance from one foot print in a track to the next print made by
the same foot (diagram b). A ruler or any object (such as a knife or a
ski pole) can be used for measurement.
If snow conditions are conducive, the
footprint itself can be very instructive. The three main distinctions in
prints are: presence or absence of claws, number and spacing of toes,
and dimensions of the print. Persistence in following a back can often
lead to finding a clear print.
In addition to characteristics of track
pattern and print, the habitat where a track was made can help identify
a track. At high mountain settings like the park, many animals are only
present in certain elevation ranges. Similar looking tracks, such as
pine marten and mink, mustela vison, can be distinguished in part by
their location -- such as running between trees (pine marten) or to and
from streams (mink).
The chart offers a summary of tracks
and some of their characteristics for animals active in winter at Crater
Lake. This is, of course, simplified as there are a number of books
available on animal tracks and behavior for more comprehensive study.
Be aware that other phenomena can
produce track-like patterns in the snow: drippings from trees, small
amounts of snow rolling down steep slopes, wind drifts. Being alert to
unusual tracks, such as those made by bird feet or wing beats, can also
add to an outing.
For those enjoying the backcountry at
Crater Lake National Park in winter, or on a quick visit to the Rim
Village area, the ever-present snow cover can reveal the often missed
world of animal movement and behavior. Tracking yields the same
excitement as solving a good mystery, with the added benefits of outdoor
exercise and education. Tracking may even provide valuable information
on rare or endangered species which often go unseen in the park.
|
Animal |
Track group |
Avg. straddle
Avg. stride |
Where found |
|
Common Tracks |
|
Pine Marten |
2-print bound
 |
3-4.5"
24" |
Throughout park |
|
Douglas Squirrel |
4-print bound
 |
2.5-3.5"
19" |
All park forests |
|
Deer Mouse |
4-print bound
 |
1.4-1.8"
3.7" |
Throughout park |
|
Bushtail Woodrat |
4-print bound
 |
2.3-2.7"
11" |
Rock slides,
pines, buildings |
|
Snowshoe Hare |
4-print bound
 |
6-8"
32" |
All park forests |
|
Long-tailed
Weasel |
2-print bound
 |
1.8-2.8"
20" |
Throughout park,
may be near water |
|
Less Common
Tracks |
|
Coyote |
alternating
 |
4-7"
18" |
Throughout park |
|
Mink |
2-print bound
 |
2.3-3.5"
22" |
Near creeks |
|
Porcupine |
alternating
 |
5.5-9"
7" |
Throughout park |
|
Rare Tracks |
|
Bobcat |
alternating
 |
5-7"
12"
|
Low elevations |
|
Short-tailed
Weasel |
2-print bound
 |
1.1-1.7"
14" |
Throughout park |
|
Nutall's
Cottontail |
4-print bound
 |
4-5"
24" |
Ponderosa pine
forests |
|
Northern Water
Shrew |
4-print bound
 |
0.9-1.1"
3.5" |
Near streams |
|
Meadow Vole |
2-print bound
 |
1.3-2"
6.5" |
High mountain
open areas |
Table 1. Animal tracks. Direction of travel is left
to right.
Further Information
Tom Brown, Jr. and Morgan Brandt,
Tom Brown's Field Guide to Nature Observation and Tracking, New
York: Berkeley Books, 1983.
Louise R. Forrest, Field Guide to
Tracking Animals in Snow,
Harrisburg, PA: Stackpole Books, 1988.
James Halfpenny, A Field Guide to
Mammal Tracking in North America, Boulder, CO: Johnson Books, 1986.
Donald W. Stokes, A Guide to Nature
in Winter, Boston: Little, Brown and Company, 1976.
Donald and Lillian Stokes, Animal
Tracking and Behavior,
Boston: Little, Brown and Company, 1986.