Thursday, January 10, 2013

Tracks in the snow

What animal made these tracks?

Sometimes we do not need to see an animal to learn something about it.  Animals often leave signs of their activities: nests and bedding sites, evidence of feeding, scat, hair or feathers, and especially tracks.

If we look at an animal's tracks we can learn many things about it.
  • How large is it?
  • Is it heavy or light?
  • Was it moving fast or slow?
  • How was it moving?

Mammals in Michigan move on the ground in one of four ways: walking, waddling, hopping, or bounding.

Walkers typically have long legs and narrow bodies.  Their footprints are usually round or oval shaped and always have an even number of toes. Their tracks usually form a fairly straight line with front and rear prints staggered from one side to the other.   Examples of walkers include deer, foxes, bobcats, etc.

Waddlers usually have wide bodies and shorter legs.  Their feet are generally wide at the heal and get wider toward the toes forming a trapezoid shape.  Their tracks are spread wider apart than those of walkers and would straddle a straight line rather than being on it.  Like a walker, waddlers' footprints are also staggered. Some examples of waddlers include black bear, opossum, and raccoon.

Hoppers move by pushing off with their long springy hind feet.  When they are moving fast all four feet are in the air at the same time.  They land front feet first and their back feet will actually land in front of the position of their front feet.  When following their tracks their smaller front prints will be behind their paired larger rear footprints.  Their feet are generally shaped like long skinny triangles. Some examples of hoppers include rabbits, squirrels, and mice.

The mammals in Mid-Michigan that bound are all members of the weasel family.  This includes mink, otter, marten, and fisher.  These mammals all have long skinny bodies and very short legs.  Their footprints are oval or teardrop shaped and might be mistaken for a mammal that walks except for the number of toes.  Bounders have 5 toes on both their front and hind feet.  Bounding is similar to hopping in a way. Their footprints are also paired, but the front prints are often obscured by the rear feet which will land in the same location as the front prints.

So how did the mammal in the top photo move? Here is a closeup of one of the sets of prints.

Track closeup

The tracks are in pairs.  They are shaped like long skinny triangles (especially the rear feet).  The rear footprints are in front of the front feet.  All four prints are clearly visible. These clues tell us that this mammal hops.  Without anything for scale it is difficult to tell exactly which animal made these tracks, but we can make some guesses.  Rabbits can be eliminated as the source of the tracks - rabbit feet tend to be very furry-these tracks are clearly defined.  The sets of tracks are very close together - this probably eliminates squirrels which will usually hop further between sets of tracks.  These tracks appear to belong to a mouse, probably either a Deer Mouse of White-footed Mouse.

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