Little Tiny Predators

     Shrews are, arguably, the smallest mammals in Pennsylvania.  Weighing in at less than an ounce, these insect eaters are often confused with their cousins the moles.  Moles hunt for insects and earthworms underground, burrowing through the soil and rarely coming out above ground.  Shrews, on the other hand, hunt above ground, although they do tunnel through snow and fallen leaves.
     Moles are known for the tunnels and mole hills that they leave behind.  The presence of shrews is only visible in the winter when there is snow cover.  The amount of shrew evidence can be astounding, as we have found this winter at Lutherlyn.

     In the picture above, you can see a shrew trail entering a tunnel in the snow.  The trail and tunnel are about 5/8" wide.  In the photo below, you can see a shrew trail crossing a gray fox trail.  The fox print is about 1 1/2" wide.

                                          

     These tiny predators are amazing for their size.  They live fast and die young.  A shrew's heart may beat 1,200 times in a minute!  With a metabolism like that, it is no wonder that they have to eat almost constantly.  Young shrews reach adulthood in four to six weeks after birth.  However, shrews rarely live for longer than one year.  They are easily killed by floods, sudden temperature changes, starvation, and even fright.  Predators also kill some, but most are not eaten since shrews give off a musky odor that most predators do not find palatable.

     One of the shrew species that lives in Pennsylvania, the northern short-tailed, has toxic saliva.  When it bites prey, the shrew's saliva can slow down or even kill the insects, worms or other creatures that it wants to eat.
     It has got to be hard to find enough food in the winter to keep that little body going.  I suppose that explains all of the tracks that we find throughout the forest.  These animals have to spend most of their day trying to find enough food to keep their little heart beating.  One of the benefits of this long winter is that it has made me take notice of how animals survive bitter cold and snow.  It has really made me appreciate many of these creatures that we seldom see, but are supremely adapted to survive (and thrive) in a long cold winter.

Snow Rollers

   It is always fun to see something that you have never seen before.  Such was the case this past Monday morning in some parts of western Pennsylvania.  Many of us awoke to what appeared to be snow balls or snow "boulders" strewn across lawns, farm fields, even the basketball court and softball field at Lutherlyn.  For most of us, this was our first glimpse of snow rollers.

   Snow rollers were formed by a "perfect storm" of conditions.  We had about five inches of powdery snow fall on Saturday.  On Sunday night the temperature warmed up into the 30s, which made the snow more cohesive.  A strong wind (20-25 mph) then began to blow and it was able to roll the snow particles across open areas.  The particles accumulated in much the same way that a snow ball is rolled to make a snowman.

   If you look closely at the above picture, you can even see the track left by the snow roller as it was blown across the landscape.  Most of the snow rollers at Lutherlyn were no bigger than a soccer ball, but I saw one in a neighbor's yard that was 20" long and 9" in diameter.  The majority of the snow rollers were solid, but there were a few with a hole in the middle.  These have been coined "snownuts" for their resemblance to doughnuts.

To me, it is a good lesson.  There is always something new, something that you have never seen before, if you only take the time to look and explore.  Sometimes you have to look really hard to see something new, but other times it is right there in your front yard, as big as a basketball.

Winter Tracking

     Sure its cold out there, its winter after all, but the snow can give us so much insight into the animal world around us.  Unlike the rest of the year, the snow records the travels of the mammals who are sharing our forests and neighborhoods with us.  Deciphering the tracks is not very difficult, if you know what to look for.
     I found this print the other day.  You can very clearly see the pads of the foot and at least three toenails/claws.  Thankfully, it wasn't the only print, there was a series of prints, which are known as tracks.
    When looking at tracks, you can quickly narrow down what the animal is by looking at the type of track pattern that the animal is exhibiting.  This one is a perfect walker, which means that this animal places its hind feet in the exact spot as its front feet. So, there are only two prints, not four, left behind. There are other animals that aren't so "perfect" and you will find their hind foot print close, but not on top of their front foot print.  They are called imperfect walkers.  Other mammals, like squirrels, mice, and rabbits have large back legs and leap or hop when they move from place to place, so they are known as leapers.  Finally, members of the weasel family have four feet that are about the same size and bound when they move, so they are called bounders.

     Perfect walkers include animals like cats, dogs, and deer.  With pads and toenails present in these prints, it is certainly not a deer.  However, it could be a feline or a canine.  Our next step involves a handy measuring tape.  The two primary measurements that we need to take are the width of the trail that the animal has made (called the straddle) and the distance from the middle of one print to the next (called the stride).  This animal's straddle is about 10 centimeters and its stride is about 30 centimeters.  Those measurements are too large for a house cat and too small for a bobcat or coyote.  What's left?  How about a fox!  Now the question is:  Is it a gray fox or a red fox?
     In order to answer that question, we will need to measure the size of the print itself.  Using the handy measuring tape again, we can see that the print is 5 centimeters long and 4 centimeters wide.  That is a little small for a red fox, but perfect for a gray fox!
      These tracks give us about the only proof that we have gray foxes living at Lutherlyn.  They are very surreptitious and have only been seen rarely at camp.  However, we find tracks nearly every time that we go out in the winter.  We don't have to go far from main camp, either.  One gray fox has a habit of travelling by the lower lake nearly every night.
    When we teach students about animal tracking, they learn how to use a measuring tape and key to identify tracks.  We have created "tracking boards" for sixteen different animals.  These boards have realistically sized tracks with appropriate strides and straddles for each animal.  It is a great way for students to practice their measuring skills and learn how to use a key.  With a little practice, this knowledge can unlock all kinds of animal mysteries.