Friday, December 30, 2011

Squirrel Resurrection

Three years ago my family discovered a dead squirrel in our basement.  It was unclear how the squirrel got in, or exactly how the squirrel died, but it was in good condition when we found it.  So I convinced my dad to help me bury the squirrel so  that I could get a complete squirrel skeleton.  We wrapped the body of the squirrel in the black mesh that you put down under gardens to prevent weed growth so that the little bones would not get lost.  Next we dug a small hole out behind the shed and put the make shift mesh bag in.  After covering the body with dirt, we covered the burial with a large paving stone.

Today I dug up that squirrel!

Can you feel the anticipation??
Although the squirrel was probably fully skeletonized two years ago, I had completely forgotten about it, and usually when I am home for winter break the ground it frozen so it would be very difficult to recover the squirrel.  This winter has been surprisingly mild, so I was actually able to dig up the squirrel and sit outside for several hours sorting the skeletal remains out of the mass of dirt that has accumulated in the mesh. 

Big reveal!!! ;)

Ooooo, teeny tiny squirrel bones
After sorting out the bones from the dirt clods and roots, I was left with a nearly complete squirrel skeleton.  I was even able to collect most of the phalanges and a good number of carpals and tarsals.  I will need to look for a squirrel reference book, since I am not familiar with how many carpals and tarsals a squirrel should have.  Also, I learned that squirrels only have four toes on their front paws, though they do have five on their hind paws.  I was wondering why I only recovered four sets of metacarpals even after extensive searching so it was exciting to discover that I had actually collected them all.

Fingers and toes!!!
Ribs and verts

One interesting thing about this particular squirrel is that it was not fully grown.  I can determine this by looking at the epiphyseal fusion.  Epiphyses are the ends of the bones and form separately from the diaphysis or shaft of the element.  The epiphyses form via secondary ossification centers that are disconnected from the shaft.  As an individual grows, the shaft undergoes longitudinal growth (increase in length) reducing the space between the shaft and ends.  Eventually the portions meet along the metaphysis or growth plate and fusion occurs.  When the diaphysis and epiphysis initially come together a line can be seem at the point of union.  Over time this line is obliterated and it is impossible to see where the portions joined.  In this case, the distal femur (top of knee joint), proximal tibia (bottom of knee) and proximal humerus (at shoulder) are all unfused.  Furthermore, the fusion lines are still visible on the distal radius and ulna (wrist). 

After a little more cleaning, and research into squirrel skeletal development I will hopefully have a better idea of what happened to this little guy.  :)



  2. I don't get it. It's a qrcode image, but if you scan it, it just comes up with a blank page.

    Did you mean to do this or are you just messing with me? :P

    ps. Good luck programming your checkers playing AI and writing DNA algorithms this semester, I can't wait to here more about them. :)