## Wednesday, November 30, 2016

### Vampire Bat Incisors

Halloween is far gone, but vampire bats are always fascinating to learn about. A common misconception to many is that vampire bats are violent, threatening creatures that can kill. However, vampire bats are relatively small and rarely kill their prey, even being quite gentle in their ways. Instead of using the long canines (the fangs) on the sides, vampire bats normally use their tiny incisors on the front to cut into the skin. On top of that, the victim rarely notices the incision because of how sharp these incisors are.

Obviously, the main issue we need to discuss here is the physics behind it. So, how much force is a vampire bat's incisor actually exerting onto the prey's skin, and how does it compare with a human incisor? Based on an equation we learned in class, I noticed that the force is related to the pressure and area:

P = F/A
F = PA (where in this case, A is the area of contact between the skin and the incisor)

I found that bat incisors are typically 2 mm in width, and 0.2 mm in thickness. The total area must therefore be:

A = 2 mm x 0.2 mm
A = 0.4 mm^2

Thus, the total force required would be:

F = PA
F = 0.4P

If we look at a typical human incisor, which is about 9 mm wide and 1 mm thick, the total area is:

A = 9 mm x 1 mm
A = 9 mm^2

Comparing the bat's incisor to the the human's incisor, we can see that the force needed to apply the same pressure will be significantly greater:

F = PA
F = 9P

The force required by human incisors is almost 23 times more than that of bat incisors. So if, for any reason, you decide you want to become a humanoid vampire, perhaps sharpening your teeth or working on that jaw muscle might be a good idea.

Sources:
http://www.arkive.org/common-vampire-bat/desmodus-rotundus/
http://www.science.smith.edu/msi/pdf/642_Pteropus_vampyrus.pdf
http://www.nytimes.com/2016/11/01/science/fangs.html?rref=collection%2Fsectioncollection%2Fscience&action=click&contentCollection=science&region=stream&module=stream_unit&version=latest&contentPlacement=120&pgtype=sectionfront