Puncturing Ability of Bat Canine Teeth: The Tip

Casts of upper canine teeth of 15 species of microchiropteran bats were fixed securely into a testing machine and made to puncture the bloom side of an apple. The force necessary to break through the surface of the apple was regressed against both shape of the tip of the canine and the size of the animal. Sharper tips require less force to puncture than blunt ones. Results were also verified using giant two-dimensional models of PlexiglasTM with sharp and blunt tips that were loaded onto a PlexiglasTM beam. Fringes, or stress lines, are more highly concentrated at the point of contact for a smaller radius than for a larger radius under the same loading conditions, indicating that stress in the beam is higher and more concentrated at the sharper tip. Ours is some of the first experimental work to quantify apical sharpness of a tooth and performance as it punctures a substance.