Monday, April 2, 2012

WOLF Skull-dugery

Skull-dugery
   -Naturalists digging into a skull to see what the animal did for a living
                                     -WOLF School, 2012 


After I brush-hogged a stretch of multiflora rose along Bull Creek valley, Barb was patrolling the cut stems with her ever present spray of herbicide when she spotted a treasure. She showed me a bleached skull, 4.5" long, with the pride usually associated with discovering a large gold nugget.  When we keyed it out in The Wild Mammals of Missouri, it came up bobcat.

This find was perfectly timed when I was asked a week later to teach skulls to the WOLF* fifth grade class.  If you are familiar with that program, you know that these kids are well trained junior naturalists and you have to be well prepared when you enter that classroom.

Mammal skulls are fun to key as there a limited number of species and some simple rules to enter them into classes.  First, forward facing eyes suggests a predator, while lateral placed eyes usually means potential prey that are always looking for danger.  Think deer versus bobcat.

Pointed Molars of carnivore- Bobcat
The teeth description is crucial in identification.  While the exact number of teeth on both jaws can be critical in species identification, the types of incisors and premolars/molars as well as the presence of canines give some rapid clues about what the animal ate.

  • Herbivores (cow, horse, sheep, elk, bison and pig) generally lack canines and their molars are wavy with mountainous appearing edges where the dentine wears off, leaving the outside hard enamel.   Two-toed species such as deer, goats and sheep lack top incisors as well.
  • Gnawing herbivores (rodents such as rats, beaver, rabbits and squirrel) have curved sharp incisors to crack nuts and chew wood.  They lack canines and have wavy molars like other herbivores.
  • Carnivores have long pointed canines for grabbing and holding prey, sharp incisors and deep grooved molars with points like little canines.  A quick clue is the hard enamel covering all their teeth.
  • Omnivores such as coyote, fox, bear, skunk and raccoons eat both meat and insects as well as plant materials.  Their teeth are a cross between sharp incisors and pointed canines like carnivores and flat molars with blunted point covered with enamel.  Think of omnivores like you and I and it is easy to remember.
WOLFs at work

After fifteen minutes training, the WOLFs in teams of two spent several minutes with each of 5 unknowns.  As I expected, they nailed the types and even the species except for the more difficult raccoon.  And they did it without looking at skull pictures in The Wild Mammals of Missouri as I had done.  Score a big win for the WOLF school.

If you aren't familiar with the Wonders of Ozarks Learning Facility (WOLF) program of Springfield Public Schools, you can learn more at their web site. 
A good source of the information above is a pdf found by Googling "Dichotomous Key Skulls" and selecting the www.hillsboroughcounty.org .pdf.

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