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Key to Skulls found in Owl Pellets

Find all upper and lower skulls in your owl pellet, and then use the following key to identify the types of prey.

Skull Characteristic: choose either a or b Prey type or go to question #
1a. Skull does not have teeth
Bird (Aves)
1b. Skull has teeth Mammalia -- Go to 2
2a. Skull does not have a space between incisors and other teeth (diastema)(Fig. 1) Go to 3
2b. Skull has a diastema (a space between incisors and other teeth) Go to 4 (skip3)
3a. Skull does not have a zygomatic arch (Fig. 1); teeth reddish brown at tips Shrew (Family Soricidae)
3b. Skull has a zygomatic arch; teeth white Mole (Family Talpidae)
4a. Cheek teeth are angled (see Fig. 2) Go to 5
4b. Cheek teeth are lobed Go to 6
5a. Mandible length (see Fig. 3) 15-20 mm Vole (Subfamily Microtinae)
5b. Mandible length 25-35 mm Pocket Gopher (Family Geomyidae)
6a. Mandible length (see Fig. 3) 10-16 mm Deer Mouse (Subfamily Cricetinae)
6b. Mandible length 17-30 mm Rat (Genus Rattus)
Figure 1. Side view of upper skull. Figure 2. Chewing surface of cheek teeth. Figure 3. Side view of lower jaw.

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