MAXILLARY CANINES IN BIGHORN SHEEP

摘要

Bighorn sheep (Ovis canadensis) occasionally have small, procumbent maxillary canines that do not penetrate the gums. However, the frequency of these vestigial teeth is only 3%. We collected 25 skulls from an isolated and indigenous population of bighorn sheep in the Silver Bell Mountains, Arizona. We compared the frequency of maxillary canines with data reported in scientific literature and in the mammalogy collection at the University of Arizona, and found a significantly higher frequency of maxillary canines in bighorn sheep skulls from the Silver Bell Mountains than in skulls collected throughout the southwestern United States. We separated skulls by sex and age and found that male and female skulls (>6 months of age at death) from the Silver Bell Mountains both had a significantly higher frequency of maxillary canines than did skulls from the Southwest. Lamb skulls (<6 months of age at death) exhibited a higher frequency of maxillary canines than did lamb skulls from throughout the Southwest;however, our small sample size (Silver Bell, n = 5; Southwest, n = 12) was statistically inconclusive. The trait for maxillary canines might be maintained or inflated because of genetic isolation from other bighorn sheep populations.