Teeth wear is the best indicator of a coyote's age. Wear on the long canine teeth may be apparent, but the best indicator is wear on the front incisor teeth, located between the canine teeth. If the incisors show rounded lobes, chances are the coyote is a young animal.
Coyotes between the ages of 3 and 5 usually show wear on the incisors, and the rounded lobes may be completely worn off, leaving the teeth flat across the top. This doesn't mean that the teeth of the dominant male are worn down noticeably, only that there is some wear on the teeth.
Tooth wear works OK as an estimater for younger coyotes up to about 2 years old. The older a coyote is, the more variable tooth wear estimates become. The most accurate way to estimate age for coyotes 3 years old and more is by cementum analysis which is done by removing an incisor and sending the tooth to a lab.