Unravelling Antler Progression in Desert Mule Deer: Implications for Common Management Practices

Justin T. French, Thomas S. Janke, Juan J. Celaya, Carlos E. Gonzalez, and Louis A. Harveson

Antler characteristics are commonly used in the management of cervid species to achieve a variety of management goals. Such characteristics are commonly the basis for culling criteria. However, the efficacy of culling programs is questionable and there are few robust evaluations of criteria reliability. Without understanding how bucks’ antler sizes change through time, which we term antler progression, there is little basis for establishing or testing culling criteria.

Interest in mule deer (Odocoileus hemionus) management is increasing, but there is little information on mule deer antler progression available to managers. This phenomenon is widely studied in closely related white-tailed deer (Odocoileus virginianus), but there is considerable discord in the literature. Much debate is centered on study design and interpretation, with most studies neglecting the temporally dynamic nature of antler progression. We explicitly compared antler progression dynamics of 55 known-aged mule deer bucks on the Apache Ranch, near Van Horn Texas.

The average mule deer buck reached a peak Boone and Crockett score of 172” at 5.5 years old, but individuals varied in 2 distinct ways. 70.5% of the variation was attributable to differences in overall antler size throughout the buck’s life, which we took as a measure of Lifetime Potential. An additional 21.1% was related to the age at which bucks reached their peak score, which varied from 4.5 to 7.5 years old. Variation in Lifetime Potential serves as an objective basis for comparing culling criteria, relative to a management objective. We found that the number of yearling points fails to distinguish below-average bucks 46% of the time. The absence of G4 tines in 4.5 year olds may reliably distinguish below-average bucks, but few bucks met this criteria and it should be considered with caution.

Overall, the criteria we evaluated were unreliable and difficult to apply reliably, undermining the efficacy of culling programs. We hypothesize that supplemental feeding may reduce variability in age at peak score, but continued research is required before drawing conclusions.

For more information about this project, check out our December 2020 report in the Texas Wildlife Association magazine.

Funding sources: Apache Ranch and the Borderlands Research Institute.