Conservation and Management of Mule and Black-tailed Deer

Rocky Mountain mule deer by David Hewitt

Throughout the geographic range of mule deer and their black-tailed subspecies (Odocoileus hemionus), we see a lot of variation in body size, coat color, antler shape, behavior, and other attributes. For instance, mule deer in the southern latitudes are generally smaller than those in the north and those inhabiting the deserts appear lighter in color than those in heavily forested regions. The large degree of physical variation observed in mule deer led early naturalists to collect mule deer from a few geographically distant locations and designate them as different subspecies because they differed slightly from one another.

Sitka Black-tailed deer by David Hewitt

Recent advances in DNA analysis techniques now allow researchers to evaluate genetic data in ways that provide managers with meaningful ecological management units on an ecoregion scale throughout the range of a species. To gain insight into the genetic basis of differentiation in mule deer, we teamed up with a coalition of conservation groups to undertake one of the most ambitious projects of its kind, to study the genetic characteristics of nearly 2,000 mule and black-tailed deer from across their range.  

We have recently published the first set of analyses, detailing variation in mitochondrial DNA in mule and black-tailed deer. The mitochondrial DNA dataset is the most appropriate for evaluating the accuracy of the existing subspecies and to define large geographic units of similar deer. Future analyses will investigate nuclear DNA which will provide a much higher-resolution look at genetic diversity throughout North America and an even better tool to address conservation and management questions. Our first set of analyses have revealed some exciting results:

• Genetic variation is very high in mule deer – we identified 496 different types of mitochondrial DNA in the1,766 mule deer included in the full analysis.
• Mule deer and black-tailed deer are genetically distinct – in agreement with previous studies, we found that the two types differ by as much as 7.7%.  This is on par with differences between many closely-related species of North American mammals.  
• Black-tailed deer likely survived through the last glaciation in a refugium along the west coast of Washington and Oregon.  As a result, black-tailed deer have reduced genetic diversity compared to mule deer.
• Mule deer probably existed in many southern refugia at very high population sizes, because much of the genetic diversity in mule deer has been retained. 

Zion Mule Deer by Emily Latch

• Patterns of genetic structure across North America loosely correspond to currently recognized subspecies; however, we found three interesting deviations from this pattern: 1) the previously described ‘Inyo mule deer’ were not distinct from other mule deer in California; 2) Sitka black-tailed deer is not strongly differentiated from Columbian black-tailed deer, which suggests that the Sitka may be a coastal form of blacktail influenced by its environment; 3) some desert mule deer collected in the Texas panhandle, West Texas, and southeastern New Mexico show a strong genetic difference from surrounding areas despite the fact that they are currently not geographically isolated from other desert mule deer. 
• Support for this large scale project came from a coalition of conservation partners, including the Boone and Crockett Club, Pope and Young Club, National Fish and Wildlife Foundation, Camp Fire Conservation Fund, Safari Club International (SCI), Purdue University, Arizona Game and Fish Department, Dallas Safari Club, Seattle Chapter of SCI, University of Arizona, and California Deer Association.

The article from which information was drawn for this edition of Trophy Points is:  Latch EK, Heffelfinger JR, Fike JA, Rhodes OE.  2009.  Species-wide phylogeography of North American mule deer (Odocoileus hemionus): cryptic glacial refugia and postglacial recolonization.  Molecular Ecology 18:1730-1745. 

Trophy Points: Big Game Research On Line is complied and edited by David G. Hewitt, a Professional Member of the Boone and Crockett Club and the Stuart W. Stedman Chair for White-tailed Deer Research at the Caesar Kleberg Wildlife Research Institute.