The Harvest Records Project focused on identifying the effects of harvest on horn size of mountain sheep. Hunting is an important part of wildlife management, but there is concern over how harvest might affect the size of horns and antlers of ungulate species over time. This project evaluated how the size of horns of hunted bighorn sheep changed through times, and identified the mechanisms that caused change.
This work concluded in 2019, when master’s student Tayler LaSharr completed her graduate degree and had finished publishing the papers associated with her degree.
Main findings
Harvest records programs provide valuable insight into changes in ungulate horns, antlers, and pronghorns.
The Boone and Crockett Club, the first records program in North America, was created over a century ago to promote conservation and the ethical and sustainable management wildlife. To this day, that goal remains the foundation of numerous records programs throughout North America, and because of the diligence and enthusiasm of the individuals that created records programs, decades of measurement data exist for most species of big game that are harvested in North America. Consequently, the measurements of trophy animals kept by records programs may be one of the most robust and valuable tools available for understanding how harvest influences horn and antler size. Yet, understanding the scope of these records and what they can tell us about big game species is critical to their effective use for wildlife management.
When we compared trends in the size of horns and antlers of three different records books (Boone and Crockett Record Book, Pope and Young Record Book and Safari Club International Record Book), we found that eight of the seventeen categories differed in the direction and magnitude of temporal trends. Furthermore, although we did observe a divergence in some categories, over half of the trophy categories that we tested did not show significant differences in trends among record books, which suggests that trends evident in trophy record books may accurately represent trends that are occurring in the size of trophy males through time and not simply resulting in watered down trends of a larger range of sizes. Given their truncated nature, however, care must be taken when interpreting any observed patterns in those data, they aren’t telling the story of what’s happening in a population, just the largest animals on the landscape.
This research was published in the paper, “Biological relevance of antler, horn, and pronghorn size in records programs,” by Tayler N. LaSharr, Ryan A. Long, James R. Hefflefinger, Vernon C. Bleich, Paul R. Krausman, R. Terry Bowyer, Justin M. Shannon, Eric M. Rominger, Chadwick P. Lehman, Mike Cox, and Kevin L. Monteith in the Journal of Mammalogy in 2019.
Current harvest practices of bighorn sheep are not affecting horn size of harvested males.
Horns and antlers of ungulates play an important biological role and hold important sociological significance. From signaling strength to rivals and potential mates, to the allure they provide hunters seeking to hang impressive trophies on their living room walls, the size of horns and antlers are important. The interest in harvesting animals based on the size of horns and antlers recently has raised concern over the potential effects that hunting may have on the size of those structures over time.
Among 72 hunt areas, horn size remained unchanged in 44, decreased in 19, and actually increased in 9. The researchers found evidence that all three mechanisms caused changes in horn size, depending on the hunt area in question. In fewer than half of hunt areas where horn size declined, did evidence point to hunting as the cause of evolutionary change. In the others, nutrition and changing age structure appeared to be driving down horn size. In all, current harvest regimes in most hunt areas do not appear to be reducing horn size in bighorn sheep.
This research was published in the paper “Hunting and mountain sheep: do current harvest practices affect horn growth” by Tayler N. LaSharr, Ryan A. Long, James R. Heffelfinger, Vernon C. Bleich, Paul R. Krausman, R. Terry Bowyer, Justin M. Shannon, Robert W. Klaver, Clay E. Brewer, Mike Cox, A. Andrew Holland, Anne Hubbs, Chadwick P. Lehman, Jonathan D. Muir, Bruce Sterling, and Kevin L. Monteith in Evolutionary Applications in 2019.
Project lead
Tayler LaSharr
Collaborators, partners, and funders
This work was supported by Utah Division of Wildlife Resources, the National Wild Sheep Foundation (WSF), Wyoming Wild Sheep Foundation, Alberta Wild Sheep Foundation, California Wild Sheep Foundation, Arizona Desert Bighorn Sheep Society, Wyoming Governor’s Big Game License Coalition, Iowa Foundation for North American Wild Sheep, Utah Foundation for North American Wild Sheep, and the Pope and Young Club. Ryan Long, James Heffelfinger, Vernon Bleich, Paul Krausman, R. Terry Bowyer, Justin Shannon, Robert Klaver, Clay Brewer, Mike Cox, A. Andrew Holland, Anne Hubbs, Chadwick Lehman, Jonathan Muir, Hollie Miyasaki, and Bruce Sterling all provided valuable insight and collaboration throughout the project.