Idaho State University researchers participate in study documenting hunt harvest effects trophy horns, antlers of big game species

A new comprehensive study of records compiled by the Boone and Crockett Club concludes that big game harvest has reduced the size of horns and antlers of trophy male big game species over time.

A team of six scientists from Idaho State University, the University of Montana, Arizona Game and Fish Department, and the California Department of Fish and Game, led by Kevin L. Monteith, now at the University of Wyoming, recently analyzed a 108-year data set comprising 22,000 records among 25 trophy categories of big game inhabiting North America compiled by the Boone and Crockett Club.

The extensive study titled "Effects of harvest, culture, and climate on trends in size of horn-like structures in trophy ungulate," following intense scientific scrutiny, was published by The Wildlife Society as a prestigious Wildlife Monograph in late January.

The study concluded that there was a small, less that 2 percent, but consistent decline in horn and antler size across most trophy categories over the past century.

"All of the authors hunt, and were initially quite surprised by the outcomes from their research," said Idaho State University biological sciences Professor Terry Bowyer, who oversaw the initial analyses at ISU, "No other study, however, has spanned the time, geographic extent, simultaneously examined multiple ungulates (big game species) or amassed such a huge sample size."

Bowyer pointed out that all trophies were precisely measured by Official Measures of the Boone and Crockett Club.

"There is little doubt that our findings are real," Bowyer said. "We hope our research will be of value to fish and game agencies charged with the management of these important natural resources."

Through a series of careful analyses, the biologists ruled out a sociological effect from hunters wanting to submit trophies that met minimum criteria for inclusion in the record book, effects of a changing climate, and habitat alterations as causes of the decline. 

Evidence provided limited support for a genetic change from selective harvest of large males, and moderate support for an intensive harvest of males, in general, which would lower the age structure, allowing fewer animals to reach trophy status prior to harvest. 

The authors likewise provided management recommendations to overcome the decline, which would address both potential causes of smaller horns and antlers (a reduced harvest of males with lost opportunity being compensated by harvesting more females for populations near the carrying capacity of their environment).  They also noted, however, that the reduction in size of trophy horns and antlers was small, and that recreational, management, and conservation benefits from hunting might offset the detriments of a small reduction in size of trophies.

The studies authors included Monteith; Bowyer; ISU's Ryan Long; Vernon C. Bleich, Sierra Nevada Bighorn Sheep Recovery Program, California Department of Fish and Game; James R. Heffelfinger, Arizona Game and Fish Department; and Paul R. Krausman, Wildlife Biology Program, University of Montana.

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