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Trophy Talk: Does Hunting Hurt Horn & Antler Growth?

by Dr. Dave Samuel   |  July 2nd, 2013 0
Bighorn-sheep

While the decline in horn and antler size in the past century has been small, it definitely has the attention of wildlife biologists and managers.

For years, one of the arguments the antis used in their tirades against hunting was the idea that hunting lowers the quality of harvested animals by taking out the very best. Wildlife managers have also questioned this, and for certain species they have instituted regulations that protect smaller-horned and antlered males. So the questions are: Do these regulations work to improve horn or antler quality, and does hunting have an impact on the horn or antler size of hunted species?

The factors that might lower the quality of antlers or horns over a long period of time include: intensive hunter harvest of males, genetic change as a result of selective male harvest, climate change, habitat alterations, and the increased desire of hunters to submit smaller but eligible trophies to the record books.

These factors are difficult to assess, but a new study does just that. A team of biologists analyzed more than 22,000 Boone and Crockett records for 25 species from 1900 to 2008. The study was published by The Wildlife Society as a Wildlife Monograph (Vol. 183, Feb. 2013) and is titled, “Effects of Harvest, Culture, and Climate on Trends in Size of Horn-Like Structures in Trophy Ungulates.”

These researchers showed that over the 108 years of data examined, antler size for 17 species declined a total of 1.87 percent. For typical whitetail bucks, the decrease was 1.86 percent. This means that a 150-inch buck in 1900 would only be a 148.14-inch buck in 2008.

Typical Coues deer dropped 0.07 percent, as did Alaska-Yukon moose (-0.01 percent) and typical mule deer (-0.08 percent). Caribou species dropped as well, with the Quebec-Labrador caribou dropping 0.64 percent followed by central Canada barren ground caribou (-0.25 percent), mountain caribou (-0.16 percent), and woodland caribou (-0.05 percent). Rocky Mountain elk dropped 0.03 percent, while the Roosevelt elk dropped 0.27 percent. Columbia blacktails (typical) dropped 0.33 percent.

This study also examined the four species of wild sheep and four other horned species. For all eight species they found an overall average decline of 0.68 percent in horn size. However, the news was not all bad as five of the eight species gained in horn size (bison, muskox, pronghorn, mountain goat, bighorn sheep). Desert sheep decreased 0.13 percent as did Dall sheep (-0.14 percent) and Stone sheep (-0.11 percent). The species with the largest increase in horn size over the 108 years was muskox (+0.34 percent). Bison gained (+0.04 percent) in horn size, and so did pronghorns (+0.03 percent), mountain goats (+0.02 percent) and bighorn sheep (+0.07 percent).

The sheep have been of particular interest to wildlife managers. In this study, bighorn sheep showed a slight increase in horn size. Breaking the data down, one sees a slow but steady decline in bighorn sheep horn size until 1980, but a steady increase thereafter. That shift coincided with a more conservative harvest strategy and reintroductions into new areas.

Desert bighorns have slid steadily since 1960, even with harvest restrictions on horn size. That said, factors other than hunting may be playing a role. For example, in Arizona, studies show that the amount of winter moisture is correlated to horn size over the lifetime of an individual male. Since we have seen more persistent droughts and lower winter snowfalls in recent years, this could explain some of the decline in horn size.

There are several other possible factors that could impact antler and horn size over a 100-year period. This study examined those variables relative to horned species and came to this conclusion. “Our results provided no support for a sociological effect (a desire to submit smaller, but eligible species to the record book), effects of large-scale climate, or broad-scale habitat change as the primary explanations for downward trends in (horn) size. In contrast, our results provided moderate support for the hypothesis that intensive harvest may have resulted in a gradual shift in male age structure towards younger males, and limited support for genetic effects as a result of selective male harvest, as potential explanations for observed trends in size of horn-like structures.”

In conclusion, given the huge benefits derived from recreational hunting and their overall contributions to conservation, the small declines observed in horn and antler size during the past century may not be all that important. However, now that we know the trends, be assured that wildlife biologists and managers will be more focused on this situation.

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