Study: Big game harvest reduces size of trophy horns, antlers

Hunters might soon find themselves hanging smaller trophy antlers upon their walls, if they even notice at all.

Idaho State University Biological Sciences Professor Terry Bowyer just helped publish a report with a team of six scientists from ISU, the University of Wyoming, the University of Montana, California Fish and Game, and the Arizona Game and Fish Department. The report shows how the size of horns and antlers of trophy male big game species is reduced over time due to big game harvesting.

“So this intensive harvest had lowered the age structure of the population, and the males weren’t reaching a size which they were trophies,” Bowyer said.

The scientists analyzed a set of data collected by the Boone and Crockett Club which looks closely at more than 25 categories of big game species over a time period of 108 years.

Bowyer said they concluded, with limited support, three main reasons why the size of these horns and antlers are affected: the genetics of the animal, the age of the animal, and its nutritional condition. However, he said the primary factors all boil-down to the harvesting of these species.

“Somehow they’re changing the genetic makeup of horns and antlers by shooting animals with larger-sized antlers,” Bowyer said.

He said this effect is slowly wiping-out these larger-horned animals from the gene pool and leaving those who are younger, smaller-growing and developing at a slower pace.

The nutritional condition of the animal is important because Bowyer said malnourished females tend to give birth to smaller offspring.

“The thing that’s interesting is that the young, no matter what diet they are on, can never compensate in size,” Bowyer said. “They remain small throughout their entire lifetime which means if they’re a male, they’ll have smaller antlers.”

He also said there is a larger female population, and they tend to be more competitive when it comes to acquiring the minimal natural resources out there in the wild. Nonetheless, he said it took two generations in order to notice a change in the decreasing animal size.

However, he said this change in size is quite minimal and scientists are looking at a two-percent change over the 108 years of data collected.

Bowyer also mentioned this phenomenon can, in fact, be reversed.

“Big horn sheep, which started to decline like other game, suddenly leveled-off and apparently may have recovered when we began a very restrictive harvest … for those animals. So it suggests that whatever we observed might be reversible,” Bowyer said.

He mentioned another way to stop this downward trend is by decreasing the female population. However, he said this is a controversial topic and speaks strictly from a scientific standpoint.

Idaho Fish and Game representatives said they need more time to review the more than 30 page study before commenting on the topic.

Either way Bowyer said he has put away his deer rifle and picked up a shotgun instead, since he enjoys hunting waterfowl with his dog.

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