Bighorn sheep ram.

Harvest Records Project

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.

Among the 72 hunt areas we studied, 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, evidence pointed 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.