The Numbers Don't Lie - Or Do They?

By Tom Keegan, Idaho Department of Fish and Game Changes to the buck mule deer season in 2005 generated much interest among hunters in the Salmon Region. Buck harvest in 2005 was higher than it had been during the past few years. At first glance, it appears that the season change led to the higher harvest rate. But as is common when dealing with natural systems, things are rarely as simple as they appear. When you look at deer harvest over the past 20 years, it becomes apparent that small changes in the hunting season timing and length don't cause significant changes in the harvest rate. In 2005, hunters simply experienced an uncommonly good set of conditions that allowed for above normal harvest. Before 1991, most general buck mule deer seasons started the third Wednesday in October and ended the second Sunday in November, such as October 18 through November 12. Since then, the season has been in October. From 1991 through 1997, the season in Salmon Region was October 5-29. From 2000 through 2004, the general rifle deer season was shortened to October 5-22. With few exceptions, this was the shortest deer season in Idaho. Factors considered in setting the 2005 hunting seasons include: - Complaints about hunter crowding, which can be reduced with consistent dates across areas. - Surplus bucks were available for harvest. - Hunter numbers, weather, and forage conditions have more influence on buck harvest than small changes in season dates. In 2005, based on biological data and public comments, a statewide season of October 10-31 was selected. This season provided 22 days of hunting - four more days than the previous season. Did the season changes in 2005 change the harvest rate? About 67 percent more bucks were taken in 2005 than in 2004, which is a substantial increase. But was the increase caused solely by hunting four more days and later in the year? Major changes in harvest between years are common, even with the same season dates. For example, between 1991 and 1997 with an October 5-29 season, the regional harvest ranged from 1,406 up to 3,164 bucks. That 125 percent difference also happened in back-to-back years. This was not an isolated case; harvest during that period routinely went up or down 40 to 60 percent from year to year (see harvest chart). When seasons were shortened by taking a week off the end of the season in 2000, common sense dictated a significant reduction in buck harvest. On the surface, average buck harvest dropped about 24 percent. But hunter numbers also had dropped by 18 percent during the same period. So, all but 6 percent of the buck harvest might be attributed to fewer hunters. Some also assume that hunter success is higher when the season runs later in October because deer are closer to the rut. But hunter success during the longer, later season averaged 28 percent compared to 26 percent during the more restrictive season; not a significant difference (see success chart). In fact, the average number of days per deer harvested was actually lower during shorter seasons - 18 days vs. 22 days during the longer season. Based on harvest rates during the same dates in 2004 and 2005, one could reasonably estimate that even with no change to the 2005 season, the buck harvest would have seen about a 53 percent increase. The additional four days of hunting in 2005 accounted for only a small part of the increase in total harvest. Increases in buck harvest in 2005 were not restricted to the Salmon Region. Even in units where the season was shortened by five days, buck harvest and hunter success actually increased. So, what does it take to really change buck harvest rates over the long term? A significant change in season timing, like the one that occurred in 1991, can make a difference. Though season length remained very similar, it was shifted two weeks earlier and no longer overlapped the early breeding period. When that happened, hunter success rates dropped from 41 percent to 28 percent, even though more hunters were in the field during the October seasons. Days per harvested buck went up to 22 from 14. After looking at these comparisons, it's fairly reasonable to say that higher harvest in 2005 was a result of "all the moons aligning" - conditions were better than normal for hunters. Similar changes in harvest rates happened in the past and will happen again in the future, regardless of small changes to hunting season length and timing. That's the way hunting goes - sometimes things fall into place better than other times; and like many things in life, we don't have much control over them. Hunters took more bucks than "normal" in 2005, but the number taken likely would have been above normal even if the season had not changed. Tom Keegan is the wildlife manager in the Salmon Region.