RECOVERY OF LOW BULL:COW RATIOS OF MOOSE IN INTERIOR ALASKA

Abstract

During 1996–1999, hunters killed an estimated 24–30% of the pre-hunt bull moose (Alces alces) in Game Management Unit 20A. As a result, the 1999 post-hunt bull:cow ratios declined to 24:100, well below the management objective of 30:100. During 2000 and 2001 we shortened the hunting season from 25 to 20 days to reduce the harvest of bull moose, but kill rates of bulls remained high (23–27%) and ratios remained unacceptably low (22–26 bulls:100 cows). Subsequently, to recover bull:cow ratios to 30:100, hunters were restricted unit-wide to taking bulls with 1) spike-fork antlers, 2) antlers ≥50 inches wide, or 3) ≥3 brow tines on ≥1 antler. These restrictions were in place from 2002-2007, but results occurred rapidly. After only 2 years of antler restrictions, hunters killed an average of 36% fewer bulls compared with the previous 2-year average harvest rate (x= 715 during 2000–2001 and 455 during 2002–2003). Comparing these same 2-year  periods, average kill rates of bulls declined from 25% to 12% of the pre-hunt bull population, average number of hunters declined 24% (1,568 to 1,187), and the average hunter success rate declined from 34% to 29%. Bull:cow ratios increased from 26:100 to 32:100 after 2 years of antler restrictions. With an additional 2 years (2004–2005) of antler restrictions and high harvest of cow moose, bull:cow ratios reached 38:100. Modeling indicated that the bull:cow ratio would have stabilized at 33:100 without the high harvest of cows. The recovery of bull:cow ratios to our objective of 30:100 with 2 years of antler restrictions allowed 1) bull seasons to be lengthened from 20 to 25 days beginning in 2004 and, 2) a limited number of drawing permits for any bull during 2006–2007. Elsewhere, similar selective harvest strategies should also allow recovery of bull:cow ratios, unless the total kill rate of bulls is higher than estimated here.