Managing for Elevated Yield of Moose in Interior Alaska

Abstract

Given recent actions to increase sustained yield of moose (Alces alces) in Alaska, USA, we examined factors affecting yield and moose demographics and discussed related management. Prior studies concluded that yield and density of moose remain low in much of Interior Alaska and Yukon, Canada, despite high moose reproductive rates, because of predation from lightly harvested grizzly (Ursus arctos) and black bear (U. americanus) and wolf (Canis lupus) populations. Our study area, Game Management Unit (GMU) 20A, was also in Interior Alaska, but we describe elevated yield and density of moose. Prior to our study, a wolf control program (1976–1982) helped reverse a decline in the moose population. Subsequent to 1975, moose numbers continued a 28‐year, 7‐fold increase through the initial 8 years of our study (λB1 = 1.05 during 1996–2004, peak density = 1,299 moose/1,000 km2). During these initial 8 hunting seasons, reported harvest was composed primarily of males ( = 88%). Total harvest averaged 5% of the prehunt population and 57 moose/1,000 km2, the highest sustained harvest‐density recorded in Interior Alaska for similar‐sized areas. In contrast, sustained total harvests of <10 moose/1,000 km2 existed among low‐density, predator‐limited moose populations in Interior Alaska (≤417 moose/1,000 km2). During the final 3 years of our study (2004–2006), moose numbers declined (λB2 = 0.96) as intended using liberal harvests of female and male moose ( = 47%) that averaged 7% of the prehunt population and 97 moose/1,000 km2. We intentionally reduced high densities in the central half of GMU 20A (up to 1,741 moose/1,000 km2 in Nov) because moose were reproducing at the lowest rate measured among wild, noninsular North American populations. Calf survival was uniquely high in GMU 20A compared with 7 similar radiocollaring studies in Alaska and Yukon. Low predation was the proximate factor that allowed moose in GMU 20A to increase in density and sustain elevated yields. Bears killed only 9% of the modeled postcalving moose population annually in GMU 20A during 1996–2004, in contrast to 18–27% in 3 studies of low‐density moose populations. Thus, outside GMU 20A, higher bear predation rates can create challenges for those desiring rapid increases in sustained yield of moose. Wolves killed 8–15% of the 4 postcalving moose populations annually (10% in GMU 20A), hunters killed 2–6%, and other factors killed 1–6%. Annually during the increase phase in GMU 20A, calf moose constituted 75% of the predator‐killed moose and predators killed 4 times more moose than hunters killed. Wolf predation on calves remained largely additive at the high moose densities studied in GMU 20A. Sustainable harvest‐densities of moose can be increased several‐fold in most areas of Interior Alaska where moose density and moose: predator ratios are lower than in GMU 20A and nutritional status is higher. Steps include 1) reducing predation sufficient to allow the moose population to grow, and 2) initiating harvest of female moose to halt population grow...

Contrasting aerial moose population estimation methods and evaluating sightability in west‐central Alberta, Canada

“…In general, several years of survey data should be collected to determine trends in population size (Boertje et al 2009). However, moose densities may have actually increased in our study area.…”

Persistent effects of fire severity on early successional forests in interior Alaska

“…Moose are one of the main subsistence resources in interior Alaska (Scott et al, 2001), and their populations are managed to optimize sustainable harvest densities (Boertje et al, 2009). Forage availability is an important factor in determining moose demography (Van Ballenberghe and Ballard, 1998;Boertje et al, 2007), and consequently could be important in driving population densities.…”

Population density of Dall’s sheep in Alaska: effects of predator harvest?

“…Most studies, however, still do not account for interactions between predators, prey, and K in attempting to explain ungulate population dynamics, especially in the context of conservation (Kie et al 2003;Regelin et al 1995;Eberhardt et al 2007;Bowyer et al 2013). Our results suggest that decisions about strategies for population management of ungulates should not be made without regard to K. We note that biologists have previously attempted to manipulate moose and caribou populations in central Alaska using harvest and predator control (Boertje et al 1996(Boertje et al , 2009, without considering K (Bowyer et al 2005). This strategy had negative results, not only for moose populations and harvest, but also for agency credibility (Young and Boertje 2011).…”

“…This strategy had negative results, not only for moose populations and harvest, but also for agency credibility (Young and Boertje 2011). Managers now realize that carrying capacity (Seaton et al 2011) is an integral component of effective management of moose populations, and the metric is now incorporated in management decisions concerning moose (Boertje et al 2009(Boertje et al , 2010.…”