Causes of Neonatal Moose Calf Mortality in South Central Alaska

During spring 1977 and 1978, 136 moose (Alces alces gigas) calves were radio-collared in the Nelchina and Susitna river basins of south central Alaska in an effort to determine causes of mortality. Thirteen calves (9.5%) died as a result of collaring activities. Of 123 remaining calves exhibiting normal cow-calf bonds, contact with 3 calves was lost and 66 (55%) died of natural causes. Predation by brown bears (Ursus arctos) was the most important cause of mortality, accounting for 79% of the deaths. Timing of the deaths of radio-collared calves was similar to that of uncollared calves of radio-collared adults, which indicated that collaring did not predispose the calves to predation. Ninety-four percent of the natural mortality occurred before 19 July each year. Little scavenging of either abandoned or predatorkilled calves was observed. Radio-collared brown bears were observed on 78 kills during 1978, averaging 1 ungulate kill/6.1 observation days. Moose of all age-classes comprised 87% of the kills and calves were the most common prey (57%). Identification of brown bear as a significant predator of moose complicates attempts to understand and manage ungulate-carnivore relationships. J. WILDL. MANAGE. 45(2):335-342 The Nelchina and upper Susitna river basins of south central Alaska have been important areas for moose hunting in recent years, accounting for 18% of the annual statewide harvest. The moose population peaked in 1960, and began declining after the severe winter of 196162. Severe winters also occurred in 196566 and 1971-72. Severe winters were thought to have precipitated the decline, but factors such as predation, range deterioration, hunting, and low bull:cow ratios were also thought to have contributed (Bishop and Rausch 1974). During this decline the moose population began exhibiting low calf recruitment, reflected by moose sex and age composition counts (Alaska Department of Fish and Game [ADFG severe winters were thought to be the controlling factor (Bishop and Rausch 1974). In the mid-1970's, the population again declined and wolf predation was suspected of preventing the population from recovering (Gasaway et al. 1977). Several studies were initiated in an effort to identify the reasons for the moose population declines. Several approaches were used, as described by Franzmann and Bailey (unpubl. rep., Alaska Dep. Fish and Game, Fed. Aid Proj. W-17-9, 1977), Oldemeyer et al. (1977), Gasaway J. Wildl. Manage. 45(2):1981 335 This content downloaded from 157.55.39.95 on Sat, 11 Jun 2016 06:28:55 UTC All use subject to http://about.jstor.org/terms 336 MOOSE CALF MORTALITY IN ALASKA* Ballard et al. et al. (1977), Stephenson (unpubl. rep., Alaska Dep. Fish and Game Fed Aid Proj. W-17-8, 1978), and Ballard and Spraker (unpubl. rep., Alaska Dep. Fish and Game Fed. Aid Proj. W-17-9 and 10, 1979). The Tanana Flats and Nelchina Basin studies evaluated the effects of wolf predation on moose calf survival in part by reducing wolf densities. All study approaches attempted to enumerate predator and prey densities by using radiotelemetry and aerial surveys. In the Nelchina study, food habit studies of the gray wolf indicated that moose comprised the bulk of the year-round diet, but rates of predation on calves were not sufficient to cause the low moose calf:cow ratios in the basin (Ballard and Spraker, unpubl. rep., Alaska Dep. Fish and Game Fed. Aid Proj. W17-9 and 10, 1979). A preliminary analysis of moose population data indicated either small or no increases in numbers of calves/100 cows following reduction in wolf densities. Evaluation of several blood parameters, used by Franzmann and LeResche (1978) to assess the physical condition of Alaskan moose populations, revealed that Nelchina Basin moose rated high in comparison to other populations, and indicated that deteriorating range conditions probably were not the cause. Moose pregnancy rates determined by rectal palpation were normal (88%), and thus low initial calf production due to low bull:cow ratios was ruled out (Ballard and Taylor, unpubl. rep., Alaska Dep. Fish and Game Fed. Aid Proj. W-17-9 and 10, 1978). As a result of these studies, it became apparent that a more direct method of determining causes of moose calf mortality was needed. In Idaho, newborn elk (Cervis elaphus) calves were fitted with radio-collars and monitored to determine the causes of mortality (Schlegel 1976). Schlegel's technique was adapted to newborn moose calves concurrently for both this study and a study on the Kenai Peninsula (Franzmann et al. 1980). The objectives were to identify specific causes of moose calf mortality between parturition and November, when fall sex and age counts are conducted. This paper reports results of the Nelchina calf mortality study and brown bear predation studies, and discusses their management implications. These studies and the Kenai Peninsula moose calf mortality study (Franzmann et al. 1980) were conducted concurrently during 1977 and 1978. These studies were supported in part by Alaska Federal Aid to Wildlife Restoration Projects W-17-R. We acknowledge the fieldwork conducted by S. Eide, T. Balland, and L. Metz, ADF&G. R. Barret, Alaska State-Federal Laboratory, Palmer, performed all the necropsies. We especially thank M. Schlegel, Idaho Department Fish and Game, for sharing his radio-collar design with us and for making many suggestions. K. B. Schneider and D. E. McKnight, ADF&G, reviewed early drafts of the manuscript and made many suggestions.