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Reproductive Characteristics of Alaskan Moose

Charles C. Schwartz and Kris J. Hundertmark
The Journal of Wildlife Management
Vol. 57, No. 3 (Jul., 1993), pp. 454-468
Published by: Wiley on behalf of the Wildlife Society
DOI: 10.2307/3809270
Stable URL: http://www.jstor.org/stable/3809270
Page Count: 15
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Reproductive Characteristics of Alaskan Moose
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Abstract

Many aspects of moose (Alces alces) reproduction are poorly documented. Therefore, we quantified the estrous cycle, estrous length, gestation period, fetal development, and birth mass of calves. We evaluated empirical relationships among maternal age, mass, and previous breeding parity with litter size and neonatal sex ratio. Increased attentiveness by the bull signaled estrous behavior in cows. Estrous females did not increase activity. The estrous cycle varied from 22 to 28 days (x̄ = 24.4 days) and did not lengthen with each successive cycle. The cycle of primiparous females was shorter (P = 0.05) than pluriparous females. Gestation averaged 231 days (SD = 5.4 days) and did not differ (P > 0.05) between primiparous and pluriparous females, litters of 1 or 2 calves, among 5 years of study, or between cows bred their first or second overt estrus. Primiparous yearlings produced fewer (P = 0.005) calves (1.07/cow) than primiparous 2-year-old cows (1.60/cow). Calf production was related to body mass at time of breeding in primiparous (P = 0.0015) but not pluriparous females (P = 0.38). Fetal counts collected from wild moose on the Kenai Peninsula averaged 0.22, 1.27, and 0.14 for yearlings, cows aged 2-15, and ≥16, respectively. Mean corpora lutea counts for the same groups were 1, 1.5, and 2.0/female suggesting an ova loss of 0, 9.3, and 100% for the 3 age classes. Mass of single calves (x̄ = 16.2 kg) at birth was greater (P = 0.001) than twin calves (x̄ = 13.5 kg), but within single or twin litters, males did not have more mass than females. Change from conception to birth in fetal mass ($R^{2}=0.964$) and hind foot length ($R^{2}=0.997$) was best described with a von Bertalanffy equation, whereas total ($R^{2}=0.988$) and forehead-rump ($R^{2}=0.979$) lengths were linear. Using the hind foot length-age relationship, we accurately predicted 19 of 20 known second estrus births. This technique provides a simple means of estimating the incidence of delayed breeding in moose. These statistics defining chronology of the reproductive process, productivity, and fetal growth rates permit a more refined approach to modelling and management of wild moose populations. These baseline data facilitate analyses of the impacts of harvest of bulls on the reproductive performance of managed moose herds. Continued research needs to quantify the impacts of skewed bull:cow ratios on rut timing and their potential impacts on calf production and survival.

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