Effects of juvenile mass on reproduction and calf survival in a low-density moose population

Abstract

Moose (Alces alces) are a valuable big game species in Alaska and serve as a critical food source for residents. Near Nome, Alaska, the local moose population has remained at low densities for decades, and there is strong public interest in investigating the cause behind the population's failure to increase in abundance. Compared to other moose populations in Alaska, the population of moose near Nome does not appear to be nutritionally limited or close to carrying capacity. I sought to explore how juvenile mass, a widely used metric to assess moose nutritional status in Alaska, influences reproductive output and subsequent calf survival rates in the moose population in Game Management Units 22C and 22D near Nome by estimating calving rates of collared known-age and known-mass female moose and then monitoring their calves. I found that female moose that were heavier as juveniles had a higher probability of calving for the first time at age 2 or 3 and a higher probability of twinning. I found low calf survival rates (18%) through the first year of life and did not find a significant relationship between any maternal or calf characteristics and calf survival. Overall, it appears that this moose population is defined by low calf survival rates but high reproductive rates and high survival after the first year of life. Additionally, the metric of juvenile mass and primiparity as indicators of nutritional status appears to be variable within populations among years and may not be a reliable management tool. Additional research is warranted to further explore the effect of environmental factors on driving variation in primiparity probability.