Lifetime, known‐age moose reproduction in a nutritionally stressed population

• Published in: The Journal of Wildlife Management
• Main Authors: Boertje, Rodney D., Frye, Graham G., Young, Donald D.
• Other Authors: Alaska Department of Fish and Game
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Alces alces; Alaska
• Online Access: http://dx.doi.org/10.1002/jwmg.21613; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjwmg.21613; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jwmg.21613; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jwmg.21613

ABSTRACT Quantifying long‐term, low reproductive metrics indicative of an ungulate population's low nutritional status can help spur action to manage for moderate densities in contrast to unsustainable, high densities. We previously ranked the moose ( Alces alces gigas ) population described here as having the lowest nutritional status among 14 moose populations in Alaska, USA, primarily using reproductive indices (1996–2005) from moose with ages estimated by counting cementum annuli. Here, we detailed lifetime reproductive metrics from a subset of known‐age female moose initially radio‐collared at 9–10 months of age (7 cohorts; 1996–2002); we renewed radio‐collars as necessary. We radio‐tracked and circled these moose via aircraft at 24‐ or 48‐hour intervals to detect the presence of newborns during the 1998–2018 calving seasons, with meaningful annual sample sizes during 2000–2014. The number of snow‐free days in the year preceding parturition had a subtle positive effect on parturition probability, but we found no evidence for effects of the preceding February and March immobilization, cohort affiliation, or the preceding winter's snow cover on the probability of a female being parturient. The probability of twinning declined as the calving season progressed. Compared with moose production in populations with improved nutrition, our study population experienced low production primarily as a result of delayed maturation, occasional pauses in reproduction, and low twinning rates. Reproductive senescence occurred at normal advanced ages despite nutritional stress. We recorded a 28% parturition rate among 144 females 3 years of age (min. age of reproduction). Parturition rates were stable from 4 to 13 years of age ( = 77%), declined at 14 years of age, and peaked at 15 years of age. Females first twinned at 5 years of age (5%), and the twinning rate increased with age, peaking at 13 years of age (25%). Overall, 136 radio‐collared females with complete reproductive histories produced a mean of 5.3 calves/lifetime ...