Characteristics and dynamics of a moose population in northern New Hampshire

Abundance indices suggest that the moose (Alces alces) population in northern New Hampshire has stabilized despite favorable habitat and conservative harvest. Natural mortality of unknown cause is presumed a primary reason although little is known about moose reproduction and survival in New Hampshire. This study (2002-2005) was designed to investigate the dynamics that impact this population. Analysis of harvest reproductive data (1988-2004) indicated that average field-dressed weight of adult cows increased although corpora lutea count declined from ∼1.4- 1.2/cow in the study area and statewide. Yearling ovulation rate (∼42%) and average weight (\u3c211 kg) declined about 25% and 4%, respectively. Parturition of radio-marked cows ranged from 8 May-13 July (median=19 May) with 78% of births from 13-27 May. Calving rate of yearlings and adults (\u3e2 yr) averaged 30 and 85%, respectively, whereas twinning rate was 11%. There were 39 mortalities (49% calves) with winterkill/parasite (41%), vehicle collision (26%), and hunting (18%) the leading causes. Radio-marked cow mortality was primarily human-related and survival was 0.87. Unmarked calf (0-2 months of age) survival was 0.71with 76% of mortality in first month of life. Radio-marked calves (∼7-12 months of age) had a survival rate of 0.67 with 74% winterkill/parasite-related mortality. Estimated annual calf survival was 0.45. Although population modeling indicated a positive finite rate of increase (1.03-1.07), substituting lower confidence limits for winter survival of calves and both calves and yearling/adults predicted nearly stable (1.01) and negative (0.95) growth, respectively. A conservative physiological model was used to predict the metabolic impact of adult female winter ticks (Dermacentor albipictus) on calves over 8-weeks of engorgement. Protein deficit associated with blood loss and regeneration appeared to be the most critical problem for calves with daily losses of 30-\u3e100% of daily protein requirement over a 2-week period in moderate-severe infestations. Unseasonably warm and snowless 2001 fall conditions likely increased transmission of ticks, therefore, winter survival of calves was lowest (0.49) and cow survival was reduced \u3e10% in 2002. Currently, the perceived stability likely reflects the variation in survival, recruitment, and possibly low yearling fecundity caused by winter tick and more importantly tick epizootics. However, high fertility, calving rate, and body condition of adult cows, and summer calf survival should ensure local population recovery after epizootics that periodically inhibit population growth