Slaughter weight in relation to calving date : can area quality compensate for being born late?

Sammanfattning: The interaction between wildlife and environmental properties such as climate, water and forage availability and competition is a fundamental part when studying wildlife. In ungulates, mortality rates and reproductive success are closely linked to body condition. The trade-offs between energy allocation and reproduction traits can be affected by environmental and climatic factors. In moose (Alces alces), the access to high quality habitat affects calf survival, and moose body mass in calves and yearlings correlates to environmental conditions. Recent studies have shown that a diet based on high amounts of broad leaf is positively connected to calf body mass in moose. Also, adult moose has been observed to perform better in higher latitudes in terms of body growth. Female age is also connected to body condition in calves, as calf body weight is suggested to correlate positively to mother age. In younger females, birth date is proposed to be later, resulting in lighter calves as the forage quality is highest in the start of the growing season. In this thesis, I analysed the relationships between area quality, vegetation period, birthdate, female age, and body growth for moose mainly in three areas in Sweden. Latitude, continental climate and forage composition varied among the areas. I found that calves with higher amounts of broad leaf forests in their summer habitat had higher body weight at harvest. I found that length and start of vegetation period also were important for body growth in moose calves, as growth curves were higher for calves in the north where the vegetation period is shorter and starts later than in the south. Surprisingly, I did not find any relationship between calf body weight and female age. Ultimately, based on earlier studies, my results and with a future changing climate that might affect moose negatively, I argue, that it is important to identify the factors affecting body condition in moose in order to sustain a healthy moose population.