Topic: Ungulate species interactions and management
Factors associated with calf body mass and recruitment in Finland
Jyrki Pusenius1,
Leena Ruha2
Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Finland
Natural Resources Institute Finland, Paavo Havaksen tie 3, 90570 Oulu
Abstract This millenium moose calf recruitment has decreased in most of Finland’s 59 moose management areas (MMAs) and calf weights in many of them. We analysed the relationships between calf weights and recruitment with densities of large carnivores, other ungulates and moose, moose population structure, winter, spring and summer weather conditions, and temporal and spatial variation in landscape structure using multivariate regression analysis separately in southern and northern Finland at the level of MMAs and at a more local level of game management associations (GMAs). A negative relationship was found between large carnivore abundance and calf recruitment in southern Finland. For bears this was seen at MMA level, for wolves at GMA level. Population density of other ungulates potentially competing with moose was negatively related to moose calf recruitment and weight. High densities of white-tailed deer were associated with low calf recruitment and weights in southern Finland. High reindeer densities were associated with low calf weights in northern Finland. Negative association of hunting pressure on female moose in the previous autumn with calf recruitment in both southern and northern Finland suggests that heavy hunting pressure reduces the proportion of high-yielding females in the moose population. The positive relationships observed between adult moose sex-ratio and moose density and calf recruitment suggest that there has been no shortage of adult males and no intra-species competition. Of climatic factors, warm snowy winters, cold springs and warm summers in southern Finland, and snowy winter conditions in spring in northern Finland were associated with low calf recruitment. For calf weights, high snowfall in April throughout Finland, warm summers in southern Finland and rainy springs and dry summers in northern Finland were associated with low calf weights. Concerning landscape and forest structure, high proportions of fields, young pine forests and broadleaved forests were associated with high calf recruitment throughout Finland, and high proportions of fields and young pine forests with high calf weights in southern Finland. The results indicated that a number of different factors were associated with moose calf recruitment and weights, and their importance varied in different parts of Finland and due to spatial scale.