Evaluation of winter population density estimates of moose (Alces alces) – a long-term study

Lars Rönnegård, Håkan Sand, Henrik Andrén, Johan Månsson & Åke Pehrson

Different census methods are used to monitor and manage ungulate populations and the choice of optimal method depends on accuracy of estimates, objective of management, and economical constraints. Here we compare estimates of population size and development between four different methods (aerial counts, hunter observations, pellet group counts and a reconstruction of the population from shot moose with known age). A Swedish moose population was studied between 1973-2005 in the Grimsö Wildlife Research Area (135 km²). The highest correlation was found between the reconstruction and the aerial counts (r = 0.69, P <0.05) and the hunter observations and the aerial counts (r = 0.76, P <0.10). The pellet group counts showed low correlations with the other methods probably because prior to 1997 the sample plots were located within a small part of the research area and the moose were shown to use different parts of the research area in different years. The analysis showed that there was considerable immigration of males during a five-year period in the late 1970´s when a local hunting strategy with large proportion of shot males was implemented. We conclude that a combination of methods is important to use for accurate monitoring of ungulate populations.