Summer kill rates and predation pattern in a wolf–

Authors: Håkan Sand Petter Wabakken Barbara Zimmermann Örjan Johansson Hans C Pedersen Olof Liberg

Publish Date: 2008/02/13

Volume: 156, Issue: 1, Pages: 53-64

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Abstract

So far the vast majority of studies on large carnivore predation including kill rates and consumption have been based on winter studies Because large carnivores relying on ungulates as prey often show a preference for juveniles kill rates may be both higher and more variable during the summer season than during the rest of the year leading to serious underestimates of the total annual predation rate This study is the first to present detailed empirical data on kill rates and prey selection in a wolf–moose system during summer June–September as obtained by applying modern Global Positioning Systemcollar techniques on individual wolves Canis lupus in Scandinavia Moose Alces alces was the dominant prey species both by number 744 and biomass 956 899 of all moose killed were juveniles representing 760 of the biomass consumed by wolves Kill rate in terms of the kilogram biomass/kilogram wolf per day averaged 020 range 007–032 among wolf territories and was above or well above the daily minimum food requirements in most territories The average number of days between moose kills across wolf territories and study periods was 171 days but increased with time and size of growing moose calves during summer Over the entire summer June–September 122 days a group from two to nine of wolves killed a total of 66 confidence interval 95 56–81 moose Incorporation of body growth functions of moose calves and yearlings and wolf pups over the summer period showed that wolves adjusted their kill rate on moose so the amount of biomass/kilogram wolf was relatively constant or increased The kill rate was much higher 94–116 than estimated from the winter period As a consequence projecting winter kill rates to obtain annual estimates of predation in similar predator–prey systems may result in a significant underestimation of the total number of prey killedWe are indebted to J M Arnemo P Ahlqvist and P Segerström who captured and handled the wolves C Wikenros A Blixgard S E Bredvold A Bye M Dötterer J Enerud F Holen P Kirkeby P Larsson E Maartmann B Olsson H Rønning R Skyrud T H Strømseth OK Steinset carried out excellent fieldwork The study was supported by the Swedish Environmental Protection Agency the Swedish Association for Hunting and Wildlife Management World Wildlife Fund for Nature Sweden Swedish University of Agricultural Sciences Norwegian Directorate for Nature Management Norwegian Research Council Norwegian Institute for Nature Research Hedmark University College County Governors of Hedmark and Värmland Borregaard Skoger Glommen Skogeierforening Norskog Norges Skogeierforbund Olle and Signhild Engkvists Stiftelser Carl Tryggers Stiftelse Swedish Carnivore Association and StorElvdal Åmot Åsnes and Trysil municipalities All research presented complies with the current laws of the country in which the experiments were performed

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