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Summer kill rates and predation pattern in a wolf-moose system: can we rely on winter estimates?
Håkan Sand1, Petter Wabakken, Barbara Zimmermann
1Grimsö Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences, 73091 Riddarhyttan, Sweden. hakan.sand@ekol.slu.se
Oecologia
|February 14, 2008
Summary
Summer wolf predation on moose is significantly higher than winter rates, with wolves prioritizing young moose. This highlights the need for summer data to accurately estimate annual large carnivore impact.
Area of Science:
- Ecology
- Wildlife Biology
- Predator-Prey Dynamics
Background:
- Most large carnivore predation studies focus on winter, potentially underestimating annual kill rates.
- Large carnivores often prey on juvenile ungulates, leading to higher and more variable kill rates in summer.
- Accurate annual predation estimates require understanding seasonal variations in kill rates and prey selection.
Purpose of the Study:
- To present the first detailed empirical data on wolf (Canis lupus) kill rates and prey selection during summer.
- To quantify summer predation in a Scandinavian wolf-moose (Alces alces) system using modern tracking technology.
- To compare summer kill rates with winter estimates and assess potential annual underestimation.
Main Methods:
- Utilized Global Positioning System (GPS)-collars on individual wolves in Scandinavia.
- Monitored wolf territories from June to September, collecting data on kills and prey biomass.
- Incorporated moose calf growth functions and wolf pup nutritional needs into kill rate analysis.
Main Results:
- Moose constituted the dominant prey (74.4% by number, 95.6% by biomass), with juveniles comprising 89.9% of kills.
- Average daily kill rate was 0.20 kg biomass/kg wolf, exceeding minimum food requirements in most territories.
- Summer kill rates were 94-116% higher than winter estimates, with an average of 1.71 days between moose kills.
Conclusions:
- Summer predation rates by wolves on moose are substantially higher than previously estimated from winter studies.
- Projecting winter kill rates to annual estimates significantly underestimates total predation in wolf-ungulate systems.
- Understanding seasonal prey selection and kill rates is crucial for accurate ecological assessments of large carnivore impact.
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