May Data in Focus: Red fox reproduction monitored at Grimsö Wildlife Research Station since 1973

02 May 2023

The SITES 2023 Calendar theme is “Data in Focus”. The openly available data produced within SITES and stored on the SITES Data Portal is the “golden thread” of the infrastructure, allowing users access to ecosystem data that covers diverse habitats and climate zones across geographical gradients in Sweden. Each month follow along as we highlight a unique SITES dataset.  

Wildlife monitoring is an important part of the activities at Grimsö Wildlife Research Station. A large part of the monitoring was initiated during the 1970’s, but new data series have been added over time as methods have developed. The continuous surveys focus on topics such as population dynamics, reproduction, life history traits and body measurements and include monitoring of, e.g., moose, roe deer, red fox, voles and starlings. For example, red fox (Vulpes vulpes) reproduction has been monitored since 1973 by identifying fox litters. Around 200 fox dens are checked annually within the Grimsö Wildlife Research Area and the dens with observed reproduction are summed to mirror the total number of fox litters for that year. The variation in the local fox abundance is related to the vole population cycle and is a key factor for the dynamics of several small mammal populations across Scandinavia.

Link to Data:

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Photo: Gunnar Jansson, Graphic: Roberto Lo Monaco

The graph shows the number of fox litters at Grimsö between 1973-2021, with variations over time mainly related to vole cycles. The extra low numbers in 1985-1986 were due to an outbreak of scabies (sarcoptic mange) that regulated fox populations more or less throughout Sweden during the late 1980's and into the 1990's.