Is the heart of Fennoscandian rodent cycle still beating? A 14‐year study of small mammals and Tengmalm's owls in northern Norway

• Published in: Ecography
• Main Authors: Strann, Karl‐Birger, Yoccoz, Nigel G., Ims, Rolf A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: Kilpisjärvi; Norway; Fennoscandia; Fennoscandian; North Finland; North Norway; Northern Norway; Troms
• Online Access: http://dx.doi.org/10.1034/j.1600-0587.2002.250109.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1034%2Fj.1600-0587.2002.250109.x; https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1600-0587.2002.250109.x

Analyses of spatial and temporal patterns of the small mammal cycle in Fennoscandia have led to two main conclusions: a south‐north geographical gradient in the strength of density dependence and period length, and a change in temporal dynamics with less clear periodicity and lower amplitude of fluctuations in recent years. Fourteen years (1985–1998) of small mammals trapping and Tengmalm's owls monitoring data provided clear evidence for 3‐yr cycles of two vole species in inner Troms, north Norway, at the same latitude and only 80 km from Kilpisjärvi, north Finland, where 4–5‐yr cycles have been the norm until the end of 1980s. The response of Tengmalm's owls to variation in small rodents abundance was not delayed, as was observed in central Finland. Common shrews appeared to have more stable dynamics. The features of the cycle, and a reassessment of the previously described patterns, show that the dynamics may be different over short distances. Furthermore, snow cover and habitat fragmentation should explicitly be taken into account in any understanding of the Fennoscandian gradient, and surrogate variables such as latitude should be avoided. We stress the need for a more extensive coverage of spatial and temporal patterns in cyclicity with respect to assumed ecological causes.