Do intrinsic or extrinsic factors limit reproduction in cyclic populations of Clethrionomys glareolus and C. rufocanus?

• Published in: Ecography
• Main Author: Löfgren, Ola
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1989
• Subjects: Ecology, Evolution, Behavior and Systematics; Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1600-0587.1989.tb00822.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0587.1989.tb00822.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0587.1989.tb00822.x

Changes in reproduction and functional age structure of females in cyclic populations of Clethrionomys glareolus and C. rufocanus were studied by live‐trapping individually marked voles during 1980 to 1984 in northern Sweden. A complete population cycle was observed in both species, with a synchronous ‘summer‐decline’ in 1982. In both species, the length of the breeding season became successively shorter towards the peak, and it was extremely short at the decline. When the populations expanding, the density of breeding females increased in a sigmoid way, and thereafter it remained fairly constant throughout the summer. At the decline, the density of breeding females decreased successively from spring to autumn. Year‐born females matured and bred in all years except at the decline. Intrinsic factors, such as spacing behaviour of breeding females, are thought to limit the density of breeders in general, but only when the populations are expanding. Other factors such as deteriorating food conditions are more likely to operate at the decline.