Differences in Predation Pressure in Relation to Habitat Fragmentation: An Experiment

Abstract

Lindstrom, E. and Widen, P. 1985. Differences in pre- dation pressure in relation to habitat fragmentation: an experiment. -Oikos 45: 273- 277. In the holarctic zone many medium-sized herbivores exhibit cyclic fluctuations, which generally disappear towards the south. In Fennoscandia, cycles in abundance of te- traonid birds are found within the boreal zone but not south of it. The hypothesis that disappearance of cycles towards the south is due to increased predation pressure, pre- dicts a gradient in predation pressure in Sweden across the border between the boreal zone and the boreo-nemoral zone. This was tested using dummy nests to measure predation pressure. As predicted, we found higher predation rate south of the border and lower predation rate north of it. The rate of predation on experimental dummy nests was correlated with the abundance of corvid birds, which in turn was positively related to the proportion of agricultural land, human density and to the degree of fragmentation of forests. H. Andre'n, P. Angelstam, E. Lindstrom and P. Wide'n, Grimso Wildlife Research Sta- tion, S-770 31 Riddarhyttan, and Dept of Zoology, Univ. of Uppsala, Box 561, S-751