The Impact of Predation on Boreal Tetraonids During Vole Cycles: An Experimental Study
- 1 October 1988
- journal article
- research article
- Published by JSTOR in Journal of Animal Ecology
- Vol. 57 (3) , 859-872
- https://doi.org/10.2307/5097
Abstract
(1) Predators were removed in an experiment to study the impact of mammal predation on woodland tetraonid populations during vole cycles. Foxes and martens were killed from 1976 to 1980 on one of two similar islands in the northern Baltic. The treatment was then reversed until 1984. (2) When predators were killed, tetraonid brood sizes averaged 5.52 in August, and 77% of hens had chicks. When predator were not killed, broods averaged 3.29 chicks and 59% of hens had chicks. (3) Counts of adult capercaillie and black grouse during July and August increased by 56-80% after 2 years of predator removal. Counts at leks increased by 166-174%. (4) Removing foxes and martens had no significant effect on vole abundance during two 4-year cycles. (5) When predators were not removed, tetraonid brood sizes and the proportion of females that bred successfully were each positively correlated with vole abundance in summer. There were most chicks per adult hen when vole numbers were high and increasing slowly from summer to autumn. When foxes and martens were killed, neither brood size nor subsequent adult numbers were significantly correlated with vole abundance in summer, although losses of whole broods increased slightly when vole numbers grew most rapidly from summer to autumn. We conclude that large vole populations resulted in large autumn grouse populations mainly because they reduced predation on breeding grouse. (6) The vole numbers and increase rates that were associated with high grouse breeding success in one summer were also associated with low counts of adult grouse the next year, and thus with an increase in grouse losses from one summer to the next.This publication has 7 references indexed in Scilit:
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