Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks

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dc.contributor.author Eccard, Jana
dc.contributor.author Jokinen, Ilmari
dc.contributor.author Ylönen, Hannu
dc.date.accessioned 2012-08-20T08:42:25Z
dc.date.available 2012-08-20T08:42:25Z
dc.date.issued 2011
dc.identifier.citation Eccard, J., Jokinen, I., & Ylönen, H. (2011). Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks. BMC Ecology, 11 (16).
dc.identifier.issn 1472-6785
dc.identifier.uri http://hdl.handle.net/123456789/38311
dc.description.abstract Background: A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression. Results: We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density. Conclusions: At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency. fi
dc.language.iso eng
dc.publisher BioMed Central (BMC)
dc.relation.ispartofseries BMC Ecology
dc.relation.uri http://www.biomedcentral.com/1472-6785/11/16
dc.rights © 2011 Eccard et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
dc.subject.other dominanssi fi
dc.subject.other territoriaalisuus fi
dc.subject.other sosiaalinen kontrolli fi
dc.subject.other dominance fi
dc.subject.other territorialit fi
dc.subject.other social control fi
dc.title Loss of density-dependence and incomplete control by dominant breeders in a territorial species with density outbreaks
dc.type Article en
dc.identifier.urn URN:NBN:fi:jyu-201208202181
dc.subject.kota 118
dc.contributor.laitos Bio- ja ympäristötieteiden laitos fi
dc.contributor.laitos The Department of Biological and Environmental Science en
dc.type.uri http://purl.org/eprint/type/JournalArticle
dc.identifier.doi doi:10.1186/1472-6785-11-16
dc.description.version Publisher's PDF
eprint.status http://purl.org/eprint/type/status/PeerReviewed

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