Tests of emigration in small mammals under experimental conditions

A. R. Nelson, C. L. Johnson, W. J. Matter, R. W. Mannan

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Holding animals in enclosures that block emigration causes demographic abnormalities called "fence effects." Experimenters have built exits that require animals to move through unfavorable conditions to leave enclosures. There are doubts about whether individuals that cross these challenging exits are true emigrants. We tested whether an exit that required house mice (Mus musculus) to swim through a water-filled trough was used only by mice triggered to emigrate from an experimental enclosure. Also, we examined the responses of mice to the availability of resources and the presence of conspecific adult animals in a small enclosure with an exit and in an enclosure made by joining two single enclosures. All mice left a barren enclosure within 12 h but no mice left during 7-day trials in a resource-rich enclosure during spring and summer. At the end of trials with repeated introduction of pairs of mice, about 85% of resident mice were the first mice added. Nearly all mice added later left the enclosure. A relatively constant number of mice became residents in small enclosures and about 2.3 times as many mice resided in double enclosures. Mice readily found and used exits when motivated to leave and did not accidentally pass through exits during routine exploration. Thus, mice that stayed in enclosures were not "fenced in" by the water-filled exit and exhibited residency as in nature. Tests of exits should give ecologists confidence that animals can display normal residency and emigration behaviors in experimental settings. The defense of resources by residents and the emigration of excess animals resulted in a consistent limit to the number of animals able to reside in enclosures.

Original languageEnglish (US)
Pages (from-to)2056-2060
Number of pages5
JournalCanadian Journal of Zoology
Issue number12
StatePublished - Dec 1 2002

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology


Dive into the research topics of 'Tests of emigration in small mammals under experimental conditions'. Together they form a unique fingerprint.

Cite this