title: Temporal behaviour profiles of Mus musculus in nature are affected by population activity.
abstract: Animals have circadian clocks that govern their activity pattern, resulting in 24h rhythms in physiology and behaviour. Under laboratory conditions, light is the major external signal that affects temporal patterns in behaviour, and Mus musculus is strictly nocturnal in its behaviour. In the present study we questioned whether under natural conditions, environmental factors other than light affect the temporal profile of mice. In order to test this, we investigated the activity patterns of free-ranging M. musculus in a natural habitat, using sensors and a camera integrated into a recording unit that the mice could freely enter and leave. Our data show that mice have seasonal fluctuations in activity duration (6.7±0.82 h in summer, 11.3±1.80 h in winter). Furthermore, although primarily nocturnal, wild mice also exhibit daytime activity from spring until late autumn. A multivariate analysis revealed that the major factor correlating with increased daytime activity was population activity, defined as the number of visits to the recording site. Day length had a small but significant effect. Further analysis revealed that the relative population activity (compared to the past couple of days) is a better predictor of daytime activity than absolute population activity. Light intensity and temperature did not have a significant effect on daytime activity. The amount of variance explained by external factors is 51.9%, leaving surprisingly little unexplained variance that might be attributed to the internal clock. Our data further indicate that mice determine population activity by comparing a given night with the preceding 2-7 nights, a time frame suggesting a role for olfactory cues. We conclude that relative population activity is a major factor controlling the temporal activity patterns of M. musculus in an unrestricted natural population.
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Robbers
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Eva A S
authors.initials: EA
authors.lastname: Koster
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Doortje I
authors.initials: DI
authors.lastname: Krijbolder
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Amanda
authors.initials: A
authors.lastname: Ruijs
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: Sander
authors.initials: S
authors.lastname: van Berloo
authors.affiliation: Laboratory for Neurophysiology, Department of Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands. Electronic address: http://www.johannahmeijer.com/
authors.forename: Johanna H
authors.initials: JH
authors.lastname: Meijer
mesh_terms: D056044:Actigraphy; D000818:Animals; D000835:Animals, Wild / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D008027:Light; D051379:Mice / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D015999:Multivariate Analysis; D017440:Photoperiod; D012044:Regression Analysis; D012621:Seasons; D012919:Social Behavior; D013696:Temperature; D014741:Video Recording
keywords: Behaviour; Circadian; Diurnal; Ecology; Mice; Nature; Nocturnal; Olfaction; Population; Season; Wild