Document Detail

Natural entrainment without dawn and dusk: the case of the European ground squirrel (Spermophilus citellus).
MedLine Citation:
PMID:  10447309     Owner:  NLM     Status:  MEDLINE    
Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in their burrows on average 2.87 h (SD = 0.47) before civil twilight at dusk. Daily patterns of light perceived by these burrowing mammals were measured with light-sensitive radio collar transmitters in an enclosure (the Netherlands) and in the field (Hungary). The observational data are corroborated by the telemetry data, which show clear daily patterns of timing of light perception including light perceived from the burrow entrances. The first light was observed by the animals on average 3.54 h (enclosure, SD = 0.45) and 3.60 h (field, SD = 0.31) after civil twilight at dawn, whereas the final observed light was on average 3.04 h (enclosure, SD = 0.64) and 2.02 h (field, SD = 0.72) before civil twilight at dusk. Thus, the animals do not perceive the rapid natural light-dark (LD) transitions that occur at civil twilight. Instead, they generate their own pattern of exposure to light within the natural LD cycle. The classical phase response model for entrainment by light or dark pulses cannot explain how the circadian system of this species remains entrained to the external, natural LD cycle while the major LD transitions are created by its own behavior.
R A Hut; B E van Oort; S Daan
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of biological rhythms     Volume:  14     ISSN:  0748-7304     ISO Abbreviation:  J. Biol. Rhythms     Publication Date:  1999 Aug 
Date Detail:
Created Date:  1999-12-10     Completed Date:  1999-12-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8700115     Medline TA:  J Biol Rhythms     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  290-9     Citation Subset:  IM    
Zoological Laboratory, University of Groningen, The Netherlands.
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MeSH Terms
Behavior, Animal / physiology*,  radiation effects
Circadian Rhythm* / radiation effects
Data Collection
Regression Analysis
Sciuridae / physiology*
Telemetry / methods

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