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Influences of Light on Activity of Small Mammals
Author(s) -
Kavanau J. Lee
Publication year - 1969
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936245
Subject(s) - dusk , nocturnal , darkness , daylight , artificial light , ecology , illuminance , zoology , biology , foraging , physics , optics , botany
The locomotion of eastern chipmunks and least weasels in activity wheels was studied at various illuminance levels on regimes employing both artificial twilights and abrupt changes between day and night light. Several properties of the running of the chipmunks and weasels, and of the white—footed mice of earlier studies, all show the same qualitative dependence on light level. All three animals have a strong tendency to run in only one direction for extended periods of time. They get their directional bearings for this orientation from sightings of nearby objects. The artificial moon is the preferential orientational reference object for mice, whereas other objects in the enclosure seem to be preferred by chipmunks and weasels. The weasels are stimulated to activity by artificial dusks and inhibited by artificial dawn, but not by sudden onset of bright light. The chipmunks are stimulated to activity by artificial dawn. When the length of the daylight period is comparable to that in the wild, they cease activity several hours before dusk. An early "unexpected" dusk or darkness presented while they are active merely slows down their running. These findings and those with white—footed mice suggest the importance of simulating twilights in laboratory investigations of activity and rhythmicity. The fact that the least weasel was 98% nocturnal in light conditions simulating those in the wild suggests that its visual system is evolving from a nocturnal to an arrhythmic type, for this animal is arrhythmic in the field.