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Science 28 April 1967:
Vol. 156. no. 3774, pp. 531 - 534
DOI: 10.1126/science.156.3774.531
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Articles

Natural Free-Running Period in Vertebrate Animal Populations

Charles H. Lowe 1, David S. Hinds 1, Peter J. Lardner 2, and Keith E. Justice 3

1 Department of Zoology, University of Arizona, Tucson 85721
2 Department of Biology, Dickinson College, Carlisle, Pennsylvania
3 Departmiient of Population and Environmental Biology, University of California, Irvine 92650

Regression analysis (analysis of covariance) is contrasted with the conventional "mean period length" for estimating the length of period of the spontaneous activity frequency (free-running period) in population samples of Gila monsters (Heloderma suspectum) and kangaroo rats (Dipodomys merriami) in the Sonoran Desert. The mean period length in each population does not differ significantly from 24:00 hours (P > .05) and it does not differ significantly (P > .05) between the species studied; the probability that the free-running period a(in constant dark) in natural populations of Gila monsters and kangaroo rats is different from 24:00.0 is less than 1 in 1000 (P < .001). The so-called "mean period length" is of little or no use for precise determination of the period and phase relationships in circadian rhythms; moreover, it is entirely without value for statistical testing of differences either within or between populations.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Stability, Precision, and Near-24-Hour Period of the Human Circadian Pacemaker.
C. A. Czeisler, J. F. Duffy, T. L. Shanahan, E. N. Brown, J. F. Mitchell, D. W. Rimmer, J. M. Ronda, E. J. Silva, J. S. Allan, J. S. Emens, et al. (1999)
Science 284, 2177-2181
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Circadian Activity Rhythm of the Deer Mouse, Peromyscus: Effect of Deuterium Oxide.
R. B. Suter and K. S. Rawson (1968)
Science 160, 1011-1014
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