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- Title
Growth of laboratory-reared ship rats ( Rattus rattus L.).
- Authors
BENTLEY, E. W.; TAYLOR, EILEEN J.
- Abstract
SUMMARY Mean weight-on-age curves for eighty-two male and sixty-five female Rattus rattus reared in the laboratory show that at birth the males were slightly heavier on the average than the females; for a week or two the females gained weight more quickly, but at 5-6 weeks of age the males became significantly heavier again and remained so. A change in growth rate seemed to occur in both sexes at about 7 days and again at about 6 weeks in the males and at 8-9 weeks in the females. In the females initial weight was significantly correlated with maximum weight: in the males it was significantly negatively correlated with the age at which maximum weight was achieved. In both sexes, at all ages from birth onwards, some rats weighed twice as much as others. This militates against the use in the field of weight as a guide to age. Variability in weight was very largely a consequence of differences between litters. The mean maximum weight attained by seventy-two males was 215g.; the heaviest weighed 305g. The mean maximum reached by fifty females was 173g. and the heaviest weighed 260g. The mean age of attainment of maximum weight was 504 days for males and 553 days for females: the difference was not significant. The mean age at death of the males that died of 'natural' causes was 779: that of the females was 837 days. This difference was also non-significant. Longevity was significantly correlated with both maximum weight and the age at which it was attained. Life tables are presented for male and female rats that survived to 35 days and died both from 'natural' causes and from all causes. Factors are given for calculating the corresponding probabilities of survival from birth. The average number of rats per litter was 6·2: the ratio of the two sexes at birth did not differ significantly from unity. No differences in body weight could be distinguished between the two colour forms of Rattus rattus that are commonest in Britain.
- Publication
Annals of Applied Biology, 1965, Vol 55, Issue 2, p193
- ISSN
0003-4746
- Publication type
Article
- DOI
10.1111/j.1744-7348.1965.tb07933.x