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Behavioural “vigour” in inbred and hybrid mice

1964; Elsevier BV; Volume: 12; Issue: 2-3 Linguagem: Inglês

10.1016/0003-3472(64)90020-x

1095-8282

S. A. Barnett, Sybil G. Scott,

Animal Behavior and Welfare Studies

Laboratory mice, Mus musculus, were bred at two environmental temperatures, namely, 21 °C and −3 °C, and aspects of their behaviour observed. Inbred strains, A, A2G, C57BL and GFF were used; F1 mice were produced by crossing the inbred strains; and an outbred stock was derived by crossing all four. General activity was recorded in three inbred strains, F1 mice from two crosses, and outbred mice, during a period of 5 days, in a cage crossed at three points by a beam of light; breaking the beam activated a counter. C57BL mice were more active than A or A2G; the F1 and outbred mice resembled C57BL or were more active still. Cold reduced activity in all the kinds of mice studied. Activity was usually higher on the first than on subsequent days. “Functionless” gnawing was studied over a period of 7 days (a) by weighing the amount of cubed diet gnawed and wasted, (b) by supplying balsa wood and recording the amount chewed off. The mice were (i) solitary or (ii) in groups of 3. At 21 °C, of the four inbred strains, A2G gnawed most, C57BL rather little. F1 mice (from 7 crosses) usually wasted more food, and always (8 crosses) gnawed more balsa wood, than their parent strains. Outbred mice, when alone, gnawed more balsa wood than inbred strains and more than most F1 types. All kinds of mice gnawed less, when kept in groups, than when alone. No functionless gnawing was observed at −3 °C in any class of mice. “Nest-building” was studied by hanging 24 paper strips over the side of the cage. In simple nest-building there was no nest already present; in double nest-building there was already a nest of cotton wool. All inbred mice were slow to pull down the paper strips; all F1 mice from 10 crosses, and the outbred mice, were quick to respond to them. The rate of response tended to be higher in double nest-building. F1 and outbred mice tended to make better nests, of cotton wool and paper combined, than inbred mice. At −3 °C the response to the paper strips was usually slower than at 21 °C; and the final nests in the cold were, on the whole, no better than in the warm. If “general drive” is defined in terms of output of mechanical energy, then low temperature reduced general drive in these experiments; heterozygosis may have increased it; heterozygosis certainly increased speed of response to new conditions.