L. Bartos et Pf. Brain, PHYSIOLOGICAL-RESPONSES TO SOCIAL-STATUS AND HOUSING CONDITIONS IN MALE-MICE SUBJECT TO FOOD COMPETITION TESTS, Bollettino di zoologia, 60(3), 1993, pp. 293-296
Seventy eight male mice were individually housed at weaning. After 14
days of isolation, the males were allocated to 13 permanent groups of
three mice (Triads), 13 permanent groups of two mice (Couples) and 13
mice remaining in isolation for 21 days. Four 10-min observation perio
ds, each preceded by 24 hours of food deprivation, were carried out in
a neutral cage. In one of the shorter walls of this cage a plastic tu
be was connected to the cage. A pellet of food was firmly attached to
the inner surface of the tube and the behaviour of the mice was record
ed on a videotape. Twenty-four hours after finishing the last observat
ion, the mice were killed and selected organs cleaned and weighed. Rel
ative organ weight differences between dominant and subordinate males
showed similar tendencies in both Triads and Couples. Dominants had he
avier testes, thymuses, intact and squeezed seminal vesicles, squeezed
preputial and prostates and lighter adrenals than subordinates. Howev
er, Triads and Couples showed differences of degree. While significant
differences between dominant and subordinated mice were evident in Tr
iads for testes, thymuses, intact and squeezed seminal vesicles, adren
als and prostates, in Couples, significance was achieved only for the
thymus, adrenal and prostate. The number of attacks directed towards o
ther mice (higher in Triads than Couples) thus seems to have a more im
portant influence on relative organ weights than being attacked. Isola
ted males appeared partly stressed by isolation and/or food deprivatio
n (showing a relative increase in adrenal and lower thymus, squeezed p
reputial and prostate weights when compared to dominants) but they wer
e closer to the dominants of social groups in to having heavier testes
than subordinated mice.