Abstract: The costs associated with initial conflicts could be reduced if animals can assess the fighting ability of possible future opponents by watching their contest success against other individuals. We tested this hypothesis by conducting repeated dyadic dominance trials on size-matched juvenile rainbow trout,Oncorhynchus mykiss. In the first trial a dyadic contest was `observed' by a single fish separated by a transparent divider. In the second trial, the observer was paired against either the `familiar' dominant fish or an unfamiliar dominant fish from the first trial. We predicted that observers should settle conflicts with previewed opponents faster and with less aggression than those with unfamiliar fish. This prediction was supported for observers that lost against a previewed competitor, since these fish reduced their aggression more rapidly than did unfamiliar observers. Familiar observers that won, however, showed a more rapid increase in aggression compared with unfamiliar winning observers. This suggests that, regardless of whether an observer challenges the initial dominant, this `decision' is taken more rapidly in conflicts with preassessed contestants, because of the a priori information about their fighting ability. Since preassessment could save energy and allow effort to be concentrated on contests with a high payoff/probability of winning, selection may favour preview strategies when contest competition over resources is important for fitness.

Abstract: Social, genetic and reproductive consequences of natal dispersal were investigated in female horses,Equus caballus, living in a herd with a natural social structure. Dispersal did not as a rule reduce the level of competition the young mares faced: they did not selectively join groups with fewer resident females than the groups they left, and they did not attain higher ranks; there was also no tendency for females to disperse to groups with the fewest resident females, and they suffered more aggression from the mares in their new groups than in their natal groups. These results therefore do not support the hypothesis that a function of natal dispersal is to reduce intra-sexual competition. The young mares nevertheless dispersed non-randomly, generally joining harems with one stallion and at least two subadult females; and they preferred to move to groups with familiar females but no familiar males. As a result, most were closely related to some females of their new groups, but distantly related or unrelated to the male(s). Since after dispersal the young mares bred only with a male of their new groups, inbreeding coefficients of most (85%) of their offspring were lower than from matings between half siblings. These results are consistent with the hypothesis that a function of natal dispersal is to avoid close inbreeding. Dispersal did not appear to involve reproductive costs: the young mares suffered no delay in age at first reproduction, and the survival rates of their first foals tended to be higher if the females had emigrated, although not significantly so.

Abstract: Flehmen behaviour in Welsh pony (Equus caballus) mares and foals living on pasture was observed during 807 h of focal sampling. A series of flehmens performed at one site was defined as a flehmen incident. Colts exhibited flehmen incidents and performed flehmen more frequently during an incident than did fillies or mares. Filies exhibited flehmen incidents more frequently than did mares, but did not flehmen more frequently during an incident. Colts exhibited a peak frequency of performing flehmen and of flehmen incidents during weeks 1-4 with a subsequent linear decrease in frequency up to weeks 17-20. Usually, flehmen occurred without the subject having had direct contact of the nostrils, lips, or tongue with a possible stimulant. Twenty-six per cent of the flehmen incidents occurred during or after urination by another pony. Seven per cent of the incidents occurred during or after urination by the pony showing flehmen.

Abstract: During the pre-maturation period crowded males of Schistocerca gregaria are more active than isolated ones but the greater part of their extra activity is not locomotory but consists of the kicking movements made in response to contact with other locusts. Isolated males walk less often during this period but tend to jump (or fly) more than crowded ones. Activity increases with maturity and the increase is greater in the isolated males so that in spite of the absence of mechanical stimulation by other locusts their locomotor activity is now at least as great as that of the crowded ones and their jumping activity greater. Within one batch there is a tendency for those males which are most active during the first two weeks of adult life to mature earliest. The activity of young males crowded with fledglings is at first similar to that of males crowded with older locusts, but after the first two weeks the activity of both mature and immature males is depressed by crowding with fledglings. Mature males habitually isolated become less active when temporarily crowded with fledglings, but not when crowded with mature males. Mature and immature males habitually crowded with fledglings become more active when temporarily isolated and still more active when crowded with each other, or with other mature males. The inhibiting effect of the fledglings on maturation and their depressive effect on activity should in natural conditions promote synchronization of maturation and the cohesion of the group. There was little difference in activity between young males kept in single pairs and in isolation, except that in one experiment the isolated ones jumped more often. Young males kept in pairs with mature males are more active during the first week of adult life than those kept in pairs with each other. The males paired with mature males were also seen feeding much less often than those paired with each other. This was the only treatment in which a significant effect on the frequency of feeding was recorded. The femoral vibrations made by both mature and immature males in response to stimulation by mature males, occur less often in habitually crowded males than in those temporarily crowded or kept with one mature male only. This is presumably the result of habituation to the stimulus. The behaviour of wild Schistocerca males in a large outdoor cage was very similar to that of a low density laboratory group. All results suggest that there is an association between high activity and rapid maturation. This is compatible with the conclusion from earlier work that a low level of feeding is associated with rapid maturation.

Abstract: Summary Three groups of eight female golden hamsters without prior breeding experience were presented with three newborn pups for a 15 min test period. Group V were virgin females, group P pregnant females and group L lactating females. Groups P and L were tested within 24 hr of parturition. Group V attacked and killed all pups presented. Group P showed maternal responses after initial attacks while group L accepted the pups. Groups P and L did not differ significantly on measures of maternal responsiveness but all three groups differed significantly from one another on measures of attacking behaviour and the eating of young.