Abstract: Over a 16-year period (1979-1994), long-term investigations were carried out on 14 Misaki feral stallions to analyze changes in harem size and the reproductive success. Harem size changed with the age of the stallions. Most stallions formed harem groups with four to five mares at the age of 4-6 and then the number of mares increased rapidly to the maximum at the age of 6-9 years. Thereafter, harem size decreased gradually to a minimum with advancing age. The harem size of 60 stable harem groups ranged from 1 to 9, and the average varied from a minimum mean of 1.8 in 1988 to a maximum mean of 5.3 in 1982. Mean harem size increased as adult sex ratio increased and a significant and positive correlation was found between them. One hundred and ninety-eight sire-foal pairs were determined by a paternity test with blood types and consort relations between stallions and mares during the study period. Out of 99 foals which were born in the stable harem groups, the true sires of 84 foals (85%) were the harem stallions in which the foals were born but the remaining 15 foals (15%) were sired by other harem stallions. Two out of three stallions which were studied throughout their lifetime produced 24 and 25 foals in 10 and 11 years of their reproductive lifespan, respectively. Another one produced only five foals in 6 years. The number of foals sired by the harem stallions was less than two over harem size 7 and some of the foals born in the harem were sired by other harem stallions. These results suggest that if a particular stallion monopolizes too many mares, he could not sire so many offspring because he could not always prevent his rival stallions from mating with his mares in wild or feral circumstances.

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: Viewing dominance as an attribute of repeated agonistic interactions between two individuals, the present paper reviews theoretical approaches towards concepts of dominance, methods of measurement, and basic principles and problems connected with social dominance in domestic pigs. Domestic pigs are able to establish social organization structures during all stages of their ontogeny. According to definition, dominance relationships occur when a consistent asymmetry of the result of dyadic agonistic interactions can be assessed. This must not necessarily be connected immediately with a better availability of resources, or a high stability of existing dominance relationships, or a functional definition of dominance. When sociometric characteristics are calculated, it seems to be appropriate to use them for different levels of a biological system (individual, individual pair, group). Investigations of social behaviour and dominance in farm animals should take into account that mechanisms of social behaviour in confined environments are often carried out in parts only. Connections of the dominance concept with other concepts of behavioural regulation should be theoretically considered and further investigated by experimental studies.

Abstract: Abstract  Natural conceptual discriminations have been tested in many different species, including pigeons and a variety of non-human primates. The ability of four male squirrel monkeys (Saimiri sciureus) to learn and use the natural concept “squirrel monkey” was investigated in this study. After a training phase, subjects were presented with novel stimuli in transfer and test trials. All subjects performed at a rate significantly above chance on the first test trial (p<.001), indicating that squirrel monkeys can utilize natural concepts in the laboratory.