The types of social organisation displayed by the African antelope species have been assigned in this paper to five classes, distinguished largely by the strategies used by the reproductively active males in securing mating rights, and the effects of those strategies on other social castes. The paper attempts to show that these strategies are appropriate to each class because of the effects of other, ecological, aspects of their ways of life. The paper describes different feeding styles among antelope, in terms of selection of food items and coverage of home ranges. It argues that these feeding styles bear a relationship to maximum group size of feeding animals through the influence of dispersion of food items upon group cohesion. The feeding styles also bear a relationship to body size and to habitat choice, both of which influence the antelope species' antipredator behaviour. Thus feeding style is related to anti-predator behaviour which, in many species, influences minimum group size. Group size and the pattern of movement over the annual home range affect the likelihood of females being found in a given place at a given time, and it is this likelihood which, to a large extent, determines the kind of strategy a male must employ to achieve mating rights. The effects of the different strategies employed by males can be seen in such aspects of each species' biology as sexual dimorphism, adult sex ratio, and differential distribution of the sexes.

Summary Sexual dimorphism in mammals is not entirely satisfactorily explained by the models that are advanced to account for it among birds. This may be because species‐specific styles of being dimorphic, and of attaining mature dimorphic state, are not clearly recognized. Mature dimorphism is a syndrome involving body size, appearance and weaponry; each facet and the whole syndrome may have functions in both fighting and signalling. The mature dimorphic stage has to be reached by growth and change from juvenile and sub‐adult states. The occurrence of the separate facets of the dimorphic syndrome are reviewed in species of Bovidae, Cervidae and Macropodidae, large, diverse families of eutherian (the first two) and metatherian mammals, which have broadly similar ecological adaptations. In each family the smallest species tend to be homomorphic, with small, inconspicuous weapons. Greatest dimorphism in size is found in medium‐sized bovids and cervids, and the larger macropodids (in which no species exceeds 100 kg male weight); the range of species showing greatest dimorphism in size also shows the most exaggerated weapons. Mature dimorphism is reached by different patterns of growth, which may be determinate and similar in the sexes (leading to homomorphism), determinate but differing between the sexes, or indeterminate and differing, both of which lead to heteromorphism. The syndromes of dimorphism and patterns of growth are associated and a classification of styles of dimorphism is presented. The adaptiveness of the styles is suggested in terms of what is known of the socio‐ecology, in particular the male reproductive strategies, of the species. The various styles of heteromorphy appear to be associated with males' way of achieving polygyny: such as by non‐resource‐based territoriality, by dominance‐determined access to oestrous females, or by wandering and formation of a consortship with pro‐oestrous females. The relevance of the species' ecology of use of resources to these styles of dimorphism and mate‐acquisition is briefly discussed.

An emerging infectious facial cancer threatens Tasmanian devils with extinction. The disease is likely to occur across the range of the devil within 5 years. This urgent time frame requires management options that can be implemented immediately: the establishment of insurance populations, in captivity, wild-living on islands, and aiming for eradication in areas that can be isolated. The long-term options of the spontaneous or assisted evolution of resistance or development of a field-deliverable vaccine are unlikely to be available in time. The disease's characteristic allograft transmission through intimate contact simplifies isolation of insurance populations and breaking transmission in suppression trials. Better knowledge of contact matrices in wild devils will help focus timing and demographic targets of removals. A metapopulation approach is needed that integrates captive and wild-living island and peninsula (disease suppression) populations to minimize the loss of genetic diversity over 50 years until either extinction and reintroduction can occur, resistance evolves or a fielddeliverable vaccine is developed. Given the importance of the insurance populations and the low genetic diversity of devils, a conservative target for retention of 95% genetic diversity is recommended. Encouraging preliminary results of the first disease-suppression trial on a large peninsula show fewer late stage tumors and no apparent population decline. Limiting geographic spread or suppressing the disease on a broadscale are both unlikely to be feasible. Since the synergy of devil decline and impending fox establishment could have devastating consequences for Tasmanian wildlife, it is crucial to manage the dynamics of new and old predator species together.

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa, in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbour's behaviour.

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