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Dowdle, W. R., & Schild, G. C. (1976). Influenza: its antigenic variation and ecology. Bull Pan Am Health Organ, 10(3), 193–195.
Abstract: Influenza viruses have two surface antigens, the glycoprotein structures hemagglutinin (HA) and neuraminidase (NA). Antibodies to each of these are associated with immunity, but the structures themselves are antigenically variable. When an antigenic change is gradual over time it is referred to as a drift, while a sudden complete or major change in either or both antigens is termed a shift. The mechanism of antigenic drift is usually attributed to selection of preexisting mutants by pressure from increasing immunity in the human population. The mechanism of antigenic shift is less clear, but one tentative hypothesis is that shifts arise from mammalian or avian reservoirs, or through genetic recombination of human and animal influenza strains.
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Schoen Ams,. (1976). Behaviour of young shetland welsh ponies. Biol Behav, 1, 192–216.
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SCHOEN AMS et al,. (1976). Behavior of young shetland and welsh ponies. Biol Behav, 1, 192–216.
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Hagen H,. (1976). Verhalten beim Steppenzebra. Die Welt der Tiere, , 170–172.
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Smith, J. M., & Parker, G. A. (1976). The logic of asymmetric contests. Anim. Behav., 24(1), 159–175.
Abstract: A theoretical analysis is made of the evolution of behavioural strategies in contest situations. It is assumed that behaviour will evolve so as to maximize individual fitness. If so, a population will evolve an [`]evolutionarily stable strategy', or ESS, which can be defined as a strategy such that, if all members of a population adopt it, no [`]mutant' strategy can do better. A number of simple models of contest situations are analysed from this point of view. It is concluded that in [`]symmetric' contests the ESS is likely to be a [`]mixed' strategy; that is, either the population will be genetically polymorphic or individuals will be behaviourally variable. Most real contests are probably asymmetric, either in pay-off to the contestants, or in size or weapons, or in some [`]uncorrelated' fashion; i.e. in a fashion which does not substantially bias either the pay-offs or the likely outcome of an escalated contest. An example of an uncorrelated asymmetry is that between the [`]discoverer' of a resource and a [`]late-comer'. It is shown that the ESS in asymmetric contests will usually be to permit the asymmetric cue to settle the contest without escalation. Escalated contests will, however, occur if information to the contestants about the asymmetry is imperfect.
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Ödberg Fo,. (1976). A study on eliminative and grazing behaviour – the use of the field by captive horses. Equine Vet J, 8, 147–149.
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Joubert, E., & Louw, G. N. (1976). Preliminary observations on the digestive and renal efficiency of Hartmann's zebra Equus zebra hartmannae. Madoqua, 10, 119–121.
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Smuts Gl,. (1976). Population characteristics of Burchell's Zebra in the Krüger National Park. S Afr J Wildl Res, 6, 99–112.
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Kirkpatrick, J. F., Vail, R., Devous, S., Schwend, S., Baker, C. B., & Wiesner, L. (1976). Diurnal variation of plasma testosterone in wild stallions. Biol Reprod, 15(1), 98–101.
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Keiper Rr,. (1976). Interactions between cattle egrets and feral ponies. Proc Pennsyl Acad, 50, 89–90.
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