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Klingel, H. (1982). Social organization of feral horses. J Reprod Fertil Suppl, 32, 89–95.
Abstract: The basic social unit in feral horses is the family group consisting of one stallion, one to a few unrelated mares and their foals. Surplus stallions associate in bachelor groups. Stallions are instrumental in bringing mares together in a unit which then persists even without a stallion. The similarity of social organization in populations living in a variety of different habitats indicates that feral horses have reverted to the habits of their wild ancestors, and that domestication has had no influence on this basic behavioural feature.
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Klingel, H. (1975). Social organization and reproduction in equids. J Reprod Fertil Suppl, (23), 7–11.
Abstract: There are two distinct types of social organization and, accordingly, two types of mating systems in equids. In the horse, Plains zebra and Mountain zebra, the adults live in non-territorial and cohesive one-male groups and in stallion groups. The family stallions have exclusive mating rights which are respected by all others. In Grevy's zebra and in the African and Asiatic wild asses, the stallions are permanently territorial and have exclusive mating rights within their territories. Ecological and evolutionary aspects are discussed.
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Turner, J. W. J., & Kirkpatrick, J. F. (1982). Androgens, behaviour and fertility control in feral stallions. J Reprod Fertil Suppl, 32, 79–87.
Abstract: This field study of feral stallions in Montana and Idaho examines and correlates the seasonal pattern of plasma androgens and specific sociosexual behaviour and reports the effect of a long-acting androgenic steroid on this behaviour and on fertility. Plasma testosterone was measured by competitive protein binding assay in samples obtained by jugular venepuncture from captured animals. In samples taken from 34 sexually mature stallions in 6 different months during the year, a definite seasonal pattern in testosterone was present, with a peak in May (3.04 +/- 0.63 ng/ml) and a nadir in December (1.55 +/- 0.34 ng/ml). Values were less than 2.0 ng/ml in non-breeding months and greater than 2.4 ng/ml in breeding months. Behavioural endpoints measured were (1) stallion scent marking in response to elimination by mares (elimination marking), (2) mounting and (3) copulation. The frequencies of each of these endpoints followed closely the seasonal pattern seen for plasma androgens. In the fertility study microcapsulated testosterone propionate (microTP) was administered i.m. to 10 harem stud stallions 3 months before the 1980 breeding season. In these stallions and in 10 control harem studs, the above behavioural endpoints were examined in the 1980 and 1981 breeding seasons, and foal counts were made in 1981. There were no direct inhibitory or stimulatory effects of microTP treatment on any of the behavioural endpoints in either year. In 1981 foals were produced in 87.5% of the control bands and 28.4% of the microTP-treated bands. These results indicate that microencapsulated testosterone propionate can provide effective fertility control in feral horses without causing significant alterations in sociosexual behaviour.
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