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Stahlbaum, C. C., & Houpt, K. A. (1989). The role of the Flehmen response in the behavioral repertoire of the stallion. Physiol. Behav., 45(6), 1207–1214.
Abstract: The role of the Flehmen response in equine behavior was investigated under field and laboratory conditions. In Experiment 1, a field study made of five stallions on pasture with between three and eighteen mares each during the season indicated the following: 1) The Flehmen response was most frequently preceded by nasal, rather than oral, investigation of substances; 2) The stallions' rate of Flehmen varied with the estrous cycles of the mares; 3) The rate of Flehmen response did not show a variation with time of day; and 4) The Flehmen response was most frequently followed by marking behaviors rather than courtship behaviors. The results suggest that the Flehmen response is not an immediate component of sexual behavior, e.g., courtship of the stallion but may be involved in the overall monitoring of the mare's estrous cycle. Therefore the Flehmen response may contribute to the chemosensory priming of the stallion for reproduction. In Experiment 2 stallions were presented with urine or feces of mares in various stages of the reproductive cycle as well as with their own or other males' urine or feces. The occurrence of sniffing and Flehmen was used to determine the discriminatory ability of the stallions. Stallions can differentiate the sex of a horse on the basis of its feces alone, but cannot differentiate on the basis of urine. This ability may explain the function of fecal marking behavior of stallions.
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Cancedda, M. (1990). [Social and behavioral organization of horses on the Giara (Sardinia): distribution and aggregation]. Boll Soc Ital Biol Sper, 66(11), 1089–1096.
Abstract: In this paper some considerations on the environment of the 42 Kmq of the volcanic-basaltic Giara tableland are discussed. Conditioning by the environment and its effect on the distribution of a population of 712 horses is illustrated in view of their social and behavioural organization.
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Boyd, L. (1986). Behavior problems of equids in zoos. Vet Clin North Am Equine Pract, 2(3), 653–664.
Abstract: Behavior problems in zoo equids commonly result from a failure to provide for needs basic to equine nature. Equids are gregarious, and failure to provide companions may result in pacing. Wild equids spend 60 to 70 per cent of their time grazing, and failure to provide ad libitum roughage contributes to the problems of pacing, cribbing, wood chewing, and coprophagia. Mimicking the normal processes of juvenile dispersal, bachelor-herd formation, and mate acquisition reduces the likelihood of agonistic and reproductive behavior problems. Infanticide can be avoided by introducing new stallions to herds containing only nonpregnant mares and older foals.
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Khalil, A. M., Murakami, N., & Kaseda, Y. (1998). Relationship between plasma testosterone concentrations and age, breeding season and harem size in Misaki feral horses. J Vet Med Sci, 60(5), 643–645.
Abstract: Jugular vein blood samples were collected from 23 young and sexual mature feral stallions to examine the relationship between plasma testosterone concentration and age, breeding season or harem size. Testosterone concentration increased with the age of the stallions until they formed their own harems, at about 4 to 6 years old. Seasonal variations in testosterone concentrations were observed, and found to be significantly higher (P<0.001) throughout the breeding season than non-breeding season, from 3 years of age. Testosterone levels were correlated with harem size for individual stallions. It can be inferred from these results that there is a relationship between plasma testosterone concentration and age, breeding season and harem size.
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Beaver, B. V. (1986). Aggressive behavior problems. Vet Clin North Am Equine Pract, 2(3), 635–644.
Abstract: Accurate diagnosis of the cause of aggression in horses is essential to determining the appropriate course of action. The affective forms of aggression include fear-induced, pain-induced, intermale, dominance, protective, maternal, learned, and redirected aggressions. Non-affective aggression includes play and sex-related forms. Irritable aggression and hypertestosteronism in mares are medical problems, whereas genetic factors, brain dysfunction, and self-mutilation are also concerns.
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Baum, M. J. (2006). Mammalian animal models of psychosexual differentiation: when is 'translation' to the human situation possible? Horm Behav, 50(4), 579–588.
Abstract: Clinical investigators have been forced primarily to use experiments of nature (e.g., cloacal exstrophy; androgen insensitivity, congenital adrenal hyperplasia) to assess the contribution of fetal sex hormone exposure to the development of male- and female-typical profiles of gender identity and role behavior as well as sexual orientation. In this review, I summarize the results of numerous correlative as well as mechanistic animal experiments that shed significant light on general neuroendocrine mechanisms controlling the differentiation of neural circuits controlling sexual partner preference (sexual orientation) in mammalian species including man. I also argue, however, that results of animal studies can, at best, provide only indirect insights into the neuroendocrine determinants of human gender identity and role behaviors.
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Villani, M., Cairoli, F., Kindahl, H., Galeati, G., Faustini, M., Carluccio, A., et al. (2006). Effects of mating on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF2alpha in stallions. Reprod Domest Anim, 41(6), 544–548.
Abstract: Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the jugular vein with heparinized tubes, 20 and 10 min before oestrous mare exposure, at exposure and 10, 20, 30 min after dismounting. Testosterone concentrations showed a sharp rise 10 min after mating (p < 0.001), reached a plateau, and then showed a further increase 30 min after mating (p < 0.001). Cortisol concentrations increased 10 min after mating (p < 0.001) and remained at high levels in the subsequent samples taken. A peak of oestrone sulphate was observed 10 min after mating (p < 0.001). 15-Ketodihydro-PGF(2alpha) concentrations decreased rapidly at the moment of the exposure of the stallions to an oestrous mare (p < 0.05), returned to pre-mating concentrations and then decreased again 30 min after mating (p < 0.05).
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Danchin, E., Giraldeau, L. - A., Valone, T. J., & Wagner, R. H. (2004). Public information: from nosy neighbors to cultural evolution. Science, 305(5683), 487–491.
Abstract: Psychologists, economists, and advertising moguls have long known that human decision-making is strongly influenced by the behavior of others. A rapidly accumulating body of evidence suggests that the same is true in animals. Individuals can use information arising from cues inadvertently produced by the behavior of other individuals with similar requirements. Many of these cues provide public information about the quality of alternatives. The use of public information is taxonomically widespread and can enhance fitness. Public information can lead to cultural evolution, which we suggest may then affect biological evolution.
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Keiper, R. R. (1986). Social structure. Vet Clin North Am Equine Pract, 2(3), 465–484.
Abstract: Socially feral horses live in stable social groups characterized by one adult male, a number of adult females, and their offspring up to 2 years of age. Extra males either live by themselves or with other males in bachelor groups. The bands occupy nondefended home ranges that often overlap. Many abnormal behaviors seen in domestic horses occur because some aspect of their normal social behavior cannot be carried out in captivity.
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Uehara, T., Yokomizo, H., & Iwasa, Y. (2005). Mate-choice copying as Bayesian decision making. Am Nat, 165(3), 403–410.
Abstract: Mate-choice copying by females has been reported in fishes (e.g., guppies) and lekking birds. Presumably, females assess males' quality using both information from direct observation of males and information acquired by observing other females' choices. Here, we study mathematically the conditions under which mate-choice copying is advantageous on the basis of Bayesian decision theory. A female may observe the mate choice of another female, called the model female, who has performed an optimal choice based on her own judgment. The conditions required for the focal female to choose the same mate as that chosen by the model female should depend on the male's appearance to her, the reliability of her own judgment of male quality, and the reliability of the model females. When three or more females are involved, the optimal mate choice critically depends on whether multiple model females make decisions independently or they themselves copy the choices of others. If two equally reliable females choose different males, the choice of the second female, made knowing the choice of the first, should have a stronger effect on the choice of the third (focal) female. This “last-choice precedence” should be tested experimentally.
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