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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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Houpt, K. A., Thornton, S. N., & Allen, W. R. (1989). Vasopressin in dehydrated and rehydrated ponies. Physiol. Behav., 45(3), 659–661.
Abstract: Six pony mares deprived of water for 24 hours showed significant increases in plasma vasopressin (2.8 pg/ml) and osmolality (9 mosmol/kg). When water was made available the ponies drank rapidly (5 of 6 drank to satiety within 90 seconds) and corrected their fluid deficits precisely. Vasopressin did not return to predehydration levels until osmolality did after 15 minutes of access to water. The horse differs from rodents and humans, but is similar to pigs in that vasopressin levels do not fall before osmolality returns to normal. Oropharyngeal factors, therefore, may not be as important in vasopressin release in horses as in other species.
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Shaw, E. B., Houpt, K. A., & Holmes, D. F. (1988). Body temperature and behaviour of mares during the last two weeks of pregnancy. Equine Vet J, 20(3), 199–202.
Abstract: Average daily core body temperature and behavioural patterns of pregnant mares were studied, in search of definitive signs of parturition within 24 h of the event. Nineteen pony mares were sampled twice daily for core body temperature. A significant temperature drop, averaging 0.1 degrees C (0.2 degrees F) was observed during the day prior to parturition. Between 18.00 h and 06.00 h, during the two weeks before parturition, Thoroughbred and Standardbred mares (n = 52) spent an average 66.8 per cent of their time standing, 27.0 per cent eating, 4.9 per cent lying in sternal recumbency, 1.0 per cent lying in lateral recumbency, and 0.3 per cent walking. On the night before parturition, mares spent significantly less time lying in sternal recumbency than on previous nights and on the night of parturition all behaviour patterns except eating were significantly different from the nights of the two weeks before parturition. There was an increase in walking (5.3 per cent), lying in sternal recumbency (8 per cent) and lying in lateral recumbency (5.3 per cent) whereas standing (53.3 per cent) was decreased. In 58 observed pregnancies, 54 mares (97 per cent) foaled in a recumbent position and 50 mares (86 per cent) foaled between 18.00 h and 06.00 h.
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Houpt, K. A., Perry, P. J., Hintz, H. F., & Houpt, T. R. (1988). Effect of meal frequency on fluid balance and behavior of ponies. Physiol. Behav., 42(5), 401–407.
Abstract: Twelve ponies were fed their total daily ration either as one large meal or divided into six small meals. Pre- and post-feeding behavior was recorded six times a day. Blood samples were taken for 30 min before and two hr after the meal. Plasma protein increased from 7.0 to a peak of 7.3 g/dl with small meals and from 7.3 to 8.1 g/dl with large meals, and returned to pre-feeding levels by 90 min post-feeding. Hematocrit rose from 33.3 to 34.1% with small meals and from 33.0 to 36.0% with large meals. These rapid and short-lived increases indicate a decrease in plasma volume. Plasma osmolality rose with feeding from 283 to 285 mosmoles/kg with small meals and from 281 to 288 mosmoles/kg with large meals. Water availability had no significant effect on blood changes. Digestibility and rate of passage were measured with chromic oxide, but there were no differences. Vocalizing (neighing) and walking occurred more often before than after feeding, while eating bedding and engaging in other oral behaviors were more frequent after feeding.
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Hogan, E. S., Houpt, K. A., & Sweeney, K. (1988). The effect of enclosure size on social interactions and daily activity patterns of the captive Asiatic wild horse (Equus przewalskii). Appl. Anim. Behav. Sci., 21(1-2), 147–168.
Abstract: Two herds of Przewalski horses at the Minnesota Zoological Garden were observed during 1980 in each of 2 enclosures that differed in size. The larger enclosure was a 3.4-ha pasture; the smaller enclosure was a 17 x 30-m grass-less pen. One herd was composed of a stallion, 3 adult mares and 2 foals. The other consisted of a stallion and 2 mares. All occurrences of aggression, mutual grooming and snapping were recorded, and 5-min scan-samples of the activity state of each horse were taken. The time budgets, frequency of aggression and frequency of mutual grooming differed significantly with enclosure size for both herds. More time was spent pacing and milling in the smaller enclosure, and the frequency of aggressions and of mutual grooming was also higher. Only the foals exhibited snapping; frequency of snapping did not vary with enclosure size. More time was spent feeding in the larger enclosure. Provision of hay in the smaller enclosure eliminated the differences in time spent feeding. A second study was conducted during the spring of 1984 in an intermediate-sized enclosure, 0.4 ha, a sub-division of the pasture on which the horses were kept in 1980. One herd consisted of a stallion, 2 mares and 2 yearlings; the other consisted of a stallion, 3 mares and a foal. One of the stallions and all of the mares were those studied in 1980, but that stallion and one of the mares were in different herds than they had been in 1980. The frequency of aggression was similar to that observed in 1980.
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Houpt, K. A., & Fraser, A. F. (1988). Przewalski horses. Appl. Anim. Behav. Sci., 21(1-2), 1–3.
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Boyd, L. E., Carbonaro, D. A., & Houpt, K. A. (1988). The 24-hour time budget of Przewalski horses. Appl. Anim. Behav. Sci., 21(1-2), 5–17.
Abstract: A herd of 8 Przewalski horses were observed on pasture in summer. Fifteen-minute focal animal samples were used to determine the time budget of the horses during the periods 00.00-04.00, 04.00-08.00, 08.00-12.00, 12.00-16.00, 16.00-20.00 and 20.00-24.00 h EDT. The behavioral states recorded were feeding (grazing and eating grain), nursing, drinking, standing, stand-resting, self-grooming, mutual grooming, locomoting, playing, and lying laterally and sternally. The average number of behavioral states occurring per hour, and the defecation, urination, aggression and vocalization rates were also determined. Overall, the horses spent 46.4 +/- 5.9% of their time feeding, 1.3 +/- 0.1% nursing, 0.5 +/- 0.1% drinking, 20.6 +/- 5.4% standing, 15.7 +/- 3.2% stand-resting, 1.7 +/- 0.2% self-grooming, 2.2 +/- 0.7% mutual grooming, 7.4 +/- 1.0% locomoting, 1.2 +/- 0.3% playing, 1.2 +/- 0.5% lying laterally and 4.1 +/- 3.0% lying sternally. The horses averaged 45.2 +/- 5.8 behavioral states per hour, and 0.2 +/- 0.0 defecations, 0.3 +/- 0.0 urinations, 1.5 +/- 0.3 aggressions and 0.7 +/- 0.1 vocalizations per hour. The horses spent the greatest amount of time foraging between 20.00 and 04.00 h, when the temperatures were lower. They spent 68.2 +/- 2.2% of their time between 20.00 and 24.00 h feeding, but only 31.2 +/- 2.1% of their time feeding between 08.00 and 12.00 h. Recumbent rest was most common between 00.00 and 04.00 h. As temperatures rose during the daylight hours, the horses spent more time drinking and standing, rather than grazing. Stand-resting was the most common form of rest during the day. The horses exhibited the greatest number of activities per hour from 08.00 to 20.00 h. While standing in close proximity to one another during these hours, the horses exhibited the highest number of aggressions per hour (1.9-2.4).
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Crowell-Davis, S. L., Houpt, K. A., & Kane, L. (1987). Play development in Welsh pony (Equus caballus) foals. Appl. Anim. Behav. Sci., 18(2), 119–131.
Abstract: The structure of the play of colts and fillies living on pasture was studied from birth (n = 15) for up to 24 weeks. Foal play was categorized as running and bucking alone, running and bucking in a group, interactive (contact or combat) play, play with an object, and play at an adult. The rate of play decreased with increasing age and ambient temperature. Fillies and colts played with equal frequency, but engaged in some different types of play at different rates. There was no difference between colts and fillies in the proportion of play bouts of running and bucking in a group or playing with an object. Fillies engaged in running and bucking alone more than colts. Colts engaged in interactive play and play at an adult more than fillies. While there was no significant difference between colts and fillies in the duration of either type of running and bucking play, the interactive play bouts of colts were significantly longer than those of fillies. Both mares and stallions were tolerant of foal play which involved use of their body as a play object, including mounting play. Both fillies and colts engaged in mounting play. Foals used various natural objects found in the pasture for repeated bouts of play with inanimate objects, a behaviour which may explain, from a developmental perspective, the occasional use of “tools” in adult equids. The sex differences in type of play were consistent with the social structure of unmanaged adults in which males must compete with each other in order to associate with females.
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Houpt, K. A. (1986). Stable vices and trailer problems. Vet Clin North Am Equine Pract, 2(3), 623–633.
Abstract: Stable vices include oral vices such as cribbing, wood chewing, and coprophagia, as well as stall walking, weaving, pawing, and stall kicking. Some of these behaviors are escape behaviors; others are forms of self-stimulation. Most can be eliminated by pasturing rather than stall confinement. Trailering problems include failure to load, scrambling in the moving trailer, struggling in the stationary trailer, and refusal to unload. Gradual habituation to entering the trailer, the presence of another horse, or a change in trailer type can be used to treat these problems.
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Crowell-Davis, S. L., & Houpt, K. A. (1986). Maternal behavior. Vet Clin North Am Equine Pract, 2(3), 557–571.
Abstract: Parturition in mares is rapid and is followed by a brief period of sensitivity to imprinting on a foal. There is large individual variation in normal maternal style, but normal mothers actively defend their foal, remain near the foal when it is sleeping, tolerate or assist nursing, and do not injure their own foal. Disturbance of a mare and foal during the early imprinting period can predispose a mare to rejection of her foal; therefore, it should be avoided. There are a variety of forms of foal rejection and numerous etiologies. Therefore, each case should be evaluated individually.
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