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Penzhorn Bl,. (1987). Descriptions of incisors of known – age Cape Mountain Zebras from the Mountain Zebra National park. Onderstepoort J vet Res, 54, 135–141.
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Penzhorn Bl, G. R. (1987). Incisor wear in free – ranging Cape mountain zebras. S Afr J Wildl Res, 17, 99–102.
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Penzhorn Bl, L. P. (1987). Comparisons of reproductive parameters of two Cape mountain zebra populations. J Reprod Fert Suppl, 35, 661–663.
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Schilder Mbh, B. P. (1987). Ethological investigations on a herd of Plains Zebra in a safari park: Time – budgets, reproduction and food competition. App Anim Behav Sci, 18, 45–56.
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SUMMERS PM et al,. (1987). Sucessful transfer of the embryos of Przewalski's horses and Grant's zebra to domestic mares. J Reprod Fert, 80, 13–20.
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Lane, J. G., & Mair, T. S. (1987). Observations on headshaking in the horse. Equine Vet J, 19(4), 331–336.
Abstract: The clinical records of 100 cases of headshaking in horses were reviewed. Possible causes of the abnormal behaviour were identified in 11 animals; these included ear mite infestation, otitis interna, cranial nerve dysfunction, cervical injury, ocular disease, guttural pouch mycosis, dental periapical osteitis and suspected vasomotor rhinitis. However, in only two of these could it be shown that correction of the abnormality led to elimination of the headshaking. The additional clinical signs exhibited by the other idiopathic cases of headshaking included evidence of nasal irritation, sneezing and snorting, nasal discharge, coughing and excessive lacrimation. Many of these horses also showed a marked seasonal pattern with respect to the onset of the disease and the recurrence of signs in subsequent years. The clinical presentation of idiopathic headshakers and the seasonal incidence of the signs closely resemble allergic rhinitis in man.
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Sherwin, C. M., & Johnson, K. G. (1987). The influence of social factors on the use of shade by sheep. Appl. Anim. Behav. Sci., 18(2), 143–155.
Abstract: Individual differences in shading behaviour within a flock of sheep could be due to differences in thermoregulatory capabilities or to the influence of social factors. The possible influence of social factors on shade-use is examined in this paper. Two measures of dominance were made on 39 Merino wethers. These were based on the hierarchy determined by butting during feeding and on priority of access to limited feed. Leadership was also assessed while driving the sheep to a woolshed and as the sheep entered weighing scales. These behavioural traits were compared with leadership to shade and shade-use observed on 9 days during summer in a small pastureless enclosure containing natural shade. Maximum ambient temperature on these 9 days varied between 29.0 and 39.5[degree sign]C. All behavioural traits examined were significantly repeatable. The two dominance ranks were negatively correlated (P<0.05). The butting hierarchy was correlated with shading behaviour; those sheep that butted the larger proportion of the flock were seen to shade for longer periods of time (P=0.05). This relationship became more significant as environmental temperature increased. Significant (P<0.05) differences in the amount of time each sheep spent shading were evident throughout the flock, but in particular seven individuals shaded much less than others. Shade-use increased in hot weather and was slightly more strongly correlated with radiation load than with air temperature. The non-shading leadership ranks were related neither to each other nor to the leadership to shade. However, the sheep that moved to shade first remained there longest (P<0.05). Reduced motivation to feed did not appear to explain early movement to shade. Few overtly aggressive or other interactions between animals were seen to be associated with movements to or within shade. Nonetheless, the results indicate that social forces do exert some influence on shade-use.
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Kacelnik, A. (1987). Information primacy or preference for familiar foraging techniques? A critique of Inglis & Ferguson. Anim. Behav., 35(3), 925–926.
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Berger, J., & Cunningham, C. (1987). Influence of Familiarity on Frequency of Inbreeding in Wild Horses. Evolution, 41, 229–231.
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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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