Franke Stevens, E. (1990). Instability of harems of feral horses in relation to season and presence of subordinate stallions. Behaviour, 112(3-4), 149–161.
Abstract: Male horses (Equus caballus) defend harems of females (bands) year-round and throughout their lifetimes. A male's lifetime reproductive success depends upon the number of females in his harem. Although harems have previously been reported as remaining stable over many years, during the two years of this study 30 % of the adult females in an island population of feral horses changed harems during late winter. The seasonal differences in harem stability resulted from seasonal differences in the abundance and distribution of food. The spacing between band members was greater and the frequency of social interactions between them was lower in winter than in summer. In addition, the amount of time devoted to grazing increased in winter. These differences are attributed to the lower availability of suitable vegetation duirng winter. Harem stability did not depend on the age of females, the size of the harem, nor the age of the harem stallion, but did depend on the presence of subordinate stallions attached to the band. All of the females that changed bands left single-male bands; multi-male bands were stable throughout the study.
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Stevens, J. A. (1994). Zebras in Turmoil. Int Wildl, 24, 4–12.
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Thackeray, J. F. (1988). Zebras from wonderwerk cave, northern Cape province, South Africa: attempts to distinguish Equus burchelli and E. quagga. Suid- Afrikaanse Tydsskrif vir Wetenskap, 84, 99–101.
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Westlin-van Aarde, L. M., van Aarde, R. J., & Skinner, J. D. (1988). Reproduction in female Hartmann's zebra. J Reprod Fert, 84, 505–511.
Abstract: Ovaries, fetuses and plasma were collected from zebra mares shot in the Etosha National Park in Namibia between 15 and 25 August 1983. Ovarian weight was affected by reproductive status and most of the non-pregnant mares were anoestrous. The number of follicles varied between individuals and only pro-oestrous/oestrous mares had follicles larger than 20 mm in diameter. The largest follicle in pregnant mares was only 9 mm in diameter. Corpora lutea and corpora albicantia were found in non-pregnant as well as pregnant mares: 4 pregnant mares had only corpora albicantia. The presence of secondary corpora lutea could not be confirmed in any of the pregnant mares. Implantation was estimated to occur at around 73 days of gestation, and most mares (84%) had conceived between November and April. Peripheral concentrations of plasma progesterone during pregnancy varied from 0·5 to 2·4 ng/ml.
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Wiesner, J., & V. Hegel, G. (1990). Zur Immobilisation von Wildequiden mit STH 2130 und Tiletamin/Zolazepam. Tierärzl Prax, 18, 151–154.
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Winkler A,. (1992). The feeding ecology of the Cape Mountain zebra in the Mountain Zebra National Park. Doctoral thesis, , .
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Würbel, H. (1990). The relationship between social structure and mating system in donkeys & Mating strategies of male donkeys in a promiscuous mating system"l structure and mating system in donkeys &. Diploma thesis, , Faculty of Natural Sciences, University of Berne, Switzerland.
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Zeeb, K., & Schnitzter, U. (1978). Equus caballus (Equidae) – Ruheverhalten, Hinlegen und Aufstehen. E.C., Film E 1620 des IWF Begleittext.
Abstract: Equus caballus (Equidae)-Behaviour at Rest, Lying down and Rising. The film shows the
behaviour at rest of the primitive horses of the Duke of Croy at DulmenNestphalia. With
the aid of several individual animals, complete relaxation, reclining and rising are shown.
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Bohnet, W. (2007). Expressive behaviour to assess the emotional states in horses. Dtsch Tierarztl Wochenschr, 114(3), 91–97.
Abstract: The emotional states such as feelings and emotions are not easy to assess by objective methods in animals as well as in humans. Beside measuring physiological variables an aid to assess the emotional states is the analysis of expressive behaviour of an individual respecting the relating context. Especially developed in mammals, which live in obligatory social i.e. in stable permanent social communities, are facial expression and gesture. Also horses display a differentiated expressive behaviour, which can be observed and analysed by humans. Moreover it could be demonstrated, that in situations of stress the display shown by horses (gesture, facial expression, posture) correlate with corresponding physiological reactions. Thus the expressive behaviour is suitable to assess the emotional states of horses depending on the situation.
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Boogert, N. J., Reader, S. M., & Laland, K. N. (2006). The relation between social rank, neophobia and individual learning in starlings. Anim. Behav., 72(6), 1229–1239.
Abstract: Researchers with diverse interests in topics ranging from the formation of dominance hierarchies and social intelligence to animal personalities have predicted specific, and often conflicting, relations between social rank, neophobia and learning ability. We investigated the relations between these variables in captive groups of wild-caught starlings, Sturnus vulgaris, adopting a multidimensional approach to social rank and neophobia. Both agonistic and competitive rank orders were determined for each group and we tested individuals in the absence of their groupmates for object neophobia, latency to feed in a novel environment and performance on an extractive foraging task. In each starling group, the fastest learners occupied the highest competitive ranks, supporting the hypothesis that cognitive ability is positively correlated with social dominance. Competitive rank orders, however, did not correlate significantly with agonistic rank orders. Situation-specific foraging neophobia was suggested: individuals showed consistency in their latencies to feed near a variety of novel objects, but no significant correlation was found between this measure of object neophobia and latency to feed in a novel environment. Starlings fastest to feed in the novel environment were fastest in solving the foraging task. We discuss the implications of these findings for researchers studying hierarchy formation in animal groups, social intelligence and animal personalities.
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