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Nitschelm D, H. V. D. C. (1977). The influence of chlormadinone acetate treatment on the concentration of some stereoids in the blood, on the ovarian activity, and on the sexual behaviour of the.. Tijdschr Diergeneesk, 102, 61–872.
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Olsen Fw, H. R. (1977). Food relations of wild free – roaming horses to livestock and big game, Red Desert, Wyoming. J Range Mgmt, 30, 17–20.
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Potter Rl, H. R. (1979). Feral burro food habits and habitat relations, Grand Canyon National Park, Arizona. Symposium on the Ecology and Behavior of wild and feral Equids, Laramie, , 143–157.
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Salter Re, H. J. (1978). Habitat utilization by feral horses in western Alberta. Naturaliste can., 105, 309–321.
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Salter Re, H. J. (1980). Range relationships of feral horses with wild ungulates and cattle in western Alberta. J Range Mgmt, 33, 266–271.
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Schilder, M. B. H. (1990). Social behaviour and social arganization of a herd of plains zebra in a safari park. Ph.D. thesis, , University of Utrecht.
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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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Kroodsma, D. E., & Miller, E. H. (Eds.). (1996). Ecology and evolution of acoustic communication in birds. Ithaca: Cornell University Press.
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Stahl, J., Tolsma, P. H., Loonen, M. J. J. E., & Drent, R. H. (2001). Subordinates explore but dominants profit: resource competition in high Arctic barnacle goose flocks.61(1), 257–264.
Abstract: Social dominance plays an important role in assessing and obtaining access to patchy or scarce food sources in group-foraging herbivores. We investigated the foraging strategies of individuals with respect to their social position in the group in a flock of nonbreeding, moulting barnacle geese, Branta leucopsis, on high Arctic Spitsbergen. We first determined the dominance rank of individually marked birds. The dominance of an individual was best described by its age and its sex-specific body mass. Mating status explained the large variation in dominance among younger birds, as unpaired yearlings ranked lowest. In an artificially created, competitive situation, subordinate individuals occupied explorative front positions in the flock and were the first to find sites with experimentally enriched vegetation. Nevertheless, they were displaced quickly from these favourable sites by more dominant geese which were able to monopolize them. The enhanced sites were subsequently visited preferentially by individuals that succeeded in feeding there when the exclosures were first opened. Data on walking speed of foraging individuals and nearest-neighbour distances in the group suggest that subordinates try to compensate for a lower energy intake by exploring and by lengthening the foraging bout. Observations of our focal birds during the following breeding season revealed that females that returned to the study area were significantly more dominant in the previous year than those not seen in the area again.
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Tebbich, S., Taborsky, M., & Winkler, H. (1996). Social manipulation causes cooperation in keas.52(1), 1–10.
Abstract: Abstract. This study assessed whether keas,Nestor notabilis, are able to cooperate in an instrumental task. Seven birds of a captive group were tested in group situations and in dyads. At least two individuals had to manipulate an apparatus to obtain food but only one participant was rewarded. One bird had to push down a lever to enable another one to collect food from a box. The distribution of the two different roles was clearly dependent on hierarchy. The higher ranking individual always obtained the reward and each bird changed its role according to dominance status. Owing to the non-linear hierarchy in the group, each bird participating in cooperative interactions had at least one submissive partner. Therefore, in group situations the reward was distributed symmetrically and cooperation was persistent. In dyadic test situations, three individual keas aggressively manipulated their respective subordinate partners to open the apparatus. Their dominance status enabled them to force cooperation.
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