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Baer, K. L., Potter, G. D., Friend, T. H., & Beaver, B. V. (1983). Observation effects on learning in horses. Appl. Animal. Ethol., 11(2), 123–129.
Abstract: Sixteen horses, divided into 2 groups of 8, were used to study observational learning in horses. One group served as controls while the other group served as the treated group (observers). Observers were allowed to watch a correctly performed discrimination task for 5 days prior to testing their learning response using the same task. Discrimination testing was conducted on all horses daily for 14 days, with criterion set at 7 out of 8 responses correct with the last 5 consecutively correct. The maximum number of trials performed without reaching criterion was limited to 20 per day. Mean trials to criteria (MT) by group were: control, 11.25; observer, 10.70. Mean error (ME) scores were: control, 2.37; observer, 2.02. Average initial discrimination error scores were 11.13 for control and 10.38 for observers (P < 0.10). Asymptote was reached by Day 8 for both control and observer groups. Analysis of variance with repeated measures showed an extreme-day effect indicative of learning (P < 0.01), with non-significant differences in learning rate between experimental groups. Whether the initial ability of the horses to perform a discrimination learning task was enhanced by observation of other horses' performance of that task was not obvious from these data.
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Ellis, L. (1995). Dominance and reproductive success among nonhuman animals: A cross-species comparison. Ethol. a. Sociob., 16(4), 257–333.
Abstract: This paper updates and extends Dewsbury's (1982) review of the literature on dominance and reproductive success (RS). The findings from approximately 700 studies are included, over two thirds of which were unavailable to Dewsbury. In order to give a highly condensed and yet meaningful overview, the main findings are represented in four tables, one for male nonprimates, one for female nonprimates, one for male primates, and one for female primates. In the tables for males, findings are analyzed in terms of six different indicators of RS, and in the tables for females, in terms of eight RS indicators. Outside the primate order, evidence largely supported the hypothesis that high-ranking males enjoy greater RS than do subordinate males. For females, studies are more evenly divided between those supporting the hypothesis that high rank and RS are positively correlated and those indicating no significant rank-RS relationship. This may reflect both the lower saliency of hierarchical relationships among females, as well as the lower variability in RS among females, relative to males. Among primates, a complex picture has emerged, especially in the case of males. Much of the complexity appears due to the importance of age and seniority in affecting dominance rank. Also, in some primate species, female preferences for sex partners seem to have little to do with the male's dominance rank, at least at the time mating takes place. Nevertheless, the majority of studies suggest that high- to middle-ranking males have at least a slight lifetime reproductive advantage over the lowest ranking males.
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Houpt, K. A., Law, K., & Martinisi, V. (1978). Dominance hierarchies in domestic horses. Appl. Animal. Ethol., 4(3), 273–283.
Abstract: Dominance hierarchies were studied in 11 herds of domestic horses and ponies (Equus caballus). A paired feeding test was utilized to establish the dominance--subordination relationship between each pair of animals in a herd. Aggressive actions, threats, bites, kicks and chases were also recorded. In small herds linear hierarchies were formed, but in large herds triangular relationships were observed. Aggression was correlated with dominance rank. Body weight, but not age, appear to affect rank in the equine hierarchy. Juvenile horses were more likely to share feed with each other than were adult horses and were usually subordinate to adult horses. The daughters of a dominant mare were dominant within their own herds.
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Houpt, K. A. (1980). Review of some research areas of applied and theoretical interest in domestic animal behavior. Appl. Animal. Ethol., 6(2), 111–119.
Abstract: There are numerous areas worthy of study in the field of domestic animal behavior or applied ethology. In this paper a few areas are offerred as particularly worthy of attention. These areas are worthwhile either because they have received little or no study and are of basic interest or because they have application to current problems of livestock production. The study of cat behavior falls in the former category. Neither the food and water sources, the reproductive success rate nor even the social interactions of cats in the large populations found in both rural and urban environments are known. Pigs as a species have already been the subjects of many behavior studies; nevertheless, there are still gaps in our knowledge of the underlying principles of swine behavior. The physiological basis of maternal behavior, for example, has not been studied in swine or in any domestic species. The sensory basis of udder location by the neonatal piglet deserves study also. Some aspects of olfactory and vocal communication of pigs have been studied, but only one of what may be a large number of pheromones of pigs has been chemically identified. The message conveyed by the vocal interactions between adult swine of the same sex is unknown, as is the role of facial and postural expressions in porcine communication. The two major problems of pig behavior under conditions of intensive livestock management are tail biting and reproductive failure. The application of behavioral techniques to these problems might help to attenuate those problems as well as broaden our understanding of normal pig behavior. Horse behavior has also been a relatively neglected field of study. Of particular interest is the significance of the flehmen gesture used by both mares and stallions in a variety of situations. Flehmen may be related to the function of the vomeronasal organ, but both observational and physiological studies should be performed to verify the hypothesis.
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