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Macfadden, B. J. (2005). Evolution. Fossil horses--evidence for evolution. Science, 307(5716), 1728–1730.
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Moehlman, P. D. (2005). Endangered wild equids. Sci Am, 292(3), 74–81.
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Robinson, H. C. (2007). Equine interspecies aggression (Vol. 160).
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Burden, F., & Trawford, A. (2006). Equine interspecies aggression Comment on (Vol. 159).
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Sundaresan, S. R., Fischhoff, I. R., Dushoff, J., & Rubenstein, D. I. (2007). Network metrics reveal differences in social organization between two fission-fusion species, Grevy's zebra and onager. Oecologia, 151(1), 140–149.
Abstract: For species in which group membership frequently changes, it has been a challenge to characterize variation in individual interactions and social structure. Quantifying this variation is necessary to test hypotheses about ecological determinants of social patterns and to make predictions about how group dynamics affect the development of cooperative relationships and transmission processes. Network models have recently become popular for analyzing individual contacts within a population context. We use network metrics to compare populations of Grevy's zebra (Equus grevyi) and onagers (Equus hemionus khur). These closely related equids, previously described as having the same social system, inhabit environments differing in the distribution of food, water, and predators. Grevy's zebra and onagers are one example of many sets of coarsely similar fission-fusion species and populations, observed elsewhere in other ungulates, primates, and cetaceans. Our analysis of the population association networks reveals contrasts consistent with their distinctive environments. Grevy's zebra individuals are more selective in their association choices. Grevy's zebra form stable cliques, while onager associations are more fluid. We find evidence that females associate assortatively by reproductive state in Grevy's zebra but not in onagers. The current approach demonstrates the utility of network metrics for identifying fine-grained variation among individuals and populations in association patterns. From our analysis, we can make testable predictions about behavioral mechanisms underlying social structure and its effects on transmission processes.
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Pluhácek, J., Bartos, L., Bartosová, J., & Kotrba, R. (2010). Feeding behaviour affects nursing behaviour in captive plains zebra (Equus burchellii). Appl. Anim. Behav. Sci., 128(1-4), 97–102.
Abstract: Equids spend more than half of the day feeding. Lactation is a very demanding form of maternal investment. In an environment such as a zoo, where no grass but several feeding sites are present, conflict between suckling behaviour of the foal and feeding behaviour of the lactating mother should occur. We observed 20 foals of captive plains zebra, Equus burchellii, at the Dvur Králové Zoo, Czech Republic, and collected data concerning suckling events during 17 months of observation. First, we examined whether feeding by the mother while nursing affected suckling behaviour. We found that when the mother was feeding, the proportion of suckling bouts she terminated decreased with increasing age of the foal, whereas it did not change when she was not feeding. This result supported the trade-off between suckling and feeding behaviour which has been reported in other ungulates. Second, we examined what affected interruptions of feeding behaviour of the mother during the suckling bout. The proportion of interruptions of feeding by the mother during nursing increased with increasing age of her foal. This coincides with declining time spent nursing. In addition, younger mothers interrupted their feeding behaviour during suckling bouts more often than older ones. Mothers interrupted feeding during the suckling bout more often when they nursed a daughter than when they nursed a son. The results of our study show that feeding while suckling could reduce parent-offspring conflict and improve welfare of captive foals and mares.
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Kiltie, R. A., Fan, J., & Laine, A. F. (1995). A wavelet-based metric for visual texture discrimination with applications in evolutionary ecology. Math Biosci, 126(1), 21–39.
Abstract: Much work on natural and sexual selection is concerned with the conspicuousness of visual patterns (textures) on animal and plant surfaces. Previous attempts by evolutionary biologists to quantify apparency of such textures have involved subjective estimates of conspicuousness or statistical analyses based on transect samples. We present a method based on wavelet analysis that avoids subjectivity and that uses more of the information in image textures than transects do. Like the human visual system for texture discrimination, and probably like that of other vertebrates, this method is based on localized analysis of orientation and frequency components of the patterns composing visual textures. As examples of the metric's utility, we present analyses of crypsis for tigers, zebras, and peppered moth morphs.
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Dierenfeld, E. S. (1994). Vitamin E in exotics: effects, evaluation and ecology. J Nutr, 124(12 Suppl), 2579s–2581s.
Abstract: The pathophysiology and lesions associated with vitamin E deficiency are similar between domestic and exotic species, and circulating plasma concentrations are also similar between comparable groups. However, many ecological variables must be considered for the most relevant comparisons. Tissue values of vitamin E, apart from plasma, are unknown for most exotics. Dietary vitamin E requirements of exotic species and domestics appear to differ; based on natural foodstuff analyses and clinical observations, between 50 and 200 mg vitamin E/kg DM are necessary to prevent vitamin E deficiency, 5- to 10-fold higher than current livestock recommendations.
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Zhao, C. J., Qin, Y. H., Lee, X. H., & Wu, C. (2006). Molecular and cytogenetic paternity testing of a male offspring of a hinny. J Anim Breed Genet, 123(6), 403–405.
Abstract: An alleged male foal of a female mule, whose sire and grandparents were unknown, was identified for its pedigree. Parentage testing was conducted by comparing polymorphism of 12 microsatellite DNA sites and mitochondrial D-loop sequences of the male foal and the female mule. Both the sequence analysis of species-specific DNA fragments and a cytogenetic analysis were performed to identify the species of the foal and its parents. The results showed that the alleged female mule is actually a hinny, and the male foal, which possesses 62 chromosomes, qualifies as an offspring of the female hinny and a jack donkey.
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Briard, L., Dorn, C., & Petit, O. (2015). Personality and Affinities Play a Key Role in the Organisation of Collective Movements in a Group of Domestic Horses. Ethology, 121(9), 888–902.
Abstract: Understanding how groups of individuals with different motives come to daily decisions about the exploitation of their environment is a key question in animal behaviour. While interindividual differences are often seen only as a threat to group cohesion, growing evidence shows that they may to some extent facilitate effective collective action. Recent studies suggest that personality differences influence how individuals are attracted to conspecifics and affect their behaviour as an initiator or a follower. However, most of the existing studies are limited to a few taxa, mainly social fish and arthropods. Horses are social herbivores that live in long-lasting groups and show identifiable personality differences between individuals. We studied a group of 38 individuals living in a 30-ha hilly pasture. Over 200 h, we sought to identify how far individual differences such as personality and affinity distribution affect the dynamic of their collective movements. First, we report that individuals distribute their relationships according to similar personality and hierarchical rank. This is the first study that demonstrates a positive assortment between unrelated individuals according to personality in a mammal species. Second, we measured individual propensity to initiate and found that bold individuals initiated more often than shy individuals. However, their success in terms of number of followers and joining duration did not depend on their individual characteristics. Moreover, joining process is influenced by social network, with preferred partners following each other and bolder individuals being located more often at the front of the movement. Our results illustrate the importance of taking into account interindividual behavioural differences in studies of social behaviours.
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