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Bailey, A., Williams, N., Palmer, M., & Geering, R. (2000). The farmer as service provider: the demand for agricultural commodities and equine services. Agricultural Systems, 66(3), 191–204.
Abstract: In recent years there has been much interest in alternative sources of income for farmers. This is because economic theory suggests that demand for agricultural commodities is inelastic so that, as incomes in society as a whole increase, those of farmers do not necessarily keep pace — hence the current problems with falling real farm incomes. In contrast the demand for services is relatively elastic. Thus it is logical to divert agricultural resources into service provision. One such service is provided by equine enterprises. We have estimated the own price and income elasticities of demand for selected agricultural commodities and for ‘equine services’. Our results confirm that demand for equine services is more elastic than for agricultural commodities. Thus diversification into horse enterprises is likely to have long term benefits for farmers vis á vis traditional agricultural production.
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Hagen, S. J., & Eaton, W. A. (2000). Two-state expansion and collapse of a polypeptide. J Mol Biol, 301(4), 1019–1027.
Abstract: The initial phase of folding for many proteins is presumed to be the collapse of the polypeptide chain from expanded to compact, but still denatured, conformations. Theory and simulations suggest that this collapse may be a two-state transition, characterized by barrier-crossing kinetics, while the collapse of homopolymers is continuous and multi-phasic. We have used a laser temperature-jump with fluorescence spectroscopy to measure the complete time-course of the collapse of denatured cytochrome c with nanosecond time resolution. We find the process to be exponential in time and thermally activated, with an apparent activation energy approximately 9 k(B)T (after correction for solvent viscosity). These results indicate that polypeptide collapse is kinetically a two-state transition. Because of the observed free energy barrier, the time scale of polypeptide collapse is dramatically slower than is predicted by Langevin models for homopolymer collapse.
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Emery, N. J. (2000). The eyes have it: the neuroethology, function and evolution of social gaze. Neurosci Biobehav Rev, 24(6), 581–604.
Abstract: Gaze is an important component of social interaction. The function, evolution and neurobiology of gaze processing are therefore of interest to a number of researchers. This review discusses the evolutionary role of social gaze in vertebrates (focusing on primates), and a hypothesis that this role has changed substantially for primates compared to other animals. This change may have been driven by morphological changes to the face and eyes of primates, limitations in the facial anatomy of other vertebrates, changes in the ecology of the environment in which primates live, and a necessity to communicate information about the environment, emotional and mental states. The eyes represent different levels of signal value depending on the status, disposition and emotional state of the sender and receiver of such signals. There are regions in the monkey and human brain which contain neurons that respond selectively to faces, bodies and eye gaze. The ability to follow another individual's gaze direction is affected in individuals with autism and other psychopathological disorders, and after particular localized brain lesions. The hypothesis that gaze following is “hard-wired” in the brain, and may be localized within a circuit linking the superior temporal sulcus, amygdala and orbitofrontal cortex is discussed.
Keywords: Animals; *Eye; Fixation, Ocular; Humans; *Social Behavior
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Sapolsky, R. M., Romero, L. M., & Munck, A. U. (2000). How Do Glucocorticoids Influence Stress Responses? Integrating Permissive, Suppressive, Stimulatory, and Preparative Actions. Endocr Rev, 21(1), 55–89.
Abstract: The secretion of glucocorticoids (GCs) is a classic endocrine response to stress. Despite that, it remains controversial as to what purpose GCs serve at such times. One view, stretching back to the time of Hans Selye, posits that GCs help mediate the ongoing or pending stress response, either via basal levels of GCs permitting other facets of the stress response to emerge efficaciously, and/or by stress levels of GCs actively stimulating the stress response. In contrast, a revisionist viewpoint posits that GCs suppress the stress response, preventing it from being pathologically overactivated. In this review, we consider recent findings regarding GC action and, based on them, generate criteria for determining whether a particular GC action permits, stimulates, or suppresses an ongoing stress-response or, as an additional category, is preparative for a subsequent stressor. We apply these GC actions to the realms of cardiovascular function, fluid volume and hemorrhage, immunity and inflammation, metabolism, neurobiology, and reproductive physiology. We find that GC actions fall into markedly different categories, depending on the physiological endpoint in question, with evidence for mediating effects in some cases, and suppressive or preparative in others. We then attempt to assimilate these heterogeneous GC actions into a physiological whole.
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Müller, A. E., & Thalmann, U. (2000). Origin and evolution of primate social organisation: a reconstruction. Biological Reviews, 75, 405–435.
Abstract: Abstract
The evolution and origin of primate social organisation has attracted the attention of many researchers, and a solitary pattern, believed to be present in most nocturnal prosimians, has been generally considered as the most primitive system. Nocturnal prosimians are in fact mostly seen alone during their nightly activities and therefore termed “solitary foragers”, but that does not mean that they are not social. Moreover, designating their social organisation as “solitary”, implies that their way of life is uniform in all species. It has, however, emerged over the last decades that all of them exhibit not only some kind of social network but also that those networks differ among species. There is a need to classify these social networks in the same manner as with group-living (gregarious) animals if we wish to link up the different forms of primate social organisation with ecological, morphological or phylogenetic variables. In this review, we establish a basic classification based on spatial relations and sociality in order to describe and cope properly with the social organisation patterns of the different species of nocturnal prosimians and other mammals that do not forage in cohesive groups. In attempting to trace the ancestral pattern of primate social organisation, the Malagasy mouse and dwarf lemurs and the Afro-Asian bushbabies and lorises are of special interest because they are thought to approach the ancestral conditions most closely. These species have generally been believed to exhibit a dispersed harem system as their pattern of social organisation (“dispersed” means that individuals forage solitarily but exhibit a social network). Therefore, the ancestral pattern of primate social organisation was inferred to be a dispersed harem. In fact, new field data on cheirogaleids combined with a review of patterns of social organisation in strepsirhines (lemurs, bushbabies and lorises) revealed that they exhibit either dispersed multi-male systems or dispersed monogamy rather than a dispersed harem system. Therefore, the concept of a dispersed harem system as the ancestral condition of primate social organisation can no longer be supported. In combination with data on social organisation patterns in “primitive” placentals and marsupials, and in monotremes, it is in fact most probable that promiscuity is the ancestral pattern for mammalian social organisation. Subsequently, a dispersed multi-male system derived from promiscuity should be regarded as the ancestral condition for primates. We further suggest that the gregarious patterns of social organisation in Aotus and Avahi, and the dispersed form in Tarsius evolved from the gregarious patterns of diurnal primates rather than from the dispersed nocturnal type. It is consequently proposed that, in addition to Aotus and Tarsius, Avahi is also secondarily nocturnal. |
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Rogers, L. J. (2000). Evolution of hemispheric specialization: advantages and disadvantages. Brain Lang, 73(2), 236–253.
Abstract: Lateralization of the brain appeared early in evolution and many of its features appear to have been retained, possibly even in humans. We now have a considerable amount of information on the different forms of lateralization in a number of species, and the commonalities of these are discussed, but there has been relatively little investigation of the advantages of being lateralized. This article reports new findings on the differences between lateralized and nonlateralized chicks. The lateralized chicks were exposed to light for 24 h on day 19 of incubation, a treatment known to lead to lateralization of a number of visually guided responses, and the nonlateralized chicks were incubated in the dark. When they were feeding, the lateralized chicks were found to detect a stimulus resembling a raptor with shorter latency than nonlateralized chicks. This difference was not a nonspecific effect caused by the light-exposed chicks being more distressed by the stimulus. Instead, it appears to be a genuine advantage conferred by having a lateralized brain. It is suggested that having a lateralized brain allows dual attention to the tasks of feeding (right eye and left hemisphere) and vigilance for predators (left eye and right hemisphere). Nonlateralized chicks appear to perform these dual tasks less efficiently than lateralized ones. Reference is made to other species in discussing these results.
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Lyn, H., & Savage-Rumbaugh, E. S. (2000). Observational word learning in two bonobos (Pan paniscus): ostensive and non-ostensive contexts. Language & Communication, 20(3), 255–273.
Abstract: Word learning has been extensively studied in humans. Children seem to be able to map new words onto objects with only one exposure to the referent. This ability has been called “fast mapping”(Carey, 1978 and Carey). Using a modified human paradigm, this paper explores two language-competent bonobos' (Pan paniscus) abilities to map new words to objects in realistic surroundings with few exposures to the referents. This paper also investigates the necessity of the apes maintaining visual contact (ostensive context) with the item to map the novel name onto the novel object. The bonobos tested in this experiment were able to map new words onto objects and could do so without visual contact with the items.
Keywords: Language acquisition; Bonobo; Fast mapping
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Wilson O. E.,. (2000). Sociobiology: The new Synthesis (Vol. 25th edition). Cambridge: Belknap Press.
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Mech L.D. (2000). Leadership in Wolf, Canis lupus, Packs. Can Field Nat, 114(2), 259–263.
Abstract: I examine leadership in Wolf (Canis lupus) packs based on published observations and data gathered during summers from 1986 to 1998 studying a free-ranging pack of Wolves on Ellesmere Island that were habituated to my presence. The breeding male tended to initiate activities associated with foraging and travel, and the breeding female to initiate, and predominate in, pup care and protection. However, there was considerable overlap and interaction during these activities such that leadership could be considered a joint function. In packs with multiple breeders, quantitative information about leadership is needed.
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Beauchamp, G. (2000). Individual Differences In Activity And Exploration Influence Leadership In Pairs Of Foraging Zebra Finches. Behaviour, 137, 301–314.
Abstract: This study investigated the role of dominance and level of activity and exploration on leadership in zebra finches (Taenopygia guttata) searching for food. In pairs of zebra finches fairly matched in size and that experienced the same level of food deprivation, the same bird consistently reached first one foraging patch over several trials. The same pattern of arrival to food occurred when resources were provided in two distant patches available concurrently, a situation that would potentially allow subordinates a greater access to resources. In further testing, the formation of new pairs with the same birds led to several changes in leadership, indicating that leadership is not an absolute feature. The member of a pair that proved to be the most active and exploratory during independent, solitary trials became the leader in nearly all pairs tested. The same pattern held true in newly rearranged pairs where individuals often experienced changes in dominance status. Dominance failed to be associated with leadership in all tests. The results suggest that in a relatively egalitarian species, level of activity and exploration may be a stronger predictor of leadership than dominance.
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