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Templeton, J. J., Kamil, A. C., & Balda, R. P. (1999). Sociality and social learning in two species of corvids: The pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana). J. Comp. Psychol., 113(4), 450–455.
Abstract: The hypothesis that social learning is an adaptive specialization for social living predicts that social species should learn better socially than they do individually, but that nonsocial species should not exhibit a similar enhancement of performance under social learning conditions. The authors compared individual and social learning abilities in 2 corvid species: the highly social pinyon jay (Gymnorhinus cyanocephalus) and the less social Clark's nutcracker (Nucifraga columbiana). The birds were tested on 2 different tasks under individual and social learning conditions. Half learned a motor task individually and a discrimination task socially; the other half learned the motor task socially and the discrimination task individually. Pinyon jays learned faster socially than they did individually, but nutcrackers performed equally well under both learning conditions. Results support the hypothesis that social learning is an adaptive specialization for social living in pinyon jays. (PsycINFO Database Record (c) 2007 APA, all rights reserved)
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Wittig, R. M., & Boesch, C. (2003). Food Competition and Linear Dominance Hierarchy Among Female Chimpanzees of the Ta National Park. Int. J. Primatol., 24(4), 847–867.
Abstract: Dominance rank in female chimpanzees correlates positively with reproductive success. Although a high rank obviously has an advantage for females, clear (linear) hierarchies in female chimpanzees have not been detected. Following the predictions of the socio-ecological model, the type of food competition should affect the dominance relationships among females. We investigated food competition and relationships among 11 adult female chimpanzees in the Ta National Park, C+ete d'Ivoire (West Africa). We detected a formal linear dominance hierarchy among the females based on greeting behaviour directed from the subordinate to the dominant female. Females faced contest competition over food, and it increased when either the food was monopolizable or the number of competitors increased. Winning contests over food, but not age, was related to the dominance rank. Affiliative relationships among the females did not help to explain the absence of greetings in some dyads. However comparison post hoc among chimpanzee study sites made differences in the dominance relationships apparent. We discuss them based on social relationships among females, contest competition and predation. The cross-site comparison indicates that the differences in female dominance hierarchies among the chimpanzee study sites are affected by food competition, predation risk and observation time.
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Wittig, R. M., & Boesch, C. (2003). “Decision-making” in conflicts of wild chimpanzees (Pan troglodytes): an extension of the Relational Model. Behav. Ecol. Sociobiol., 54(5), 491–504.
Abstract: >We examined the “decision-making” process of aggressive interactions within a community of wild chimpanzees ( Pan troglodytes verus) in the Taï National Park, Côte d’Ivoire (West Africa). Costs and benefits were investigated for 876 dyadic aggressive interactions among 18 adults (including 4 independent adolescents) of either sex. An extended version of the Relational Model was developed to describe the dynamics of the “decision-making” process in Taï chimpanzees, which suggests that the net benefit determines the occurrence of conflicts. Both sexes fought more frequently for the resources that were most important to them, food for females and social contexts for males. Individuals used two different strategies according to their likelihood of winning the aggressive interaction, determined by the dominance relationship of the conflict partners. Dominant initiators had longer and more intense aggressive interactions, but they limited their social disadvantages by fighting non-cooperative partners. Subordinate initiators had shorter and less intense aggressive interactions, but risked more social costs, which they could reduce afterwards by reconciliation. Both strategies included a positive overall net benefit. The extended Relational Model fits the complexity of wild chimpanzee conflicts and allows for more flexibility in the “decision-making” compared to the original version.
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Wittig, R. M., & Boesch, C. (2003). The Choice of Post-conflict Interactions in Wild Chimpanzees (Pan troglodytes). Behaviour, 140(11), 1527–1559.
Abstract: Some costs of conflicts remain after an aggressive interaction has been terminated. Postconflict management in social living animals can reduce those costs by means of a variety of interactions implemented after aggression (e.g.reconciliation, consolation, redirected aggression). Each post-conflict interaction (PCI) provides different advantages and disadvantages, although the functions may sometimes overlap. Individuals can therefore choose a PCI to achieve the most favourable outcome within a given conflict situation. We examined 876 dyadic aggressive interactions among 18 wild chimpanzees (Pan troglodytes verus) of both sexes in the Tai National Park, Céte d'Ivoire. We investigated which conflict-condition led to which type of PCI and related the choice of PCI to its advantages and disadvantages. Tai chimpanzees used reconciliation to resolve conflicts among high value partners and when approaching the former opponent was unlikely to entail further aggression. Consolation seemed to substitute for reconciliation, when were opponents low value partners or approaching the former opponent was too risky, such as when further aggression was likely. Tai chimpanzees renewed aggression after undecided conflicts and when losers were unexpected. They used redirected aggression after long conflicts, possibly because friendly PCIs were likely to fail. However, Tai chimpanzees continued with business as usual when conflicts were very short, and they avoided further interactions when the accessibility of the resource was unlimited. Tai chimpanzees appeared to follow a clear-cut evaluation process as they seemed to weigh advantages against disadvantages for the appropriate choice of PCI.
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Belonje, P. C., & van Niekerk, C. H. (1975). A review of the influence of nutrition upon the oestrous cycle and early pregnancy in the mare. J Reprod Fertil Suppl, (23), 167–169.
Abstract: Attention is drawn to the beneficial effect of improved nutrition during winter and early spring on the ovarian activity of mares. Furthermore, the necessity of an adequate plane of nutrition during early pregnancy to prevent embryonic resorption is stressed.
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Berger, J., & Cunningham, C. (1987). Influence of Familiarity on Frequency of Inbreeding in Wild Horses. Evolution, 41, 229–231.
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Berger, J., & Cunningham, C. (1988). Size-Related Effects on Search Times in North American Grassland Female Ungulates. Ecology, 69(1), 177–183.
Abstract: Feeding and searching (= vigilance) rates arise as a result of many interrelated factors including trophic level, diet, reproductive condition, sex, habitat, body mass, and potential predation pressure. Because of unique ecological conditions in which the confounding influences of all but two of these variables could be minimized, we examined the hypothesis that body mass alone accounts for interspecific differences in search times, and tested it with females of four sympatric native North American ungulates (Bison bison, Antilocapra americana, Ovis canadensis, and Odocoileus hemionus). When the effects of group size were controlled, smaller bodied species were more vigilant (per unit body mass) than larger ones. However, search times (ST) also scaled to body mass, and between 81 and 97% of the ST variance was explained by either exponential or power functions. To remove the potential bias that predators exert different influences on species of varying size, search times of bison in areas with and without their major predator, wolves (Canis lupus), were contrasted; search times did not differ between sites. Our results highlight the importance of designing field research that controls for confounding variables prior to attempting to scale behavioral processes to ecological events. See full-text article at JSTOR
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Vieuille, C., Berger, F., Le Pape, G., & Bellanger, D. (2003). Sow behaviour involved in the crushing of piglets in outdoor farrowing huts--a brief report. Appl. Anim. Behav. Sci., 80(2), 109–115.
Abstract: This study focuses on maternal activities involved in the trapping of piglets by the sow's body in outdoor farrowing systems and examine the mother-piglet context leading either to the death of piglets or to their survival. The behaviour of six Large-WhitexLandrace sows and their litters was continuously video recorded at their first and second parity, during the 40 h following parturition. Crushing mainly occurred at evening and night, during the first 12 h of farrowing and involved changes between lying, sitting and standing positions, as well as between udder and side lying. No piglet died from savaging. Nevertheless, aggressive behaviours of sows were observed, particularly in their first maternal experience. The immediate context of trapping was related to the labour of the sow and to the feeding and resting of piglets. The immediate crushing context was related to active avoidance of restless piglets while lying down, as well as sitting and standing behaviours. These results are discussed in terms of differential reactions of the sow to suckling attempts of piglets.
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Blunden, A. S., Smith, K. C., Whitwell, K. E., & Dunn, K. A. (1998). Systemic infection by equid herpesvirus-1 in a Grevy's zebra stallion (Equus grevyi) with particular reference to genital pathology. J Comp Pathol, 119(4), 485–493.
Abstract: A severe multi-systemic form of equid herpesvirus-1 infection is described in an adult zebra stallion. There was multifocal necrotizing rhinitis, marked hydrothorax and pulmonary oedema, with viral antigen expression in degenerating epithelial cells, local endothelial cells and intravascular leucocytes of the nasal mucosa and lung. Specific localization of EHV-1 infection was seen in the testes and epididymides, including infection of Leydig cells and germinal epithelium, which would have facilitated venereal shedding of virus in life. The case provided a unique opportunity to study hitherto undescribed aspects of the pathogenesis of naturally occurring EHV-1 infection in the male equine genital tract. Restriction digests of the isolate demonstrated a pattern similar to that of EHV-1 isolates previously recovered from aborted zebra and onager fetuses.
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Briand Petersen, J. C., & Casebeer, R. L. (1971). A bibliography relating to the ecology and energetics of East African large mammals. E. Afr. Wildl. J., 9, 1–23.
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