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Wolfe Ml,. (1986). Population dynamics of feral horses in western North America. J Equine Vet Sc, 6, 231–235.
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Kirkpatrick, J. F., & Turner, J. W. J. (1986). Comparative reproductive biology of North American feral horses. J. Equine Vet. Sci., 6, 224–230.
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Zumpe, D., & Michael, R. P. (1986). Dominance index: A simple measure of relative dominance status in primates. Am. J. Primatol., 10(4), 291–300.
Abstract: A simple measure of relative dominance status (cardinal rank) is described which we have termed the dominance index. Like more familiar techniques for assessing rank order, it is based on the direction of aggressive and submissive behaviors between all possible paired combinations of animals in a social group. Using data from five groups of female rhesus monkeys, it reliably produced the same ordinal ranks as fight interaction matrices. There was also good agreement with the cardinal ranks produced by two additional measures of dominance and with those produced by observer ratings. The dominance index can be calculated when fights have not actually occurred and is largely independent of the frequency of agonistic interactions. It has, therefore, wide application and can estimate dominance during brief sampling periods (one hour) and also in stable groups when agonistic interactions are low. Its application is described in experiments in which the male in a group of females was changed and the hormonal status of the females was altered. Estrogen increased female dominance status relative to other females.
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Zentall, S. S., & Zentall, T. R. (1986). Hyperactivity ratings: statistical regression provides an insufficient explanation of practice effects. J Pediatr Psychol, 11(3), 393–396.
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Zentall, T. R., Jackson-Smith, P., Jagielo, J. A., & Nallan, G. B. (1986). Categorical shape and color coding by pigeons. J Exp Psychol Anim Behav Process, 12(2), 153–159.
Abstract: Categorical coding is the tendency to respond similarly to discriminated stimuli. Past research indicates that pigeons can categorize colors according to at least three spectral regions. Two present experiments assessed the categorical coding of shapes and the existence of a higher order color category (all colors). Pigeons were trained on two independent tasks (matching-to-sample, and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials one of the two comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the two stimuli from the other task was introduced suggested categorical coding rules. In Experiment 1 evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Experiment 2 replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Overall, the results indicate that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical.
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Urcuioli, P. J., & Zentall, T. R. (1986). Retrospective coding in pigeons' delayed matching-to-sample. J Exp Psychol Anim Behav Process, 12(1), 69–77.
Abstract: In this study we examined how coding processes in pigeons' delayed matching-to-sample were affected by the stimuli to be remembered. In Experiment 1, two groups of pigeons initially learned 0-delay matching-to-sample with identical comparison stimuli (vertical and horizontal lines) but with different sample stimuli (red and green hues or vertical and horizontal lines). Longer delays were then introduced between sample offset and comparison onset to assess whether pigeons were prospectively coding the same events (viz., the correct line comparisons) or retrospectively coding different events (viz., their respective sample stimuli). The hue-sample group matched more accurately and showed a slower rate of forgetting than the line-sample group. In Experiment 2, pigeons were trained with either hues or lines as both sample and comparison stimuli, or with hue samples and line comparisons or vice versa. Subsequent delay tests revealed that the hue-sample groups remembered more accurately and generally showed slower rates of forgetting than the line-sample groups. Comparison dimension had little or no effect on performance. Together, these data suggest that pigeons retrospectively code the samples in delayed matching-to-sample.
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Takai, S., Narita, K., Ando, K., & Tsubaki, S. (1986). Ecology of Rhodococcus (Corynebacterium) equi in soil on a horse-breeding farm. Vet Microbiol, 12(2), 169–177.
Abstract: The ecology of Rhodococcus (Corynebacterium) equi in soil was studied on a horse-breeding farm. R. equi was cultured from soil at a depth of 0, 10, and 20 cm on the six sites of the farm at monthly intervals for 10 months from March to December of 1983. The highest numbers of R. equi were found in the surface soil. The mean number of bacteria in soil samples at every depth increased remarkably from 0 or 10(2) to 10(4) colony-forming units (CFU) g-1 of soil in the middle of April, and later decreased gradually. R. equi inoculated into six soil exudate broths prepared from surface soils at separate sites yielded suspensions with different optical densities, indicating differences in growth. The distribution of serotypes in the soil was similar to that in the horses on the farm. These findings indicated that R. equi could multiply in the soil and flourish in the cycle existing between horses and their soil environment.
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Cynx, J., Hulse, S. H., & Polyzois, S. (1986). A psychophysical measure of pitch discrimination loss resulting from a frequency range constraint in European starlings (Sturnus vulgaris). J Exp Psychol Anim Behav Process, 12(4), 394–402.
Abstract: Earlier research (Hulse & Cynx, 1985) revealed that a number of species of songbirds acquired a pitch discrimination between rising and falling sequences in an arbitrarily defined training range of frequencies, but then failed to generalize the discrimination to new frequency ranges--a frequency range constraint. The two experiments here provide a psychophysical estimate of how pitch discrimination deteriorated in one species as sequences were stepped out from the training range. The gradient showing loss of discrimination was much sharper than would have been anticipated by stimulus generalization or the training procedures, and appeared unaffected by the removal of rising and falling frequency information. The frequency range constraint and its psychophysical properties have implications both for the analysis of birdsong and the study of animal cognition.
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Nelissen, M. H. J. (1986). The effect of tied rank numbers on the linearity of dominance hierarchies. Behav. Process., 12(2), 159–168.
Abstract: The occurence of tied rank numbers in dominance hierarchies is discussed, especially its effect on the linearity of the hierarchy. This linearity is measured with Landau's index, that is calculated for several hierarchies with tied ranks on one, two of three levels. Linearity is mostly affected by ties in small groups with many ties. A distinction is made between a hierarchy of individuals and hierarchical levels. The phenomenon of despotism is called an extreme case of tied ranks. It is proposed to regard hierarchies with a linearity in a continuous scale.
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Skalka P,. (1986). Breeding the Hartmann's mountain zebra, Equus zebra hartmannae Matschie, 1898, in the world and in Czechoslovakia. Gazella, 13, 127–138.
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