|
Byrne, R. W., & Whiten, A. (1990). Tactical deception in primates: the 1990 database (Vol. 27). German Primate Center.
|
Edgar, G. K., & Smith, A. T. (1990). Hemifield differences in perceived spatial frequency. Perception, 19(6), 759–766.
Abstract: Measurements of the perceived spatial frequency of stationary sinewave gratings were made with the gratings presented at the same eccentricity in the left, right, upper, and lower visual hemifields. Ten subjects performed the task binocularly with spatial frequencies of 1, 2, and 4 cycles deg-1. Two of these subjects also performed the task monocularly at 2 cycles deg-1. In the majority of cases, the spatial frequency of stimuli presented in the left and lower visual hemifields was overestimated relative to stimuli presented in the right and upper visual hemifields. The results were similar for all spatial frequencies tested, and the direction of the asymmetry was the same whether viewing was with the left eye, right eye or binocular, suggesting that the differences in perceived spatial frequency are not retinal in origin.
|
Gordon, I. J., & Lindsay, W. K. (1990). Could Mammalian Herbivores “Manage” Their Resources? Oikos, 59(2), 270–280.
Abstract: The concept of resource management has gone hand in hand with group selection arguments. For this reason, it has been cast aside in the era of evolutionary theory which assumes that foraging strategies must have evolved under selection operating to maximise an individual's inclusive fitness. However, results from empirical studies show that under favourable environmental and social circumstances, resource management could be selectively advantageous. Much of the recent literature on plant-herbivore interactions suggest that herbivory can result in changes in the resource base which are assumed to increase the intake and fitness of the herbivore. As a result, a number of authors suggest that herbivores manage their resource utilisation to maximise the flow of nutrients from these resources. Long term territoriality or the exclusive use of a home range are the social systems most likely to favour selection for prudent resource exploitation. This review argues that, in many habitats, resource management strategies are not feasible, as individuals have little control over the way resources are depleted and renewed. Thus far, very little evidence is available showing that herbivorous mammals actively manage the resources which they utilise.
|
Duncan, P., Foose, T. J., Gordon, I. J., Gakahu, C. G., & Lloyd, M. (1990). Comparative nutrient extraction from forages by grazing bovids and equids: a test of the nutritional model of equid/bovid competition and coexistence. Oecologia, 84(3), 411–418.
Abstract: Ruminants are unevenly distributed across the range of body sizes observed in herbivorous mammals; among extant East African species they predominate, in numbers and species richness, in the medium body sizes (10-600 kg). The small and the large species are all hind-gut fermenters. Some medium-sized hind-gut fermenters, equid perissodactyls, coexist with the grazing ruminants, principally bovid artiodactyls, in grassland ecosystems. These patterns have been explained by two complementary models based on differences between the digestive physiology of ruminants and hind-gut fermenters. The Demment and Van Soest (1985) model accounts for the absence of ruminants among the small and large species, while the Bell/Janis/Foose model accounts both for the predominance of ruminants, and their co-existence with equids among the medium-sized species (Bell 1971; Janis 1976; Foose 1982). The latter model assumes that the rumen is competitively superior to the hind-gut system on medium quality forages, and that hind-gut fermenters persist because of their ability to eat more, and thus to extract more nutrients per day from high fibre, low quality forages. Data presented here demonstrate that compared to similarly sized grazing ruminants (bovids), hind-gut fermenters (equids) have higher rates of food intake which more than compensate for their lesser ability to digest plant material. As a consequence equids extract more nutrients per day than bovids not only from low quality foods, but from the whole range of forages eaten by animals of this size. Neither of the current nutritional models, nor refinements of them satisfactorily explain the preponderance of the bovids among medium-sized ungulates; alternative hypotheses are presented.
|
Dublin, H. T., Sinclair, A. R. E., Boutin, S., Anderson, E., Jago, M., & Arcese, P. (1990). Does competition regulate ungulate populations? Further evidence from Serengeti, Tanzania. Oecologia, 82(2), 283–288.
Abstract: Changes in populations of several ungulate species in the Serengeti-Mara region of East Africa over the past 30 years suggest several hypotheses for their regulation and coexistence. Recent censuses in the 1980s have allowed us to test the hypotheses that: (1) there was competition between wildebeest (Connochaetes taurinus) and Thomson's gazelle (Gazella thomsoni). This predicted that gazelle numbers should have declined in the 1980s when wildebeest were food limited. Census figures show no change in gazelle numbers between 1978 and 1986, a result contrary to the interspecific competition hypothesis; (2) wildebeest and African buffalo (Syncerus caffer) populations were regulated by intraspecific competition for food. Since both populations reached food limitation in the 1970s, the hypothesis predicted that the populations should have been stable in the 1980s. The results confirm these predictions for wildebeest and the buffalo population in the Mara reserve. In the Serengeti the buffalo population declined 41% over the period 1976-1984. The decline was not evenly distributed over the park, some areas showing an 80-90% decline, others no change or an increase in numbers. The decline was associated with proximity to human habitation; (3) an outbreak of the viral disease, rinderpest, in 1982 may have been the cause of the drop in buffalo population. Blood serum samples to measure the prevalence of antibodies were collected from areas of decreasing, stable and increasing populations. If rinderpest was the cause of decrease there should be a negative relationship between the prevalence of rinderpest and the instantaneous rate of increase (r). The results showed no relationship. We conclude that rinderpest was not the major cause of the drop in buffalo numbers. Elephant (Loxodonta africana) numbers dropped 81% in Serengeti in the period 1977-1986. In the Mara there was little change. The evidence suggests that extensive poaching in northern and western Serengeti during 1979-1984 accounted for the drop in both elephant and buffalo numbers.
|
Wittling, W. (1990). Psychophysiological correlates of human brain asymmetry: Blood pressure changes during lateralized presentation of an emotionally laden film. Neuropsychologia, 28(5), 457–470.
Abstract: Fifty adult subjects were shown an emotionally positive film either in their left or right hemisphere by means of a technique for lateralizing visual input that allows prolonged viewing while permitting free ocular scanning. It was found that the cerebral hemispheres markedly differ in their capability to regulate blood pressure during emotionally laden situations of a distinctly positive nature. Right-hemispheric film presentation caused a significantly higher increase in systolic and diastolic pressure that left-hemispheric viewing of the same film. Moreover, hemisphere asymmetries were further increased if lateralized stimulus presentation and the lateralized carrying out of a stimulus-related response were combined within the same hemisphere, thereby enhancing unilateral processing. Finally, males and females clearly differed with respect to interhemispheric regulation of blood pressure.
|
|
Stander, P. E., Nott, T.B., Lindeque, P.M., & Lindeque, M. (1990). Mass marking of zebras in the Etosha National Park, Namibia. Madoqua, 17(1), 47–49.
|
Huizinga, H. A., Boukamp, M., & Smolders, G. (1990). Estimated parameters of field performance testing of mares from the Dutch Warmblood riding horse population. Livestock Production Science, 26(4), 291–299.
Abstract: The field performance testing (FPT) of mares of the Dutch Warmblood riding horse population is evaluated. Phenotypic and genetic parameters of scored traits are estimated and the genetic relationship with performance of half-sibs in dressage and jumping competition are estimated. Data from 1984 to 1987 are used, covering scores from 2023 at least 3-year-old mares. Seven subjectively scored traits are considered, walk, trot, canter, riding ability, character, jumping ability and total score. Analysis of data is according to a sire model. Variance and covariance components are estimated by Restricted Maximum Likelihood (REML) procedures. Estimates of heritability are moderately low for gaits (average 0.19), jumping ability (0.15) and total score (0.17) and extremely low for riding ability (0.03) and character (0.06). Dressage in competition is most correlated with riding ability (0.83) and is moderately correlated with total score (0.41) from FPT of mares. Jumping competition is most correlated with jumping ability (0.48) and not correlated with total score (0.05) from field test of mares. Some possible bias owing to previous knowledge and preselection is discussed. It is concluded that efficiency of present FPT of mares is limited for selection of broodmares for dressage and jumping ability in competition.
|
Philipsson, J., Arnason, T., & Bergsten, K. (1990). Alternative selection strategies for performance of the Swedish warmblood horse. Livestock Production Science, 24(3), 273–285.
Abstract: The Swedish riding horse population includes about 6000 broodmares and 150 breeding stallions. The overall breeding goal is to produce riding horses competitive in several disciplines, i.e. dressage as well as showjumping and eventing. The effectiveness of this multi-purpose objective was studied in alternative strategies for selecting stallions and mares as candidate dams for them. The alternative selection strategies for stallions included 1-stage (conformation), 2-stage (conformation and performance test) and 3-stage (conformation, performance test and competition results at advanced levels) selection schemes. The mare selection schemes included the corresponding 1- and 2-stage selection schemes. The results clearly showed the 2-stage selection procedure to be most efficient, especially for stallions. It is important that the intensity in selection after the performance test is kept high. Differences in defining the breeding objective are less important, provided the selection is based on a performance test including both dressage and jumping. According to the results, the development of the Swedish performance testing scheme, in which now only 30% of the tested stallions are selected for breeding, seems justified. In mare selection schemes, performance tests also seem to be justified, especially if jumping ability is to be improved. Differences between field and station tests are only minor and since the volume of testing can be much higher in the field this would allow a much stronger selection and should thus be preferred.
|
|
Tomasello, M. (1990). Cultural transmission in the tool use and communicatory signalling of chimpanzees? In S. T. Parker, & K. R. Gibson (Eds.), Language and Intelligence in Monkeys and Apes. (pp. 274–311). Cambridge: Cambridge University Press.
|
