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Elzenga, J. W, |
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Title |
Why zebras are striped |
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Year |
1992 |
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Swara |
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Swara |
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15 |
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4 |
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28-30 |
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from Professor Hans Klingels Equine Reference List |
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yes |
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1068 |
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Author |
Mills, M.G.L.; Shenk, M.G.L. |
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Title |
Predator--Prey Relationships: The Impact of Lion Predation on Wildebeest and Zebra Populations |
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Journal Article |
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Year |
1992 |
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The Journal of Animal Ecology |
Abbreviated Journal |
T. J. Anim. Ecol. |
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61 |
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3 |
Pages |
693-702 |
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1. The role of lion Panthera leo predation in the dynamics of blue wildebeest Connochaetes taurinus and zebra Equus burchelli populations was investigated through simulation models. The data used in the models were from intensive observations over 4 years in the south-east of the Kruger National Park. 2. Population estimates of wildebeest and zebra were made from aerial surveys, sex and age ratios from ground counts. Lion numbers were determined from observations of marked and radio-collared animals. Predation was studied by following lions for continuous periods of up to 336 h. 3. Two models were constructed. Model 1 ascertained the number of killing lions (adult females) that could be supported by each prey population while remaining stable. A single model was constructed for the sedentary wildebeest population. A summer and winter model was constructed for the semi-migratory zebra population. The sensitivity of the parameters in the model was tested by changing their value by 10%. In model 2, the kill age structure for each species was changed to determine the number of killing lions the altered prey selection parameters could support. 4. There was no difference in the vulnerability of either species to predation. Zebra foals (<1 year) were killed more frequently than expected. No selection for sex or by season could be found for either species. 5. Model 1 predicted that the wildebeest population stabilizes with 7.7 killing lions, close to the number in the study area. The winter zebra population stabilizes with 6.8 killing lions and the summer zebra population with 19.4. Manipulation of kill rate followed by adult fecundity rate had the greatest effect on population size of both species. In model 2, wildebeest predation was made selective towards calves and zebra predation was made non-selective for sex and age. With these parameters the wildebeest population stabilizes with 10.7 killing lions and the zebra population with 5.4 in winter and 15.1 in summer. 6. The models suggest that lion predation affected wildebeest more severely than zebra during the study. This was through the way in which lions selected their prey, and because of the sedentary behaviour of the wildebeest, as opposed to the semi-migratory behaviour of the zebra. |
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Equine Behaviour @ team @ |
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2376 |
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Author |
Timney, B.; Keil, K. |
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Title |
Visual acuity in the horse |
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Journal Article |
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Year |
1992 |
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Vision Research |
Abbreviated Journal |
Vis. Res. |
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32 |
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12 |
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2289-2293 |
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Horse Visual acuity Visual discrimination |
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We assessed the ease with which horses could learn visual discriminations and measured their resolution acuity. We trained three horses to press their noses against one of two large wooden panels to receive a small food reward. Following training on a series of two-choice discrimination tasks, resolution acuity was measured. Although there was some variability between animals, the best acuity obtained was 23.3 c deg-1. Within the margin of error imposed by limited anatomical data, the obtained values are consistent with predictions based on retinal ganglion cell density estimates and posterior nodal distance/axial length ratios. They suggest that the resolution acuity of the horse is limited by ganglion cell density in the temporal portion of the narrow visual streak. |
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refbase @ user @ |
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851 |
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Author |
Eisgruber, H.; Stolle, F.A. |
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Title |
[Clostridia in carcasses and fresh meat--a literature review] |
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Journal Article |
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Year |
1992 |
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Zentralblatt fur Veterinarmedizin. Reihe B. Journal of Veterinary Medicine. Series B |
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Zentralbl Veterinarmed B |
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39 |
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10 |
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746-754 |
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Abattoirs; Animals; Cattle; Clostridium/*growth & development; *Food Microbiology; Horses; Meat/*microbiology; Muscles/*microbiology; Sheep; Swine |
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Clostridia are of large clinical importance as well as in the field of food hygiene, where they are responsible for spoilage but they also have a certain significance as food poisoning organisms. Information on the ecology of Clostridia in samples of deep muscle tissue of slaughtered animals is insufficient. This article is intended to increase the knowledge on the occurrence of different Clostridia species in slaughtered animals. The main emphasis is put on the significance of clostridia in meat hygiene. The theoretical basis of the so called original content of microorganisms (intrinsic bacteria), the factors and pathways of Clostridia spreading in muscles and organs are demonstrated. |
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Institut fur Hygiene und Technologie, Ludwig-Maximilians-Universitat Munchen |
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Clostridien in Schlachttierkorpern und frischem Fleisch--Eine Literaturubersicht |
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0514-7166 |
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PMID:1492516 |
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Equine Behaviour @ team @ |
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2668 |
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