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Kuckelkorn, B. (1994). Assessment of pregnancy in Kiang mares (Equus hemionus holdereri ) using estrogen determination in feces. Theriogenology, 42(1), 37–42.
Abstract: Analysis of fecal estrogens was used to diagnose pregnancy in 6 Kiang mares (Equus hemionus holdereri ) that were kept at Tierpark Berlin. Three extraction methods were compared and were followed by an established RIA for total estrogen. Extraction of desiccated feces with chloroform/n-hexane and KOH, with and without enzyme hydrolysis showed better results than extraction with diethylether without hydrolysis. Pregnancy was confirmed by observation of foaling in 2 mares that showed estrogen concentrations between 800 and 1800 ng/g and in 1 mare that showed widely fluctuating values between 500 and 1300 ng/g of feces. Two mares with estrogen concentrations below 500 ng/g were not seen to foal. The method using chloroform/n-hexane and KOH without enzyme hydrolysis seems practical for non-invasive evaluation of the endocrine status in this endangered Equidae species.
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Sappington, B. F., & Goldman, L. (1994). Discrimination learning and concept formation in the Arabian horse. J. Anim Sci., 72(12), 3080–3087.
Abstract: Discrimination learning and concept formation abilities were investigated in four mature Arabian horses. A series of two-choice discrimination problems were presented on stimulus panels that could open to allow access to food bowls. Selection of the correct stimulus resulted in food reinforcement, and an incorrect choice was not rewarded. The positions of the correct and incorrect stimuli were varied randomly during each test session, and the criterion for learning each problem was 85% correct for two consecutive sessions of 30 or 40 trials. Testing progressed through six discrimination problems. The first four were simple pattern discriminations, but the last two incorporated several different triangles as correct stimuli and thus involved the concept of triangularity. Two of the subjects successfully completed only simple pattern discriminations, one showed evidence of learning in the first concept problem, and one completed all six tests, including the two concept formation problems. The results demonstrate complex pattern discrimination ability in horses, and suggest that they may also have the ability to form and use concepts in problem solving.
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Marinier, S. L., & Alexander, A. J. (1994). The use of a maze in testing learning and memory in horses. Appl. Anim. Behav. Sci., 39(2), 177–182.
Abstract: Two mazes were used to test the learning ability and memory of horses, and changes in these abilities. Testing was done on four occasions. On Occasion 1, the horses were run through Maze A until they had reached the criterion of three consecutive correct runs. A week later (Occasion 2), they were retested in Maze A to the same criterion as a measure of memory. On Occasion 3,2 months later, the horses were run through Mazes A and B until they reached the criterion. Occasion 4 took place 1 week later when they were run through Mazes A and B. An estimation of changes in ability to learn came from a comparison of results from Occasions 1 and 3. Similarly, changes in ability to remember came from a comparison of results from Occasions 2 and 4. Nine horses with a variable amount of riding training were the subjects. All horses were able to learn the maze, but the ability varied among horses. There was no obvious correlation between quality of handling of the horses and learning ability. Once the horses had learned the maze, they remembered it perfectly on subsequent occasions. There were changes in the memory and learning ability of the horses, but no clear explanation for this could be found.
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Mal, M. E., McCall, C. A., Cummins, K. A., & Newland, M. C. (1994). Influence of preweaning handling methods on post-weaning learning ability and manageability of foals. Appl. Anim. Behav. Sci., 40(3-4), 187–195.
Abstract: Twenty-three foals were used to determine if different amounts of handling between birth and weaning affected their later learning ability and manageability. Foals were assigned to one of three treatments: non-handled (NH) foals were not handled except for necessary maintenance procedures; intermediately handled (IH) foals were handled daily in two 10-min sessions for 7 days after birth and then not handled except for necessary maintenance procedures; extensively handled (EH) foals were handled daily for 7 days as were IH foals and then handled for 10 min once weekly until weaning. Foals were weaned at 120 +/- 10 days of age. On days 1, 3, and 15 after weaning, foals were subjected to a one-trial learning test. The learning test consisted of placing the foal in a familiar pen with an 1.5 X .6-m apparatus containing 40 15 X 15-cm compartments. Number of visits to the apparatus and compartment visited were recorded for 5 min. A small amount of concentrate feed then was placed in a target compartment, and visits were recorded for an additional 5 min. On day 16 after weaning, foals were subjected to a manageability test in which flight distance from an unfamiliar handler and reaction to a novel stimulus were recorded. Split-plot analysis of variance revealed no treatment differences in performance on the learning test (P > .05). Foal performance on the test was greater on day 15 than on day 1 or day 3 (P < .01). Analysis of variance indicated handling treatment had no effect (P > .05) on foal performance during the manageability test. Results indicate that this preweaning handling regimen has no effect on foal learning ability or manageability as measured by these procedures.
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Pick, D. F., Lovell, G., Brown, S., & Dail, D. (1994). Equine color perception revisited. Appl. Anim. Behav. Sci., 42(1), 61–65.
Abstract: An attempt to replicate Grzimek (1952; Z. Tierpsychol., 27: 330-338) is reported where a Quarter-Horse mare chose between colored and gray stimuli for food reinforcement. Stimuli varied across a broad range of reflectance values. A double-blind procedure with additional controls for auditory, olfactory, tactile, and position cues was used. The subject could reliably discriminate blue (462 nm) vs. gray, and red (700 nm) vs. gray without regard to reflectance (P<0.001), but could not discriminate green (496 nm) vs. gray. It is suggested that horses are dichromats in a manner similar to swine and cattle.
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(1994). Winter horse care. Journal of Equine Veterinary Science, 14(2), 115–117.
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Moehlman, P. D. (1994). Behavior and Ecology of Feral Asses (2nd edition). Ph.D. thesis, , Univ. of Wisconsin, Madison.
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Boesch, C. (1994). Cooperative hunting in wild chimpanzees. Anim. Behav., 48(3), 653–667.
Abstract: A model for the evolution of cooperation shows that two conditions are necessary for cooperation to be stable: a hunting success rate that is low for single hunters and increases with group size, and a social mechanism limiting access to meat by non-hunters. Testing this model on TaI chimpanzees, Pan troglodytes, showed that (1) it pays for individuals to hunt in groups of three or four rather than alone or in pairs, and (2) cooperation is stable because hunters gain more at these group sizes than cheaters, owing to a meat-sharing pattern in which hunting, dominance and age, in that order, determine how much an individual gets. In addition, hunters provide cheaters (about 45% of the meat eaters) with the surplus they produce during the hunts. Thus, cooperation in Tai male chimpanzees is an evolutionarily stable strategy, and its success allows cheating to be an evolutionarily stable strategy for Tai female chimpanzees. In Gombe chimpanzees, cooperation is not stable, first, because hunting success is very high for single hunters, and second, because no social mechanism exists that limits access to meat by non-hunters. The analysis showed that some assumptions made when discussing cooperation in other social hunters might be wrong. This might downgrade our general perception of the importance of cooperation as an evolutionary cause of sociality.
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Manson, J. H. (1994). Male aggression: a cost of female mate choice in Cayo Santiago rhesus macaques. Anim. Behav., 48, 473–475.
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McLaren, B. E., & Peterson, R. O. (1994). Wolves, Moose, and Tree Rings on Isle Royale. Science, 266(5190), 1555–1558.
Abstract: Investigation of tree growth in Isle Royale National Park in Michigan revealed the influence of herbivores and carnivores on plants in an intimately linked food chain. Plant growth rates were regulated by cycles in animal density and responded to annual changes in primary productivity only when released from herbivory by wolf predation. Isle Royale's dendrochronology complements a rich literature on food chain control in aquatic systems, which often supports a trophic cascade model. This study provides evidence of top-down control in a forested ecosystem.
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