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Author |
Shettleworth, S.J.; Plowright, C.M. |
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Title |
How pigeons estimate rates of prey encounter |
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Journal Article |
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Year |
1992 |
Publication  |
Journal of experimental psychology. Animal behavior processes |
Abbreviated Journal |
J Exp Psychol Anim Behav Process |
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Volume |
18 |
Issue |
3 |
Pages |
219-235 |
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Keywords |
Analysis of Variance; Animals; *Appetitive Behavior; Columbidae; Conditioning, Operant; Food Preferences/*psychology; Motivation; *Predatory Behavior; *Probability Learning; *Reinforcement Schedule; Social Environment |
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Abstract |
Pigeons were trained on operant schedules simulating successive encounters with prey items. When items were encountered on variable-interval schedules, birds were more likely to accept a poor item (long delay to food) the longer they had just searched, as if they were averaging prey density over a short memory window (Experiment 1). Responding as if the immediate future would be like the immediate past was reversed when a short search predicted a long search next time (Experiment 2). Experience with different degrees of environmental predictability appeared to change the length of the memory window (Experiment 3). The results may reflect linear waiting (Higa, Wynne, & Staddon, 1991), but they differ in some respects. The findings have implications for possible mechanisms of adjusting behavior to current reinforcement conditions. |
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Department of Psychology, University of Toronto, Ontario, Canada |
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0097-7403 |
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PMID:1619391 |
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Call Number |
refbase @ user @ |
Serial |
382 |
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Author |
Kristjansson, T.; Bjornsdottir, S.; Sigurdsson, A.; Andersson, L.S.; Lindgren, G.; Helyar, S.J.; Klonowski, A.M.; Arnason, T. |
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Title |
The effect of the ‘Gait keeper’ mutation in the DMRT3 gene on gaiting ability in Icelandic horses |
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Journal Article |
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Year |
2014 |
Publication |
Journal of Animal Breeding and Genetics |
Abbreviated Journal |
J. Anim. Breed. Genet. |
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n/a-n/a |
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Keywords |
Gaiting ability; genotype effect; genotype probability |
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Abstract |
A nonsense mutation in DMRT3 (‘Gait keeper’ mutation) has a predominant effect on gaiting ability in horses, being permissive for the ability to perform lateral gaits and having a favourable effect on speed capacity in trot. The DMRT3 mutant allele (A) has been found in high frequency in gaited breeds and breeds bred for harness racing, while other horse breeds were homozygous for the wild-type allele (C). The aim of this study was to evaluate further the effect of the DMRT3 nonsense mutation on the gait quality and speed capacity in the multigaited Icelandic horse and demonstrate how the frequencies of the A- and C- alleles have changed in the Icelandic horse population in recent decades. It was confirmed that homozygosity for the DMRT3 nonsense mutation relates to the ability to pace. It further had a favourable effect on scores in breeding field tests for the lateral gait tölt, demonstrated by better beat quality, speed capacity and suppleness. Horses with the CA genotype had on the other hand significantly higher scores for walk, trot, canter and gallop, and they performed better beat and suspension in trot and gallop. These results indicate that the AA genotype reinforces the coordination of ipsilateral legs, with the subsequent negative effect on the synchronized movement of diagonal legs compared with the CA genotype. The frequency of the A-allele has increased in recent decades with a corresponding decrease in the frequency of the C-allele. The estimated frequency of the A-allele in the Icelandic horse population in 2012 was 0.94. Selective breeding for lateral gaits in the Icelandic horse population has apparently altered the frequency of DMRT3 genotypes with a predicted loss of the C-allele in relatively few years. The results have practical implications for breeding and training of Icelandic horses and other gaited horse breeds. |
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1439-0388 |
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Equine Behaviour @ team @ |
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5831 |
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Author |
Wallner, B.; Brem, G.; Muller, M.; Achmann, R. |
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Title |
Fixed nucleotide differences on the Y chromosome indicate clear divergence between Equus przewalskii and Equus caballus |
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Journal Article |
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Year |
2003 |
Publication |
Animal Genetics |
Abbreviated Journal |
Anim Genet |
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Volume |
34 |
Issue |
6 |
Pages |
453-456 |
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Keywords |
Animals; Base Sequence; DNA, Mitochondrial/genetics; Genetic Variation/*genetics; Horses/classification/*genetics; Male; Molecular Sequence Data; Phylogeny; Probability; Species Specificity; Y Chromosome/*genetics |
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Abstract |
The phylogenetic relationship between Equus przewalskii and E. caballus is often a matter of debate. Although these taxa have different chromosome numbers, they do not form monophyletic clades in a phylogenetic tree based on mtDNA sequences. Here we report sequence variation from five newly identified Y chromosome regions of the horse. Two fixed nucleotide differences on the Y chromosome clearly display Przewalski's horse and domestic horse as sister taxa. At both positions the Przewalski's horse haplotype shows the ancestral state, in common with the members of the zebra/ass lineage. We discuss the factors that may have led to the differences in mtDNA and Y-chromosomal observations. |
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Institut fur Tierzucht und Genetik, Veterinarmedizinische Universitat Wien, Veterinarplatz, Wien, Austria. wallner@i122server.vu-wien.ac.at |
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0268-9146 |
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PMID:14687077 |
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Call Number |
Equine Behaviour @ team @ |
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5038 |
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Author |
Atwill, E.R.; Mohammed, H.O.; Lopez, J.W. |
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Title |
Evaluation of travel and use as a risk factor for seropositivity to Ehrlichia risticii in horses of New York state |
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Journal Article |
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Year |
1996 |
Publication |
American Journal of Veterinary Research |
Abbreviated Journal |
Am J Vet Res |
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Volume |
57 |
Issue |
3 |
Pages |
272-277 |
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Keywords |
Animals; Cross-Sectional Studies; Ehrlichiosis/epidemiology/*veterinary; Female; *Horse Diseases; Horses; Male; New York/epidemiology; Probability; Random Allocation; Risk Factors; *Travel |
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Abstract |
OBJECTIVES--To determine whether mean annual frequency and destination of equine travel was associated with exposure to Ehrlichia risticii and whether these associations were modified by horses' place of residence. DESIGN--Cross-sectional study. SAMPLE POPULATION--511 equine operations containing 2,587 horses were visited in New York state from a target population of 39,000 operations. PROCEDURE--Each horse was tested for serum antibodies against E risticii, using indirect fluorescent antibody. Information on the horse's travel history, farm's management practices, and surrounding ecology was obtained by personal interview and resource maps. Statistical analyses were performed on 2 cohorts of animals: all horses enrolled in the study and horses born on the property or that resided at least 4 years on the farm. Three county-based risk regions (RR) were identified by use of cluster analysis. RESULTS--Mean seroprevalence for each of the 3 RR was 2.4 (low risk), 8.5 (moderate risk), and 18.5% (high risk) for cohort 1 and 2.5, 8.0, and 18.4% for cohort 2. Among cohorts 1 and 2, pleasure riding and breeding trips were associated with exposure to E risticii, but horse residence (low, moderate, or high RR) was an effect modifier for these associations. Among cohort 1 and stratifying the analysis according to the RR for the travel destination, trail riding at low RR and trail riding at high RR were associated with exposure. Among cohort 2 and stratifying the analysis according to the RR for the travel destination, breeding trips were associated with exposure, and strong effect modification was present for horse residence (low, moderate, or high RR). CONCLUSIONS--Only certain types of travel to specific RR were associated with higher risk of exposure to E risticii. In many instances, travel was not associated, or was associated, with a reduced risk of exposure. |
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Address |
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA |
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English |
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ISSN |
0002-9645 |
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Notes |
PMID:8669754 |
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Call Number |
Equine Behaviour @ team @ |
Serial |
2658 |
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