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George Jr M, R. O. (1986). Mitochondrial DNA evolution in the genus Equus. Molecular Biol Evol, 3, 535–546.
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Giraldeau, L. - A., & Lefebvre, L. (1986). Exchangeable producer and scrounger roles in a captive flock of feral pigeons: a case for the skill pool effect. Anim. Behav., 34(3), 797–803.
Abstract: We investigated the foraging producer-scrounger system of a captive flock of feral pigeons (Columba livia) by monitoring the number of food patches each individual produced. In one experiment, three different patch types were tested on the whole flock while, in a second, flock composition was varied for one patch type. In all cases we found non-uniform distributions of the number of patches produced per individual, which suggests the existence of producer and scrounger roles. This result could not be explained by either dominance or variability in individual learning ability. Individuals switched roles in response to changes both in food patch type and flock composition. These results are discussed in light of the skill pool hypothesis, which suggests that, in a group, different foraging specialists will profit by parasitizing each other's food discoveries.
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Gittleman, J. L. (1986). Carnivore Life History Patterns: Allometric, Phylogenetic, and Ecological Associations. Am Nat, 127(6), 744–771.
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Godfrey Eb, L. P. (1986). Wild horsres mangement: An economic perspective. J Equine Vet Sc, 6, 266–273.
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Goodall, J. (1986). The Chimpanzees of Gombe.
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GRAHAM A et al,. (1986). An aerial survey of horses and other karge animals in Alice Springs and Gulf regions. Cons Comm North Terr Alice Springs Techn Rep, .
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Groves Cp,. (1986). The taxonomy, distribution and adaptations of recent equids. In: Equids in the ancient world 11-51, .
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Groves Cp,. (1986). The taxonomy, distrubution, and adaptations of recent equids. Tübinger Atlas Vorderer Orient Beihefte Reihe A 19, , 11–65.
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Heffner, R. S., & Heffner, H. E. (1986). Localization of tones by horses: use of binaural cues and the role of the superior olivary complex. Behav Neurosci, 100(1), 93–103.
Abstract: The ability of horses to use binaural time and intensity difference cues to localize sound was assessed in free-field localization tests by using pure tones. The animals were required to discriminate the locus of a single tone pip ranging in frequency from 250 Hz to 25 kHz emitted by loudspeakers located 30 degrees to the left and right of the animals' midline (60 degrees total separation). Three animals were tested with a two-choice procedure; 2 additional animals were tested with a conditioned avoidance procedure. All 5 animals were able to localize 250 Hz, 500 Hz, and 1 kHz but were completely unable to localize 2 kHz and above. Because the frequency of ambiguity for the binaural phase cue delta phi for horses in this test was calculated to be 1.5 kHz, these results indicate that horses can use binaural time differences in the form of delta phi but are unable to use binaural intensity differences. This finding was supported by an unconditioned orientation test involving 4 additional horses, which showed that horses correctly orient to a 500-Hz tone pip but not to an 8-kHz tone pip. Analysis of the superior olivary complex, the brain stem nucleus at which binaural interactions first take place, reveals that the lateral superior olive (LSO) is relatively small in the horse and lacks the laminar arrangement of bipolar cells characteristic of the LSO of most mammals that can use binaural delta I.
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Heird, J. C., Lokey, C. E., & Cogan, D. C. (1986). Repeatability and comparison of two maze tests to measure learning ability in horses. Appl. Anim. Behav. Sci., 16(2), 103–119.
Abstract: Sixteen Quarter Horses were randomly divided into two groups after sorting by age and sex. After a 10-day preconditioning period, each animal was scored for emotionality and trainability. Each group then completed a series of learning tasks in a modified T-maze for 20 consecutive days. Group P/D was initially tested on a simple place-learning task, while Group D/P was trained in a visual discrimination task. The groups were tested alternately on the two tasks with 10-day extinction periods between each task. Upon reaching a criterion of 11 of 12 correct responses (the last 8 responses consecutive), a horse was retired for the day. If this criterion was not attained, the horse completed 20 trials. Learning occurred at a faster rate on the discrimination tasks compared to the gradual learning curves observed on place tasks. Animals learned more rapidly and reached higher levels of performance as the series of tasks progressed. Trainability and emotionality scores tended to predict the final level of learning achieved. Correlations of performance ranks within emotionality and training groups were higher between tasks of the same type than between the different tasks. Rank correlations between odd and even days on each task indicated that the within-group rankings were more consistent on the discrimination task than on the place task.
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