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Voith, V. L. (1986). Principles of learning. The Veterinary clinics of North America. Equine practice, 2(3), 485–506.
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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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Zentall, T. R., Jackson-Smith, P., Jagielo, J. A., & Nallan, G. B. (1986). Categorical shape and color coding by pigeons. J Exp Psychol Anim Behav Process, 12(2), 153–159.
Abstract: Categorical coding is the tendency to respond similarly to discriminated stimuli. Past research indicates that pigeons can categorize colors according to at least three spectral regions. Two present experiments assessed the categorical coding of shapes and the existence of a higher order color category (all colors). Pigeons were trained on two independent tasks (matching-to-sample, and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials one of the two comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the two stimuli from the other task was introduced suggested categorical coding rules. In Experiment 1 evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Experiment 2 replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Overall, the results indicate that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical.
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Keiper, R. R., & Sambraus, H. H. (1986). The stability of equine dominance hierarchies and the effects of kinship, proximity and foaling status on hierarchy rank. Appl. Anim. Behav. Sci., 16(2), 121–130.
Abstract: Dominance hierarchies were determined in four bands of feral horses living on Assateague Island. The bands varied in size from 10 to 16 horses, and consisted of one stallion, several mares and their offspring. The animals ranged in age from less than 1 to over 18 years. Field observation of all social interactions during the summer of 1981 was used to determine dominance. 1981 hierarchies for three of the bands were compared with hierarchies determined for the same bands in 1978, and showed that hierarchies change over time. Age was significantly correlated with rank. Mares with foals did not rank any higher in the hierarchies than mares without foals. Kinship did not appear to have an effect on dominance rank either, since neither juvenile nor adult offspring ranks correlated with the ranks of their mothers. The band stallion was not the highest-ranking animal of any band, but the location of the stallion peripheral to the main body of the band, the nature of his interactions with band members, and his length of residence in the band may have contributed to his low rank.
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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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Crowell-Davis, S. L., Houpt, K. A., & Carini, C. M. (1986). Mutual grooming and nearest-neighbor relationships among foals of Equus caballus. Appl. Anim. Behav. Sci., 15(2), 113–123.
Abstract: A 3-year study was carried out on the developmental behavior of foals from birth to 24 weeks of age and the behavior of mares living with foals. Mutual-grooming partners of foals were primarily other foals. The peak frequency of mutual grooming occurred during Weeks 9-12, when fillies mutual-groomed 1.6 times h-1 and colts mutual-groomed 0.9 times h-1. Fillies mutual-groomed more frequently than colts (P < 0.025). Fillies mutual-groomed randomly with colts and other fillies (P < 0.05), whereas colts mutual-groomed almost exclusively with fillies (P = 0.03). At all ages studied, if a foal's nearest neighbor was not its mother, it was more likely to be another foal than would be expected if the foal was associating randomly with non-mother ponies. Fillies were more likely than expected to have a filly rather than a colt as their nearest neighbor (P = 0.01). Thus, during their first few months of life, the foals studied exhibited patterns of behavior which were consistent with the development of the usual social milieu of unmanaged adults, in which several mares form a cohesive herd with one or more stallions associating with them.
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Takai, S., Narita, K., Ando, K., & Tsubaki, S. (1986). Ecology of Rhodococcus (Corynebacterium) equi in soil on a horse-breeding farm. Vet Microbiol, 12(2), 169–177.
Abstract: The ecology of Rhodococcus (Corynebacterium) equi in soil was studied on a horse-breeding farm. R. equi was cultured from soil at a depth of 0, 10, and 20 cm on the six sites of the farm at monthly intervals for 10 months from March to December of 1983. The highest numbers of R. equi were found in the surface soil. The mean number of bacteria in soil samples at every depth increased remarkably from 0 or 10(2) to 10(4) colony-forming units (CFU) g-1 of soil in the middle of April, and later decreased gradually. R. equi inoculated into six soil exudate broths prepared from surface soils at separate sites yielded suspensions with different optical densities, indicating differences in growth. The distribution of serotypes in the soil was similar to that in the horses on the farm. These findings indicated that R. equi could multiply in the soil and flourish in the cycle existing between horses and their soil environment.
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Nelissen, M. H. J. (1986). The effect of tied rank numbers on the linearity of dominance hierarchies. Behav. Process., 12(2), 159–168.
Abstract: The occurence of tied rank numbers in dominance hierarchies is discussed, especially its effect on the linearity of the hierarchy. This linearity is measured with Landau's index, that is calculated for several hierarchies with tied ranks on one, two of three levels. Linearity is mostly affected by ties in small groups with many ties. A distinction is made between a hierarchy of individuals and hierarchical levels. The phenomenon of despotism is called an extreme case of tied ranks. It is proposed to regard hierarchies with a linearity in a continuous scale.
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Lima, S. L. (1986). Predation Risk and Unpredictable Feeding Conditions: Determinants of Body Mass in Birds. Ecology, 67(2), 377–385.
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Barette, C., & Vandal, D. (1986). Social rank, dominance, antler size, and access to food in snow-bound wild woodland caribou. Behaviour, 97(1-2), 118–146.
Abstract: We spent two winters studying the social behaviour of wild woodland caribou (Rangifer tarandus caribou) at a time when their main food (ground lichens; Cladina sp.) is available only at snow craters dug by the animals. The competition for access to such craters was severe, the animals constantly trying to take over the craters of others. During a two-month period when a group maintained a constant size (20) and composition (all age-sex classes represented), we could rank the animals in a rather linear dominance hierarchy (Landau's index = 0.87). Rank was correlated with access to resources, percent of time spent active, and percent of time feeding in craters. It was also correlated with age and antler size. However, rank is not an attribute of individuals, but of a relationship between individuals. As such it is only an intervening variable between physical attributes and access to resources, a variable whose value has meaning only within a given group. Among the three attributes studied (age, sex, antler size), the latter was by far the best predictor of the occurrence and outcome of interactions. Between two individuals within any of the three age-sex classes studied (adult and yearling males and adult females), the one with larger antlers initiated significantly more often, escalated its aggression (to the point of hitting the target) less often, and enjoyed a higher success rate in obtaining resources. When their antlers were larger than those of an adult male target (i.e. males that had shed their antlers), adult females won almost all their interactions with adult males even though they escalated only one fourth of them. This clarifies the long-standing speculation that female caribou have antlers and shed them later than males, in order to overcome their sexual handicap in competition for food in the winter. We conclude that the link between rank and dominance of an individual on one hand, and some of its attributes on the other (e.g. sex, age, weight, antler size) is fundamentally realized by the animal itself through its active preference for targets it is likely to beat, i.e. targets with smaller antlers.
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