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Heird, J. C., Whitaker, D. D., Bell, R. W., Ramsey, C. B., & Lokey, C. E. (1986). The effects of handling at different ages on the subsequent learning ability of 2-year-old horses. Appl. Anim. Behav. Sci., 15(1), 15–25.
Abstract: Forty weanling Quarter Horses, from the Pitchfork Ranch, Dickens, Texas, were randomly assigned to one of five groups based on the amount of handling they would receive. The five groups were: (1) limited handling; (2) 1 week of handling; (3) 2 weeks of handling; (4) 3 weeks of handling; (5) continuous handling for 18 months. As 2-year-olds, the horses were tested in a simple place-learning T-maze after being preconditioned. A maximum of 30 daily trials were conducted for 20 consecutive days, with feed location alternating between sides on successive days. If a horse met the criterion of 11 out of 12 correct responses with 8 correct responses being consecutive, it was retired without completing the 30 trials. Group 1 made fewer correct responses during the 20 days than any other group except Group 3. All groups achieved learning by Day 10, but the most-handled group reached a consistently higher percentage of correct responses earlier than the less-handled groups. Group 5, the group receiving the most handling, was the least emotional, as determined by the animals' reactivity to a novel stimulus, and received the highest scores for trainability after being ridden. Preconditioning trainability scores, or estimates of the horses' ability to learn prior to conditioning and testing, tended to predict maze-learning ability. These scores were also significantly correlated with post-maze training scores.
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Liang, K. - Y., & Zeger, S. L. (1986). Longitudinal data analysis using generalized linear models. Biometrika, 73(1), 13–22.
Abstract: This paper proposes an extension of generalized linear models to the analysis of longitudinal data. We introduce a class of estimating equations that give consistent estimates of the regression parameters and of their variance under mild assumptions about the time dependence. The estimating equations are derived without specifying the joint distribution of a subject's observations yet they reduce to the score equations for niultivariate Gaussian outcomes. Asymptotic theory is presented for the general class of estimators. Specific cases in which we assume independence, m-dependence and exchangeable correlation structures from each subject are discussed. Efficiency of the pioposecl estimators in two simple situations is considered. The approach is closely related to quasi-likelihood.
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McNaughton, S. J., & Georgiadis, N. J. (1986). Ecology of African Grazing and Browsing Mammals. Annual Review of Ecology and Systematics, 17, 39–66.
Abstract: INTRODUCTION Africa is the earth's second largest continent, comprising 20% of its surface. Largely tropical, Africa extends as well into temperate zones to 37 N and 35 S. Eastern and southern Africa display steep elevation gradients due to the prevalence there of volcanic orogeny and rifting (29). Local landscapes are distinguished by substantial geological heterogeneity, dissected land forms, and resultant steep gradients of precipitation and vegetation. The consequent pronounced fragnientation of habitats and sharp juxtaposition of distinct vegetation types, combined with climatic oscillations in geological time, contributed to major adaptive radiations of the mammalian fauna (102, 120). Early zoological expeditions recorded that habitat fragmentation and wide spatial variation of animal densities and diversities were distinctive features of African ecosystems (92, 138, 162, 226). Those early records provided the bases of natural history information on animal distributions, habitat preferences, feeding habits, and general ecology; scientific research followed only much later (201). Modem scientific study of African savanna-grassland mammals began in the 1950s (23, 24, 107, 108, 148, 149, 197,203, 204, 210,230), long after the distributions and densities of the major game animals had been affected by growing human populations, colonial land and hunting policies, and virulent exotic diseases that affected the animals both directly and indirectly (57). The mammalian fauna has been increasingly isolated and fragmented within game reserves of varying size, habitat diversity, and animal species diversity; the ability to sustain it in the absence of active management is increasingly questioned (112, 187). For species with population sizes greater than 100 individuals, game reserve area (A) and faunal ...
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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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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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Cheney, D. L., & Seyfarth, R. M. (1986). The recognition of social alliances among vervet monkeys. Anim. Behav., 34, 1722–1731.
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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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Gittleman, J. L. (1986). Carnivore Life History Patterns: Allometric, Phylogenetic, and Ecological Associations. Am Nat, 127(6), 744–771.
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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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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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