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de Waal, F. B. (2000). Primates--A natural heritage of conflict resolution. Science, 289(5479), 586–590.
Abstract: The traditional notion of aggression as an antisocial instinct is being replaced by a framework that considers it a tool of competition and negotiation. When survival depends on mutual assistance, the expression of aggression is constrained by the need to maintain beneficial relationships. Moreover, evolution has produced ways of countering its disruptive consequences. For example, chimpanzees kiss and embrace after fights, and other nonhuman primates engage in similar “reconciliations.” Theoretical developments in this field carry implications for human aggression research. From families to high schools, aggressive conflict is subject to the same constraints known of cooperative animal societies. It is only when social relationships are valued that one can expect the full complement of natural checks and balances.
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Noë, R., de Waal, F. B., & van Hooff, J. A. (1980). Types of dominance in a chimpanzee colony. Folia Primatol (Basel), 34(1-2), 90–110.
Abstract: This study examines to what extent the concept of dominance can be used to describe the social structure of a group of semi-free-living chimpanzees. 15 behavioural variables, based on agonistic, competitive and affinitive behaviour patterns, have been compared with respect to the interindividual directions in which they occurred. In this analysis use was made of indices that reflect the position an individual occupies in the relationship structure. These indices were calculated per individual for all variables and subjected to factor analysis and cluster analysis. As a result, 13 of the variables could be grouped in three categories which have been labelled: (1) agonistic dominance; (2) bluff dominance, and (3) competitive dominance. Whereas the top positions in the hierarchies based on the first two closely related types of dominance were occupied by the adult males, the hierarchy based on the third type was headed by several adult females.
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Schwarzenberger, F., Mostl, E., Bamberg, E., Pammer, J., & Schmehlik, O. (1991). Concentrations of progestagens and oestrogens in the faeces of pregnant Lipizzan, trotter and thoroughbred mares. J Reprod Fertil Suppl, 44, 489–499.
Abstract: Faecal samples were collected at weekly intervals from pregnant Lipizzan mares during Weeks 7-16 following mating and from Lipizzan, Trotter and Thoroughbred mares during the last 3 months of gestation. After parturition, samples were taken daily from the Thoroughbred mares for another 6 days. Non-pregnant mares served as controls. The concentrations of unconjugated oestrogens (Eg), 20 alpha-OH-progestagens (20 alpha-G) and 20 beta-OH-progestagens (20 beta-G) were measured by enzyme immunoassay. In the faeces of Lipizzan mares, immunoreactive progestagens were significantly (P less than 0.01) elevated above the levels in non-pregnant mares by Week 11, and Eg by Week 13 of pregnancy onwards. During the last 3 months of gestation, concentrations of Eg were significantly higher in Trotter mares than in Lipizzan and Thoroughbred mares. Concentrations of 20 alpha-G and 20 beta-G increased to maximal values in the last month of gestation. There was no significant difference among the 3 breeds with respect to 20 alpha-G but, during the 10 weeks before parturition, concentrations of 20 beta-G in the Lipizzan mares were significantly lower (P less than 0.05) than those in the Thoroughbred mares. They were also significantly lower than those of the Trotter mares during the last 4 weeks of gestation. After parturition, the concentrations of Eg and progestagens had declined to baseline values by Days 3 and 4 respectively. From these results we conclude that high concentrations of progestagens with 20 alpha- and 20 beta-hydroxyl groups are present in the faeces of pregnant mares, especially during the last month of gestation.
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Broom, M. (2002). A unified model of dominance hierarchy formation and maintenance. J. Theor. Biol., 219(1), 63–72.
Abstract: In many different species it is common for animals to spend large portions of their lives in groups. Such groups need to divide available resources amongst the individuals they contain and this is often achieved by means of a dominance hierarchy. Sometimes hierarchies are stable over a long period of time and new individuals slot into pre-determined positions, but there are many situations where this is not so and a hierarchy is formed out of a group of individuals meeting for the first time. There are several different models both of the formation of such dominance hierarchies and of already existing hierarchies. These models often treat the two phases as entirely separate, whereas in reality, if there is a genuine formation phase to the hierarchy, behaviour in this phase will be governed by the rewards available, which in turn depends upon how the hierarchy operates once it has been formed. This paper describes a method of unifying models of these two distinct phases, assuming that the hierarchy formed is stable. In particular a framework is introduced which allows a variety of different models of each of the two parts to be used in conjunction with each other, thus enabling a wide range of situations to be modelled. Some examples are given to show how this works in practice.
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Kumar, P., Timoney, J. F., Southgate, H. H., & Sheoran, A. S. (2000). Light and scanning electron microscopic studies of the nasal turbinates of the horse. Anat Histol Embryol, 29(2), 103–109.
Abstract: The nasal turbinates of 5 young horses were studied by light and scanning electron-microscopy. Stratified cuboidal epithelium lined the rostral part of the dorsal and ventral nasal turbinates of the vestibular region. The polyangular microvillus cells of this region were separated by linear depressions. The mid and caudal parts of the dorsal and ventral nasal turbinates and the rostral part of the ethmoturbinates were lined by pseudostratified columnar ciliated respiratory epithelium. Numerous cilia with dilated blebs on the ciliated cells concealed adjacent non-ciliated supporting cells and goblet cells. The olfactory zone consisting of the olfactory vesicle and a dense network of olfactory cilia localized to the caudal part of the ethmoturbinates. The three regions were delineated from each other by transitional zones.
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Deuel, N. R., & Lawrence, L. M. (1987). Laterality in the gallop gait of horses. J Biomech, 20(6), 645–649.
Abstract: Bilateral asymmetry in gallop stride limb contact patterns of four Quarter Horse fillies was documented by high-speed cinematography. Horses were filmed with rider by two cameras simultaneously while galloping along a straightaway. Even though signaled for each gallop lead an equivalent number of times, horses frequently switched leads, selecting the left lead nearly twice as often as the right. Velocities and stride lengths were greater for the left lead than the right, but stride frequencies did not differ between leads. Velocity effects were partitioned out in limb contact data analysis to enable the determination of persistent gallop stride asymmetries. The contact duration for the trailing (right) fore limb on the left lead exceeded the contact duration for the trailing (left) fore limb on the right lead. Selecting the right fore limb as the trailing fore limb may have allowed horses to use it to withstand the greater stresses and caused them to preferentially gallop with the left fore limb leading. Laterality may have an important influence on equine gallop motion patterns and thereby influence athletic performance.
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Janik, V. M. (2000). Whistle matching in wild bottlenose dolphins (Tursiops truncatus). Science, 289(5483), 1355–1357.
Abstract: Dolphin communication is suspected to be complex, on the basis of their call repertoires, cognitive abilities, and ability to modify signals through vocal learning. Because of the difficulties involved in observing and recording individual cetaceans, very little is known about how they use their calls. This report shows that wild, unrestrained bottlenose dolphins use their learned whistles in matching interactions, in which an individual responds to a whistle of a conspecific by emitting the same whistle type. Vocal matching occurred over distances of up to 580 meters and is indicative of animals addressing each other individually.
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Viscido, S. V., Miller, M., & Wethey, D. S. (2002). The dilemma of the selfish herd: the search for a realistic movement rule. J. Theor. Biol., 217(2), 183–194.
Abstract: The selfish herd hypothesis predicts that aggregations form because individuals move toward one another to minimize their own predation risk. The “dilemma of the selfish herd” is that movement rules that are easy for individuals to follow, fail to produce true aggregations, while rules that produce aggregations require individual behavior so complex that one may doubt most animals can follow them. If natural selection at the individual level is responsible for herding behavior, a solution to the dilemma must exist. Using computer simulations, we examined four different movement rules. Relative predation risk was different for all four movement rules (p<0.05). We defined three criteria for measuring the quality of a movement rule. A good movement rule should (a) be statistically likely to benefit an individual that follows it, (b) be something we can imagine most animals are capable of following, and (c) result in a centrally compact flock. The local crowded horizon rule, which allowed individuals to take the positions of many flock-mates into account, but decreased the influence of flock-mates with distance, best satisfied these criteria. The local crowded horizon rule was very sensitive to the animal's perceptive ability. Therefore, the animal's ability to detect its neighbors is an important factor in the dynamics of group formation.
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Bergstrom, C. T., & Lachmann, M. (1998). Signaling among relatives. III. Talk is cheap. Proc. Natl. Acad. Sci. U.S.A., 95(9), 5100–5105.
Abstract: The Sir Philip Sidney game has been used by numerous authors to show how signal cost can facilitate honest signaling among relatives. Here, we demonstrate that, in this game, honest cost-free signals are possible as well, under very general conditions. Moreover, these cost-free signals are better for all participants than the previously explored alternatives. Recent empirical evidence suggests that begging is energetically inexpensive for nestling birds; this finding led some researchers to question the applicability of the costly signaling framework to nestling begging. Our results show that cost-free or inexpensive signals, as observed empirically, fall within the framework of signaling theory.
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Brannon, E. M., & Terrace, H. S. (1998). Ordering of the numerosities 1 to 9 by monkeys. Science, 282(5389), 746–749.
Abstract: A fundamental question in cognitive science is whether animals can represent numerosity (a property of a stimulus that is defined by the number of discriminable elements it contains) and use numerical representations computationally. Here, it was shown that rhesus monkeys represent the numerosity of visual stimuli and detect their ordinal disparity. Two monkeys were first trained to respond to exemplars of the numerosities 1 to 4 in an ascending numerical order (1 --> 2 --> 3 --> 4). As a control for non-numerical cues, exemplars were varied with respect to size, shape, and color. The monkeys were later tested, without reward, on their ability to order stimulus pairs composed of the novel numerosities 5 to 9. Both monkeys responded in an ascending order to the novel numerosities. These results show that rhesus monkeys represent the numerosities 1 to 9 on an ordinal scale.
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