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Reebs, S. G. (2000). Can a minority of informed leaders determine the foraging movements of a fish shoal? Anim. Behav., 59(2), 403–409.
Abstract: There is no information on whether the daily foraging movements of fish shoals are the result of chance, the collective will of all shoalmates, or the leadership of a few individuals. This study tested the latter possibility. Shoals of 12 golden shiners, Notemigonus crysoleucas, were trained to expect food around midday in one of the brightly lit corners of their tank. They displayed daily food-anticipatory activity by leaving the shady area of their tank and spending more and more time in the food corner up to the normal time of feeding. Past this normal time they remained in the shade, even on test days when no food was delivered. Most of these experienced individuals were then replaced by naïve ones. The resulting ratio of experienced:naïve fish could be 5:7, 3:9 or 1:11. On their own, naïve individuals would normally spend the whole day in the shade, but in all tests the experienced individual(s) were able to entrain these more numerous naïve fish out of the shade and into the brightly lit food corner at the right time of day. Entrainment was stronger in the 5:7 than in the 1:11 experiment. The test shoals never split up and were always led by the same fish, presumably the experienced individuals. These results indicate that in a strongly gregarious species, such as the golden shiner, a minority of informed individuals can lead a shoal to food, either through social facilitation of foraging movements or by eliciting following behaviour.
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Hare, B., Call, J., Agnetta, B., & Tomasello, M. (2000). Chimpanzees know what conspecifics do and do not see. Anim. Behav., 59(4), 771–785.
Abstract: We report a series of experiments on social problem solving in chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual were put into competition over two pieces of food. In all experiments dominants obtained virtually all of the foods to which they had good visual and physical access. However, subordinates were successful quite often in three situations in which they had better visual access to the food than the dominant, for example, when the food was positioned so that only the subordinate (and not the dominant) could see it. In some cases, the subordinate might have been monitoring the behaviour of the dominant directly and simply avoided the food that the dominant was moving towards (which just happened to be the one it could see). In other cases, however, we ruled out this possibility by giving subordinates a small headstart and forcing them to make their choice (to go to the food that both competitors could see, or the food that only they could see) before the dominant was released into the area. Together with other recent studies, the present investigation suggests that chimpanzees know what conspecifics can and cannot see, and, furthermore, that they use this knowledge to devise effective social-cognitive strategies in naturally occurring food competition situations.
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Goncalves, D. M., Oliveira, R. F., Korner, K., Poschadel, J. R., & Schlupp, I. (2000). Using video playbacks to study visual communication in a marine fish, Salaria pavo. Anim. Behav., 60(3), 351–357.
Abstract: Video playbacks have been successfully applied to the study of visual communication in several groups of animals. However, this technique is controversial as video monitors are designed with the human visual system in mind. Differences between the visual capabilities of humans and other animals will lead to perceptually different interpretations of video images. We simultaneously presented males and females of the peacock blenny, Salaria pavo, with a live conspecific male and an online video image of the same individual. Video images failed to elicit appropriate responses. Males were aggressive towards the live male but not towards video images of the same male. Similarly, females courted only the live male and spent more time near this stimulus. In contrast, females of the gynogenetic poecilid Poecilia formosa showed an equal preference for a live and video image of a P. mexicana male, suggesting a response to live animals as strong as to video images. We discuss differences between the species that may explain their opposite reaction to video images.
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Engh, A. L., Esch, K., Smale, L., & Holekamp, K. E. (2000). Mechanisms of maternal rank 'inheritance' in the spotted hyaena, Crocuta crocuta. Anim. Behav., 60(3), 323–332.
Abstract: Maternal rank [`]inheritance', the process by which juveniles attain positions in the dominance hierarchy adjacent to those of their mothers, occurs in both cercopithecine primates and spotted hyaenas. Maternal rank is acquired in primates through defensive maternal interventions, coalitionary support and unprovoked aggression ([`]harassment') directed by adult females towards offspring of lower-ranking individuals. Genetic heritability of rank-related traits plays a negligible role in primate rank acquisition. Because the social lives of Crocuta and cercopithecine primates share many common features, we examined whether the same mechanisms might operate in both taxa to promote maternal rank [`]inheritance'. We observed a large clan of free-living spotted hyaenas in Kenya to test predictions of four mechanistic hypotheses. Hyaena rank acquisition did not appear to be directly affected by genetic heritability. Unprovoked aggression from adult female hyaenas was not directed preferentially towards low-ranking cubs. However, high-ranking mothers intervened on behalf of their cubs more frequently and more effectively than low-ranking mothers. Maternal interventions and supportive coalitions appeared to reinforce aggression directed at [`]appropriate' conspecific targets, whereas coalitionary aggression directed at cubs apparently functioned to extinguish their aggressive behaviour towards [`]inappropriate' targets. Young hyaenas and primates thus appear to [`]inherit' their mothers' ranks by strikingly similar mechanisms.
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Call, J., Aureli, F., & de Waal, F. B. M. (2002). Postconflict third-party affiliation in stumptailed macaques. Anim. Behav., 63(2), 209–216.
Abstract: Stumptailed macaques, Macaca arctoides, are characterized by high levels of postconflict affiliative contacts between opponents. We investigated the occurrence of postconflict affiliative contacts between opponents and third parties that were not involved in the original conflict. We collected 10-min focal observations during postconflict and control periods in which we recorded all aggressive and affiliative behaviours between opponents and third parties. We distinguished three types of third parties depending on the relationship with the focal animal: own kin, opponent's kin and individuals unrelated to both opponents. We analysed the interactions with third parties separately, while distinguishing two classes of affiliative behaviours: (1) allogrooming and contact sitting and (2) sociosexual behaviours (e.g. genital inspection). The macaques showed differences between postconflict and control periods in their affiliative contacts with third parties. Aggressors received more postconflict grooming and contact sitting from their opponents' kin, received more sociosexual behaviour from their own kin and unrelated individuals, and directed more sociosexual behaviour to unrelated individuals. Victims received and directed less postconflict grooming from and towards their own kin. They received more postconflict sociosexual behaviour from all partners except their own kin and directed more sociosexual behaviour to all partners except the opponent's kin. This study establishes the occurrence of multiple postconflict triadic affiliation in stumptailed macaques, and is the first to show that victims receive contacts from third parties in a cercopithecine species, a behaviour previously described only in chimpanzees. It also highlights the importance of analysing the different affiliative behaviours separately in postconflict situations. Otherwise, many of the patterns we report, especially those involving victims, would have been missed.
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Tomasello, M., Hare, B., & Fogleman, T. (2001). The ontogeny of gaze following in chimpanzees, Pan troglodytes, and rhesus macaques, Macaca mulatta. Anim. Behav., 61(2), 335–343.
Abstract: Primates follow the gaze direction of conspecifics to outside objects. We followed the ontogeny of this social-cognitive skill for two species: rhesus macaques and chimpanzees. In the first two experiments, using both a cross-sectional and a longitudinal design, we exposed individuals of different ages to a human looking in a specified direction. Rhesus infants first began reliably to follow the direction of this gaze at the end of the early infancy period, at about 5.5 months of age. Chimpanzees did not reliably follow human gaze until 3-4 years; this corresponds to the latter part of the late infancy period for this species. In the third experiment we exposed individuals of the same two species to a human repeatedly looking to the same location (with no special object at that location) to see if subjects would learn to ignore the looks. Only adults of the two species diminished their gaze-following behaviour over trials. This suggests that in the period between infancy and adulthood individuals of both species come to integrate their gaze-following skills with their more general social-cognitive knowledge about other animate beings and their behaviour, and so become able to deploy their gaze-following skills in a more flexible manner.
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Shettleworth, S. J. (2001). Animal cognition and animal behaviour. Anim. Behav., 61(2), 277–286.
Abstract: Cognitive processes such as perception, learning, memory and decision making play an important role in mate choice, foraging and many other behaviours. In this review, I summarize a few key ideas about animal cognition developed in a recent book (Shettleworth 1998, Cognition, Evolution and Behaviour) and briefly review some areas in which interdisciplinary research on animal cognition is currently proving especially productive. Cognition, broadly defined, includes all ways in which animals take in information through the senses, process, retain and decide to act on it. Studying animal cognition does not entail any particular position on whether or to what degree animals are conscious. Neither does it entail rejecting behaviourism in that one of the greatest challenges in studing animal cognition is to formulate clear behavioural criteria for inferring specific mental processes. Tests of whether or not apparently goal-directed behaviour is controlled by a representation of its goal, episodic-like memory in birds, and deceptive behaviour in monkeys provide examples. Functional modelling has been integrated with analyses of cognitive mechanisms in a number of areas, including studies of communication, models of how predator learning and attention affect the evolution of conspicuous and cryptic prey, tests of the relationship betweeen ecological demands on spatial cognition and brain evolution, and in research on social learning. Rather than a `new field' of cognitive ecology, such interdisciplinary research on animal cognition exemplifies a revival of interest in proximate mechanisms of behaviour.
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Kasuya, E. (2001). Mann-Whitney U test when variances are unequal. Anim. Behav., 61(6), 1247–1249.
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Gosling, L. M., & Roberts, S. C. (2001). Testing ideas about the function of scent marks in territories from spatial patterns. Anim. Behav., 62(3), F7–F10.
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Kudo, H., & Dunbar, R. I. M. (2001). Neocortex size and social network size in primates. Anim. Behav., 62(4), 711–722.
Abstract: Primates use social grooming to service coalitions and it has been suggested that these directly affect the fitness of their members by allowing them to reduce the intrinsic costs associated with living in large groups. We tested two hypotheses about the size of grooming cliques that derive from this suggestion: (1) that grooming clique size should correlate with relative neocortex size and (2) that the size of grooming cliques should be proportional to the size of the groups they have to support. Both predictions were confirmed, although we show that, in respect of neocortex size, there are as many as four statistically distinct grades within the primates (including humans). Analysis of the patterns of grooming among males and females suggested that large primate social groups often consist of a set of smaller female subgroups (in some cases, matrilinearly based coalitions) that are linked by individual males. This may be because males insert themselves into the interstices between weakly bonded female subgroups rather than because they actually hold these subunits together.
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