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It is widely believed that overcrowding promotes increased aggression in animals, although some species, such as primates, have adopted formal mechanisms that help to alleviate social tension. A study of captive rhesus monkeys under diverse population densities is presented. It is shown that increasing density caused make monkeys to increase huddling and grooming behaviour, although aggression rates did not increase. It is concluded that different patterns of responses to overcrowding may depend upon the stability and strength of relationships.

Former opponents in corral-housed pigtail macaques, Macaca nemestrina, are selectively attracted to each other after a conflict, but well estabished and newly formed groups differ regarding reconciliation. Conflicts are reconclied more often between opponents with strong affiliation. The members of well-established groups reconcile more often than those of a newly formed one. The former group distributes its affiliative behavior less evenly, and focuses on relatively smaller number of partners. This produces more intense ties which increases the chances of reconciliation after conflict.

The spatial density model suggests that aggressive response increases with an increase in spatial density, and the coping model demonstrates improved social behavior in crowded conditions. These were assessed through a short-term crowding experiment involving an established group of 61 rhesus monkeys, Macaca mulatta, crowded into a familiar area, one-fifth the size of its normal enclosure. Evidence was apparent only in part for both models, and it was observed that the monkeys had a conflict avoidance strategy. An increase in huddling and a decrease in grooming were observed among kin. Avoidance and the bared-teeth display were significant among same-sexed adult partners.

Data from three studies on two captive groups of rhesus monkeys, Macaca mulatta, were used to test a hierarchical multiple regression model of adult social organization. The model followed the literature in assuming that matrilineal kinship affects rank distance, i.e. that the rank positions of related adults are generally closer to one another than the positions of unrelated adults. Rank distance, in turn, was assumed to affect affiliative behaviour, tolerance at feeding and drinking sites, and aggression. The model was tested with matrix permutation techniques that allow dyadic variation to be taken completely into account. The results confimed that rank distance correlates with a range of social behaviour independently of the effects of kinship. Several alternative functional explanations of the role of rank distance were compared; attraction among individuals with similar ranks appeared the most explanation. The study also addressed the general applicability of a previously reported 'class' division in one of the two groups. The division could not be replicated, and may have been a temporary structural phenomenon.

IMAGINE THAT YOU'RE A WRITER AND YOU have decided to offer your readers a first-hand account of the politically correct primate, the idol of the left, known for its 'gay' [...]

The societies of monkeys and apes share common social structure, which is passed on from one generation to the next by social learning and hierarchy based on kinship. The Tibetan macaque number around 450 and have about 20 different species. Their communal relationships are one-sided, with dominant monkeys having unlimited privileges and the subordinates having almost no rights. Aside from the domination factor, they share many characteristics with stumptail societies such as excited shrieks and squeals, friendly embraces, and calls.

SCIENTISTS are supposed to study animals in a totally objective fashion, similar to the way in which we inspect a rock, or measure the circumference of a tree trunk. Emotions [...]

A purported replication by P. G. Roma, A. Silberberg, A. M. Ruggiero, and S. J. Suomi (2006) of the authors' previous study (S. F. Brosnan & F. B. M. de Waal, 2003) claims to contradict their finding that capuchin monkeys (Cebus apella) refuse to exchange with an experimenter if theft partner receives a superior reward. Roma et al. used no exchange task, however, or any other task. Roma et al. offered frustration as explanation of their findings, yet failed to statistically prove that the effect of frustration is stronger than that of inequity. They also misrepresented the dependent measure of the authors' study. Reanalysis of the authors' own data indicated no role of frustration, that is, no effect of previous experience with a superior reward. The authors conclude that Roma et al.'s study is not a replication and does not disprove the authors' findings. Keywords: inequity, inequity aversion, capuchin monkeys, Cebus apella

Tomasello et al. propose that shared intentionality is a uniquely human ability. In light of this, we discuss several cultural behaviors that seem to result from a motivation to share experiences with others, suggest evidence for coordination and collaboration among chimpanzees, and cite recent findings that counter the argument that the predominance of emulation in chimpanzees reflects a deficit in intention reading.

Tactical deception has been widely reported in primates on a functional basis, but details of behavioral mechanisms are usually unspecified. We tested a pair of chimpanzees ( Pan troglodytes) in the informed forager paradigm, in which the subordinate saw the location of hidden food and the dominant did not. We employed cross-correlations to examine temporal contingencies between chimpanzees' behavior: specifically how the direction of the subordinate's gaze and movement functioned to manipulate the dominant's searching behavior through two tactics, withholding, and misleading information. In Experiment 1, not only did the informed subordinate tend to stop walking toward a single high value food, but she also refrained from gazing toward it, thus, withholding potentially revealing cues from her searching competitor. In a second experiment, in which a moderate value food was hidden in addition to the high value food, whenever the subordinate alternated her gaze between the dominant and the moderate value food, she often paused walking for 5 s; this frequently recruited the dominant to the inferior food, functioning as a 'decoy.' The subordinate flexibly concealed and revealed gaze toward a goal, which suggests that not only can chimpanzees use visual cues to make predictions about behavior, but also that chimpanzees may understand that other individuals can exploit their gaze direction. These results substantiate descriptive reports of how chimpanzees use gaze to manipulate others, and to our knowledge are the first quantitative data to identify behavioral mechanisms of tactical deception. RESEARCH HIGHLIGHTS Cross correlations show a subordinate chimpanzee tactically deceived a dominant by not gazing toward a valuable food (withholding), and recruiting to a 'decoy' food (misleading). Chimpanzees understand that others can exploit their gaze direction. [ABSTRACT FROM AUTHOR]

Biologists believe kindness toward one's kin is a genetic investment, a way of spreading genes. A mother dog expressed an unusual sacrifice in rearing three tigers. This scenario is an example of altruism. The dog's behavior can be explained as a motivation to provide care. Animals are selfish and such behavior evolved to serve self-interest.

In 1739, the Scottish philosopher David Hume wrote: 'When any hypothesis ... is advanc'd to explain a mental operation, which is common to men and beasts, we must apply the [...]

The Simian Tongue: The Long Debate about Animal Language by Gregory Radick University of Chicago Press: 2008. 544 pp. $45 People sometimes view the scientific community through rose-coloured glasses. I [...]

Henrich et al. describe an innovative research program investigating cross-cultural differences in the selfishness axiom (in economic games) in humans, yet humans are not the only species to show such variation. Chimpanzees and capuchin monkeys show signs of deviating from the standard self-interest paradigm in experimental settings by refusing to take foods that are less valuable than those earned by conspecifics, indicating that they, too, may pay attention to relative gains. However, it is less clear whether these species also show the other-regarding preferences seen in humans.