Abstract: We describe a series of playback experiments designed to test whether free-ranging baboons, Papio cynocephalus ursinus, recognize the calls of other group members and also associate signallers with their close genetic relatives. Pairs of unrelated females were played sequences of calls that mimicked a fight between their relatives. As controls, the same females heard sequences that involved either (1) only the more dominant female's relative or (2) neither of the females' relatives. When call sequences involved their relatives, subjects looked towards the speaker for a longer duration than when the sequences involved nonkin. When the sequences involved the other female's relative, they also looked towards that female. Subjects did not look towards one another when call sequences involved nonkin. Dominant subjects were more likely to supplant their subordinate partners following playbacks of sequences that mimicked a dispute between their relatives than following the two control trials. In contrast, both subjects were more likely to approach one another and to interact in a friendly manner following the two control trials than following the test trial. Results indicate that female baboons recognize the screams and threat grunts not only of their own close relatives but also of unrelated individuals. They also replicate previous studies in suggesting that female monkeys recognize the close associates of other individuals and adjust their interactions with others according to recent events involving individuals other than themselves. Copyright 1999 The Association for the Study of Animal Behaviour.

Abstract: Complex social relationships among nonhuman primates appear to contribute to individual reproductive success. Experiments with and behavioral observations of natural populations suggest that sophisticated cognitive mechanisms may underlie primate social relationships. Similar capacities are usually less apparent in the nonsocial realm, supporting the view that at least some aspects of primate intelligence evolved to solve the challenges of interacting with conspecifics.

Abstract: In many of the studies reviewed in this book, eavesdropping takes the
following form: a subject has the opportunity to monitor, or eavesdrop upon, an
interaction between two other animals,Aand B. The subject then uses the information
obtained through these observations to assess A`s and B`s relative dominance
or attractiveness as a mate (e.g. Mennill et al., 2002; Ch. 2). For example, Oliveira
et al. (1998) found that male fighting fish Betta splendens that had witnessed two
other males involved in an aggressive interaction subsequently responded more
strongly to the loser of that interaction than the winner. Subjects-behaviour could
not have been influenced by any inherent differences between the two males, because
subjects responded equally strongly to the winner and the loser of competitive
interactions they had not observed. Similarly, Peake et al. (2001) presented
male great tits Parus major with the opportunity to monitor an apparent competitive
interaction between two strangers by simulating a singing contest using two
loudspeakers. The relative timing of the singing bouts (as measured by the degree
of overlap between the two songs) provided information about each “contestants”
relative status. Following the singing interaction, one of the “contestants” was
introduced into the male`s territory. Males responded significantly less strongly
to singers that had apparently just “lost” the interaction (see also McGregor &
Dabelsteen, 1996; Naguib et al., 1999; Ch. 2).
What information does an individual acquire when it eavesdrops on others?
In theory, an eavesdropper could acquire information of many different sorts:
about A, about B, about the relationship between A and B, or about the place of
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A`s and B`s relationship in a larger social framework. The exact information acquired
will probably reflect the particular species social structure. For example,
songbirds like great tits live in communities in which six or seven neighbours
surround each territory-holding male. Males appear to benefit from the knowledge
that certain individuals occupy specific areas (e.g. Brooks & Falls, 1975), that
competitive interactions between two different neighbours have particular outcomes,
and that these outcomes are stable over time. We would, therefore, expect
an eavesdropping great tit not only to learn that neighbour A was dominant to
neighbour B, for example, but also to form the expectation that A was likely to
defeat B in all future encounters. More speculatively, because the outcome of territorial
interactions are often site specific (reviewed by Bradbury & Vehrencamp,
1998), we would expect eavesdropping tits to learn further that A dominates B
in some areas but B dominates A in others. In contrast, the information gained
from monitoring neighbours interactions would unlikely be sufficient to allow
the eavesdropper to rank all of its neighbours in a linear dominance hierarchy,
because not all neighbouring males would come into contact with one another.
Such information would be difficult if not impossible to acquire; it might also be
of little functional value.
In contrast, species that live in large, permanent social groups have a much
greater opportunity to monitor the social interactions of many different individuals
simultaneously. Monkey species such as baboons Papio cynocephalus, for
example, typically live in groups of 80 or more individuals, which include several
matrilineal families arranged in a stable, linear dominance rank order (Silk et al.,
1999). Offspring assume ranks similar to those of their mothers, and females maintain
close bonds with their matrilineal kin throughout their lives. Cutting across
these stable long-term relationships based on rank and kinship are more transient
bonds: for example, the temporary associations formed between unrelated
females whose infants are of similar ages, and the “friendships” formed between
adult males and lactating females as an apparent adaptation against infanticide
(Palombit et al., 1997, 2001). In order to compete successfully within such groups, it
would seem advantageous for individuals to recognize who outranks whom, who
is closely bonded to whom, and who is likely to be allied to whom (Harcourt, 1988,
1992; Cheney & Seyfarth, 1990; see below). The ability to adopt a third party`s perspective
and discriminate among the social relationships that exist among others
would seem to be of great selective benefit.
In this chapter, we review evidence for eavesdropping in selected primate
species and we consider what sort of information is acquired when one individual
observes or listens in on the interactions of others. We then compare eavesdropping
by primates with eavesdropping in other animal species, focusing on both
potential differences and directions for further research

Abstract: Lactating female baboons, Papio cynocephalusoften maintain close associations with particular males. There are at least three proposed benefits of 'friendships' to females: (1) male protection against potentially infanticidal males; (2) male protection against harassment by dominant females; (3) male attachment to an infant that develops into future care of juveniles. These hypotheses were examined in a population of chacma baboons, P. c. ursinusin which male infanticide accounted for at least 38% of infant mortality. Almost all mothers of young infants formed strong bonds with one or two males with whom they had copulated during the cycle in which they conceived their infants. Females were primarily responsible for maintaining friendships during lactation, but they terminated these relationships if their infants died. In playbacks of females' screams, male friends responded more strongly than control males. They also responded more strongly to the screams of female friends than to the screams of control females. Following an infant's death, however, male friends responded less strongly than control males to the same females' screams. Finally, male friends responded more strongly than control males to playback sequences in which female screams were combined with the threat vocalizations of a potentially infanticidal alpha male, but not when female screams were combined with the threat calls of a non-infanticidal male or the alpha female. Both observations and experiments suggest that the benefits of friendships to females derive from the protection of their infants against infanticide.1997The Association for the Study of Animal Behaviour

Abstract: Many animals appear to monitor changes in other individuals' dominance ranks and social relationships and to track changes in them. However, it is not known whether they also track changes in very transient relationships. Rapid recognition of a temporary separation between a dominant male and a sexually receptive female, for example, should be adaptive in species where subordinate males use opportunistic strategies to achieve mating success. Dominant male baboons (Papio hamadryas ursinus) form sexual consortships with oestrous females that are characterized by mate guarding and close proximity. To assess whether subordinate males track temporary changes in the status of other males' consortships, we conducted playback experiments using a two-speaker paradigm. In the test condition, subjects heard the consort male's grunts played from one speaker and his consort female's copulation call played from a speaker approximately 40 m away. This sequence suggested that the male and female had temporarily separated and that the female was mating with another male. In a control trial, subjects heard another dominant male's grunts played from one speaker and the female's copulation call played from the other. In a second control trial, conducted within 24 h after the consortship had ended, subjects again heard the consort male's grunt and the female's copulation call played from separate speakers. As predicted, subjects responded strongly only in the test condition. Eavesdropping upon the temporal and spatial juxtaposition of other individuals' vocalizations may be one strategy by which male baboons achieve sneaky matings.