Julia Fischer

Baboon loud calls advertise male quality: acoustic features and their relation to rank, age, and exhaustion

Free-ranging adult male baboons give loud two-syllable ‘wahoo’ calls during dawn choruses, interactions between groups, when chasing females, and in aggressive interactions with other males. Previous research has shown that the rate and duration of these contest wahoos are correlated with a male’s competitive ability: high-ranking males call more often, call at faster rates, and call for longer bouts than do low-ranking males. Here we report that acoustic features of wahoos also reveal information about male competitive ability. High-ranking males give wahoos with higher fundamental frequencies (F0) and longer ‘hoo’ syllables. Within-subject analyses revealed that, as males fall in rank, the hoo syllables tend to shorten within a period of months. As males age and continue to fall in rank, F0 declines, hoo syllables shorten, and formant dispersion decreases. Independent of age and rank, within bouts of calling F0 declines and hoo syllables become shorter. Because wahoos are often given while males are running or leaping through trees, variation in these acoustic features may function as an indicator of a male’s stamina. The acoustic features of contest wahoos thus potentially allow listeners to assess a male’s competitive ability.

Factors Affecting Reproduction and Mortality Among Baboons in the Okavango Delta, Botswana

We present results of a 10-year study of free-ranging gray-footed chacma baboons (Papio ursinus griseipes) in the Okavango Delta of Botswana. The majority of deaths among adult females and juveniles were due to predation, while infants were more likely to die of infanticide. There were strong seasonal effects on birth and mortality, with the majority of conceptions occurring during the period of highest rainfall. Mortality due to predation and infanticide was highest during the 3-mo period when flooding was at its peak, when the group was more scattered and constrained to move along predictable routes. The reproductive parameters most likely to be associated with superior competitive ability—interbirth interval and infant growth rates—conferred a slight fitness advantage on high-ranking females. However, it was counterbalanced by the effects of infanticide and predation. Infanticide affected high- and low-ranking females more than middle-ranking females, while predation affected females of all ranks relatively equally. As a result, there were few rank-related differences in estimated female lifetime reproductive success.

Loud calls as indicators of dominance in male baboons (Papio cynocephalus ursinus)

Adult male baboons (Papio cynocephalus) give loud two-syllable wahoo calls during dawn choruses, interactions between groups, when chasing females, and in aggressive interactions with other males. These contest wahoos are acoustically different from alarm wahoos given to predators. In a study of free-ranging baboons in the Okavango Delta, Botswana, we found no significant correlations between the acoustic features of wahoos and adult male size; however, acoustic features were correlated with male dominance rank, age, and calling bout length. Here we show that other measures of calling behavior also appear to function as honest indicators of stamina and competitive ability. High-ranking males were more likely than middle- or low-ranking males to participate in wahoo bouts. They called at significantly higher rates, and their bouts were longer and contained more calls. All males were significantly more likely to participate in wahoo bouts with another male if their opponents rank was similar to their own. Bouts involving males of similar ranks were longer, contained more wahoos, and involved calling at higher rates, than other bouts. In contests between males of similar ranks, the subordinate and dominant were equally likely to end the bout, whereas in contests involving males of disparate ranks, subordinates were significantly more likely to end the bout. Bouts involving males of similar rank were significantly more likely than others to escalate and result in physical fighting.

Acoustic features of male baboon loud calls: Influences of context, age, and individuality

The acoustic structure of loud calls (wahoos) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer hoo duration, and a relatively louder hoo portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained.

Baboon responses to graded bark variants

We studied chacma baboons’, Papio cynocephalus ursinus, responses to conspecific ‘barks’ in a free-ranging population in the Okavango Delta of Botswana. These barks grade from tonal, harmonically rich calls to calls having a noisier, harsher structure. Tonal or clear barks are typically given when the signaller is at risk of losing contact with the group or when a mother and infant have become separated (‘contact barks’). The harsher variants are given in response to predators (‘alarm barks’). In both contexts, however, we also observed acoustically intermediate forms. Using the habituation–recovery method we tested whether baboons discriminated between (1) clear contact barks versus harsh alarm barks, and (2) clear contact barks versus intermediate alarm barks. Calls were selected according to the results of a discriminant function analysis conducted on a suite of acoustic parameters. In these experiments, animals showed a significant recovery of response only after playback of the harsh alarm call. We performed another set of experiments using single exemplars of clear and intermediate contact barks, or intermediate and harsh alarm barks. Animals responded only to the playback of a harsh alarm bark. Apparently, only this harsh variant was placed in a category that warranted a response. We hypothesize that baboons’ responses were to a large degree influenced by their assessment of context. uf6d9 2001 The Association for the Study of Animal Behaviour

Large anomalous Hall effect driven by a nonvanishing Berry curvature in the noncolinear antiferromagnet Mn3Ge

A large anomalous Hall effect is observed in the triangular antiferromagnet Mn3Ge arising from an intrinsic electronic Berry phase. It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)−1 at 2 K and ~50 (ohm·cm)−1 at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)−1, comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect–based data storage devices.

Functional referents and acoustic similarity revisited: the case of Barbary macaque alarm calls

Abstract. Barbary macaques (Macaca sylvanus) utter shrill barks in response to disturbances in their surroundings. In some cases, the majority of group members react by running away or climbing up a tree. In many other instances, however, group members show no overt reaction to these calls. We conducted a series of playback experiments to identify the factors underlying subjects responses. We presented calls given in response to dogs that had elicited escape responses and calls that had failed to do so. We also presented calls given in response to snakes and to the observer approaching the sleeping-trees at night. An acoustic analysis of the calls presented in the playback experiments (electronic supplementary material, audioclip S1) revealed significant differences among calls given in response to dogs, the observer approaching at night, and snakes. However, the analysis did not detect any differences between calls given in response to dogs that were related to whether or not they had elicited escape responses in the first place. Correspondingly, after playback of calls given in response to dogs, we observed no difference in subjects responses in relation to whether or not the calls had initially elicited escape responses. Subjects showed startle or escape responses significantly more often after playbacks of calls given in response to dogs than after calls given in response to observers. Playbacks of calls given in response to snakes failed to elicit specific responses such as standing bipedally or scanning the grass. Although these findings may imply that responses depend on the external referent, they also indicate that there is no clear-cut relationship between the information available to the listeners and their subsequent responses. This insight forces us to extend current approaches to identifying the meaning of animal signals.

An overview of the Barbary macaque, Macaca sylvanus, vocal repertoire

This study provides an overview of the vocalizations of Barbary macaques, Macaca sylvanus. Spectrographic displays of calls are presented along with photographs of the accompanying facial gestures. We give a general description of the contexts in which the different calls are uttered, with special regard to the age and sex of the caller. The vocal repertoire of Barbary macaques mainly consists of screams, shrill barks, geckers, low-frequency pants and grunts, with gradation occurring within and between call types. The spectrograms document that typically, Barbary macaques produce series of several consecutive calls. The influence of habitat, social structure and phylogenetic descent on the morphology of the repertoire and call diversity are discussed in comparison to other species.

Prospective object search in dogs: mixed evidence for knowledge of What and Where

We investigated whether two dogs that had been specially trained to retrieve objects by their names were able to integrate information about the identity (What) as well as the location (Where) of those objects so that they could plan their search accordingly. In a first study, two sets of objects were placed in two separate rooms and subjects were asked to retrieve the objects, one after the other. Both dogs remembered the identity of the objects as they reliably retrieved the correct objects. One of the dogs was also able to integrate information about the object’s location as he chose the correct location in which the object had been placed. Further investigation of the second dog’s behavior revealed that she followed a more stereotyped search strategy. Despite this variation in performance, this study provides evidence for the memory of What and Where in a domestic dog and shows the prospective use of such information in a search task.

A pluralistic account of word learning

How do language learners come to understand the meaning of words? This is an intriguing question that has given rise to a vast research field [1]. One smaller aspect within this research field is how novel words are mapped onto novel objects. We studied this question in a domestic dog, Rico, who had already learned the names of more than 200 toys. We found that he was able to link a novel word to a novel object on the basis of exclusion [2]. Markman and Abelev have taken a closer look at how Rico’s behavior could be accounted for ([3], this issue). Their main concern is that Rico selected the new toy among the familiar ones because of an inherent novelty preference. They also critically discuss the importance of rewarding Rico after fetching the novel toy. Finally, they note that only experiments that pit reference against associative learning (e.g. [4]) can uncover a true understanding of reference. In the following, we will briefly address these concerns.