Harold Gouzoules

Rhesus monkey (Macaca mulatta) screams : representational signalling in the recruitment of agonistic aid

Abstract Free-ranging rhesus monkeys on Cayo Santiago (Puerto Rico) give five acoustically distinct scream vocalizations during agonistic encounters. These calls are thought to be an important mechanism in the recruitment of support from allies against opponents. Alliance formation during agonistic encounters is known to vary with the dominance rank and matrilineal relatedness of opponents, as well as with the severity of aggression. In contrast to previous interpretations of screams as graded signals reflecting the level of arousal of the caller, we found these calls to be much more discrete, with each of the five acoustic types significantly associated with a particular class of opponent and level of physical aggression. We performed a series of field experiments in which tape-recorded screams of immature rhesus monkeys were played to their mothers in the absence of any other information. The results suggest that the information necessary for differential responses is conveyed by the scream vocalizations themselves. We conclude that screams are representational signals that refer to external objects and events and function in the system of agonistic alliance formation.

Behavioural dominance and reproductive success in female Japanese monkeys (Macaca fuscata)

Eight years of reproductive data (including 248 births) from a translocated troop of Japanese monkeys (Macaca fuscata) living in a 42-ha enclosure provided three measures of female reproductive success: fecundity, survival of infants to 1 year of age, and age at first parturition. No significant relationship was found between social dominance and these measures. Social dominance was considered with respect to both matrilineal and individual female rank. Additional data on female dominance ranks over four generations of adult females revealed no significant concordance over time. The finding that ranks may not be stable over the lifetime of a female is a significant one because the variation in reproductive success among the females of a group is likely to be further diminished by any instability. For 34 females that were adults for the 8-year period considered, there was no significant correlation between the average rank of a female and either fecundity or survivorship of infants to 1 year of age. These data considered along with the results of other studies of female dominance and reproduction suggest that any effect of female social dominance on reproductive success is probably dependent upon resource availability, with significant benefits accruing to high-ranking individuals only during subsistence periods. It is suggested that dominance competition among female macaques may be a behavioural strategy with a variable payoff.

Lifetime Reproductive Success in Female Japanese Macaques

Lifetime reproductive success, measured by the number of offspring surviving to age five, varied from 0 to 10 in a group of 33 provisioned female Japanese macaques. Of the three contributors to reproductive success, the number of reproductive years, fecundity per year and survivorship of offspring to reproductive age, the first accounted for two-thirds of the variation. Fecundity per year and survivorship were negatively correlated, indicating reproductive costs of reducing interbirth interval. No other demographic measure used, nor the behavioral measure dominance rank, significantly correlated with lifetime reproductive success or its components. Age-specific changes in fecundity and infant survival were not found for this sample, neither could cessation of reproduction, even in very old females, be demonstrated.

Audience effects on food calls in captive brown capuchin monkeys, Cebus apella

Brown capuchins give distinct calls upon encountering food. Based on studies on other species that point at divisibility of food and audience as critical variables, we predicted that capuchins would adjust their food calling for both the amount of food and the nature of their audience. We predicted that the food-associated call serves to attract conspecifics in certain conditions. Twelve female capuchins were tested in two food-quantity conditions (large and small) and four audience conditions with a control (higher-ranking female, lower-ranking female, high-ranking male, entire group and alone). All subjects called more for larger than smaller amounts and the highest-ranking females called less than others. Subjects called more in the presence of a group than for any other audience, and this applied most strikingly to high-ranking subjects. This result may be related to the presence of kin rather than group size. We also analysed the acoustic parameters of the calls, predicting that, under conditions where call production rose, those acoustic variables associated with heightened arousal would rise in value. However, call production and those acoustic features were not always correlated. These results suggest that food calls in this species do not solely reflect arousal caused by food and are influenced by multiple audience effects.

Population dynamics of Arashiyama west Japanese macaques

Demographic data have been collected on the Arashiyama Japanese macaque population from 1954 until the present, through the fissioning of the original group into two parts in 1966, and through the translocation of one of the two groups to Texas in 1972. Population dynamics are reported for the Arashiyama West group in Texas during 1972 to 1979 and then compared to data from Japan. After a short period of adjustment for the translocated group, during which time natality rates were relatively low and mortality rates were relatively high, many aspects of population structure, birth rates, and survivorship showed trends similar to those observed in Japan. This suggests that both long-term homeostatic processes and shorter-term responses to environmental fluctuations are significant to the study of nonhuman primate demography.

Japanese monkey group translocation: Effects on seasonal breeding

A 150-member troop of Japanese monkeys (Macaca fuscata)was translocated from its temperate native habitat, near Kyoto, Japan, to a 42-ha enclosure near Laredo, Texas, in February 1972. The seasonal timing and distribution of 430 births recorded over the period 1954–1971 were compared to those of 186 births recorded in Texas from 1973 to 1979. Despite striking climatological and environmental differences between the pre- and the postranslocation sites, the timing of the birth season remaines unchanged, although the distribution of births was altered. These findings, considered in light of other published data on the seasonality of mating in macaques, suggest that a phenomenon akin to social drift may account for much of the intertroop variation that occurs.

Why macaque screams differ

Screams of four species of macaques (Macaca mulatta, M. nemestrina, M. nigra, M. arctoides) were compared for similarities and differences with respect to predictions of Morton’s motivation‐structural rules [Morton, Am. Nat. 111, 855–869 (1977)]. Screams from victims of attack that involved contact aggression (pulling, pushing, slapping, grappling, and biting) from a higher‐ranking opponent were examined. For each species, 100 screams from females three years of age or older were digitized and acoustic features of each call measured. Discriminant function analysis was used to determine whether or not the 400 vocalizations could be assigned to the correct caller species on the basis of their acoustic structure. Calls were assigned to the correct species at a significantly higher rate (93.5%) than expected by chance. Each of the four macaque species used acoustically distinct screams in a shared context. While the differences in the species’ vocalizations suggest no simple correlation between immediate cont...

Primate communication. Edited by Charles T. Snowdon, Charles H. Brown, and Michael R. Petersen

This volume grew from a symposium on primate communication at the VIIIth Congress of the International Primatoiogical Society, held in Parma, Italy, in 1980. Its authors deal with diverse communication modalities from a variety of research perspectives, ranging over evolutionary, ecological, ontogenetic, psychophysical, perceptual, cognitive, and social questions. Of the 16 chapters, 11 deal with vocal behavior, reflecting the recent rapid advances in this area of communication research. In some chapters, techniques and methodology outshine their practical application to date. Gautier and Gautier-Hions use of radiotelemetry to obtain a complete and remarkably high-quality vocal record from a captive mixed-taxa Cercopithecus group yield 3855 calls in only 129 minutes. While the benefits of recording each individual on a different channel are elegantly demonstrated, some of the questions considered by the authors require a broader data base than was available. For example, it is doubtful that from so brief a study any real insight into the ontogeny of vocal repertoire usage can be gained. In another chapter, Jurgens employs a sophisticated neurcethological approach to classifying squirrel monkey vocalizations, allowing animals implanted with intracerebral electrodes to control callinducing electrostimulation, but the research is designed on the assumption that vocalizations are merely expressions of specific emotional states, a view not shared by all other contributors. Working with the same species, Smith and her colleagues report that squirrel monkey chuck vocalizations appear to communicate about affiliative relationships, implying cognitive as well as affective substrates. Several contributors suggest that the natural communication systems of nonhuman primates are far more complex than previously thought.