Out of the mouths of baboons: stress,life history,and dental development in the Awash National Park hybrid zone,Ethiopia

The techniques of dental histology provide a method for reconstructing much of the life history of an individual, as accentuated increments visible in polarized light microscopy record incidents of physiological stress during the formation of dental tissues. Combined with counts of the normal periodic growth increments, they provide a means of reconstructing the chronology of dental development, age at death, and the ages at which stress occurs. In this study, we determine age at death and reconstruct the chronology of dental development in two male anubis baboons from Uganda and two female baboons from the Awash National Park hybrid zone. For the female baboons, we used the dates of death and rainfall records for the region to determine date of birth, ages at periods of physiological stress, dates at which these stresses occurred, and rainfall amounts for those months.Ages determined histologically for each specimen are comparable to ages estimated from dental emergence schedules and dental scores for wild baboons. Crown formation times are longer than those reported in radiographic studies of captive yellow baboons. Age at initiation of crown formation is similar to that reported for radiographic studies, but ages at completion of crown formation are consistently later. The pattern of stresses is similar in the two female baboons, suggesting that individual life history intersects with local ecology to produce a pattern of accentuated increments occurring during the weaning process and at the onset of menarche, as well as during the first postweaning dry and rainy periods.     

Group Composition and Adult Sex-ratio of Hamadryas Baboons (Papio hamadryas hamadryas) in Central Eritrea

During a survey of the geographical distribution and abundance of hamadryas baboons (Papio hamadryas hamadryas) in central Eritrea, we collected detailed demographic data on six bands at four sites in different ecogeographical zones. The proportions of age-sex classes within the six bands differed only with respect to juveniles. The general social organization of the Eritrean hamadryas baboons is similar to that reported for Ethiopia and Saudi Arabia. Eritrean hamadryas baboons live in a nested fission-fusion system, with one-male units as the basic social entity. Although the baboons were not provisioned, as they are in many places in Saudi Arabia, and habitat quality in Eritrea is lower than that in Ethiopia, sex-ratios and group composition corresponded more to those found in the Saudi Arabian population. Sex-ratios within the study population, in bands and also in one-male units were significantly more female-biased than in Ethiopian ones, and one-male units tended to be larger. Data from Eritrea suggest that these differences are due to a combination of a heavily fluctuating rainfall pattern and differential maturation of the sexes.     

Life history and the competitive environment: trajectories of growth,maturation, and reproductive output among chacma baboons

The social environment is a key feature influencing primate life histories. Chacma baboons (Papio hamadryas ursinus) are a female-bonded species with a strict linear dominance hierarchy. In this species, the allocation of energy to competing demands of growth and reproduction is hypothesized to vary as a function of competitive ability, which in turn increases with social rank. Since growth rate is a major component of life history models, measures of age-specific growth were used to analyze variation in life history traits across social ranks. Weights of 42 immature baboons were obtained without sedation or baiting from a troop of well-habituated chacma baboons in the Okavango Delta, Botswana. Using demographic and weight data from this wild population, five main findings emerged: 1) Weight for age and growth rate of infant and juvenile females are positively associated with maternal rank. 2) Male growth is not influenced by maternal rank. 3) Female growth shows smaller variation across feeding conditions than male growth. 4) Low-ranking adult females continue investment in offspring through prolonged lactation until they reach a weight comparable to that of high-ranking infants. 5) The benefit of rank to reproductive success shown in this study is 0.83 additional offspring. Reproductive span determined predominantly by age at maturation contributes 27-38% to the difference in expected number of offspring by rank, vs. 62-73% due to reproductive rate. These findings have major implications for understanding the role of social environment in phenotypic plasticity of life history traits, and in the evolution of primate life histories.     

Living on the edge: life‐history of olive baboons at Gashaka‐Gumti National Park,Nigeria

Baboons are the most successful and ubiquitous African primates, renowned for their behavioral and reproductive flexibility, which enable them to inhabit a wide variety of habitat types. Owing to a number of long‐term field studies, comparative behavioral, developmental, demographic, and life‐history data are available from several populations, but study sites show a heavy bias toward South and East African savannahs, with little research in West or Central Africa. Life‐history data from such areas are important if we are fully to understand the nature of the environmental factors that limit baboon distribution. Here, we present demographic data for olive baboons at Gashaka‐Gumti National Park (GGNP), Nigeria, collected from December 2000–February 2006, and use these data to test comparative models of baboon life‐history. The GGNP habitat, which includes large areas of rainforest, is an environment in which baboons are little studied, and rainfall is much higher than at previous study sites. GGNP troop size data are presented from censuses, as well as life‐history data for two troops, one of which is within the park and wild‐feeding (Kwano troop), whereas the other dwells at the park edge, and supplements its diet by crop‐raiding (Gamgam troop). Troop sizes at GGNP are small compared with other field sites, but fit within previously suggested ranges for baboons under these climatic conditions. Inter‐birth intervals in Kwano troop were long compared with most studied populations, and values were not as predicted by comparative models. Consistent with known effects of food enhancement, Gamgam troop experienced shorter inter‐birth intervals and lower infant mortality than Kwano troop. We indicate some possible factors that exclude baboons from true rainforest, and suggest that the clearing of forests in Central and West Africa for agricultural land may allow baboons to extend their range into regions from which they are currently excluded. Am. J. Primatol. 71:293–304, 2009. © 2009 Wiley‐Liss, Inc.     

Group housing of hamadryas baboons: a new cage design based upon field studies of social organization

The hamadryas subspecies, which is utilized extensively for laboratory research, has a social structure unique among baboons. Field studies have shown that small one male units are the basic grouping in a complex multi-level social system. A housing design for a research colony of hamadryas baboons was conceived to reflect this unique social organization and related behavioral patterns. The outcome of combining such ethological considerations with practical dictates for housing large laboratory primates has been assessed in terms of reproductive performance, animal health and utilization for research. Various benefits of this approach to cage design for hamadryas baboons are identified in this report.     

Group Composition of Guinea Baboons (<Emphasis Type="Italic">Papio papio</Emphasis>) at a Water Place Suggests a Fluid Social Organization

Baboon social systems are among the most studied in primates. Solid knowledge of the hamadryas and savannah baboon systems has accumulated, leading to a dichotomic view of baboon social systems. Hamadryas baboons live in multilayered troops based on 1-male units whereas savannah baboons live in multimale multifemale groups based on a network of related females. Less attention has been paid to their West African congenerics, the Guinea baboons, Papio papio. To fill this gap, in 2007 we initiated a long-term study of a baboon troop ranging in the Niokolo Koba National Park in southeastern Senegal. Earlier studies suggested a tendency for a multilayered social system in Guinea baboons, similar to the hamadryas baboon organization. Therefore, as a first approach to analyzing variability in party size and composition, we observed members of the troop crossing an open area from a fixed point for 3 mo during the dry and wet seasons. We counted individuals and recorded changes in composition of both arriving and departing parties. Party size and composition were highly variable on both a daily and a seasonal basis; 45.9% of the arriving parties changed in composition while crossing the open area, either splitting into smaller parties or fusing into larger ones, suggesting a fluid organization. Our data support the existence of neither a hamadryas baboon-like multilayered social organization nor a stable medium-sized multimale multifemale group as in savannah baboons. In light of our data we may need to revise the dichotomic view of baboon social systems and include space for greater variability of their social systems.     

A Papionin Multilevel Society as a Model for Hominin Social Evolution

Multilevel societies are unique in their ability to facilitate the maintenance of strong and consistent social bonds among some individuals while allowing separation among others, which may be especially important when social and sexual bonds carry significant and reliable benefits to individuals within social groups. Here we examine the importance of social and sexual bonds in the multilevel society of hamadryas baboons (Papio hamadryas) and apply these principles to social evolution in Plio-Pleistocene hominins. The behavior, adaptations, and socioecology of baboons (Papio spp.) have long been recognized as providing an important comparative sample to elucidate the processes of human evolution, and the social system of hamadryas baboons in particular shares even more similarities with humans than that of other baboons. Here we draw parallels between processes during the evolution of hamadryas social organization and those characterizing late Pliocene or early Pleistocene hominins, most likely Homo erectus. The higher costs of reproduction faced by female Homo erectus, exacerbated by an increased reliance on difficult to acquire, nutrient-dense foods, are commonly thought to have been alleviated by a strengthening of male–female bonds (via male provisioning and the evolution of monogamy) or by the assistance of older, postreproductive females (via grandmothering). We suggest that both of these social arrangements could have been present in Plio-Pleistocene hominins if we assume the development of a multilevel society such as that in hamadryas baboons. The evolution of a multilevel society thus underlies the adaptive potential for the complexity that we see in modern human social organization.     

Allocare patterns among cercopithecines

Cercopithecines show two general patterns of allocare. Many guenons permit extensive contact with young infants, while most baboons and macaques restrict early contact. Here social, ecological and life history variables among cercopithecines are examined for evidence of relationships with allocare patterns. This analysis suggests that in this group early allocare is most extensive in species with relatively relaxed social relationships among females, marked seasonal breeding and rapid rates of reproduction.     

One-male harems and female social dynamics in Guinea baboons

Little is known about the mating system and social organization of Guinea baboons. This study investigated whether Guinea baboons have a harem-based mating system similar to that of hamadryas and gelada baboons and whether one-male mating units also correspond to social units. Ten adult females in a captive multi-male multi-female group of Guinea baboons were focally observed 2 h per week for 12 weeks, and all observed copulations within the group were recorded. Some males copulated with a single female while others had harems of 2-4 females. All females copulated with a single male except 1 female that switched harems early in the study. The focal females had higher rates of social interaction with their harem members, especially their harem male, than with individuals outside the harem. Females appeared to be subordinate to the harem male but little or no physical aggression or herding behavior from the male was observed. Variation in female social interactions within the harem was not accounted for by their sexual interactions with the male or their genetic relatedness with the females. Females, however, appeared to maintain social relationships with their female relatives in other harems. Taken together, the results of this study show that both mating and affiliative interactions in Guinea baboons are concentrated within one-male units and that the social dynamics within and between these units share some similarities as well as differences with those of hamadryas and gelada baboons.     

Social factors increase fecal testosterone levels in wild male gray-cheeked mangabeys (Lophocebus albigena)

Testosterone can be expected to play a significant role in mediating behavior and life history in social animals, but the number of species with data from the wild is still too small to make generalizations. We investigated the influence of social factors (social status, aggression, and reproductive females) and environmental variation (rainfall and temperature) on fecal testosterone concentrations in wild male gray-cheeked mangabeys (Lophocebus albigena) living in five groups in Kibale National Park, Uganda. This species is phylogenetically closely related to baboons, but is arboreal, with multi-male, multi-female groups rarely exceeding 20 individuals. We analyzed 358 fecal samples from 21 adult males. We found that the highest-ranking males had the highest testosterone concentrations while immigrant males had the lowest testosterone concentrations. Aggression was not correlated with testosterone levels. The presence of females with sexual swellings at their most tumescent stage increased testosterone concentrations in all males. Finally, individuals tended to have lower testosterone when the temperature was higher.     

Life history of hamadryas baboons: Physical development,infant mortality,reproductive parameters and family relationships

Demographic and life history parameters were estimated for a band of free-ranging hamadryas baboons, observed for 5.5 years in Ethiopia. Age-related changes in body weight and dentition were found to be delayed relative to laboratory-reared baboons. On the average, females reached menarche at 4.3 years of age and had their first infant at the age of 6.1 years. The mean interbirth interval was 24 months if the infant survived this period. The survival of infants and juveniles was higher compared to Amboseli yellow baboons, but somewhat lower than in gelada baboons in the Simen Mountains. Males acquired their first juvenile or adult female at the age of 8.5 to 11 years. Male-female pair-bonds lasted several years in most cases. The Cone Rock baboons were organized in a four-level social structure. The troop could split into bands, bands were divided into clans, and clans into one-male units with bachelor followers. The exchange of individuals between social units predominantly occurred within the band. All males of known origin became adult members of their presumed natal clan. Most females transferred also within clans, and juvenile females tended to remain in their natal clan. Females lost by one male to several rivals tended to reassemble in the same new one-male units later on.     

Dominance-seeking strategies in primates: an evolutionary perspective

The thesis advanced in this paper is that there are basic social influence strategies and attendant principles that are characteristic of social primates. A model for analyzing and comparing social influence strategies in primates, with particular attention to dominance-seeking strategies, is advanced. The utility of the model is illustrated by reference to studies of social influence strategies in baboons, chimpanzees, and humans. Emphasis is placed on the role of communication as the vehicle for social competence. Speculation is offered about the importance of the evolution of symbolic communication in expanding the repertoire of dominance-seeking strategies in human primates. Paper presented at the XII Congress of the International Primatological Society, Brasilia, Brasil 24–29, July, 1988.     

Affiliation Among Females in Wild Hamadryas Baboons (Papio hamadryas hamadryas)

Previous researchers of hamadryas baboons have described a star-shaped sociogram, whereby the strongest social bonds within hamadryas one-male units are between a leader male and his females and bonds among females are weak by comparison. This type of social organization is also known as cross-bonding to distinguish it from the female-bonding found in most papionin monkeys. Models of female primate socioecology suggest that hamadryas baboons lack female bonding due to their reliance on scarce, widely-dispersed food resources. Here, I report observational data from a wild population of hamadryas baboons in Ethiopia indicating that, while females varied widely in their frequency of social interaction with other females, most females spent about as much social time with other females as they did with the leader male and some females even crossed unit boundaries to interact with one another. The size of a unit was positively correlated with the tendency of its females to interact with other females and was negatively correlated with the tendency of its females to interact with the leader male. Females were equally likely to spend social time with other females whether or not the leader male was available for social interaction at the time. Overall, this study suggests that a star-shaped sociogram does not characterize all hamadryas baboons and that female hamadryas may be, to some extent, female-bonded as well as cross-bonded. The lack of more pronounced female bonding in hamadryas is probably due to the behavior of males rather than to ecological factors.     

CLINAL VARIATION IN SEED TRAITS INFLUENCING LIFE CYCLE TIMING IN ARABIDOPSIS THALIANA

Early life‐history transitions are crucial determinants of lifetime survival and fecundity. Adaptive evolution in early life‐history traits involves a complex interplay between the developing plant and its current and future environments. We examined the plant's earliest life‐history traits, dissecting an integrated suite of pregermination processes: primary dormancy, thermal induction of secondary dormancy, and seasonal germination response. We examined genetic variation in the three processes, genetic correlations among the processes, and the scaling of germination phenology with the source populations’ climates. A spring annual life history was associated with genetic propensities toward both strong primary dormancy and heat‐induced secondary dormancy, alone or in combination. Lineages with similar proportions of winter and spring annual life history have both weak primary dormancy and weak thermal dormancy induction. A genetic bias to adopt a spring annual strategy, mediated by rapid loss of primary dormancy and high thermal dormancy induction, is associated with a climatic gradient characterized by increasing temperature in summer and rainfall in winter. This study highlights the importance of considering combinations of multiple genetically based traits along a climatic gradient as adaptive strategies differentiating annual plant life‐history strategies. Despite the genetic‐climatic cline, there is polymorphism for life‐history strategies within populations, classically interpreted as bet hedging in an unpredictable world.     

A guide to practical babooning: Historical,social, and cognitive contingency

As ecologically adaptable animals, baboons are distributed widely across Africa, and display a variety of morphological and behavioral differences that reflect both local ecology and a complex evolutionary history. As long‐lived, slowly reproducing animals, baboons face numerous ecological challenges to survival and successful reproduction. As group‐living animals, the social world presents an equally diverse array of challenges that require the negotiation of individual needs within the constraints imposed by others. Understanding how all these facets of baboon evolutionary history, life history, ecology, sociality, and cognition fit together is an enormous but engaging challenge, and despite one hundred years of study, it is clear there is a still much to learn about the various natural histories of baboons. What also is clear, however, is that an appreciation of contingency holds the key to understanding all these facets of baboon evolution and behavior. In what follows, I hope to illustrate exactly what I mean by this, highlighting along the way that history is not to be ignored, variability is information and not merely “noise”, and that behavioral and cognitive complexity can be two very different things.     

Host plant use by competing acacia-ants: mutualists monopolize while parasites share hosts

Protective ant-plant mutualisms that are exploited by non-defending parasitic ants represent prominent model systems for ecology and evolutionary biology. The mutualist Pseudomyrmex ferrugineus is an obligate plant-ant and fully depends on acacias for nesting space and food. The parasite Pseudomyrmex gracilis facultatively nests on acacias and uses host-derived food rewards but also external food sources. Integrative analyses of genetic microsatellite data, cuticular hydrocarbons and behavioral assays showed that an individual acacia might be inhabited by the workers of several P. gracilis queens, whereas one P. ferrugineus colony monopolizes one or more host trees. Despite these differences in social organization, neither of the species exhibited aggressive behavior among conspecific workers sharing a tree regardless of their relatedness. This lack of aggression corresponds to the high similarity of cuticular hydrocarbon profiles among ants living on the same tree. Host sharing by unrelated colonies, or the presence of several queens in a single colony are discussed as strategies by which parasite colonies could achieve the observed social organization. We argue that in ecological terms, the non-aggressive behavior of non-sibling P. gracilis workers--regardless of the route to achieve this social structure--enables this species to efficiently occupy and exploit a host plant. By contrast, single large and long-lived colonies of the mutualist P. ferrugineus monopolize individual host plants and defend them aggressively against invaders from other trees. Our findings highlight the necessity for using several methods in combination to fully understand how differing life history strategies affect social organization in ants.     

Evidence for varying social strategies across the day in chacma baboons

Strong social bonds can make an important contribution to individual fitness, but we still have only a limited understanding of the temporal period relevant to the adjustment of social relationships. While there is growing recognition of the importance of strong bonds that persist for years, social relationships can also vary over weeks and months, suggesting that social strategies may be optimized over shorter timescales. Using biological market theory as a framework, we explore whether temporal variation in the benefits of social relationships might be sufficient to generate daily adjustments of social strategies in wild baboons. Data on grooming, one measure of social relationships, were collected from 60 chacma baboons (Papio ursinus) across two troops over a six month period. Our analyses suggest that social strategies can show diurnal variation, with subordinates preferentially grooming more dominant individuals earlier in the day compared with later in the day. These findings indicate that group-living animals may optimize certain elements of their social strategies over relatively short time periods.     

Greeting movements among adult males in a colony of baboons:Papio hamadryas,P. cynocephalus and their hybrids

Seven greeting movements performed by four adult males belonging to a colony of baboons (Papio hamadryas, P. cynocephalus and their hybrids) were described. The hamadryas male has more number and more refined repertoire of movements than the yellow baboons, what would mean that the greeting movements possess a species-specific nature. This characteristic is expressed also by the existence of some inappropriate responses of the yellow baboons to the greeting of the hamadryas male. The differences in the greeting movements between both species would be explained as characteristic consequences of their social system organization. The hybrid male, having acquired a system organization similar to that of the hamadryas male, has acquired the same signal code, too, according to this system. The hybridization tendency would be adaptive in those colonies or troops with mixed species.     

Do human ‘life history strategies’ exist?

Interest in incorporating life history research from evolutionary biology into the human sciences has grown rapidly in recent years. Two core features of this research have the potential to prove valuable in strengthening theoretical frameworks in the health and social sciences: the idea that there is a fundamental trade-off between reproduction and health; and that environmental influences are important in determining how life histories develop. However, the literature on human life histories has increasingly travelled away from its origins in biology, and become conceptually diverse. For example, there are differences of opinion between evolutionary researchers about the extent to which behavioural traits associate with life history traits to form ‘life history strategies’. Here, I review the different approaches to human life histories from evolutionary anthropologists, developmental psychologists and personality psychologists, in order to assess the evidence for human ‘life history strategies’. While there is precedent in biology for the argument that some behavioural traits, notably risk-taking behaviour, may be linked in predictable ways with life history traits, there is little theoretical or empirical justification for including a very wide range of behavioural traits in a ‘life history strategy’. Given the potential of life history approaches to provide a powerful theoretical framework for understanding human health and behaviour, I then recommend productive ways forward for the field: 1) greater focus on the life history trade-offs which underlie proposed strategies; 2) greater precision when using the language of life history theory and life history strategies; 3) collecting more empirical data, from a diverse range of populations, on linkages between life history traits, behavioural traits and the environment, including the underlying mechanisms which generate these linkages; and 4) greater integration with the social and health sciences.