Physical maturation and age estimates of yellow baboons,Papio cynocephalus,in Amboseli National Park,Kenya

In a longitudinal study of individually identified wild baboons in Amboseli National Park, Kenya, we collected data on physical development and reproductive maturation. Confirming and extending our earlier results, we demonstrated that the ratio of ages at which developmental milestones occur in the field as compared to those under extensive provisioning or in captivity were approximately 5:3. The age range for some developmental milestones was quite narrow and discrete, while for others there was considerable between-individual variability and more gradual changes. For infants, only the change from pink to gray of the paracallosal skin occurred within a brief age span. For older animals two important developmental events are readily identified and occur within a fairly narrow age range: Rapid enlargement of testes at 5 to 6 years for males and onset of menarche at 4 to 5 ½ years for females. In the present report, we considered some consequences of accelerated or delayed maturation. We further explored the need to employ different age-class criteria for different research problems.     

Proximate and ultimate causes of reproductive suppression among female yellow baboons at Mikumi National Park,Tanzania

Attack coalitions, whereby two or more individuals attack another animal simultaneously, were studied in 53 sexually mature female baboons from one small and two large troops at Mikumi National Park, Tanzania. For 14 months, three observers recorded coalition behavior throughout the day, using focal group sampling on a behavior-dependent basis. Coalition rates were considerably greater in the two large troops than in the small troop, and primarily involved natal females rather than males. Coalition frequencies corresponded closely to measures of reproductive synchrony, both within and between troops. Involvement in attack coalition behavior depended on the reproductive states and ranks of both attackers and recipients. The first few females to give birth in the cohort received particularly high amounts of coalition aggression just before and immediately after giving birth. Receipt of attack coalitions was significantly associated with an increased number of cycles to conception and longer interbirth intervals, as well spontaneous abortion, premature birth, and prolonged gestation. A parallel study on survivorship patterns of immature baboons at Mikumi provided evidence for ultimate cause of the observed coalition patterns. These combined results suggest that attack coalition behavior is a form of reproductive competition whereby females attempt to suppress the reproduction of others at predictably competitive times and thereby reduce the competition their own infants face from the time they are weaned.     

Activity patterns of yellow baboons (Papio cynocephalus) in the amboseli National Park,Kenya

Quantitative data on the ways in which adult yellow baboons (Papio cynocephalus) distribute their time among various activities are presented. Baboons spend approximately three-quarters of their time feeding or moving. Interseasonal variability in the proportions of time spent feeding and socializing is statistically significant, as are individual differences in the proportions of time spent feeding and moving. Although males and females spend approximately equal proportions of time in each of the activity states, the distributions of the durations of activity bouts show significant intersexual differences in central tendency and dispersion that are consistent with a model of intersexual differences in overall foraging strategies. Consistent diurnal patterns are conspicuously absent, and the relationship between this finding and other ecological variables is discussed.     

The waning of dependence in infant free-ranging yellow baboons (Papio cynocephalus) of Mikumi National Park

Development toward independence during the early years of baboon life is reflected in the infant's transition from riding on its mother to walking on its own during progressions from one location to another. This transition was studied during the first year of life in 55 infants from two differently sized troops living in Mikumi National Park, Tanzania. There was a nearly linear transition in the first year from almost 100% ventral riding to almost 100% walking. The amount of dorsal riding started near zero, reached a plateau lasting from about the 15th to the 26th wk of life, and then gradually declined to zero. Dorsal riding did not replace ventral; rather, dorsal riding increased in frequency until it occurred about as often as ventral riding. Prolonged ventral riding by infants of the smaller of the two troops may have been due to spacing differences or to greater nervousness among members of the smaller troop. There were no significant differences in riding or walking associated with the time of day or the infant's sex. The rate of transition from riding to walking was greatest from about the fifth to the seventh months, which may be especially significant time in the early development of independence.     

Sun avoidance in the yellow baboons (Papio cynocephalus cynocephalus) of Ruaha National Park, Tanzania. Variations with season, behavior and weather

Do free-ranging baboons avoid traveling towards the sun? Sun avoidance, in addition to resource and predator locations, may influence troop movement and non-random use of the home range. This paper investigates how sun avoidance, as measured by facial exposure to sunlight, influences directional choices. It hypothesizes that baboons should avoid the sun in the hot, dry season and show indifference to it in the cool, lush season. This paper also hypothesizes that baboons employ sun-avoidance behaviors more while they forage or travel to resting sites than when they travel to foraging sites or engage in active social behaviors; lastly this paper hypothesizes that sun altitude, temperature, humidity, and cloud cover influence sun-avoidance behavior. Using focal-animal techniques on 21 males from free-ranging baboon troops, I collected locational data, accurate to within 1.6 m, over 15 months. I calculated the difference between baboon bearings and the sun’s azimuth in angular degrees. Both linear and circular statistics indicate that baboons put significantly (P<0.01) more than 90° between their bearing and the sun’s azimuth under certain conditions. Contrary to hypotheses based on the detrimental effects of insolation, baboons in the cool, lush season avoid the sun, while baboons in the hot, dry season do not. In the lush season, the extent to which baboons avoid the sun does not depend on their other behaviors. Dry-season baboons demonstrate stronger sun avoidance while resting than when engaged in other behaviors. Finally, in the dry season, temperature drives sun avoidance; humidity drives it in the lush season.     

Demography of Amboseli baboons, 1963–1983

Repeated censuses of a population of yellow baboons (Papio cynocephalus) in Amboseli National Park, Kenya, revealed a decrease from over 2,500 animals in 1963–1964 to 123 individuals in 1979, or from a density of about 73 to 1.8 baboons per km² over a 15-year period. Median group size decreased from 43 in 1964 to 27 in 1979. The largest and smallest groups declined the most; groups near the median have maintained fairly stable size and age distributions. The population seemed to have stabilized by 1983 at approximately 150 animals in six groups (median group size 28; density 2.2/km²). Although baboon population and group size appeared to be stable during 1963–1964, the age distribution and demographic parameters (age-specific mortality and natality for one social group) during that year indicate that the population decline had already started. The rate of population decline was greatest in the 1964–1969 period and remained appreciable during the next 5 years. The decline of the baboon population was paralleled by that of other Amboseli savannah woodland mammalian species and took place during a period of very high mortality of fever trees (Acacia xanthophloea) and extensive invasion of the area by halophytes, a transition brought on by rising ground water and consequent elevation of the soil salinity zone. In this and several other primate populations, mortality of infants and juveniles appears to be the demographic variable most sensitive to environmental change.     

Nuclear DNA polymorphisms in a wild population of yellow baboons (Papio hamadryas cynocephalus) from Mikumi National Park,Tanzania

Yellow baboons (Papio hamadryas cynocephalus) from Mikumi National Park, Tanzania were studied for polymorphisms in nuclear DNA. The study population consists of four social groups that inhabit overlapping home ranges and exchange males. As a result, these groups are considered to be members of a single interbreeding population. Human DNA clones were used as probes to screen five loci (AT3, REN, HEXB, VIM, and APOB) for restriction fragment length polymorphisms (RFLP). A total of 14 polymorphisms, at least one at each locus, was detected in a panel of 27 baboons tested using six restriction enzymes for each locus. Eleven of these RFLP systems have average heterozygosity values greater than 0.40. This initial screening demonstrates that human DNA clones can be used to detect significant numbers of informative DNA polymorphisms in single-copy nuclear genes of this species and suggests that the average proportion of nucleotides polymorphic across nuclear loci in this population may be between 1.0% and 1.3%. © 1993 Wiley-Liss, Inc.     

Social relationships and ritualized greetings in adult male baboons (Papio cynocephalus anubis)

Greetings involving exchanges of ritualized sexual gestures are a common form of interaction among adult male baboons, although relatively little attention has been paid to them. In this study, we investigate how greetings reflect important aspects of the male's social relationships, including dominance rank, age/residence status, and cooperative tendencies. The results are based on over 600 greetings among 12 adult males recorded during a 4-month study of a troop of wild olive baboons near Gilgil, Kenya. Four of the adult males were older, lower-ranking, long-term residents, which frequently formed coalitions to take estrous females away from the eight young, higher-ranking males. Virtually all dyads greeted: greetings occurred more than twice as often as other types of male-male interactions; and nearly all greetings occurred in a neutral context, in which there was no resource at stake. The percentage of greetings completed, the frequency with which different gestures were employed, and the roles adopted by each male varied significantly across old-old, old-young, and young-young dyads. Greetings between young adult males were often interrupted or actively resisted, consistent with their unstable and ambiguous dominance relationships. Greetings between old-old dyads were usually completed and appeared consistent with their cooperative relationships. One pair of old males formed a stable, reciprocal coalition against young males, and this pair's greetings showed remarkable symmetry of roles. Greetings, we hypothesize, function to allow males to negotiate important aspects of their relationships, including cooperation.     

An electrified enclosure of 650 m2 designed for rearing baboons (Papio papio)

A system for an electrified enclosure designed for baboons is described. Live wires were alternated with grounded wires in order to increase the likelihood of electric shock if an animal tried to escape. A sinusoidal current of 50-Hz frequency, 650-V voltage, and 10 mA was used and proved to be quite efficient and not dangerous. In order to make the apparatus more reliable the electric main sources were connected to an automatic control system which monitored irregularities in the supply and switches to an emergency circuit if necessary.     

Lifetime reproductive success, longevity, and reproductive life history of female yellow baboons (Papio cynocephalus) of Mikumi National Park, Tanzania

The relationship between longevity and lifetime reproductive success (LRS) was studied in free-ranging female baboons of Mikumi National Park, Tanzania. A severe population decline occurred between the 12th and 20th years of the study. The total sample consisted of 72 females born and reaching adulthood before the start of the population decline. There were 27 females who were adult at the start of the study and 45 who became adult within the 12 years prior to the decline. The subjects were studied until all 72 were dead and all of their offspring were either dead or at least six years old; this took 24 years. The relationship of longevity to LRS was statistically significant for the total sample and for both sub-samples, with 70% of the total variance in LRS accounted for by longevity. Longevity was linked to LRS via a chain of statistically significant relationships: The longer the life span, the longer the reproductive life; the longer the reproductive life, the more offspring produced; the more offspring produced, the higher the LRS. Mean LRS, life span, and reproductive longevity all differed between the two sub-samples. Since the sub-samples were time-linked to a population decline affecting longevity, either sub-sample separately would fail to reflect the broader picture. This illustrates the importance of appreciable sample sizes from long-term studies in helping understand the dynamics between life history estimates and ecological conditions in variable environments.     

Use of females by male olive baboons (Papio anubis)

Wild male olive baboons (Papio anubis) used females and infants as agonistic buffers. Male residency status determined whether a male used females or whether they were used against him. The success of the strategy depended on the cooperation of the female and the context of the interaction. Female cooperation correlated with preexisting social affiliation with the male user. Male choice of female or infant buffers represented a compromise between the potential effectiveness of each in different situations and the social and spatial availability of females and infants. Nonreproductive social relationships may provide long-term strategic benefits to the individuals who invest in them.     

A-B-O blood groups in Kenya olive baboons (Papio anubis)

A feral population of 183 Kenyan olive baboons representing 5 troops was surveyed for salivary ABO-like antigens. Unlike previously reported populations, a high frequency of the O allele and low frequency of the B allele were detected. This observation may be the result of founder effect and/or genetic drift.     

Agonism,ranking, and the social behavior of adult male baboons

An ingrained technique in primatological analysis is to rank individual animals in a hierarchical system that is usually but not always based on the outcome of agonistic encounters. An explication of group structre and function is then sought by correlation these rankings with aspects of behavior. When the behavior of the adult males in a free-ranging troop of olive baboons is examined, ranking is found to be inadequate to represent the behavioral variability existing between individuals. The relationships maintained by these animals is analyzed, emphasizing amounts of time devoted to specific activities, and it is recommended that affiliative rather than agonistic behavior be stressed in future studies.     

Patterns of coalition formation by adult female baboons in Amboseli, Kenya

Coalitionary support in agonistic interactions is generally thought to be costly to the actor and beneficial to the recipient. Explanations for such cooperative interactions usually invoke kin selection, reciprocal altruism or mutualism. We evaluated the role of these factors and individual benefits in shaping the pattern of coalitionary activity among adult female savannah baboons, Papio cynocephalus, in Amboseli, Kenya. There is a broad consensus that, when ecological conditions favour collective defence of resources, selection favours investment in social relationships with those likely to provide coalitionary support. The primary features of social organization in female-bonded groups, including female philopatry, linear dominance hierarchies, acquisition of maternal rank and well-differentiated female relationships, are thought to be functionally linked to the existence of alliances between females. Female savannah baboons display these characteristics, but the frequency and function of their coalitionary aggression is disputed. In our five study groups, 4-6% of all disputes between females led to intervention by third parties. Adult females selectively supported close maternal kin. There was no evidence that females traded grooming for support or reciprocated support with nonkin. High-ranking females participated in coalitionary aggression most frequently, perhaps because they derived more benefits from group membership than other females did or could provide support at lower cost. Females typically supported the higher ranking of two contestants when they intervened in disputes between subordinates, so most coalitions reinforced the existing dominance hierarchy. Results indicate that female baboons participate in coalitionary aggression in a manner strongly influenced by nepotism and individual benefits.     

Insect and meat eating among infant and adult baboons (Papio cynocephalus) of Mikumi National Park, Tanzania

It has been suggested that baboon predation upon vertebrates may tend to peak in the dry season because insect food is then less available, and that males obtain animal nutrients primarily from vertebrates whereas other troop members obtain them primarily from invertebrates. The development of meat and insect eating by 22 male and 24 female infants studied for 25 months was compared with that of 18 male and 46 female adults studied for 37 months. Systematic sampling allowed quantitative comparisons between meat and insect eating, infants and adults, and males and females. Infants ate no meat, but their insect eating began early and increased steadily during the first year of life. In comparison with insect foods, meat was a minor ingredient of the adult's diet. Insect eating occurred less during dry than during rainy months, but meat eating was spread across the year. Reliable sex differences in insect eating did not occur. The findings were related to theories offered to explain the attractiveness of animal foods to primates and to the suggestion that a sex difference in predatory inclinations of hominid ancestors may have been a preadaptation underlying the eventual emergence of male hunting and female gathering.     

Aspects of the Feeding and Reproductive Biology of the Lake Tanganyikan Cichlid, Lamprologus ornatipinnis (Pisces, Cichlidae)

This project investigated the reproductive and feeding biology of Lamprologus ornatipinnis. Specimens were collected monthly from North Bay, Mbita Island, Zambia for a year. Dentition was examined under a scanning electron microscope, stomach contents were analysed using the Index of Relative Importance (IRI) and mean Gonado-somatic Indices (GSI) were calculated for each month to reveal spawning peaks. Both males and females possess an outer row of six (premaxilla) and eight (dentary) enlarged canines. The remaining inner rows consist of small, recurved canine-like teeth. The lower pharyngeal bone possesses enlarged centrally placed molars with an increasing number of smaller bevelled teeth laterally. This dentition is very similar to a typical benthic arthropod and mollusc eater. Stomach content analysis revealed that L. ornatipinnis feeds predominantly on Chironomidae, Copepoda and Ostracoda. The importance of these prey items in the diet differed significantly between the months sampled. Percentage volume of Copepoda and Cyclopoida was greater in female stomachs than males and the % number of Chironomidae greater in males than females. Gonadosomatic Index (GSI) values indicated males and females breed throughout the year. Females, however have a significant peak (p<0.05) in breeding activity from July to October that coincides with the increased abundance of plankton at this time.