Showing papers in "Primates in 2003"
TL;DR: Comparison of long-term changes in group composition and individual movements between ELGs in Kahuzi and MGs in the Virungas suggest that the occurrence of infanticide may promote kin-male association within a group.
Abstract: We analysed intra-specific variation in the social organization of gorillas and ecological and social factors influencing them, based on recent data on diet, day journey length, home range size, group size and proportion of multi-male groups in three subspecies [western lowland gorillas (WLG); eastern lowland gorillas (ELG); mountain gorillas (MG)]. Median group size was similar across subspecies and across habitats, but the extraordinarily large group including >30 gorillas was only found in habitat with dense terrestrial herbaceous vegetation. Within-group competition may determine the upper limit of group size in frugivorous WLGs and ELGs in lowland habitats with scarce undergrowth. A frugivorous diet may be a causal factor of subgrouping in multi-male groups of WLGs and ELGs, while a folivorous diet may prevent subgrouping in multi-male groups of MGs. Social factors, rather than ecological factors, may play an important role in the formation of multi-male groups and their cohesiveness in MGs. High gregariousness of female gorillas and their prolonged association with a protector male are explained by their vulnerability to both infanticide (MGs) and predators (ELGs). Comparison of long-term changes in group composition and individual movements between ELGs in Kahuzi and MGs in the Virungas suggest that the occurrence of infanticide may promote kin-male association within a group. Threat of infanticide may stimulate MG females to transfer into multi-male groups to seek reliable protection and maturing MG males to stay in their natal groups after maturity. By contrast, the absence of infanticide may facilitate ELG females to associate with infants and other females at transfer and ELG males to establish large groups in a short period by taking females from their natal groups, by luring females from neighbouring groups, or by takeover of a widow group after the death of its leading male. These conditions may prevent ELG and WLG maturing males from remaining to reproduce in their natal groups and possibly result in a rare occurrence of multi-male groups in their habitats. Similar reproductive features of MG and ELG females suggest both female strategies have been adaptive in their evolutionary history.
133 citations
TL;DR: The occurrence of lethal coalitional attacks in a species lacking fission–fusion social organization poses a challenge to the more specific version of the imbalance-of-power hypothesis proposed by Manson and Wrangham in 1991 to explain chimpanzee and human intergroup aggression.
Abstract: During 12 years of observation, we have observed three confirmed and two inferred lethal coalitionary attacks on adult male white-faced capuchins (Cebus capucinus) by members of two habituated social groups at Lomas Barbudal Biological Reserve, Costa Rica. In one case, an alpha male was badly wounded and evicted from his group, and when later found by his former groupmates he was attacked by several of them and died less than 24 h later. In two other cases, lone extra-group males were mobbed by adult and immature males of a bisexual group. One victim's abdomen was torn open and he died less than 24 h later. A second victim was quite badly bitten but may have escaped. The fourth and fifth cases resulted from intergroup encounters. One victim lost the use of both arms but may have survived, whereas the other died of unknown causes within an hour of the attack. The observed death rate from coalitionary aggression at our site is approximately the same as that reported for eastern chimpanzees. Because at least three of the five observed incidents involved large coalitions attacking lone victims, they support the general hypothesis that imbalances of power contribute to intraspecific killing in primates. However, the occurrence of lethal coalitional attacks in a species lacking fission–fusion social organization poses a challenge to the more specific version of the imbalance-of-power hypothesis proposed by Manson and Wrangham in 1991 to explain chimpanzee and human intergroup aggression.
107 citations
TL;DR: Altitudinal variations in availability of seed/fruit foods seem to have influenced the altitudinal variation in diet, and Japanese macaques relied on seed/fruits heavily in the lower zone for a longer period than in the higher zones.
Abstract: Altitudinal and seasonal variations in the diet of Japanese macaques in Yakushima, southwestern Japan, were studied for 2 years by means of fecal analysis. The altitudinal range of fecal samples collected was 30 m to 1,203 m above sea level, and it was divided into three zones: low-zone forest (0–399 m), middle-zone forest (400–799 m), and high-zone forest (800 m–1,230 m). There was a considerable altitudinal and seasonal variation in the macaques' diet. Seed/fruit and animal matter were eaten more in the lower zones, whereas more fiber and fungi were consumed in the higher zones. In all of the zones, they ate seed/fruits the most in autumn (September–November) and the least in spring (March–April). They ate fibrous food the most in spring and the least in autumn. Macaques relied on seed/fruits heavily in the lower zone for a longer period than in the higher zones. Macaques in the high-zone forest ate almost no seed/fruit foods from March to May. Altitudinal variations in availability of seed/fruit foods seem to have influenced the altitudinal variations in diet. Total basal area of seed/fruit-food trees, species richness of seed/fruit-foods, main seed/fruit-food types available, and annual fleshy-fruit production all decreased with increasing altitude. Both interannual variation and annual cyclicity of diet were found in all zones.
106 citations
TL;DR: The chimpanzee correctly chose her own pictures in response to her vocalizations only by exclusion, and she did not show vocal self-recognition.
Abstract: Identification of vocalizers was examined using an auditory-visual matching-to-sample task with a female chimpanzee. She succeeded in selecting the picture of the vocalizer in response to various types of vocalizations: pant hoots, pant grunts, and screams. When pant hoots by two chimpanzees were presented as a "duet", she could identify both of the vocalizers. These results suggest that researchers have underestimated the capability of vocalizer identification in chimpanzees. The chimpanzee correctly chose her own pictures in response to her vocalizations only by exclusion, and she did not show vocal self-recognition. The effect of acoustical modification (pitch shift and filtration) on the performance suggested that pitch is an important cue for the vocalizer identification.
99 citations
TL;DR: The hypothesis that juveniles are more vulnerable to starvation than adults was not supported among male Japanese macaques in predator-free Yakushima because the age difference in daily food intake was smaller than expected from metabolic demands.
Abstract: Age differences in food intake and dietary selection were studied for 8 months among wild male Japanese macaques (Macaca fuscata) under non-predatory situations. Juveniles' feeding time was longer than adult males' in some months, in particular in mating seasons, but did not differ in the other months. Juveniles' feeding speed was slower than that of adult males. However, the age difference in average feeding speed was smaller (90%) than that in expected daily energy expenditure (62–58%). The extent of age difference in feeding speed varied with the food type: the difference was large for fibrous foods, but small for fruits or seeds. As a consequence of the age differences in time spent feeding and feeding speed, the age difference in daily food intake was smaller than expected from metabolic demands. Thus, the hypothesis that juveniles are more vulnerable to starvation than adults was not supported among male Japanese macaques in predator-free Yakushima. Juveniles ate more animal matter, while adult males ate more fibrous foods.
75 citations
TL;DR: Study of party size and party composition in wild long-haired spider monkeys found that overall party size was larger in the fruit-abundant season and that for males, party formation may facilitate the defense of resources from neighboring groups more than provide predation avoidance.
Abstract: Spider monkeys exhibit a fission-fusion type of social organization I studied party size and party composition in wild long-haired spider monkeys (Ateles belzebuth belzebuth) in three study periods at La Macarena, Colombia and found that overall party size was larger in the fruit-abundant season Mean party size in which males were observed was relatively stable across seasons In contrast, the mean party size of females varied Females were observed in larger parties in the fruit-abundant season than in the fruit-scarce season Moreover, whereas males associated with each other at an almost equal frequency across seasons, females associated with each other more frequently in the fruit-abundant season Females with infants or small juveniles were more often in association with other individuals than were cycling females The intensity of individual relationships varied according to season, such that even mothers and sons were not always strongly associated In a large party, females with infants may gain from predation avoidance but they are at a disadvantage in terms of scramble competition The balance between these factors may change with fruit availability and may influence party size in different periods For males, party formation may facilitate the defense of resources from neighboring groups more than provide predation avoidance
75 citations
TL;DR: Phalanges of the KNM-BG 35250 Nacholapithecus kerioi skeleton from the Middle Miocene of Kenya are described to suggest positional modes supporting more weight on the forelimb, and which occur more frequently on vertical supports, which cannot be incorporated into this dichotomy.
Abstract: We describe phalanges of the KNM-BG 35250 Nacholapithecus kerioi skeleton from the Middle Miocene of Kenya. Phalanges of N. kerioi display similarities to those of Proconsul heseloni despite their enhanced robusticity. They do not show highly specialized features as in living suspensory primates. However, N. kerioi manifests several distinctive features that are observed in neither living arboreal quadrupeds nor P. heseloni or P. nyanzae. The most remarkable of them is its phalangeal elongation. N. kerioi phalanges (particularly pedal) are as long as those of Pan despite its much smaller body size. While lengthened digits enable a secure grip of supports and are especially adaptive for grasping large vertical trunks, the skeletal and soft tissues are subjected to greater stress. Probably, strong selective pressures favored powerful hallucal/pollical assisted grips. Although this functional adaptation does not exclude the possible use of the terrestrial environment, arboreal behavioral modes must have been crucial in its positional repertoire. N. kerioi is distinguished from P. heseloni in the greater size of its manual phalanges over its pedal phalanges. These derived features of N. kerioi suggest positional modes supporting more weight on the forelimb, and which occur more frequently on vertical supports. If Proconsul is referred to as an "above-branch arboreal quadruped" with a deliberate and effective climbing capability, N. kerioi may be thought of as an "orthograde climber". While living apes are powerful orthograde climbers, they are also more or less suspensory specialists. Suspensory behavior (plus climbing) and pronograde quadrupedalism (plus climbing) are the two main arboreal behavioral adaptations in living anthropoids. Thus, N. kerioi is an unusual fossil primate in that it cannot be incorporated into this dichotomy. It is plausible that a N. kerioi-like orthograde climber with large forelimbs and cheiridia was a precursor of suspensory living apes, and N. kerioi may demonstrate what an initial hominoid of this grade might have looked like.
65 citations
TL;DR: The hypothesis that (1) the monthly fruit abundance affects the monthly party size in the sites where the fruit availability is as low as to limit the party size during a major part of a year, while (2) the party Size does not increase with the increase in the monthly Fruit abundance, but is affected by other social factors, in the Sites where the minimum of Monthly Fruit abundance is high enough for chimpanzees to form parties of an adequate size is proposed.
Abstract: We examined the relationship between fruit abundance and chimpanzee (Pan troglodytes) party size by comparing data from four study sites: the Kalinzu Forest Reserve, Uganda, the Djinji Camp and Guga Camp in the Ndoki Forest, Congo, and Kahuzi-Biega National Park, Democratic Republic of Congo. Although the difference in the fruit abundance between the sites was responsible for the difference in the party size between the sites, the seasonal changes in fruit abundance did not explain the changes in the party size in each study site. Across the four study sites, there were significant correlations of the mean and minimum of monthly party size with the mean of monthly fruiting-tree density, and a significant correlation of the maximum of monthly party sizes with the minimum of monthly fruiting-tree density. We proposed a hypothesis that (1) the monthly fruit abundance affects the monthly party size in the sites where the fruit availability is as low as to limit the party size during a major part of a year, while (2) the party size does not increase with the increase in the monthly fruit abundance, but is affected by other social factors, in the sites where the minimum of monthly fruit abundance is high enough for chimpanzees to form parties of an adequate size.
64 citations
TL;DR: Japanese macaques leap shorter distances at a time than do long-tailed macaques, which indicates that body size may be related to leaping distance more than the frequency of leaping and the distance covered by leaping.
Abstract: Positional behavior was quantitatively studied in identified free-ranging Japanese macaques (Macaca fuscata). Five male and 11 female adults were observed in a forested mountain habitat. Data were analyzed for proportion of bout distance, number and time of each locomotion and postural type. Japanese macaques are semiterrestrial, and mainly walk and run quadrupedally. This supports the notion that Macaca are generally quadrupeds. Sex differences in positional behavior were found in the preference of substrate and types of positional behavior. Males and females tend to be terrestrial and arboreal, respectively. Males leap more frequently and longer in distance than do females when they are feeding in trees. These sex differences are considered to be related to differences in morphology, food choice, social activity, and the nursing of infants. Frequencies of leaping and the distance covered by leaping in Japanese macaques are more than those of long-tailed macaques which are arboreal quadrupeds. However, Japanese macaques leap shorter distances at a time than do long-tailed macaques, which indicates that body size may be related to leaping distance more than the frequency of leaping and the distance covered by leaping. Japanese macaques are not as specialized for terrestrial locomotion as pig-tailed macaques. They use both terrestrial and arboreal supports, and are considered to be semi-terrestrial quadrupeds, somewhere between the arboreal long-tailed macaque and the terrestrial pig-tailed macaque.
63 citations
TL;DR: Environmental related differences in annual rhythms between closely related small nocturnal lemurs emerged that allow them to cope with contrasting patterns of seasonal changes in their habitats.
Abstract: To investigate for the first time the relationship between contrasting patterns of seasonal changes of the environment and activity, body mass and reproduction for small nocturnal primates in nature, we compared a population of golden brown mouse lemur (Microcebus ravelobensis) in a dry deciduous forest of northwestern Madagascar and of the brown mouse lemur (Microcebus rufus) in an evergreen rain forest of eastern Madagascar. Both species live under similar photoperiodic conditions. Golden brown mouse lemurs (GBML) were active during the whole period (May to December) irrespective of changing environmental conditions. In contrast, a part of the population of brown mouse lemurs (BML) showed prolonged seasonal torpor, related to body mass during periods of short day length and low ambient temperatures. Differences between species might be due to differences in ambient temperature and food supply. Body weight and tail thickness (adipose tissue reserve) did not show prominent differences between short and long photoperiods in GBML, whereas both differ significantly in BML, suggesting species-specific differences in the photoperiodically driven control of metabolism. Both species showed a seasonal reproduction. The rate of growth and size of the testes were similar and preceded estrous onset in both species suggesting a photoperiodic control of reproduction in males. The estrous onset in females occurred earlier in GBML than in BML. Estrous females were observed over at least 4 months in the former, but in only 1 month in the latter species. Intraspecific variation of estrous onset in GBML may be explained by body mass. Interspecific variation of female reproduction indicates species-specific differences in the control of reproduction. Thus, environmentally related differences in annual rhythms between closely related small nocturnal lemurs emerged that allow them to cope with contrasting patterns of seasonal changes in their habitats.
62 citations
TL;DR: The anatomy of the hyo-laryngeal complex was examined in various species of anthropoids to compare the configuration, the shape of the basihyal and thyroid cartilage, and the length of the lateral thyrohyoid ligaments, which hypothesized that the descent of the larynx evolved in two steps.
Abstract: The descent of the larynx is a key phenomenon not only in postnatal development, but also in the evolution of human speech. The positional change of the larynx is affected by the descent of the hyoid bone in relation to the mandible and cranial base, and that of the laryngeal framework in relation to the hyoid bone. The phylogeny of the spatial configuration of the hyo-laryngeal complex is one of the most important sources of information for elucidating the evolution of laryngeal descent. In the present study, the anatomy of the complex was examined in various species of anthropoids to compare the configuration, the shape of the basihyal and thyroid cartilage, and the length of the lateral thyrohyoid ligaments. Non-human hominoids share most features with humans, while cercopithecoids and ceboids have anatomical features that sharply contrast to humans, except for the form of the thyroid cartilage in ceboids. The laryngeal framework in hominoids is well separated from and assured of mobility independent of the hyoid. In cercopithecoids and ceboids, it is, by contrast, locked into and tied tightly with the hyoid so that the hyo-laryngeal complex acts as a functional unit. This spatial configuration is considered to be significantly related to the mechanism that prevents aspiration, including epiglottic movement and vestibular closure. Non-human hominoids are inferred to share the mechanism with human adults, not with cercopithecoids and ceboids, although their larynx is located as high as the latter. Consequently, it is hypothesized that the descent of the larynx evolved in two steps. The first step would have been descent of the thyroid in relation to the hyoid for the evolution of the mechanism preventing aspiration, which occurred in the common ancestor of hominoids. The second step, descent of the hyoid within the neck, occurred during hominid evolution for human speech.
TL;DR: Preliminary data on the consumption of tannin-rich plants by sifakas living in the Kirindy forest, western Madagascar suggests that an increase in tannIn ingestion may be a self-medicating behavior with multiple directly adaptive benefits to female reproduction.
Abstract: In this study we report preliminary data on the consumption of tannin-rich plants by sifakas (Propithecus verreauxi verreauxi) living in the Kirindy forest, western Madagascar. Sifakas spent most of their time feeding on only a few plant species. The tannin intake during the period between the pregnancy and birth season was significantly higher in pregnant females or females with lactating infants than in non-reproductive females and males. These periparturient females secured a larger proportion of condensed tannins by short feeding bouts on plants not included in the group's limited preferred food species. The measured increase in tannin intake is puzzling in light of the fact that tannins are commonly known for their protein-binding properties. Since protein demands are highest in pregnant and lactating females, possible medicinal benefits of tannin ingestion are considered. Tannin consumption is associated with an increase in body weight and stimulation of milk secretion. Veterinarians administer tannins as an astringent, anti-hemorrhagic and anti-abortive. Their high potential as an alternative anthelminthic has also recently been recognized. Thus, when viewed as self-medicating behavior, controlled increase in tannin intake could have multiple prophylactic advantages for females during the periparturient period. The high selectivity in their plant choice, and the presence of unusual feeding habits by a particular group of individuals (females with infants) limited in time (birth season), suggests that an increase in tannin ingestion may be a self-medicating behavior with multiple directly adaptive benefits to female reproduction.
TL;DR: The vocal data in this study provide evidence of at least three acoustic forms of galago within the Allen's group which are predicted to represent three distinct species.
Abstract: This study identifies populations currently classified as Allen's galago (Galago alleni) at ten locations in Gabon, Cameroon and Bioko Island. Morphological diversity was evident both within and between populations. Attention to the loud calls revealed three distinct vocal profiles which are consistent within biogeographical regions. This work is based on the Recognition Concept of Species which refers to a Specific Mate Recognition System. Galagos rely less on visual signals than diurnal primates and recognise each other principally by means of auditory and olfactory signals. Galagos possess repertoires of loud calls relating to contact and alarm which are thought to be species-specific. Other studies of nocturnal prosimians (galagos, tarsiers) have demonstrated that the unique loud call repertoires are reliable indicators of species boundaries; whereas characters such as body size and pelage coloration are highly variable, even within populations. The vocal data in this study provide evidence of at least three acoustic forms of galago within the Allen's group which are predicted to represent three distinct species: the Allen's form on Bioko Island and south-west Cameroon, the Gabon form in southern Cameroon and northern Gabon and the Makande form in Gabon south of the Ogooue river. Some populations may be vulnerable to extinction due to limited distributions and habitat destruction.
TL;DR: The results suggest that the chimpanzees showed visual preference for the photographs of humans over those of their own species, and that the degree of this visual preference was not in accordance with phylogenetic distance from the subjects' species, chimpanzees.
Abstract: With a free-choice task, visual preference was estimated in five adult chimpanzees (Pan troglodytes). The subjects were presented with digitized color photographs of various species of primates on a CRT screen. Their touching responses to the photographs were reinforced by food reward irrespective of which photographs they touched. The results revealed that all chimpanzees touched the photographs of humans significantly more than any other species, or phylogenetic families of primates. This tendency was consistent across different stimulus sets. The results suggest that the chimpanzees showed visual preference for the photographs of humans over those of their own species. The results also suggest that the degree of this visual preference was not in accordance with phylogenetic distance from the subjects' species, chimpanzees. The preference for humans was stronger in the case of the colored photographs than in monochromatic ones. All of the five chimpanzees had been in captivity for at least 16 years. They were reared by humans from just after their birth, or at least from 1.5 years old. Their preference might have developed through social experience, especially that during infanthood.
TL;DR: A detailed endocranial cast of the olfactory bulb of Amphipithecus mogaungensis was studied in comparison with some Paleogene primates, finding that the location and bilobed form are more similar to those of omomyoids than of adapiforms.
Abstract: A detailed endocranial cast of the olfactory bulb of Amphipithecus mogaungensis, a latest middle Eocene primate from the Pondaung Formation (Myanmar), was studied in comparison with some Paleogene primates, the olfactory bulb of which has been reported The olfactory bulb of Amphipithecus is located just anterior to the postorbital constriction, that is, within the interorbital septum It is relatively large and pedunculate, not overlapped by the frontal lobe, and consists of two parallell aligned bodies The relative volume of the olfactory bulb shows the same pattern as in adapiforms, but the location and bilobed form are more similar to those of omomyoids than of adapiforms
TL;DR: Findings were consistent with Charnov's theoretical model of mammalian life-history evolution in that patas with high adult and juvenile mortality showed early and frequent reproduction in spite of large body size.
Abstract: Based on long-term, although intermittent, observations (2 years 4 months of 14 years), we present data on birth seasonality, age at first birth, interbirth intervals, mortality rates, age at first emigration, and population change of a wild population of West African patas monkeys ( Etythrocebus patas patas) in northern Cameroon. Birth season was from the end of December until the middle of February, corresponding to the mid-dry season. In spite of large body size, the patas females had the earliest age at first birth (36.5 monthsold) and the shortest interbirth intervals (12 months) compared to the closely related wild forest guenons. Age at first emigration of the males was considered to occur between 2.5 and 4.5 years. The group size of the focal group drastically decreased between 1984 and 1987, and steadily increased until 1994, then decreased again in 1997. The neighboring group also showed a similar trend in group size. The population decreases were likely to be caused by drought over 3 years. Annual crude adult mortality rate was 4% during population increase periods (PIP) between 1987 and 1994. It rose to 22% during all the periods (AP), including drought over 3 years. Despite their smaller body size, the rate of the wild forest guenons ( Cercopithecus mitis) (4%) was the same and much lower than those of the patas during PIP and AP, respectively. The annual average juvenile mortality rate was 13% during PIP and it also rose to 37% during AP. That of wild forest guenons ( C. ascanius) (10-12%) was a little lower and much lower than those of the patas during PIP and AP, respectively. These findings were consistent with Charnov's theoretical model of mammalian life-history evolution in that patas with high adult and juvenile mortality showed early and frequent reproduction in spite of large body size. Charnov also considered high adult mortality as a selective force and high juvenile mortality as a density-dependent consequence of high fecundity. Our results support the former but not the latter research findings.
TL;DR: This article investigated the ability of three chimpanzees and three orangutans to track the position of a reward after a series of displacements, where the reward was placed under one of two opaque containers resting on a platform.
Abstract: This study investigated the ability of three chimpanzees and three orangutans to track the position of a reward after a series of displacements. The reward was placed under one of two opaque containers resting on a platform. Experiment 1 investigated rotational displacements in which the platform was rotated 0°, 180°, or 360°. Experiment 2 investigated transpositional displacements in which the platform remained stationary while the containers either remained stationary, or swapped their positions (in a one- two- or three-step sequence). In both experiments, the initial position of the reward was indicated either by directly showing the reward under the containers, or by placing a landmark, which had been previously associated with the reward, on top of the baited container. Subjects successfully tracked the reward through rotations and transpositions when they had seen it, but their performance substantially deteriorated when the landmark indicated the reward's initial position, even though subjects successfully used the landmark to find the reward in the absence of displacements. This decrease was especially pronounced in rotational displacements. A language-trained orangutan outperformed all the other apes and solved all problems.
TL;DR: Results indicate that with increasing age females are more likely to concentrate on related females when they have grooming interactions with other females, and this tendency seems to be more apparent for low-ranking females.
Abstract: The present study investigated the influence of dominance rank in combination with kinship on age-related differences in social grooming among adult females in a free-ranging group of Japanese monkeys (Macaca fuscata). Eighty-three adult females were divided into six sub-groups according to age-class (younger: 5–9 years old; middle: 10–14 years old; older: 15–22 years old) and dominance rank (high and low rank). The ratio of the number of unrelated females that each female groomed to the total number of available unrelated females and grooming bouts which she gave to unrelated females decreased with increasing age for both high- and low-ranking females, whereas age did not appear to affect corresponding values for related females. On the other hand, compared with low-ranking females, high-ranking females of all age-classes received grooming more often from a larger number of unrelated females. Moreover, older females of low rank received grooming less often from a smaller number of unrelated females than younger females of low rank. These results indicate that with increasing age females are more likely to concentrate on related females when they have grooming interactions with other females. This tendency seems to be more apparent for low-ranking females. Moreover, the present findings also indicate that older high-ranking females could maintain their social attractiveness as high as younger high-ranking females.
TL;DR: A new confirmed case and one suspected case of infanticide, as well as one case of abortion at the time of male leader change, are described in the new gelada baboon population in Arsi.
Abstract: In 1989 a new gelada baboon (Theropithecus gelada) population was found in Arsi, on the opposite side of the Rift Valley to that of the known gelada populations of Semien and Showa. Previous comparisons of units of the band at Gado Goro, Arsi, in the same season in consecutive years, indicated that unit structure is less stable among Arsi geladas as compared to the Semien population. Gelada units of the band at Gado-Goro were studied for 7 months in order to investigate the processes of social changes. Changes in unit structure were observed. Provisioning was carried out for 1.5 months at the beginning of the 7-month study period, in order to capture and obtain blood samples from the geladas. Following this, changes in male leadership of some units were observed, presumably as a consequence of the capture. However, natural changes also occurred. One change in unit structure occurred after a female gave birth, and changes in another unit occurred after the disappearance of the leader male. These changes involved female desertion of a unit, her subsequent transfer to a male unit, and culminated in the formation of a unit consisting of one female and one male. One successful and one attempted case of unification of units, and one case of change of a unit leader male are reported. These changes occurred among eight resident units in a period of 7 months (196 female months). Though the types of social changes were not much different from previous observations in Semien National Park, their frequencies seemed to be much higher. The characteristics of Arsi gelada social changes are proposed to be related to the small size of the units. We also describe a new confirmed case and one suspected case of infanticide, as well as one case of abortion at the time of male leader change.
TL;DR: This paper is a review of the paleo-geographic events, the zoogeography, and faunal sorting which influenced P. paniscus divergence from the Proto-pan ancestor within the recent Miocene through Pliocene Epochs, approximately 10–2 MYA.
Abstract: Pan paniscus is unique in the group of African apes because of its range south of the Congo River Examination of the bio-geographical journey of the genus Pan to the species P paniscus is important when discussing the evolution of African apes This paper is a review of the paleo-geographic events, the zoogeography, and faunal sorting which influenced P paniscus divergence from the Proto-pan ancestor within the recent Miocene through Pliocene Epochs, approximately 10-2 MYA Finally, by elucidating modern day evidence of food plant forms in the southern periphery exploited by P paniscus in the forest/savanna mosaic habitat, we are able to conclude with those extrinsic events that most influenced the occurrence and distribution of P paniscus
TL;DR: There is considerable species variation in the excretion of these hormones during the menstrual cycle and comparative studies could be approached with a single method.
Abstract: Urinary estrone conjugates (E(1)C), pregnanediol-3-glucuronide (PdG), and follicle-stimulating hormone (FSH) were determined by enzyme immunoassays (EIAs) during the normal menstrual cycle in the orangutan, gorilla, chimpanzee, and bonobo. Furthermore, the data were compared to those levels in the human and long-tailed macaque. The results showed a typical preovulatory E(1)C surge and postovulatory increase in PdG in all species. The pattern of E(1)C during the menstrual cycle in the great apes more closely resembled the human than do the long-tailed macaque. A major difference of E(1)C pattern between these species appeared in the luteal phase. In the great apes and the human, E(1)C exhibited two peaks, the first peak detected at approximately mid cycle and the second peak detected during the luteal phase. On the other hand, in the long-tailed macaque, increase of E(1)C in the luteal phase was small or nonexistent. The gorilla, chimpanzee, and bonobo exhibited similar PdG trends. The orangutan excreted one tenth less PdG than these species during the luteal phase. The long-tailed macaque also excreted low levels of PdG. The patterns of FSH in orangutan, chimpanzee, bonobo and long-tailed macaque showed a marked mid-cycle rise and an early follicular phase rise, similar to those in the human. Comparing similar taxa, a large difference was found in FSH of gorilla; there were three peaks during the menstrual cycle. Thus, there is considerable species variation in the excretion of these hormones during the menstrual cycle and comparative studies could be approached with a single method. The methods and baseline data presented here provide the basis for a practical approach to evaluation and monitoring of ovarian events in the female great apes.
TL;DR: Why the results are inconsistent with a well known body weight–diet relationship (Jarman–Bell principle) is discussed, as energy-efficient locomotion enables patas to exploit not only small dispersed food items of high quality but also areas where high-quality foods are distributed in clumps.
Abstract: Phytochemical or nutrient analyses of primate diets have revealed clues to their food selection in a single species. On the other hand, few interspecific comparisons of phytochemical or nutrient composition of primate diets have been made, although diets are considered to differ in phytochemical or nutrient content from primate species to species, since different species have different body weights and different morphological and physiological characteristics. I compared the nutrient content of diet between patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus) living sympatrically in Cameroon. Patas subsisted on a smaller number of food items, most of which were also tantalus food items. Then, I compared the protein–fiber ratio and the available energy content of the food items eaten by patas (patas foods) with those items eaten only by tantalus (tantalus foods). Both variables were higher in patas than tantalus foods, although there was no significant difference in available energy of plant foods. Next, when I performed discriminant analysis for patas foods and tantalus foods, employing the above two variables, a discriminant function with positive coefficients for both variables was obtained. The mean discriminant-function score of patas foods was higher than that of tantalus foods. Despite being somewhat larger in weight, patas selectively fed on a smaller number of foods of higher quality than did tantalus. I discuss why the results are inconsistent with a well known body weight–diet relationship (Jarman–Bell principle). Energy-efficient locomotion enables patas to exploit not only small dispersed food items of high quality but also areas where high-quality foods are distributed in clumps.
TL;DR: Japanese macaques exhibit an annual reproductive cycle that apparently is maintained intrinsically and, within the Toimisaki–Kinkazan latitudinal zone, earlier mean birth dates at higher latitudes may permit infants to achieve an adequate level of development before the earlier onset of poor winter food conditions.
Abstract: Japanese macaques, Macaca fuscata, exhibit an annual reproductive cycle that apparently is maintained intrinsically. Translocation of nine troops to new latitudes within the northern hemisphere has had minimal effect on the timing of birth seasonality in these troops; translocation of one troop to the southern hemisphere has resulted in a 6-month forward displacement of birth seasonality in this troop. Limited available evidence indicates that, in the latitudinal zone between Toimisaki (31 degrees 22'N) and Kinkazan (38 degrees 17'N), mean birth date in in-situ troops becomes earlier as latitude of troop localities increases; the same relationship between mean birth date and latitude apparently does not apply to in-situ troops south and north of the Toimisaki-Kinkazan latitudinal zone. Within the Toimisaki-Kinkazan latitudinal zone, earlier mean birth dates at higher latitudes may permit infants to achieve an adequate level of development before the earlier onset of poor winter food conditions. South of the Toimisaki-Kinkazan latitudinal zone, winters are relatively mild and may be less of a factor in infant survival; north of this zone, poor winter food conditions persist so long that earlier infant births may be maladaptive.
TL;DR: Posture, locomotion, and trunk-sacral anatomy of chimpanzees may have prevented fractures in Wansombo, an old female chimpanzee from Mahale, whose BMD was below human osteoporosis criteria.
Abstract: We examined bone mineral density (BMD) of the femoral neck and lumbar vertebrae of four chimpanzee skeletons from Mahale Mountains National Park, Tanzania, and four captive ones, with a dual energy X-ray absorptiometer. The BMD of Wansombo, an old female chimpanzee from Mahale, was remarkably lower than the mean of the other six younger adult female chimpanzees and categorized as osteoporosis. Posture, locomotion, and trunk-sacral anatomy of chimpanzees may have prevented fractures in Wansombo, whose BMD was below human osteoporosis criteria.
TL;DR: This study demonstrates that female competition for access to food should not be analyzed separately from male influences on females and suggests that a more integral role of males in socioecological models of the evolution of primate social systems should be considered.
Abstract: We studied the social and foraging behavior of two captive groups of sooty mangabeys under two different spatial food situations. These food conditions were clumped (food was placed in a box) and dispersed (food was dispersed over the entire enclosure). In each group five adult females and two adult males were observed. As a criterion for food competition, individual differences in the relative food intake were used. Adult female mangabeys had a linear, stable, and unidirectional dominance hierarchy. Access to food was rank dependent among females only under clumped food distribution, as current models of the evolution of primate social systems predict. However, feeding success appeared to be mediated not by female but by male agonistic behavior toward females. High-ranking females received relatively less aggression from males and could, therefore, stay and feed longer in the feeding area. Male tolerance of higher-ranking females seems to mediate female feeding success under restricted food resources. The establishment of a special relationship with a high-ranking male might, therefore, be a strategy to get better access to food. This study demonstrates that female competition for access to food should not be analyzed separately from male influences on females and suggests that a more integral role of males in socioecological models of the evolution of primate social systems should be considered.
TL;DR: Lucky could not discriminate the stimuli that the other chimpanzees could and this is the first behavioral evidence of color vision deficiency in chimpanzees.
Abstract: Although color vision deficiency is very rare among Old World monkeys and apes, one male chimpanzee (Lucky) was identified as protanomalous by genetic and physiological analyses. This study assessed behavioral phenotypes of Lucky and four chimpanzees with normal color vision by discrimination task using the modified Ishihara pseudo-isochromatic plates. Lucky could not discriminate the stimuli that the other chimpanzees could. This is the first behavioral evidence of color vision deficiency in chimpanzees.
TL;DR: Results showed that this degeneration must be early onset familial macular degeneration controlled by autosomal dominant gene(s).
Abstract: The mode of inheritance of macular degeneration was determined with 45 cynomolgus monkeys (18 females and 27 males) who were the offspring of one breeding male with typical macular degeneration. In the first generation, 27 offspring (10 females and 17 males) were born from mating between the macular degeneration-affected founder male and 5 normal female breeders. Among them, 18 monkeys (9 females and 9 males) were judged as having macular degeneration (affected). Next, the distribution of affected offspring was examined with 18 offspring who were born from 3 different mating pairs, normal vs normal, affected vs normal and affected vs affected, when they became 2 years old. All of the 9 monkeys (4 females and 5 males) obtained from the 2 pairs of normal vs normal were normal. On the other hand, 6 affected monkeys (3 females and 3 males) were detected in 8 offspring from the mating pair of affected vs normal, and the single offspring produced by the mating pair of affected vs affected was affected. These results showed that this degeneration must be early onset familial macular degeneration controlled by autosomal dominant gene(s).
TL;DR: The results showed that the female, but not the males, presented an above-chance performance for stimuli resembling hue conditions under which tamarins forage (oranges vs greens).
Abstract: Colour is one cue that monkeys use for perceptual segregation of targets and to identify food resources. For fruit-eating primates such as Saguinus, an accurate colour perception would be advantageous to help find ripe fruits at distance. The colour vision abilities of black-handed tamarins (Saguinus midas niger) were assessed through a discrimination learning paradigm using Munsell colour chips as stimuli. Pairs of chips were chosen from an early experiment with protan and deutan humans. The monkeys (three males and one female) were tested with stimuli of the same hue, but different brightness values, in order to make sure that discriminations were based on colour rather than brightness cues. The results showed that the female, but not the males, presented an above-chance performance for stimuli resembling hue conditions under which tamarins forage (oranges vs greens). Colour vision in S. m. niger is discussed according to the advantages and disadvantages of dichromatism in daily search for food as well as to aspects regarding polymorphism in New World monkeys.
TL;DR: The result indicates that the vertebral centrum articular area, the lumbar column length and the body weight are strongly correlated with each other and that such relationships are similar between platyrrhines and cercopithecids.
Abstract: We investigated allometric relationships between vertebral centrum cranial surface areas and body weight and skeletal lumbar length in extant platyrrhine and cercopithecid species. Platyrrhines have smaller lumbar vertebral centra regarding the cranial surface area relative to their body weight than extant catarrhines. However, the stress to the spine of quadrupeds is not only influenced by the body weight but also its length, which contributes to the amount of bending moment. Our results indicated that platyrrhines and cercopithecids have similar lumbar vertebral centrum surface areas when they are scaled on the product of the body weight and skeletal lumbar length. Platyrrhines generally tend to have relatively short lumbar columns for a given body weight. As a result of this tendency, their vertebral centra appear relatively small if only body weight is taken into account. The centrum surface area is rather constant relative to the product of the body weight and skeletal lumbar length within platyrrhines or cercopithecids, despite the fact that skeletal lumbar length is in itself rather variable relative to body weight. This result indicates that the vertebral centrum articular area, the lumbar column length and the body weight are strongly correlated with each other and that such relationships are similar between platyrrhines and cercopithecids. These relationships were observed using both the zygapophyseal and rib definitions of the lumbar vertebrae. However, they were more clearly observed when the zygapophyseal definition was adopted. It appeared that lumbar vertebrae of Proconsul nyanzae (KNM-MW 13142) had distinctively smaller surface areas relative to its body weight and lumbar length than for platyrrhines and cercopithecids, differing from extant hominoids, which have comparatively larger lumbar vertebrae. In the case of Morotopithecus, the lumbar vertebral surface area seems to be as large as in extant platyrrhines and cercopithecids if it had a reduced number of lumbar vertebrae. It is uncertain whether its lumbar vertebral surface area was as large as in extant hominoids.
TL;DR: Use of non-invasive genetic analysis determined the paternity of an infant born to a female chimpanzee released by HELP into the Conkouati-Douli National Park, Republic of Congo, thus demonstrating successful reproduction in wild-released orphan chimpanzees.
Abstract: We report a case of successful reproduction in wild-released orphan chimpanzees. Using non-invasive genetic analysis, we determined the paternity of an infant born to a female chimpanzee released by HELP (Habitat Ecologique et Liberte des Primates) Congo into the Conkouati-Douli National Park, Republic of Congo. The sire was a released male, thus demonstrating successful reproduction in both male and female released chimpanzees. These results provide evidence that release into the wild may be a viable response to the plight of orphan chimpanzees in Africa, and we discuss further applications of non-invasive genetic tagging to release programs.