摘要:

A 22-month field study was carried out on free-ranging mantled howlers in Costa Rica. Six female and 5 male infants were observed systematically from birth until they died, left the group, or the study ended. Interaction patterns, activity patterns, and proximity data were analyzed from 703 h of focal observations and 753 h of ad lib observations. Developmental trends in weaning and nonmother care were associated with mothers’ feeding patterns, suggesting an increase in maternal feeding efficiency. As howler immigration patterns resulted in groups of adults of low relatedness, analyses based on social bonding or kin selection were inappropriate, and socialization patterns instead appeared to prepare howler infants to respond predictably in an adult world. Females, which were more sociable as adults, were also more sociable as infants, initiating interactions and reacting positively. They also exibited less weaning stress than males. Males, which were forced out of the group sooner, remained solitary longer, and primarily interacted with adult females as adults, were forced to be independent sooner, reacted negatively to interactions, and ceased interacting with adult males by 3 months of age. Ecological constraints on development could not be determined from this study, although there was no evidence for developmental trends being influenced by predator stres

ISSN:0015-5713    

DOI:10.1159/000156422

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

During the second half-year of life, capuchin monkey infants maintain close contacts to kin-related animals. Apart from these contacts, they frequently interact with other infants and juveniles 1 year older. During this period of life the ‘peer phase’ begins in the life of the infants. Furthermore, gender differences, especially in respect to social play, become obvi

ISSN:0015-5713    

DOI:10.1159/000156423

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Food-sharing behaviour was observed in 9 captive families of cotton-top tamarins (range 4–14 individuals per group), during meals of fresh fruit. Food was transferred to infants by their parents and older sibs in response to begging, and was also offered to them without prior solicitation. Older, mature, reproductively suppressed individuals shared more than young immature monkeys. Infants in larger families received more food than those in smaller ones, though individuals in smaller families shared more. Transfer to infants increased to a maximum at 12 weeks of age and then declined gradually. At one year of age they no longer received food from others. Food sharing by older siblings is a form of helping behaviour which may increase their inclusive fitness, and benefit parents, both directly, by reducing the costs they incur in rearing young, and indirectly, by increasing the amount of food available to infant

ISSN:0015-5713    

DOI:10.1159/000156424

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Medial hypothalamic lesions cause major deficits in sexual receptivity in a variety of mammalian species. Effects of such lesions upon sexual receptivity in female primates have not been investigated. Two experiments are described in which thermal lesions were made in the hypothalamus in 11 ovariectomized or ovariectomized/adrenalectomized, oestradiol-treated common marmosets. Proceptivity (sexual initiating behaviour) was reduced or abolished by lesions in the dorsomedial or ventromedial hypothalamus. Sexual receptivity was unaffected except in 3 females in which damage to the ventromedial area was associated with a 25–42% increase in terminations of males’ mounts. However, this effect was reversed by treating females with oestradiol. Therefore, medial hypothalamic lesions have pronounced effects upon proceptivity in the marmoset, whereas effects upon receptivity are much less pronounced or absent. These results are discussed in relation to the evolution of the hormonal control of receptivity in anthropoid primates as compared to other mamm

ISSN:0015-5713    

DOI:10.1159/000156425

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The samango monkey occurs at the southern limit of the range of Cercopithecus mitis. Greater climatic seasonality at this latitude results in more predictable fruiting patterns. In addition, there are no diurnal sympatric primate frugivores. Under these conditions, the diet and feeding strategies of samango monkeys would be expected to differ notably from those of central or east African C. mitis subspecies. Contrary to these expectations, the preliminary observations reported here indicate that diets of samango and blue monkeys differ only superficially in the proportions of items eaten. Similarities in feeding behaviour are especially marked during the dry season period when fruit is not abundant. Both samango and blue monkeys tend to be less selective in their choice of food species and to eat available food species regardless of their energy content; a shift toward less nutritious items such as leaves is also noted. Feeding behaviour during the summer wet season is characterized by the selection of fruits with high-energy values. A high proportion of visits by the monkeys to areas of greater food availability suggests a concentration of feeding effort in food patches and the selection of higher energy food species within patches.

ISSN:0015-5713    

DOI:10.1159/000156426

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Field and laboratory studies of arm-swinging in gibbons reveal its singularity even compared to spider monkeys. On the basis of principal components and discriminant analyses of size-corrected forelimb variables, this study confirms their morphological uniqueness and the more generalized nature of the spider monkey forelimb. Long forearms, well-developed scapular spines, and sagittally thicker radial shafts are features associated strictly with gibbon arm-swinging. On the other hand, large humeral heads, projecting medial epicondyles, and axially elongated scapulae, traditionally regarded as arm-swinging traits, are probably more important for climbing.

ISSN:0015-5713    

DOI:10.1159/000156427

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Reported incidences of tool use and tool making for three wild chimpanzee populations increase from Mahale (12 and 3 types of use and making, respectively), Gombe (16 and 3) to Taï (19 and 6). Sticks are commonly used and prepared at all three sites. However, Taï chimpanzees seem to perform more modifications on the material before using it. They are also the only chimpanzees seen to pound objects with tools and to combine two different tool uses to get access to one food item. Tool making is the rule for abundant material (grass, twigs), but appears to be rarer for scarce, hard material (clubs, stones). Factors involved in the acquisition and the benefit of tool use are discussed along with factors affecting the frequency and complexity of tool making in chimpanzee

ISSN:0015-5713    

DOI:10.1159/000156428

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156429

出版商:S. Karger AG    

年代:1990

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156430

出版商:S. Karger AG    

年代:1990

数据来源: Karger