摘要:

Patterns of home range use by a mountain gorilla group are examined here in relation to variation in food abundance and quality, diet quality and rainfall, to interactions between different social units and to the distribution of hazards (poaching risk). Variation in habitat quality influenced both long-term area occupation densities and shorter-term movement parameters (day journey length and the distance moved between consecutive feeding sites). Observed home range use patterns increased the gorillas’ foraging efficiency. Rainfall influenced the evenness of home range use slightly, but this was the only seasonal variability. Interactions with other gorillas and poaching risk had proximate effects superimposed on the fundamental influence of food distribution patterns. Data from a larger sample of groups show a positive influence of group size on day journey length, but this was apparent only at very small and relatively large group sizes. The absolute distance travelled per day tends to be short even for large groups. The data support arguments that the costs of social foraging are low for mountain gorilla

ISSN:0015-5713    

DOI:10.1159/000156521

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156522

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

In a population of about 1,300 Hanuman langurs (Presbytis entellus) living in one-male breeding structures at Jodhpur, Rajasthan, India, census data resulted in male:female sex ratios of 1.1 in infants, 1.5 in juveniles and 0.2 in adults. Long-term demographic monitoring of 144 known individuals up to the age of 30 months confirmed a higher juvenile female mortality. It is hypothesized that heavier maternal investment in males helps them to compete more successful. Once males emigrate from their natal troop, their mortality begins to exceed that of females. The strongly female-biased adult sex ratio seems to result from male-male competition: maturing males join male bands and are exposed to greater risks while traversing unfamiliar areas, occupying home ranges of harem troops and fighting with other males for possession of a female harem. A sample of 60 definitely known causes of deaths recorded over 21 years revealed that males died significantly more often than females in instantaneous ‘spectacular’ deaths from external causes, such as accidents, infanticide and predation, thus reflecting a high-risk, high-gain strategy. The sex difference in infanticide (18 males:9 females for 13 directly observed and 14 presumed cases) is not well understood because the commonly accepted hypothesis is that new harem residents try to shorten a mother’s lactational amenorrhea by killing her unweaned infant regardless of its sex. However, it might be that harem residents select against future competitors of their sons and at the same time spare female infants with which they can reproduce if their tenure (mean: 26.4 months) is long e

ISSN:0015-5713    

DOI:10.1159/000156523

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Six biometric measurements were recorded from dry mandibles of 53 Papio anubis and 84 Cercopithecus aethiops: intercondylar width, intercoronoid width, intermolar width (IMW), mesiodistal width of the condyles, height of the occlusal table and anteroposterior length of the chewing surface from P4 to M3 (CL). The mean values and correlation matrices of these variables show that, despite the difference in size, the overall shape of the mandible in male and female is similar within species. The principal component analysis shows that in P. anubis the six variables contribute almost equally to the first component (75% of total variance), suggesting that the large mandible may be force related because of the greater mechanical forces required for chewing certain foods. In C. aethiops, the contribution of IMW and CL is less in the first component (52.7% of total variance), suggesting that the biochemical forces of mastication are more complex to adapt the mandible to a shorter muzzle and a particular diet.

ISSN:0015-5713    

DOI:10.1159/000156524

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The allometric relations of postcanine tooth size were evaluated in a sample of 66 adult Galago crassicaudatus (34 males, 32 females). Postcanine tooth area and length (estimated from mesiodistal and buccolingual measurements of upper and lower cheek teeth) were scaled to 4 cranial measures: bimaxillary width, maxillo-alveolar length, mandibular length and bigonial width. Postcanine tooth size was also scaled to body weight, body length and total skull length. It was found that postcanine surface and length were significantly correlated to the cranial measures employed in females, showing positive allometric scaling. These correlations were, however, lacking in males. In neither sex was postcanine size found to be significantly correlated to body length or weight.

ISSN:0015-5713    

DOI:10.1159/000156525

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The fork-marked lemur, Phaner furcifer, is discontinuously distributed through Madagascar, but is traditionally viewed as a monotypic species. Reexamination of variations in pelage color and pattern, size and body proportions among museum specimens reveals that several geographically discrete morphs exist within the species, which is clearly polytypic. We identify and name 2 new subspecies in western Madagascar, and 1 in the north of the island. The nominate subspecies is thought to be derived from the northeastern region, and it is possible that more discrete variants are present in that region than are formally recognizable on the basis of the current inadequate documentation. The limited nature of color variation in nocturnal lemurs relative to diurnal forms may have resulted in a general tendency to underestimate subspecific diversity in the former.

ISSN:0015-5713    

DOI:10.1159/000156526

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156527

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156528

出版商:S. Karger AG    

年代:1991

数据来源: Karger

ISSN:0015-5713    

DOI:10.1159/000156529

出版商:S. Karger AG    

年代:1991

数据来源: Karger