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Andreas Koenig Jan Beise Mukesh K. Chalise Jörg U. Ganzhorn 《Behavioral ecology and sociobiology》1998,42(4):225-237
Predictions of ecological models on female social relationships (van Schaik 1989) and their links with food distribution
and the potential competitive regime are used to analyze the feeding and spatial behavior, and resource density, size, distribution,
and quality in a forest population of Hanuman langurs (Presbytis entellus). In contrast to other populations, and assumptions on folivorous primates, the females of this population exhibit a linear
dominance hierarchy. The langurs concentrated their feeding on three key resources with a low density and clumped distribution.
Two out of the three key resources contained significantly higher levels of extractable protein and soluble sugar than other
food plants, indicating high spatial variability of food quality. Even the mature leaves of the most preferred food plant
were about twice as nutritious as those from other food plants. Group spread was small and only a single high-quality resource
was used at a time. Finally, even rich resources could accommodate only a subset of a group. These findings fit predictions
made for the prevalence of within-group contest competition. Given the observed food distribution and phytochemical heterogeneity
of mature foliage, even females of folivorous species should contest for food. The effect of female dominance rank on size
and composition of feeding parties also agrees with this prediction. A comparison with data from another forest population,
where female dominance relations are weakly developed, revealed a clear-cut difference in the use and abundance of resources.
It is argued that between-population differences in female social relationships within a species may be viewed as adaptive
responses to local habitat conditions.
Received: 1 August 1997 / Accepted after revision: 7 December 1997 相似文献
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Data on langur (Presbytis entellus) populations were gathered from the literature to test the importance of three selective pressures in determining group size
and composition: predation pressure, intergroup resource defense, and conspecific threat. There were no detectable difference
in the size of groups in populations facing nearly intact predator communities compared to those populations where predators
were severely reduced in number or absent, although there was a trend for the number of adult males per group to increase
in areas with nearly intact predator communities. Using population density as an indirect measure of the frequency of intrusions
into a group’s home range and thereby as an index of the demographic pressure favoring resource defense, we predicted that
higher densities would result in larger defensive coalitions and higher numbers of females per group. This prediction was
not upheld. Our third selective pressure, conspecific threat, encompasses those selective forces resulting from physical attack
on females, infants, and juveniles. Our index of conspecific threat uses the number of non-group males divided by the number
of bisexual groups, because in langurs, the major source of conspecific threat derives from non-group males who, following
group take-over, kill infants, wound females, and expel juveniles from groups. This index of conspecific threat was strongly
related to the mean number of resident females, was weakly related to the mean group size, but was not related to the number
of males in the group. In addition, as predicted, populations with a high index of conspecific threat had higher levels of
juvenile expulsion. These analyses were corroborated by a simulation model which used a computer-generated series of null
populations to calculate expected slopes of immatures regressed on adult females. These randomly generated populations, matched
to means and ranges of real populations, allowed us to determine if deviations of the observed slopes from the expected null
slopes could be explained by variation in predation pressure, population density, or conspecific threat. We found no evidence
that predation pressure was associated with decreases in immature survival in smaller groups, as would be predicted by the
predation-avoidance hypothesis. We found no evidence that immature survival was compromised by small group size in high-density
populations, as would be predicted by the resource-defense hypothesis. However, as the index of conspecific threat increased,
groups with larger numbers of females were more successful than groups with fewer females in reducing mortality or expulsion
of immatures. Overall, conspecific threat received the strongest support as a selective pressure influencing langur group
size and composition, suggesting that this selective pressure should be evaluated more widely as a factor influencing composition
of animal groups.
Received: 23 January 1995/Accepted after revision: 18 February 1996 相似文献
3.
Carola Borries Kristin Launhardt Cornelia Epplen Jörg T. Epplen Paul Winkler 《Behavioral ecology and sociobiology》1999,46(5):350-356
Hypotheses about the evolution of gregariousness and social organisation in primates are based on ecological explanations
as well as on social factors such as conspecific threat (especially infanticide by males). The social explanation fits well
with the conditions found in strepsirrhine primates and furthermore explains why infanticide in anthropoid primates living
in one-male groups mainly occurs when the resident male (protector) is replaced. However, whether it likewise fits to the
conditions in multimale groups will depend on the role of resident males as infant protectors, which has rarely been examined.
We investigated long-term data of wild Hanuman langurs (Presbytis entellus) inhabiting a forest near the village of Ramnagar (southern Nepal). Twenty-two eye-witnessed attacks on infants by males
were analysed in connection with male residency, paternity (DNA analyses) and sexual behaviour. Adult males played a major
role in infant defence (65%). Only the genetic father or males who had been residents when the infant was conceived were observed
to protect infants. Males who immigrated after a female had conceived may later attack her infant and were never observed
to defend it. lt seems that the males took only copulations with potentially fertile females but not with pregnant females
as clues for paternity. In the light of these results it seems likely that the risk of infanticide is an important determinant
in female-male associations even in anthropoid primate multimale groups.
Received: 22 December 1998 / Received in revised form: 30 April 1999 / Accepted: 1 May 1999 相似文献
4.
A. Koenig 《Behavioral ecology and sociobiology》2000,48(2):93-109
Van Schaik’s socioecological model predicts interrelations among food distribution, competitive regimes, and female social
relationships. To test the internal consistency of the model, feeding competition was examined in three differently sized
groups of a forest-dwelling population of Hanuman langurs (Semnopithecus entellus). The nutritional condition of females was used as a direct indicator of feeding competition and related to the seasonal
variation in resource distribution and abundance. Female dominance hierarchies were characterized by displacements. Dominance
hierarchies were significantly linear and relatively stable, but less so with increasing group size. Physical condition correlated
with dominance rank and high-ranking females were in the best condition, indicating within-group contest competition. The
strength of this relationship became less pronounced with increasing group size. The females of the medium-sized group were
in the best physical condition indicating between-group contest plus within-group scramble competition. Closer examination
revealed variable costs and benefits of group foraging with a predominance of within-group scramble competition when food
was more abundant. The results support some basic predictions of the model. Limiting food abundance was bound to ubiquitous
within-group scramble competition. The use of clumped resources translated into differences in net energy gain based on dominance.
In contrast to the predictions, group-size-related costs and benefits were related to food abundance instead of food distribution.
As predicted, within-group contest competition was linked to a linear dominance hierarchy. The absence of nepotism and coalitions
in Hanuman langurs may be attributed to dominance hierarchies that are unstable through time, probably minimizing fitness
gain via kin support.
Received: 25 May 1999 / Received in revised form: 18 February 2000 / Accepted: 25 February 2000 相似文献
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