104 research outputs found
The pivotal role of rank in grooming and support behaviour in a captive group of bonobos (Pan paniscus)
We investigated dyadic grooming relationships in a captive group of bonobos (Pan paniscus)
and questioned what social function grooming fulfils in the market of services and favors.
Hereto we examined which of two theoretical models - grooming for support (Seyfarth,
1977, 1980) or grooming according to the similarity principle (de Waal & Luttrell, 1986) -
best accounted for the observed grooming distribution. Similarity in traits did not correlate
with increased grooming or close proximity among the individuals. Therefore, the similarity
hypothesis was rejected. Seyfarths model of rank-related grooming was largely confirmed.
The animals distributed their grooming according to the rank of the receivers. We found an
exchange between grooming and receipt of support. There was more grooming up than down
the hierarchy. However, not all predictions about rank-related competition over grooming
were confirmed. We found that dyadic grooming reciprocity indeed increased with decreasing
rank distance. Yet, there was no increase of grooming within the dyad with decreasing
rank distance and high ranking individuals were not competed over at the highest rates.
The observed correlation between grooming and support received represents an important
fit with Seyfarths prediction, but does not allow for conclusions about underlying causal
processes. Other causal explanations, besides the groom to receive support hypothesis, that
could explain a similar correlation are discussed
An experimental evaluation of the consistency of competitive ability and agonistic dominance in different social contexts in captive bonobos
Bonobos have been described as a relatively egalitarian and female dominant species. The
exact nature and quality of their dominance relationships and the existence of female
dominance are current topics of dispute. We investigated the consistency across social
contexts, the stability in time, and the degree of expression of the competitive feeding
ability and agonistic dominance in a captive group of bonobos. First, we examined whether
the competitive feeding ranks and agonistic ranks differed in different dyadic contexts,
triadic contexts and the whole group context. For some pairs of animals the dominance
relationships with respect to competitive feeding altered with different group compositions.
The agonistic dominance relationships changed accordingly. The competitive feeding ranks
and agonistic ranks in the experiments correlated strongly with each other. The alpha position
was occupied by a female, but not all females outranked all males. We suggest that females
can profit from each others presence to gain inter-sexual dominance. Second, although the
agonistic rank order in the whole group remained the same over at least five years, some
dyadic competitive feeding ranks changed over time, resulting in a stronger female intersexual
dominance. Third, the degree of expression of the behaviors used to quantify dyadic
competitive and agonistic dominance was not high, in line with the popular egalitarian
epithet. Notwithstanding its low consistency across contexts, the dominance hierarchy in the
whole group has a strong predictive value for other social relationships such as grooming.
Given this strong effect of rank on other behaviours and given the strong dependency of
rank on social context, the choice of the right party members may be a crucial factor in the
fission-fusion processes of free-ranging bonobos
The feeding ecology of the lesser vasa parrot, Coracopsis nigra, in south-eastern Madagascar
The diet and feeding ecology of the Lesser Vasa Parrot, Coracopsis nigra, in the littoral forest of Sainte Luce, south-eastern Madagascar are described. Forty plant species were recorded being eaten over a 14-month study period. Coracopsis nigra is a flexible feeder and eats a large variety of ripe and unripe seeds (68%), fruits (22%) and flowers (10%). Of all fruit species consumed, 70% of fruits are eaten in an unripe condition, which may lead to an advantage over potential food competitors. Detailed observations of feeding behaviour show that generally seeds are destroyed and the Lesser Vasa Parrot is considered primarily as pre-dispersal seed predator. A clear niche separation could be found among all granivorous species of the littoral forest based on fruit and seed size, ripeness of fruits, foraging height and activity pattern, Vasa Parrots feed on unripe and ripe fruits of medium size in the canopy, while Malagasy Turtledoves forage on small but ripe seeds on the ground. At night, rodents consume mainly large and protected seeds in the canopy as well as on the ground.Ostrich 2004, 75(3): 141β14
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