The Influence of Group Size On Predator Scanning and Foraging Behaviour of Wedgecapped Capuchin Monkeys (Cebus Olivaceus)

Behaviour ◽  
1986 ◽  
Vol 98 (1-4) ◽  
pp. 240-258 ◽  
Author(s):  
Jan R. De Ruiter
Keyword(s):  
Group Size ◽  
Foraging Behaviour ◽  
Group Formation ◽  
Food Competition ◽  
Food Sources ◽  
Capuchin Monkeys ◽  
Time Budgets ◽  
Large Group ◽  
Cebus Olivaceus ◽  
Travel Distances

AbstractThe behaviour of two groups of wedgecapped capuchin monkeys, Cebus olivaceus, a small one (n = 8) and a large one (n = 25) was recorded. Time budgets and other aspects of behaviour depended on group size. The differences can be explained as: adjustment to predation risk and intra-group food competition. In order to evade predation, members of the small groups scan more and stay at greater heights than those of the large group. Higher food competition within the large group was reflected in the composition of its diet, in longer travel distances, and higher levels of social behaviour. In particular during the dry season, the large group exploited unattractive and risky food sources. These results support ALEXANDER'S hypothesis on the causes of group formation.

Food Competition in Brown Capuchin Monkeys (Cebus Apella): Quantitative Effects of Group Size and Tree Productivity

Behaviour ◽  
1988 ◽  
Vol 105 (1-2) ◽  
pp. 53-76 ◽  
Author(s):  
Charles H. Janson
Keyword(s):  
Food Intake ◽  
Group Size ◽  
Food Competition ◽  
Capuchin Monkeys ◽  
Feeding Time ◽  
Net Energy ◽  
Large Trees ◽  
Capita Food ◽  
Per Capita ◽  
Large Groups

AbstractThe effects of group size and fruit availability in tree crowns on per-capita food intake was examined for wild brown capuchin monkeys living in groups of 3-12 individuals. Per-capita feeding time was nearly exactly inversely proportional to group size in small-crowned trees with little fruit, but was essentially independent of group size in large-crowned trees with abundant fruit. Despite the use of such productive trees, per-capita feeding time in the average tree visited decreased by 50% over a 4-fold range of group sizes. This cost of indirect food competition in large groups was not compensated by increased rates of ingestion, preferential use of large trees, of a higher rate of fruit tree encounter per distance travelled. Instead, foraging effort (distance travelled, number of minutes devoted to foraging, total activity minutes per day) increased at large group sizes. Estimates of total energy intake and expenditure suggest that net energy gain is constant for individuals in group sizes of 5-12. I suggest that the upper limit to group size is set by the daylength available for foraging in large groups. Aggression in food trees increased in frequency in larger groups, but the relative feeding rates of dominants and subordinates of a given rank did not appear to depend on group size. Observed decreases in per-capita food intake due to either indirect or aggressive food competition within large groups are substantially greater than the 4% gain in mean food intake that large groups achieve by displacing smaller groups from fruit trees.

VIGILANCE IN BRONZE MANNIKIN GROUPS: THE CONTRIBUTIONS OF PREDATION RISK AND INTRA-GROUP COMPETITION

Behaviour ◽  
2000 ◽  
Vol 137 (5) ◽  
pp. 565-578 ◽  
Author(s):  
Nicola Coumi ◽  
Rob Slotow
Keyword(s):  
Predation Risk ◽  
Group Size ◽  
Foraging Behaviour ◽  
Random Numbers ◽  
Time Budgets ◽  
Group Competition ◽  
Measured Time ◽  
The Mean

AbstractWe describe foraging behaviour and time budgets of the gregarious bronze mannikin, Lonchura cucullata. In addition to being the first such study of a southern African granivore, this was the first study of a group-forager to differentiate between vigilance for other flock members (conspecifics) and vigilance for predators. We verified a perception of predation risk by placing five feeders at increasing distances from cover. The mean number of birds at a feeder decreased significantly with increasing distance from cover. We manipulated levels of aggression by restricting access to random numbers of feeding holes at various distances. The treatments succeeded in forcing birds to feed further from cover, and by inference, increased levels of aggression. We measured time budgets with focal samples on marked individuals. There was no influence of group size on time budgets. There was a non-significant (p < 0.06) trend for vigilance to increase with increasing distance from cover (predation risk). There was no pattern in the relative vigilance for predators as opposed to vigilance for other flock members (conspecifics), either with group size, distance from cover, or manipulated levels of aggression. Despite our inability to detect patterns of vigilance for other flock members, we emphasize the importance of studies to elucidate such a process.

An ecological basis for large group size in Colobus angolensis in the Nyungwe Forest, Rwanda

2001 ◽  
Vol 39 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Cheryl Fimbel ◽  
Amy Vedder ◽  
Ellen Dierenfeld ◽  
Felix Mulindahabi
Keyword(s):  
Group Size ◽  
Large Group ◽  
Colobus Angolensis ◽  
Ecological Basis

Demography and Group Structure in Wedgecapped Capuchin Monkeys, Cebus Olivaceus

Behaviour ◽  
1988 ◽  
Vol 104 (3-4) ◽  
pp. 202-232 ◽  
Author(s):  
John G. Robinson
Keyword(s):  
Sex Ratio ◽  
Life Table ◽  
Group Structure ◽  
Age Distribution ◽  
Capuchin Monkeys ◽  
Demographic Parameters ◽  
Adult Size ◽  
Sex Composition ◽  
Cebus Olivaceus ◽  
Age And Sex

AbstractThe extent to which population demography determines the age and sex composition of primate groups was examined using data from a population of wedge-capped capuchin monkeys Cebus olivaceus in central Venezuela. Demographic parameters were derived from censuses of individually recognized, aged, and sexed individuals living in nine groups over a ten year period. Animals were aged by extrapolation from census data. Animals of both sexes were classed as infants during their first year, and juveniles until they reached six years of age. Females reach sexual maturity at this time, while males were classed as subadults until they reached full adult size at age 12. Adulthood lasts at least 30 years in females, at least 24 years in males. Age-sex class specific mortality and fecundity rates generated a life table which indicated that the population was increasing (r = 0.087) between 1977 and 1986. The age and sex composition of the nine groups was described annually. On average, non-adults made up 60% of a group, with this percentage increasing with group size. There were more females than males in all groups in all years. The strong female-biased adult sex ratio (1:4.4) was a consequence of a biased birth sex ratio (1:1.9), higher female than male survivorship especially between the ages of 3 and 7 when males were dispersing, and a pronounced sexual bimaturism. The stable age distribution derived from the life table successfully predicted the observed average distribution of age-sex categories in groups. This suggests that the group structure of Cebus olivaceus groups is not a consequence of intragroup social interactions, but results from demographic parameters.

Groepsidentificatie en cognitie

2021 ◽  
Vol 113 (3) ◽  
pp. 331-361
Author(s):  
Marc Slors
Keyword(s):  
Cognitive Function ◽  
Group Formation ◽  
Group Identification ◽  
Specific Behavior ◽  
Large Group ◽  
Dress Codes ◽  
Cultural Infrastructure ◽  
Large Groups ◽  
Shared Norms ◽  
Evolutionary Explanations

Abstract Group-identification and cognition: Why trivial conventions are more important than we think In existing (evolutionary) explanations for group formation and -identification, the function of cultural conventions such as social etiquette and dress codes is limited to providing group-markers. Group formation and identification itself is explained in terms of less arbitrary and more substantial phenomena such as shared norms and institutions. In this paper I will argue that, however trivial and arbitrary, cultural conventions fulfil an important cognitive function that makes them essential to the formation of and identification with large groups. Complex role-division, both informal and institutional, is important in the functioning of any large group of people. Shared conventions enable a virtually automatic understanding of signals, scripts and rules that regulate the interaction of divided roles. They provide a cultural infrastructure within which we perceive e.g. specific behavior and clothing as a range of social-cultural affordances for role-interactions. Shared familiarity with this infrastructure is the foundation for the basic kind of trust of in-group strangers that is a requirement for the formation of large groups. This non-intellectualist view on group formation and group identification can contribute to new ways of dealing with problems in multicultural societies.

scholarly journals The Effects of Group Size and Time on the Formation of Online Communities: Evidence From Reddit

2018 ◽  
Vol 4 (4) ◽  
pp. 205630511881590 ◽  
Author(s):  
Elliot Panek ◽  
Connor Hollenbach ◽  
Jinjie Yang ◽  
Tyler Rhodes
Keyword(s):  
Multilevel Analysis ◽  
Group Size ◽  
Online Communities ◽  
Cohort Effect ◽  
Active Member ◽  
Group Discussions ◽  
Large Group ◽  
Group Member

These studies examine the influence of group size and the passage of time on two characteristics of online communities: dispersion of participation in group discussions and active member turnover from month to month. We used multilevel analysis to examine the dynamics of user contributions to discussions on Reddit, a popular website that hosts large-group discussions, across 30 groups over 6 years. As groups grow in size, participation becomes more highly concentrated among fewer members while turnover decreases. As time passes, participation becomes more widely dispersed while group member turnover increases. An increase in group member turnover appears to be the result of both a maturation effect (as each group ages, turnover increases) as well as a cohort effect (groups formed at a later date have higher turnover than groups formed earlier). We can conclude from these results that as time progresses and groups become larger, they become less community-like, but in different ways.

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