Mechanisms of the group-size effect on vigilance in Columbian ground squirrels: dilution versus detection

2007 ◽  
Vol 73 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Bonnie Fairbanks ◽  
F. Stephen Dobson
Keyword(s):  
Size Effect ◽  
Group Size ◽  
Ground Squirrels ◽  
Group Size Effect ◽  
Columbian Ground Squirrels

Kinship does not affect vigilance in Columbian ground squirrels (Urocitellus columbianus)

2010 ◽  
Vol 88 (3) ◽  
pp. 266-270 ◽  
Author(s):  
B. M. Fairbanks ◽  
F. S. Dobson
Keyword(s):  
Size Effect ◽  
Group Size ◽  
Ground Squirrels ◽  
Predator Detection ◽  
Natal Nest ◽  
Group Size Effect ◽  
Asymmetrical Effect ◽  
Group Members ◽  
Close Relatives ◽  
Columbian Ground Squirrels

Vigilance, a vital behaviour in prey species, is affected by many factors, including social group size and possibly the presence of relatives. Columbian ground squirrels ( Urocitellus columbianus (Ord, 1815)) show a group-size effect of reduced individual vigilance in larger groups owing to increased predator detection. Such groups are composed of both kin and nonkin individuals. We observed vigilance (raising head above shoulders while foraging) of yearling males and yearling and older females, and examined kin relationships that are learned in the natal nest (viz., uterine kin). We then tested for possible effects of kinship on vigilance and thus on the group-size effect. Because of the kin-biased behaviours and nepotistic alarm calls shown by ground squirrels in previous studies, we expected either a kin-cooperative influence on vigilance or a nepotistic asymmetrical effect on vigilance,. We found that the presence of kin (whether above ground or not) had little or no effect on vigilance. This lack of kin effect reveals that Columbian ground squirrels do not rely any more on close relatives than on unrelated group members for detecting predators. Thus, the presence of kin does not contribute to the group-size effect on vigilance.

scholarly journals Group size effect in nutmeg mannikin: between-individuals behavioral differences but same plasticity

2010 ◽  
Vol 21 (4) ◽  
pp. 684-689 ◽  
Author(s):  
G. Rieucau ◽  
J. Morand-Ferron ◽  
L.-A. Giraldeau
Keyword(s):  
Size Effect ◽  
Group Size ◽  
Behavioral Differences ◽  
Group Size Effect

scholarly journals Modes of Collective Action in Village Economies: Evidence from Natural and Artefactual Field Experiments in a Developing Country

2013 ◽  
Vol 30 (1) ◽  
pp. 31-51 ◽  
Author(s):  
Yasuyuki Sawada ◽  
Ryuji Kasahara ◽  
Keitaro Aoyagi ◽  
Masahiro Shoji ◽  
Mika Ueyama
Keyword(s):  
Collective Action ◽  
Size Effect ◽  
Public Goods ◽  
Group Size ◽  
Field Experiments ◽  
Free Riding ◽  
Free Rider ◽  
Individual Contribution ◽  
Free Rider Problem ◽  
Group Size Effect

In a canonical model of collective action, individual contribution to collective action is negatively correlated with group size. Yet, empirical evidence on the group size effect has been mixed, partly due to heterogeneities in group activities. In this paper, we first construct a simple model of collective action with the free rider problem, altruism, public goods, and positive externalities of social networks. We then empirically test the theoretical implications of the group size effect on individual contribution to four different types of collective action, i.e., monetary or nonmonetary contribution to directly or indirectly productive activities. To achieve this, we collect and employ artefactual field experimental data such as public goods and dictator games conducted in southern Sri Lanka under a natural experimental situation where the majority of farmers were relocated to randomly selected communities based on the government lottery. This unique situation enables us to identify the causal effects of community size on collective action. We find that the levels of collective action can be explained by the social preferences of farmers. We also show evidence of free riding by self-interested households with no landholdings. The pattern of collective action, however, differs significantly by mode of activity—collective action that is directly rather than indirectly related to production is less likely to suffer from the free rider problem. Also, monetary contribution is less likely to cause free riding than nonmonetary labor contribution. Unlike labor contributions, monetary contributions involve collection of fees which can be easily tracked and verified, possibly leading to better enforcement of collective action.

scholarly journals The group size effect and synchronization of vigilance in the Tibetan wild ass

2020 ◽  
Author(s):  
Xinxin Wang ◽  
Le Yang ◽  
Yumeng Zhao ◽  
Cong Yu ◽  
Zhongqiu Li
Keyword(s):  
Size Effect ◽  
Group Size ◽  
Nature Reserve ◽  
Prey Species ◽  
The Other ◽  
Effective Strategy ◽  
Positive Correlation ◽  
Group Size Effect ◽  
Wild Ass ◽  
Group Members

Abstract Vigilance behavior is considered as an effective strategy for prey species to detect predators. An individual benefits from living in a group by reducing the time spent being vigilant without affecting the probability of detecting a predator. However, the mechanism producing a decrease in vigilance with increasing group size is unclear. Many models of vigilance assume that group members scan independently of one another. Yet in recent studies, the other 2 patterns of vigilance, coordination and synchronization, were reported in some species. In 2 summers (2018 and 2019), we studied the group-size effect on vigilance and foraging of Tibetan wild ass in Chang Tang Nature Reserve of Tibet. We also tested whether individuals scan the environment independently, tend to coordinate their scans, or tend to synchronize their vigilance. The results showed that individuals decreased the time spent on vigilance with increasing group size, while increased the time spent foraging. Group members scanned the environment at the same time more frequently and there was a positive correlation between group members’ behaviors, indicating that Tibetan wild asses tend to synchronize their vigilance.

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