The Effects of Group Size and Position on Vigilance in Young Adults.

Essay by hot_dranUniversity, Master's November 2005

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Vigilance behavior in animals has been attributed to various scientific explanations. One of the most widely accepted functions of vigilance is to increase the ability to detect predators. This skill is better known as anti-predator vigilance. Anti-predator vigilance is described simply as a state of being alert to predators. This is an imperative ability for almost any animal's survival. Animals, as well as humans, need to constantly be aware of the dangers surrounding them. In order to stay safe from predators or other threats, animals often find safety in groups and exhibit vigilance within these groups. This may include a herd of buffalo periodically raising their heads in search of wolves, or a woman walking down the street checking both ways for cars. In an attempt to describe the functions of vigilance we have chosen to study two seemingly important facets: Group size and position.

One vital aspect of vigilance is group size.

Bertram (1980) demonstrated this relationship in a study of vigilance and group size in ostriches (Struthio camelus). The purpose of the study was to investigate and predict the reasoning behind vigilance. Bertram operationally defines vigilance in ostriches as each time an individual raised or lowered its head. The independent variable of his study was group size and included three different levels. These levels were one, two, and three or more birds. The dependent variable was vigilance rate. This was not a true experiment due to lack of manipulation, rather, Bertram conducted a systematic observational study. Bertram counted the number of times each individual raised or lowered its head, as well as, the length of time the bird kept its head raised. Bertram discovered that less vigilance occurred amongst ostriches within the larger groups. It can be concluded from the data that an increase in group...