Spatio-temporal organization during group formation in rats
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In the present study, the dynamic process of group formation in eight unfamiliar rats was followed in order to reveal how the group becomes oriented together in time and space, in light of the complexity that accompanies grouping. The focus was on who, where, and when joined together. We found that rats preferred to be in companionship over remaining alone, with all the rats gradually shifting to share the same location as a resting place. Group formation can be viewed as a tri-phasic process, with some rats gradually becoming more social than others, and thus playing a key role in group formation. Starting with seemingly independent traveling, the rats gradually converged to share the same location as a terminal (home base) for roundtrips in the arena. Because such a terminal is considered as the organizer of an individual’s spatial behavior, the shared home-base location may be viewed as the organizer of spatial behavior of the entire group. Despite huddling together, the rats continued to travel alone or in duos throughout the 3 h of testing. We suggest that resting together and traveling alone or in duos enabled the maintenance of communal relationship while reducing the complexity involved in traveling in relatively large groups. Taken together, the present results demonstrate the dynamic process during which unfamiliar rats shift from independent to group spatial behavior.
KeywordsSpatial representation Exploration Social environment Social cognition Group formation
This study was supported by the Israel Science Foundation grant 230/13 to DE. We are grateful to Naomi Paz for language editing.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This study and the maintenance conditions for the rats were carried out under the regulations and approval of the Institutional Committee for Animal Experimentation at Tel-Aviv University (permit # 04-15-061).
Online Resource 2. Group formation. This phase comprised two stages. During the first stage (first half hour) the rats begin by exploring the arena for a few minutes, briefly encountering their mates and immediately continuing to travel. After about 5 minutes, the rats start to interact more with one another, but are not yet establishing stable groups and frequently exchange partners. In the second stage (30-60 minutes), the same trends of a decrease in traveling and increased duration of resting with more and more partners continue (MP4 5636 KB)
Online Resource 3. Group stabilization. The second hour (time intervals 60-90 and 90-120) is the period in which the group had already been stabilized. The major changes that occurred in the first hour led to the formation of relatively large resting groups. However, there are still many rats in motion (alone or with one partner) despite their occasionally resting in the larger groups. This is also the time when most of the rats are sharing the same home base (MP4 3194 KB)
Online Resource 4. Group performance. The third hour (120-180 min) is the period when the dynamic processes levels off. Activity decrease further, the rats are resting together in one place, and every now and then a few rats, typically alone or with a partner, are taking roundtrips into the arena (WMV 9987 KB)
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