[The sequential structures of social behavior and their developmental changes in rats bidirectionally selected for...

Area of Science:

• Ethology
• Animal Behavior
• Neuroscience

Background:

• Emotionality varies significantly among rat strains.
• Understanding the social dynamics and dominance hierarchies in different emotional strains is crucial for behavioral research.

Purpose of the Study:

• To compare the sequential social behavior structures of Tsukuba High Emotional (THE) and Low Emotional (TLE) rat strains during dominance organization.
• To identify similarities and differences in behavioral patterns between THE and TLE rats.

Main Methods:

• Rearing 18 THE and 17 TLE rat colonies (1 female, 2 males each) for two months.
• Conducting weekly intruder tests and intra-colony observations.
• Sequentially coding social behaviors (17 items) using a microcomputer and visualizing transitions via chi-squared tests and tree structures.

Main Results:

• Dominant males in both THE and TLE strains exhibited similar sequential behavior structures, comprising four common item-groups: alpha (aggression), beta (mounting), gamma (chasing/display), and delta (submission/flight).
• Submissive behaviors (delta group) diminished as dominance was established.
• While overall structures were similar, specific inter- and intra-group behavioral transitions differed between the THE and TLE strains.
• TLE males displayed higher aggression than THE males.

Conclusions:

• Dominance organization in rats, regardless of emotional strain, leads to convergent sequential social behavior patterns.
• Subtle but significant differences in behavioral sequencing persist between high and low emotionality rat strains, highlighting the influence of emotionality on social interactions.