Resident-Intruder
Overview
The resident-intruder test is the standard paradigm for quantifying territorial aggression and social investigation in rodents. A singly-housed resident male, established in his home cage for several days, is confronted with an unfamiliar intruder male introduced into the resident's territory. The test measures aggressive behaviors (attack latency, attack frequency, bite sites), social investigation (anogenital sniffing, body investigation), and defensive/submissive responses over a fixed observation period.
Attack latency — the time from intruder introduction to the first clinch attack — is the most sensitive measure of aggression threshold, while total attack duration and number of biting attacks index aggression intensity. The test is widely used for phenotyping genetic models of aggression (e.g., 5-HT1B knockout), testing anti-aggressive pharmacotherapy, and studying the neuroendocrine basis of territorial behavior.
ConductMaze facilitates the resident-intruder test through synchronized video recording, automated behavioral event logging, and configurable session timing. The software tracks interaction onset, provides real-time alerts for excessive aggression (safety stop), and generates ethogram-compatible output for downstream behavioral coding with supervised or machine-learning classifiers.
Trial Flow
Resident Isolation
Resident singly housed for 7-14 days in test cage
Intruder Introduction
Unfamiliar male placed in resident home cage
Investigation Phase
Initial social exploration and sniffing
Aggression Onset
First attack behavior detected
Event Logging
Record attack latency, bouts, investigation time
Safety Check
Excessive wounding or distress → terminate early
Session End
Remove intruder, score behavioral categories
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Isolation Duration | days | 10 | Days resident is singly housed before test |
| Test Duration | seconds | 600 | Maximum session length |
| Intruder Strain | enum | C57BL/6J | Strain and age of intruder mouse |
| Intruder Weight | enum | Matched (±2g) | Weight matching to resident |
| Light Conditions | enum | Red light | Illumination during test (red light for active phase) |
| Max Attacks | integer | 20 | Safety stop after this many attack bouts |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Attack Latency | seconds | Time from intruder introduction to first attack — aggression threshold |
| Number of Attacks | count | Total clinch-attack bouts — aggression frequency |
| Total Attack Duration | seconds | Cumulative time spent in aggressive bouts |
| Anogenital Sniffing | seconds | Time spent in anogenital investigation of intruder |
| Body Investigation | seconds | Non-anogenital social exploration of intruder |
| Tail Rattles | count | Rapid tail vibrations — threat display frequency |
| Submissive Postures | count | Upright or supine submissive postures by intruder |
Sample Data
| Subject | Group | Attack_Latency_s | Attacks | Attack_Duration_s | Investigation_s | Tail_Rattles |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Aggression genetics — phenotyping knockout models with altered serotonergic or vasopressinergic signaling
- 2Anti-aggressive drug screening — dose-dependent reduction of attack behavior and latency
- 3Social hierarchy — establishing dominance relationships for chronic social stress paradigms
- 4Neuroendocrine research — testosterone, cortisol, and oxytocin effects on territorial behavior
- 5Post-traumatic stress — aggressive phenotypes following early-life adversity or social defeat
Related Protocols
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