A behavioral paradigm to probe dominance-hierarchy modulation of innate defense across distinct threat contexts.

(A) Schematic of behavioral paradigms. (B) Representative raster plots of behaviors during single and paired exposures. Top: looming exposure; bottom: live rat exposure. D: dominant; S: subordinate. (C) Bar graph of average time allocation for each annotated behavior. Pie charts show the proportion of behavioral categories. Paired t-test; N = 40 mice for looming exposure, N = 22 mice for rat exposure. (D) Behavior transition maps. Node size indicates the average duration of each behavior. Line thickness scales with the transition probability. (E) Matrices of behavior transition differences between single and paired conditions (paired-single). Paired t-test. (F) Transition maps of behavioral categories. *p < 0.05; ** p < 0.01; *** p < 0.001.

Social context attenuates looming-evoked defensive behavior in a rank-dependent manner.

(A) Heatmaps of average time allocation in nest, edge, and center zones during baseline, early, and late phases under single exposure. (B) Time spent in each zone per minute, normalized by zone area. Paired t-test; N = 40 mice. (C) Heatmaps of average locomotion speed across zones, with arrows indicating average velocity vectors. (D) Locomotion speed in each zone. (E) Representative moving trajectories of example mice exhibiting different behavior decisions within 5 s after looming onset. (F) Distribution of behavioral decisions following looming exposure. Chi-square test; N = 89, 84, 88, 95 trials for sD (single dominant), pD (pair dominant), sS (single subordinate), and pS (pair subordinate) groups, respectively. (G) Peak escape speed. Paired t-test; N = 12, 12, 10, 10 mice. (H) Duration of the first looming-evoked freezing bout. Paired t-test; N = 12, 12, 13, 13 mice. (I) Time spent on self-grooming across time windows. Two-way ANOVA with post hoc Tukey’s range test; N = 20 mice for all groups. (J) Time spent on rearing and up-stretch across time windows. Two-way ANOVA with post hoc Tukey’s range test; N = 20 mice for all groups. *p < 0.05; ** p < 0.01; *** p < 0.001.

Social context alleviates sustained predatory stress and fine-tunes defensive strategies across ranks.

(A) Heatmaps of average time allocation in near, center, and far zones during rat exposure. (B) Time spent in each zone per minute, normalized by zone area. Paired t-test; N = 22 mice. (C) Heatmaps of average locomotion speed, with arrows indicating average velocity vectors. (D) Speed in each zone. Paired t-test; N = 22 mice. (E) Representative trajectories of example mice displaying passive and active defense during rat exposure. (F) Distribution of behavioral categories during rat exposure. Chi-square test; N = 11 mice for each group. (G) Time spent on passive defense across time windows. Two-way ANOVA with post hoc Tukey’s range test; N = 11 mice for each group. (H) Longest freezing duration. Paired t-test; N = 11 mice for each group. (I) Time spent on active defense across time windows. Two-way ANOVA with post hoc Tukey’s range test; N = 11 mice for each group. (J) Approach frequency toward the rat. Paired t-test; N = 11 mice for each group. (K) Average investigation time toward the rat. Paired t-test; N = 11 mice for each group. *p < 0.05; *** p < 0.001.

Threat exposure reinforces social roles and promotes cohesive behavior.

(A) Time spent on social behaviors within a 1-minute window before and after looming exposure. Paired t-test; N = 19, 20 mice for Dom and Sub group. (B) Average bout duration of social behaviors before and after looming exposure. Paired t-test; N = 19, 20 mice for Dom and Sub group. (C) Time spent on social behaviors during a 5-minute window before and during rat exposure. Paired t-test; N = 11 mice for both groups. (D) Average bout duration of social behaviors before and during rat exposure. Paired t-test; N = 11 mice for both groups. (E) Percentage of social time spent on huddling before and during rat exposure. Paired t-test; N = 11 mice for both groups. (F) Schematic illustrating social interactions. * denotes proactive social behaviors. (G-J) Social interactions in the looming paradigm: (G) Percentage of proactive social bouts across ranks. (H) Average duration of proactive bouts. (I) Response rate to proactive bouts. (J) Average duration of reactive bouts. Paired t-test; N = 17, 13 mice. (K-N) Same plots for the rat paradigm. N = 9, 9 mice. *p < 0.05; ** p < 0.01; *** p < 0.001.

Behavior during habituation and additional information related to transition maps.

(A-B) Representative raster plots of behaviors during the habituation phase in single and paired exposures. (C-D) Transition probabilities between behavior pairs. Looming, N = 40 mice; rat, N = 22 mice.

Characterization of looming-evoked defensive behaviors.

(A) Time in the edge zone (green) and transitions between edge and center zones (gray) plotted against edge width. The green circle marks the elbow point, which was selected as the edge width for analysis in Figure 2. N = 39 mice. (B) Percentage of time spent in each zone across different time windows. (C-E) Difference (pair - single) of time spent in each zone during baseline (C), early (D), and late (E) phases. N = 20 mice for both dominant and subordinate groups. (F, G) Difference (pair - single) of speed in each zone during baseline and late phases. F: N = 20 mice; G: N = 17, 16, 13 mice. (H) Distribution of social time inside and outside the nest zones. N = 40, 39 for baseline and post-looming, respectively. (I) Illustration of three freezing types. Type 1 illustrates isolated freezing; type 2 illustrates freezing that overlapped with the partner’s social behavior; type 3 illustrates freezing that was followed by the animal’s own social behavior. (J, K) Percentage and duration of the three freezing types during the first freezing episode in dominant and subordinate mice. N = 14, 3, 4 mice in J and N = 16, 3, 3 mice in K. (L) Time allocation for three types of grooming. N = 20 mice for all groups. *p < 0.05; ** p < 0.01; *** p < 0.001.

Characterization of rat evoked defensive behaviors.

(A) Time in the far zone (blue) and transitions between the far and the non-far zones (gray) plotted against far zone width. The blue circle marks the elbow point, which was selected as the far zone width for analysis in Figure 3. N = 22 mice. (B) Time in the near (orange) and middle (green) zones and transitions between near and middle zones (gray) plotted against near zone width. The gray circle marks the stable point, which was selected as the near zone width for analysis in Figure 3. N = 22 mice. (C) Percentage of time spent in each zone during rat exposure. N = 22 mice. (D, E) Difference (pair - single) in time spent and speed across zones during rat exposure. N = 11 mice for each group. (F) Total freezing time. N = 11 mice for each group. (G-H) Percentage and duration of the three freezing types during the maximum freezing in dominant and subordinate mice. N = 7, 3, 1 mice in G and N = 11 mice in H. *p < 0.05; ** p < 0.01; *** p < 0.001.