Pheromone-evoked male–male territorial aggression. Male territorial aggressive behavior assessed in a resident–intruder experiment with male residents of indicated genotypes (WT: turquoise, n = 17 mice; Δ(Ano1olf/Ano2): red, n = 17 mice). A, scatter plots of single experiments showing the number of male–male attacks, the total duration of attacks, the average time per attack, the latency of the first attack, the sniffing time before the first attack, and the total time of investigative sniffing. Bars indicate means ± S.D., Mann–Whitney test of significance. ns, p > 0.05 (not significant). B, the time course of the resident's aggressive behavior (upper panel) and investigative sniffing behavior (lower panel) is represented in histograms indicating the fraction of mice showing the respective behavior at a given time point.