Effect of anosmia on the behavior of standard non-aggressive male mice opponents during agonistic encounters

This study assessed whether the differences observed in a previous experiment [Martinez M, Salvador A, Simon VM (1994): Aggressive Behavior 20:441–451] in the behavior of isolated male mice over several agonistic encounters in which they confronted either an “anosmic” or an “intact” non-aggressive “standard opponent” were due to the differences in the behavior of the opponents themselves. Ethologically-inspired analysis was used to assess the behavior of the opponents during the first agonistic encounter. Anosmic opponents spent less time in social investigation and defense and more time in immobility than intact ones. These results suggest that the differences in the behavior of the opponents could be one of the causes of the differences observed in the behavior of the aggressive males confronting them. However, more research is needed to study if other variables, such as the production of odors, are also affected by the state (deprived or intact) of the olfactory sense. These findings provide additional support for the view that the type of opponent used in studies on intermale aggression is of paramount importance.Aggr. Behav. 23:179–181, 1997.© 1997 Wiley-Liss, Inc.     

A possible confound and the role of olfaction in mouse aggressive interactions

In investigating the olfactory modulation of aggression in mice, a urine-coating technique frequently has been used. Fighters typically have been tested against castrated animals coated with either urine or water. Then, if the fighters are more aggressive toward urine-coated castrates than toward water-coated castrates, it is concluded that olfaction plays a role in this discriminatory response. However, it is possible that the fighers might react to behavioral differences between these two groups of castrates caused by the different experimental treatment. Three experiments were conducted to study this possible confound and the role of olfaction in the control of agonistic encounters. The results indicated that 1) the confound is not likely to operate; 2) even if the confound is allowed to operate, it is not an effective discriminatory cue; and 3) anosmic fighters do not exhibit differential attacks toward castrates treated with different chemo-signals. Therefore, the emission and perception of olfactory cues do play an important role in mouse agonistic interactions.