Voinilowitch M.V., Volodin I.A., Volodina E.V., 2002. Call form and its link to signaling situations during fighting in the Pallid gerbil (Gerbillus perpallidus) // Advances in Ethology. Contributions to the 4-th International Symposium on Physiology and Behaviour of Wild and Zoo Animals. Berlin. V. 37, p. 87.
The role of calling during agonistic interactions in mammals is poorly understood. Probably, animals either express their internal state or they influence the behaviour of their opponents using these calls. To answer these questions, it is necessary to conduct a study during which the relationship between call structures and behaviour of combatants is examined. Laboratory rodents, such as Pallid gerbils, are good objects for such a study. Encounters of two opponents on neutral territory represent an appropriate situation of social conflict. During social conflicts, Pallid gerbils emit calls that fall into the audible range. After a few minutes of conflict, opponents establish winner-loser asymmetry, after which all sounds originate from the loser.
In this study, we describe defensive vocal repertoire in the Pallid gerbil (Gerbillus perpallidus). We have designed 14 male-male 15-minutes conflicts between males on a neutral arena. We selected from video- and audiotapes of each of the conflicts two 60 s time intervals, corresponding to third and thirteenth minute after the winner-loser asymmetry establishing. Throughout these intervals we analysed data about winner actions (scan sampling method with 1-s scans, behaviours ranged from absence of aggression to threats or fights) and call structures of a loser (all sounds throughout these two 60-s intervals, in total 1471 analysed sounds for 14 conflicts). We analysed how the call structure depends on the immediate actions of the winner (by analysing data inside minutes) and on exposition to aggressive pressing (by analysing of cumulative effect using comparison of data for the third and thirteenth minute).
We found that increases of social pressure (demonstration of more aggressive behavior by the winner) enhances the noisiness of calls, the degree of frequency modulation, and evokes translocation of the dominant energy into higher frequency bands. In addition, the periods between calls are decreasing in duration. Only tonal sounds change, whereas the structure of purely noisy calls (where tonal component is absent) remains constant. Comparison of call structures for the third and thirteenth minute (cumulative effect) showed, that the percenatge of noisy calls was significantly higher on the thirteenth minute than on the third. Only in purely noisy calls, dominant energy was being transferred into higher frequency bands. All other parameters did not differ for the third and thirteenth minutes.
In conclusion, relationships between call structures and physical behaviour during social conflicts provide tools for a quick estimate of animal welfare in different social situations.