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Vocal sounds of 15 individuals of Crocidura leucodon (Hermann, 1780) emitted during agonistic and amicable interactions in male-male, female-female and male- -femalejdyadic encounters, and intráspecific cage groups, were studied. An analysis of spectral properties, along with an examination of context and function, were performed. The sounds registered during agonistic interactions showed an increase, then a decrease in frequency, often followed a complex undulating curve. The dominant frequency (DF) was 10.7 ± 0.05 kHz, and duration (DU) was 104.2 ± 4.4 ms. The calls emitted by shrews at investigation and grooming often ended with chirping notes (DF = 4.8 ± 0.2 kHz, DU = 23.5 ± 1.1 ms). While clustering and huddling up to the partner, the animals produced calls consisting of short notes with a very low intensity (DF = 1.0 ± 0.07 kHz, DU = 35.2 ± 0.8 ms). Based on these finding, it can be assumed that threatening sounds, emitted in agonistic encounters, allow shrews to avoid conflicts, while those, emitted when clustering and huddling up to the partner, contribute to maintenance of group cohesiveness. The variability of frequency ranges and intensity of sounds probably reflects the territorial and gregarious behaviour of C. leucodon and adaptation to communication in variable acoustic environments.
The patterns of social behaviour and spatial structure of Crocidura leucodon (Hermann, 1780) were studied against the background of the seasonal changes in its density and demographic features. Field and lab research were conducted. Field investigations (with CMR method) were conducted from 1997 to 1999 in north-western Bulgaria, in a grassland with patches of tree-shrub vegetation. In the lab, the social interactions were studied in male-male, female-female and male-female dyadic encounters during summer and autumn. A total of 26 shrews were tested. The number of C. leucodon was lowest in spring and greatest in autumn. In early summer the sex ratio was balanced, the home range of one male overlapped that of one female, and aggressiveness and marking activity was increased. So, it can be assumed that in this period males and females form pairs, which possess defended territories. Higher aggressiveness and marking activity displayed by males suggest their greater role in defending the territories. In autumn the home ranges overlapped greatly and amicable interactions prevailed over agonistic ones probably due to shifting to a gregarious way of life. So, the patterns of spatial structure and social behaviour undergo the seasonal changes in C. leucodon life-cycle and its density dynamics.
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