The range of olfactory familiarity between individuals in a population of bank voles

The aim of the study was to test a hypothesis that small rodents in natural con­ditions are able to distinguish between the scents of neighbour (N) and stranger (S) individuals of conspecific. Experiments were carried out in a 100-year-old alder forest of the association Circaeo-elongatae Alnetum (Koch. 1926), on a population of bank voles Clethrion.om.ys glareolus (Schreber, 1780). Experiment I found higher capture rates in traps with the scent of N individuals (n = 35) and showed that the rodents could distinguish between N and S scents. Analysis of 90 sheets of Bristol board laid down in the forest in experiment II showed that rodents left significantly more traces of faeces and urine on sheets with the N scents. Experiment III showed that at distances of as much as 200 m from the place of origin of a donor there had been no decrease in the interest of other voles in its scent. Experiment IV increased the distance at which a fall-off in interest in the N scent was sought. As a result of 856 observations of the reactions of voles to the scents of donors originating at different distances, it was found that voles treated as N individuals those donors coming from distances of up to about 1000 m. Analysis of 840 sheets of Bristol board with scents of donors originating between 200 and 1400 m away used in experiment V showed that those smelting of donors from 1200 and 1400 m away were visited significantly less often by the rodents than others. A distance of around 1000 m may thus be the threshold for a decline in the interest of rodents in the N scent.