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

Abstract

E. 1999. The range of olfactory familiarity between individuals in a population of bank voles. Acta Theriologica 44: 133-150.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 Clethrionomys 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 smelling 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.

The home-range concept in rodents revised

“…The marking of a place with the odour of an alien individual to signal an individual's presence would seem logically to be the proper reaction of a resident individual to an intruder. However, the results of her experiments gave results opposite to what had been assumed, in that voles showed a greater interest (and incidence of supplementary marking) with the odour (excrement) of familiar individuals as compared to that from unknowns taken from 5 km away (Owadowska 1999).…”

“…Bednarz (1997) has shown that without rain the reaction of voles may be observed for at least 8 days from the time the odour is transferred to the "sponge". Moreover, Owadowska (1999) reported that a "sponge" saturated with excrement odour from the bank vole and placed in the field would provoke reactions of varying intensity from other individuals, that deposited their own excrement upon discovering the source. Owadowska (1999) further tested the hypothesis that voles would react with greater interest to the odour of an individual foreign to the given area than to a local one whose scent is known to be that of a "neighbour".…”

“…There is also more intensive marking in the vicinity of such "sponges" [as revealed on sheets of paper (30 ´ 40 cm) laid out on the forest litter] than there is where the scent of unfamiliar individuals is involved. Both of the above reactions to the odour of another individual can be used as a measure of familiarity between individuals (Owadowska 1999). The ecological significance of such behaviours remains to be studied.…”

“…They could only become familiar with the scent of the other individual within the zone of overlap of their ranges (A). The distance to this zone from their homes (H and H') is 250 m. The distance between homes (H and H') is thus of 500 m. AfterOwadowska (1999), modified.…”

The role of chemical information in shaping the spatial activity of bank voles in a free-living population

“…It is possible that scent trails in the alder wood were distributed so densely, that the exposure of a strange individual's scent caused avoidance reactions. Some authors suggest that bank voles react positively to the scent of a familiar animal and negatively if the donor is an unknown individual (eg Rajska-Jurgiel 1976, Owadowska 1999.…”