Francine Rozenfeld

Odour cue recognition by dominant male bank voles, Clethrionomys glareolus

Abstract The behaviour shown by hierarchically paired male bank voles in response to the faecal and urine marks of strange conspecifics (dominant male, hierarchically naive male and sexually unstimulated virgin female) and of males of two other rodent species (the common vole, Microtus arvalis, and the wood mouse, Apodemus sylvaticus) was observed in their familiar laboratory enclosure. Dominant residents reacted to all rodent marks by overmarking them with their own urine and faeces. They specifically responded to the urine marks of male and female bank voles by close sniffing and to their droppings by handling and licking them. Moreover, near conspecific male marks only, they performed two other behaviour patterns (flank scratching and genitals dragging) that may be regarded as scent marking. They did so significantly more near the marks of an unknown dominant than near those of an unknown naive male. These results demonstrate that urine and faecal marks of bank voles convey olfactory signals characteristic of the species, the sex and the hierarchical background of the animal that deposited them. They also suggest that voles may use both salivary glands and specific skin glands to mask conspecific odours.

Temporal segregation in coexisting Acomys species: The role of odour

To understand the mechanisms underlying displacement (the shift from nocturnal to diurnal activity), in one of the two coexisting spiny mice (genus Acomys), the effect of chemical cues released by A. cahirinus on the time of activity of A. russatus was tested Six golden spiny mice (A. russatus), which prior to the experiments were kept separate from common spiny mice (A. cahirinus), showed nocturnal activity. They were exposed to chemical cues from the urine and faeces of conspecific and heterospecific mice of the opposite sex. The onset of activity in these mice was recorded. While the urine and faeces of conspecific mice did not have a significant effect on the time of onset of activity, heterospecific urine and faeces did cause a significant (p < 0.001) time shift and, a day after they were introduced, activity started 6.8 +/- 1.9 h earlier. This shift also took place on the second day. The results of this study suggest that the mechanism for displacement of A. russatus from nocturnal activity is by chemical signals released by A. cahirinus. Therefore, it may be concluded that chemical cues maintain time separation between these two species.

Chemical signals involved in spacing behavior of breeding female bank voles (Clethrionomys glareolus Schreber 1780, Microtidae, Rodentia)

In order to study the mechanism involved in the seasonal territoriality of breeding bank voles, the social behavior and scent marking of paired females were observed throughout a reproductive cycle. Initially unfamiliar females were kept in large laboratory pens provided with individual burrows. After a brief period of hostility, females behaved in a friendly manner towards each other, sharing the same nest even in the presence of a male and until the middle of pregnancy. They scarcely marked with urine. Continuous olfactory assessment appeared to play an important role in maintaining the friendly interactions. In late pregnant and lactating females, on the contrary, the odor of a familiar female triggered aggressiveness and scent marking with urine and probably with flank glands. These reactions may be interpreted as spacing behavior. Moreover, the interaction between females may inhibit reproduction in one of them. These results are discussed in relation with the available ecological data.

A permanent marking method to identify individual small rodents from birth to sexual maturity

This note presents plantar micro-tattooing (subcutaneous injection of Chinese ink) as a good alternative to toe-clipping, which is often used to identify individual rodents. The method was tested under laboratory conditions on voles Microtus arvalis from birth to sexual maturity. This easy, harmless and inexpensive technique could be used in the field, and not only on pups but also on adults of different species.

BURROWING BY COMMON VOLES(MICROTUS ARVALIS)IN VARIOUS SOCIAL ENVIRONMENTS

Female common voles live in groups in large burrows whereas males are probably solitary and promiscuous. At high population density, when burrows become a limiting factor, some females are forced to emigrate from their group. To investigate whether these emigrants could share new common burrows with unrelated neighbours, we analysed in the laboratory burrowing and social behaviour in dyads of unrelated wild females before and during their cohabitation. They were compared to wild male dyads. In solitary voles, no sexual difference in burrowing pattern was observed but females built a burrow more quickly than males. In both sexes, the first encounters happened in one of the burrow and were of aggressive nature; during them intruders used burrowing during offensive approaches. While males displayed hierarchy and nested for themselves, females rapidly became friendly and nested together. They reshaped their burrows in response to social nesting and had more complex burrows than solitary females or intolerant males. We may conclude that in common voles at least unrelated non breeding females may contribute to the formation of social groups. To investigate whether, within a matriarchal group, females may co-operate with their own daughters in building a new common burrow, we analysed burrowing behaviour in dyads comprising either an experienced wild mother with one of her naive daughters or two naive familiar daughters. No co-operative behaviour could be detected but experience in burrowing speeded up the building. The results strongly suggest that, within a short time, young females may improve their burrowing.

Reproduction and Urine Marking in Laboratory Groups of Female Common Voles Microtus arvalis

In laboratory groups of common voles, Microtus arvalis, consisting of one mother, two of her daughters and one male, mainly the mother reproduced. The three females spent most of the time in close body contact. By using a modified method of coloring the urine of the three females by nonmetabolizable, nontoxic dyes, we found that mothers display a higher urine marking intensity than their daughters, and urine marks from the mother were distributed more frequently than those from the daughters. The results suggest that both pheromonal and behavioral mechanisms are involved in the regulation of reproduction in matriarchal groups of common voles.

A technique for sterile culture of fresh water sponges

By treating the gemmules of freshwater sponges successively with hydrogen peroxide and with sodium hypochlorite in suitable concentrations, we obtained cultures that were free from any bacterial or fungal contaminant. This technique provides a useful tool for further studies on metabolic and antibiotic activities, and of the behaviour of isolated cells cultivated in artificial media.

Home site scent marking with urine and an oral secretion in the golden spiny mouse (Acomys russatus)

Captive golden spiny mice (Acomys russatus) use odors from different sources to mark their home area. The marking behavior is sexually dimorphic, with males marking more frequently than most females. This difference may be related to mobility; females being more sedentary than males. In both sexes, the entrance to the nesting place was the main site of marking. The animals repeatedly marked this area by smearing the entrance with a thick oral secretion and by depositing small urine marks. Under the harsh ecological conditions under which A. russatus lives, nesting sites are presumably subject to fierce competition. The role of this chemical signaling in the temporal segregation between the two sympatric species, A. russatus and A. cahirinus, is discussed. Golden spiny mice also mark their food and leftovers with oral scent. This marking may have a social function in making food detection easier for the kin.

Temporal segregation in co-existing Acomys species:the possible role of nest site

Abstract The co-existence of two species of spiny mouse of the genus Acomys is possible due to temporal segregation. While the common spiny mouse A. cahirinus is nocturnal, the golden spiny mouse A. russatus is diurnal when occurring with the former. An attempt was made to investigate the role of nest site as an environmental resource for competition between these two species. Nine heterospecific pairs of mice of both the same or opposite sexes were tested using an observation pen with two nesting places attached to each side. Each pair tested was observed in the pen over a period of 48h. In eight out of the nine different pairs, A. cahirinus occupied the original nest site of A. russatus. The replacement was found to be not random. The results of this study show that A. cahirinus selects a preferred nest site and its vacated nest sites can be utilized by A. russatus.

EFFECT OF ODOUR CUES ON THE EXPLORATORY BEHAVIOUR OF FEMALE COMMON VOLES LIVING IN MATRIARCHAL GROUPS

Seven matriarchal breeding groups of common voles (Microtus arvalis) were studied to test bonding between females when given the option to leave their family group, and the hypothesis that they explore more in areas with odours from related individuals compared to areas scented with odours from unrelated individuals.Young females were observed more frequently in the proximity of their mother and were recorded more often with their sisters than alone. Except for reproductive females, all females were seen more frequently in the initial home area than in areas of exploration. Females frequented an area scented with the odour of related females more often than one with the odour of unrelated, unfamiliar females, but only shortly before dark. In most test groups only the adult females reproduced although their daughters had reached the age of sexual maturity. The results indicate that young female M. arvalis tend to stay with their mother and may delay their own reproduction. When exploring the vicinity of the burrow young females tend to prefer areas with the scent from related females and can recognize odour cues after being separated from the odour donor for 3.5 weeks. This behaviour may minimize aggressive encounters, leading to dispersal toward related individuals.