Evaluation of the social bond: a new method tested in Mus spicilegus

International audienceInnovative and fruitful studies of social bonds have been developed in recent years, although the methods used to establish the existence of a social bond between two individuals have not evolved significantly. Two types of paradigms have been currently used: the separation-reunion paradigm which evaluates the distress caused by the disruption of the social bond, and choice paradigms which test the specificity of the bond to a given individual. We have developed a new paradigm based on the idea that the cost an individual was ready to pay in order to gain access to a conspecific depended on the strength of the social bond between the two individuals. To test our paradigm we used mound-building mice, Mus spicilegus that present, in both males and females, a level of tolerance which differs greatly according to the degree of familiarity between the individuals. Our new method for testing social bond revealed unsuspected differences between males and females. Our results suggested that, at least in Mus spicilegus, strong social bonds were not necessary to the development of a high level of tolerance between individuals

Comparison of urinary scents of two related mouse species, Mus spicilegus and Mus domesticus.

International audienceWhereas the house mouse (Mus domesticus) has been studied extensively in terms of physiology/behavior and pheromonal attributes, the evolutionarily related mound-building mouse (Mus spicilegus) has received attention only recently due to its divergent behavioral traits related to olfaction. To date, no chemical studies on urinary volatile compounds have been performed on M. spicilegus. The rationale for our investigations was to determine if there are differences in urinary volatiles of intact and castrated M. spicilegus males and to explore further whether this species could utilize the same or structurally similar pheromones as the male house mouse, M. domesticus. The use of capillary gas chromatography/mass spectrometry (GC-MS) together with sorptive stir bar extraction sampling enabled quantitative comparisons between the intact and castrated M. spicilegus urinary profiles. Additionally, through GC-MS and atomic emission (sulfur-selective) detection, we identified qualitative molecular differences between intact M. spicilegus and M. domesticus. A series of volatile and odoriferous lactones and the presence of coumarin were the unique features of M. spicilegus, as was the notable absence of 2-sec-butyl-4,5-dihydrothiazole (a prominent M. domesticus male pheromone) and other sulfur-containing compounds. Castration of M. spicilegus males eliminated several substances, including delta-hexalactone and gamma-octalactone, and substantially decreased additional compounds, suggesting their possible role in chemical communication. Some other M. domesticus pheromone components were also found in M. spicilegus urine. These comparative chemical analyses support the notion of metabolic similarities as well as the uniqueness of some volatiles for M. spicilegus, which may have a distinct physiological function in reproduction and behavior

Paternal care in the mound building mouse reduces inter-litter intervals.

International audienceIn many rodent species males display paternal behaviour. The primary reported effect of this paternal care is to increase pup survival. In mammal females, pregnancy and lactation are energetically demanding, especially when they are concurrent in post-partum reproduction. To face this energy requirement, females generally lengthen the duration of their post-partum pregnancy. In the present study we tested whether paternal care could affect this duration in the monogamous mound building mouse Mus spicilegus. In this species, females have a short reproductive life that does not exceed 4 months. Reduction of inter-delivery latencies would then be an efficient way to increase reproductive success. In a male removal experiment, we showed that inter-delivery latency was shortened by male presence. Moreover, behavioural estimations of paternal involvement were correlated with inter-delivery latency. The longer the male spent inside the nest the shorter the inter-delivery latency. In the mound-building mouse, the female might be able to monopolise the parental care of a single male, which could be important for the evolution of monogamy. The characteristics of first reproduction as compared to post-partum reproduction suggest that it may contribute to the formation of a strong and exclusive social bond between the reproductive partners

Deficit in reproduction in polygynously mated females of the monogamous mound-building mouse Mus spicilegus

International audienceIn monogamous mound-building mice Mus spicilegus, facultative polygyny was observed in April, at the beginning of the reproductive season. In order to evaluate the cost of polygyny, we compared under laboratory conditions the reproductive success of trios and pairs composed of sister females mated with unrelated brother males. Females in trios were able to tolerate each other during the reproductive period and to reproduce with the same male under spatial constraints. Polygyny had, nevertheless, a strong negative effect on the reproductive success of females. The average number of young per litter was smaller in trio females than in paired females, whereas the interval between two successive litters was higher. As a result, the number of litter and the number of young per time unit was smaller in each of the trio females than in paired females. Agonistic behaviour being absent in trios, our results strongly suggested that living in trio led to pheromonal productions affecting female physiological state and reproduction. Males of trios did not obtain a better reproductive success than males in pairs

Social regulation of reproduction in the female mound-builder mouse (Mus spicilegus)

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Seasonal reproduction and delayed sexual maturity in mound-building mice Mus spicilegus

International audienceIn the mound-building mouse, Mus spicilegus, which is found from Central to Eastern Europe, reproduction is seasonal and limited to spring and summer. In autumn, the mice build voluminous mounds composed of vegetable matter covered with earth, where juvenile animals (autumnal individuals) over-winter in groups without reproducing. Autumnal animals delay reproduction until the next spring when they are 6 months old. The influence and interactions of environmental (short light period and cold temperature (C conditions) compared with long light period and temperate temperature (T conditions)) and social factors (lack of odours from breeding adults (NB conditions) compared with presence of odours from breeding adults (B conditions)) on reproduction and sexual maturation were studied. Forty groups of three autumnal individuals (two males and a female or two females and a male) were placed in four experimental conditions (CB, CNB, TB and TNB), corresponding to interactions between environmental and social factors (n = 10 groups for each condition). Of the 40 groups only one initiated reproduction during the 18 weeks of cohabitation. Subsequently, animals were separated and isolated for 1 month and then paired with unfamiliar partners. Reproduction was monitored for an additional month, and 24 out of 39 females reproduced. In addition, of eight reproducing pairs placed in C conditions and 10 reproducing pairs maintained in T conditions, all but one pair continued reproduction. It was concluded that the delay in reproduction observed in autumnal individuals was the result of the social effects of living in groups as opposed to the environmental conditions of winter

Data visualization techniques for airspace flow modeling

International audienceWith the predicted growth of air traffic, traffic flow managers need new tools to access information to support their decision making processes. Recent progress with information visualization tools enables users to explore large data sets and extract decisive knowledge. Their advantages for air traffic applications are presented in this paper. They can provide high level information to aggregate trajectories. With constant feedback due to human perception, a flow model of the airspace, reflecting its intrinsic structure, is elaborated and can be used for further research