Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Deprivation of direct adult contact during development affects social representation in a songbird

International audienceSocial cognition involves a wide array of skills that are built largely through interactions with conspecifics and therefore depend upon early social experience. Motivation for social stimuli is a key feature of social behavior and an operant conditioning task showed that isolated wild-caught adult starlings (Sturnus vulgaris) are highly motivated to access pictures of other starlings. Here, we show that hand-raised adult starlings maintained in groups of peers throughout development but without any contact with adult models were not or only poorly motivated to access pictures of conspecifics. Moreover, they did not prefer pictures of starlings to pictures of landscapes, unlike birds wild-caught as adults. These results raise questions about the role of social experience during development, particularly with adult models, in the development of social motivation and of social representation in general

To see or not to see: visual contact, a primary need for social animals?

International audienceOne characteristic of sociality is the active seeking of proximity by conspecifics. Although active interactions and physical contacts can be involved, in many cases, visual contact at least plays an important role. In the present study, we investigated whether this motivation for visual contact is strong enough to become a “primary reinforcer”. Thus, we used an operant conditioning procedure to test whether isolated adult European starlings, a social species of birds, would actively trigger social or non-social stimuli presented as 2D pictures. The results show that true conditioning with no training and no other reward than the pictures is possible. Moreover, starlings expressed a preference for pictures of conspecifics over pictures of (1) landscapes and (2) monkeys. A mere picture can therefore act as a “primary reinforcer” in an operant conditioning procedure

Social visual contact, a primary “drive” for social animals?

International audienceSocial animals are always searching for con-specifics, thereby expressing a genuine ‘social need’’. This need is illustrated by the fact that social isolation can induce isolation syndromes that can be attenuated by devices such as mirrors. Social contacts appear to be so vital for social animals that they may be ready to work to obtain social stimulations. We used here operant conditioning to investigate the possibility to use visual contact (through pictures of same sex conspecifics) as a primary reinforcer. Isolated males European starlings (Sturnus vulgaris) were offered the choice of seeing either social images (i.e. pictures of con-specifics) or non-social images (i.e. pictures of landscapes or pictures of monkeys) by triggering sensors. In contrast with most studies, our subjects were presented still pictures of conspecifics and not videos. Moreover, these pictures were used as primary reinforcers and thus were not paired with food. Our data show that starlings were ready to work and to use the apparatus (i.e. sensors) to see pictures in the absence of any other reward. Moreover, they actively and significantly preferred pictures of conspecifics to pictures of inanimate objects (landscapes) or of heterospecifics (monkeys). This suggests that 2D pictures with a social overtone can be used as primary reinforcers for isolated social birds

Adult Deprivation during development affects social motivation of a songbird

International audienceOne characteristic of sociality is the fact of being attracted by conspecifics. However, individuals reared in isolation may be disturbed by the presence of conspecifics and they can even stay away from conspecifics when given the opportunity to interact with them. This may reflect troubles in discrimination and/or social attraction. Here, we evaluated whether starlings (Sturnus vulgaris) reared with no adults would be attracted by conspecifics depicted in pictures when socially isolated. Hand-reared male starlings were offered the possibility to see either social pictures (i.e. pictures of unfamiliar conspecifics) or non-social pictures (pictures of landscapes) by triggering sensors freely. Our data showed that only half of the starlings used the sensors steadily to see pictures, and, as a group, they did not exhibit any preference for one type of pictures or the other. This contrasts with the fact that adult wild-caught starlings, when isolated, show a high motivation to obtain pictures of conspecifics. This suggests that adults are necessary for attraction by conspecifics to develop

Voir ou ne pas voir : une étude de la motivation sociale chez l’étourneau

National audienceL'environnement social joue un rôle clé dans la vie des animaux sociaux. Ces derniers peuvent exprimer leurs affinités pour un congénère par la recherche de proximité sans qu'il y ait forcément besoin de contacts ou d'interactions physiques. Ainsi, les contacts visuels avec les congénères peuvent s'avérer très importants pour certaines espèces sociales. Ceci conduit à se demander si cette motivation à être en contact visuel avec un congénère est telle qu'elle peut induire une action de la part de l'individu. Pour apporter des réponses à cette question, nous avons présenté à une espèce sociale, l'étourneau sansonnet, des stimuli standardisés, à savoir des images fixes, dans un dispositif de type conditionnement opérant. Les individus pouvaient exprimer un choix actif en déclenchant soit des stimuli sociaux soit des stimuli non sociaux. La capacité renforçatrice de stimuli visuels, en l'absence de toute récompense alimentaire, a ainsi été testée. Les résultats ont confirmé la valeur renforçatrice de stimuli purement sensoriels et une réelle préférence sensorielle (visuelle) pour les congénères

Assessing video presentations as environmental enrichment for laboratory birds.

The aim of the present study was to investigate the effects of video presentations of natural landscapes on European starlings' (Sturnus vulgaris) stereotypic behaviours (SBs) and other abnormal repetitive behaviours (ARBs) and to evaluate the impact of past experience by comparing wild-caught and hand-reared starlings' reactions. Ten wild-caught and five hand-reared starlings were presented 1-hour videos of landscapes twice a day for five successive days, while a control group of eight wild-caught and four hand-reared starlings was presented a grey screen for the same amount of time. The analysis of the starlings' behaviour revealed that the video presentations of landscapes appeared to have a positive but limited and experience-dependent effect on starlings' SBs and other ARBs compared to the controls. Indeed, whereas video presentations seemed to modulate high rates of SBs and ARBs, they did not appear to be enriching enough to prevent the emergence or the development of SBs and ARBs in an impoverished environment. They even appeared to promote a particular type of SB (somersaulting) that is thought to be linked to escape motivation. The fact that this effect was observed in hand-reared starlings suggests that videos of landscapes could elicit motivation to escape even in birds that never experienced outdoor life. These results highlight the importance of investigating stereotypic behaviour both quantitatively and qualitatively in order to provide crucial clues on animal welfare

Spatial structure of roe deer populations: towards defining management units at a landscape scale.

International audience1. A crucial question in wildlife management concerns the definition of ecologically meaningful management units. Management action needs to be co-ordinated at the appropriate spatial scale. There are few practical tools for delimiting pertinent management units for large mammals such as ungulates. 2. Previous work has favoured a molecular approach to determine genetically distinct units, but this may be too costly for routine management. In addition, recent studies have revealed fine-scale heterogeneity in population dynamics of free-ranging ungulates in relation to environmental variability. 3. We combined spatial analysis of environmental heterogeneity (vegetation cover, topography and climate), animal morphology (jaw length) and genetic structure (microsatellites) to define biologically meaningful population units for roe deer Capreolus capreolus in the Belluno province, north-eastern Italy. Jaw length is a sensitive measure of density-dependence and a good proxy for spatial and temporal variation in roe deer population growth. 4. Spatial analysis of environmental variables suggested that the study area should be divided into two, or possibly four, biogeographical regions in relation to variation in altitude and habitat type. There was significant spatial variability in jaw length across the province that clustered into two main regions (with shorter jaws in the north compared with the south), which matched the previously defined biogeographical regions. This spatial structuring was also supported by microsatellite analysis, which revealed two genetically distinct populations, one in the north and one in the south. 5. Synthesis and applications. A multiparameter approach, combining environmental information with data on indices of density-dependence such as jaw length, could be extremely useful for defining ecologically meaningful management units. Indeed, monitoring spatial and temporal variation in jaw length could provide deer managers with a simple way to index population structure and fluctuations in time and space