Selfish-herd behaviour of sheep under threat

Flocking is a striking example of collective behaviour that is found in insect swarms, fish schools and mammal herds [1]. A major factor in the evolution of flocking behaviour is thought to be predation, whereby larger and/or more cohesive groups are better at detecting predators (as, for example, in the 'many eyes theory'), and diluting the effects of predators (as in the 'selfish-herd theory') than are individuals in smaller and/or dispersed groups [2]. The former theory assumes that information (passively or actively transferred) can be disseminated more effectively in larger/cohesive groups, while the latter assumes that there are spatial benefits to individuals in a large group, since individuals can alter their spatial position relative to their group-mates and any potential predator, thus reducing their predation risk [3]. We used global positioning system (GPS) data to characterise the response of a group of 'prey' animals (a flock of sheep) to an approaching 'predator' (a herding dog). Analyses of relative sheep movement trajectories showed that sheep exhibit a strong attraction towards the centre of the flock under threat, a pattern that we could re-create using a simple model. These results support the long-standing assertion that individuals can respond to potential danger by moving towards the centre of a fleeing group [2].     

Acinetobacter infection--an emerging threat to human health

The genus Acinetobacter comprises a complex and heterogeneous group of bacteria, many of which are capable of causing a range of opportunistic, often catheter-related, infections in humans. However, Acinetobacter baumannii, as well as its close relatives belonging to genomic species 3 ("Acinetobacter pittii") and 13TU ("Acinetobacter nosocomialis"), are important nosocomial pathogens, often associated with epidemic outbreaks of infection, that are only rarely found outside of a clinical setting. These organisms are frequently pandrug-resistant and are capable of causing substantial morbidity and mortality in patients with severe underlying disease, both in the hospital and in the community. Several epidemic clonal lineages of A. baumannii have disseminated worldwide and seem to have a selective advantage over non-epidemic strains. The reasons for the success of these epidemic lineages remain to be elucidated, but could be related to the potential of these organisms to achieve very dynamic reorganization and rapid evolution of their genome, including the acquisition and expression of additional antibiotic resistance determinants, under fluctuating environmental and selective conditions.     

Temporal uncertainty, anticipation time, and cognitive coping under threat.

The effects of temporal uncertainty, anticipation time, and coping orientations on anticipatory reactions to an inevitable electric shock were investigated. One hundred eight male subjects were randomly assigned to the experimental conditions: they knew or did not know (temporal uncertainty) exactly when shock would occur; they waited either 1, 3, or 12 minutes for the shock, and were given either a vigilance, avoidance, or no orientation for preparing for the shock. Physiological measures were recorded continuously and pre- and post-trial questionnaires were completed to assess thoughts and feelings. Temporal uncertainty and anticipation time interacted to affect stress reactivity--i.e., as shock became imminent, temporal uncertainty led to the increased use of avoidant (as opposed to vigilant) modes of coping and was associated with a progressive lowering of reactivity, especially under the longer anticipation times. The results are consistent with the theory that coping processes mediate stress reactions under conditions of threat.     

Tobacco smoke in the workplace: an occupational health hazard.

Tobacco smoke, which contains over 50 known carcinogens and many other toxic agents, is a health hazard for nonsmokers who are regularly exposed to it while at work. Involuntary exposure to tobacco smoke annoys and irritates many healthy nonsmokers. Serious acute health effects are probably limited to the one fifth of the population with pre-existing health conditions that are aggravated by exposure to tobacco smoke. The consequences of long-term exposure include decreased lung function and lung cancer. Existing air quality standards for workplaces do not directly specify an acceptable level for tobacco smoke. The evidence on the composition of tobacco smoke and on the health hazards of involuntary exposure suggests that there may not be a "safe" level for such exposure.