Owls and rabbits: predation against substandard individuals of an easy prey

The interactions among the multiple factors regulating predator-prey relationships make predation a more complex process than previously thought. The degree to which substandard individuals are captured disproportionately seems to be better a function of the difficulty of prey capture than of the hunting techniques (coursing vs. ambushing predators). That is, when the capture and killing of a prey species is easy, substandard individuals will be predated in proportion to their occurrence in the prey population. In the present study, we made use of eagle owls Bubo bubo and their main prey, the rabbit Oryctolagus cuniculus: (a) the brightness of the white tails of rabbits seems to be correlated with the physical condition of individuals, (b) by using the tails of predated rabbits as an index of individual condition, we found that eagle owls seem to prefer substandard individuals (characterized by duller tails), and (c) by using information from continuous radiotracking of 14 individuals, we suggest that the difficulty of rabbit capture could be low. Although the relative benefits of preying on substandard individuals should considerably decrease when a predator is attacking an easy prey, we hypothesise that the eagle owl preference for substandard individuals could be due to the easy detection of poor individuals by a visual cue, the brightness of the rabbit tail. Several elements allow us to believe that this form of visual communication between a prey and one of its main predators could be more widespread than previously thought. In fact: (a) visual signalling plays a relevant role in intraspecific communication in eagle owls and, consequently, visual signals could also play a role in interspecific interactions, and (b) empirical studies showed that signals may inform the predator that it has been perceived, or that the prey is in a sufficiently healthy state to elude the predator.

Peroxydisulfate in MCM-48 silicas: powerful and clean materials for the removal of toxic gases

Sodium persulfate introduced into ordered MCM-48 silicas is described. The resulting materials are compared with existing activated carbon-based systems and MCM-48 containing transition metals such as Cu(II) and Cr(VI) for the decomposition of hydrogen cyanide and cyanogen. MCM-48 materials containing sodium persulfate alone improve on the protection offered by benchmark activated carbon systems and MCM-48 materials containing Cu(II) and Cr(VI), without the health risks associated with these metal ions.

Integrated palaeoecology and archaeology: a powerful approach for understanding pre-Columbian Amazonia

The old paradigm that Amazonia's tropical ecosystems prevented cultural development beyond small-scale shifting agricultural economies, that had little environmental impact, no longer holds true for much of Amazonia. A diversity of archaeological evidence, including terra preta soils, raised fields, causeways, large habitation mounds, geometric earthworks, and megalithic monuments, all point to considerable cultural complexity and environmental impacts. However, uncertainty remains over the chronology of these cultures, their diet and economy, and the scale of environmental impact and land use associated with them. Here, we argue that a cross-disciplinary approach, closely coupling palaeoecology and archaeology, can potentially resolve these uncertainties. We show how, with careful site selection (pairing small and large lakes, close proximity to archaeological sites, transects of soil pits) and choice of techniques (e.g., pollen, phytoliths, starch grains, charcoal, stable isotopes), these two disciplines can be successfully integrated to provide a powerful tool for investigating the relationship between pre-Columbian cultures and their environment.