Elephants classify human ethnic groups by odor and garment color

Animals can benefit from classifying predators or other dangers into categories, tailoring their escape strategies to the type and nature of the risk. Studies of alarm vocalizations have revealed various levels of sophistication in classification [1-5]. In many taxa, reactions to danger are inflexible, but some species can learn the level of threat presented by the local population of a predator [6-8] or by specific, recognizable individuals [9-10]. Some species distinguish several species of predator, giving differentiated warning calls and escape reactions; here we explore an animal’s classification of sub-groups within a species. We show that elephants distinguish at least two Kenyan ethnic groups, and can identify them by olfactory and color cues independently. In the Amboseli ecosystem, Kenya, Maasai warriors demonstrate virility by spearing elephants (Loxodonta africana), but Kamba agriculturalists pose little threat. Elephants showed greater fear when they detected the scent of garments previously worn by Maasai than by Kamba men, and reacted aggressively to the color associated with Maasai warriors. Elephants are therefore able to classify members of a single species into sub-groups that pose different degrees of danger

Tuning intermolecular interaction in long-range-ordered submonolayer organic films

The future success of organic electronic devices strongly depends on the ability to tailor the properties of thin films and interfaces. This calls for well-ordered thin films. However, their properties are dominantly influenced by the formation of the first molecular layer representing a template for further growth. The development of the first layer-in turn-depends on the fine balance of molecule-substrate and molecule-molecule interaction. The latter is usually attractive owing to van der Waals forces and causes the formation of islands and small crystalline grains. Here, we report on organic adsorbates exhibiting a repulsive intermolecular interaction. With increasing coverage, Sn-phthalocyanine molecules continuously rearrange on Ag(111) in a series of ordered superstructures. They always fill the surface terraces homogeneously and maximize the domain size. Thicker films also exhibit extremely large, monocrystalline grains and potentially enable bulk-like properties for thin films. The intermolecular interaction can be tuned by cooling and becomes attractive below similar to 120 K