Raptor nest decorations are a reliable threat against conspecifics

Individual quality is often signaled by phenotypic flags, such as bright plumage patches in birds. Extended phenotype signals can similarly show quality, but in these cases the signals are external to the individual, often taking the form of objects scavenged from the environment. Through multiple manipulative experiments, we showed that objects used for nest decoration by a territorial raptor, the black kite (Milvus migrans), act as reliable threats to conspecifics, revealing the viability, territory quality, and conflict dominance of the signaler. Our results suggest that animal-built structures may serve as signaling devices much more frequently than currently recognized.     

Behavioral regulation of the milieu interne in man and rat

In regulating the internal homeostatic environment mammals, by necessity, employ behavioral strategies that differ from the tactics used in coping with contingencies in the external environment. When an animal consumes a meal, the palatability of that meal is automatically adjusted in accordance with the ultimate internal effects of that meal. If the meal causes toxicosis, the animal acquires an aversion for the taste of the meal; conversely, if recuperation follows ingestion of the meal, the taste of that meal is enhanced. Unlike the learning that occurs when externally referred visual and auditory signals are followed by punishment in the form of peripheral pain or reward in the form of food in the mouth, conditioning to the homeostatic effects of food can occur in a single trial and rarely requires more than three to five trials, even though the ultimate effects of the meal are delayed for hours. Paradoxically, the animal need not be aware of the ultimate internal effect in the same sense that it is aware of external contingencies. For example, an aversion can be acquired even if the animal is unconscious when the agent of illness is administered. Thus, the way in which food-effects are stored in memory may be fundamentally different from the way in which memories of specific time-space strategies devised for external contingencies are stored. This separation of function is indicated by limbic lesions which disrupt conditioning to a buzzer that is followed by shock and facilitate conditioning to a taste that is followed by illness. Operationally speaking, one can describe both aversion conditioning and buzzer-shock conditioning in the spacetime associationistic terms of classical conditioning. However, psychologically speaking, one must realize that in aversion conditioning the animal does not act as if it were acquiring an "if-then" strategy. It acts as if a hedonic shift, or a change in the incentive value of the flavor were taking place. Such hedonic shifts are critical in regulation of the internal milieu. When an animal is in need of calories, food tends to be more palatable; as the caloric deficit is restored, food becomes less palatable. If the animal's body temperature is below optimum, a warm stimulus applied to the skin is pleasant. When body temperature is too high, the converse is true. In this way, homeostatic states monitored by internal receptors produce changes in the incentive values of external stimuli sensed by the peripheral receptors, and guide feeding behavior. In mammals at least, the gustatory system, which provides sensory control of feeding, sends fibers to the nucleus solitarius. This brainstem relay station also receives fibers from the viscera and the internal monitors of the area postrema. Ascending fibers bifurcate at the level of the pons and project toward the feeding areas of the hypothalamus and the cortex. The olfactory system which primarily projects to the limbic system does not play a primary role in adjusting food incentives. Rather, it plays a secondary role in the activation of feeding, as do other external sensory systems. This specialized conditioning mechanism, which specifically adjusts gustatory hedonic values through delayed visceral feedback, is widespread among animals, including man and rat. These two species are remarkably similar in their thresholds and preferences for gustatory stimuli. The behavioral similarities are based on the animals' having similar gustatory systems, similar convergence of gustatory and internal afferents to the nucleus solitarius, and similar midbrain regulatory mechanisms. Thus, it is not surprising that the feeding of obese rats with internal hypothalamic damage resembles the feeding of obese human beings insensitive to the internal signs of this caloric state. Obviously, man has a highly specialized form of symbolic communication and the rat does not, yet man's cognitive specialization does not prevent him from developing aversions to food consumed before illness even when he knows that his illness was not caused by food (43).     

The Near Eastern origin of cat domestication

The world's domestic cats carry patterns of sequence variation in their genome that reflect a history of domestication and breed development. A genetic assessment of 979 domestic cats and their wild progenitors-Felis silvestris silvestris (European wildcat), F. s. lybica (Near Eastern wildcat), F. s. ornata (central Asian wildcat), F. s. cafra (southern African wildcat), and F. s. bieti (Chinese desert cat)-indicated that each wild group represents a distinctive subspecies of Felis silvestris. Further analysis revealed that cats were domesticated in the Near East, probably coincident with agricultural village development in the Fertile Crescent. Domestic cats derive from at least five founders from across this region, whose descendants were transported across the world by human assistance.     

Identifying kinetic barriers to mechanical unfolding of the T. thermophila ribozyme

Mechanical unfolding trajectories for single molecules of the Tetrahymena thermophila ribozyme display eight intermediates corresponding to discrete kinetic barriers that oppose mechanical unfolding with lifetimes of seconds and rupture forces between 10 and 30 piconewtons. Barriers are magnesium dependent and correspond to known intra- and interdomain interactions. Several barrier structures are "brittle," breakage requiring high forces but small (1 to 3 nanometers) deformations. Barrier crossing is stochastic, leading to variable unfolding paths. The response of complex RNA structures to locally applied mechanical forces may be analogous to the responses of RNA during translation, messenger RNA export from the nucleus, and viral replication.     

Acute lymphocytic leukemia in owl monkeys inoculated with herpesvirus saimiri

Our study demonstrates for the first time that Herpesvirus saimiri can induce acute lymphocytic leukemia in owl monkeys (Aotus trivirgatus) and that malignant lymphoma can be induced in this species of nonhuman primates by the inoculation of the virus by various routes (intravenous, sub-cutaneous, and intradermal).     

Habitat split and the global decline of amphibians

The worldwide decline in amphibians has been attributed to several causes, especially habitat loss and disease. We identified a further factor, namely "habitat split"-defined as human-induced disconnection between habitats used by different life history stages of a species-which forces forest-associated amphibians with aquatic larvae to make risky breeding migrations between suitable aquatic and terrestrial habitats. In the Brazilian Atlantic Forest, we found that habitat split negatively affects the richness of species with aquatic larvae but not the richness of species with terrestrial development (the latter can complete their life cycle inside forest remnants). This mechanism helps to explain why species with aquatic larvae have the highest incidence of population decline. These findings reinforce the need for the conservation and restoration of riparian vegetation.     

Laboratory simulation of volcano seismicity

The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt from Mount Etna volcano (Italy) was deformed and fractured. The experiment was monitored with an array of transducers around the sample to permit full-waveform capture, location, and analysis of microseismic events. Rapid post-failure decompression of the water-filled pore volume and damage zone triggered many low-frequency events, analogous to volcanic long-period seismicity. The low frequencies were associated with pore fluid decompression and were located in the damage zone in the fractured sample; these events exhibited a weak component of shear (double-couple) slip, consistent with fluid-driven events occurring beneath active volcanoes.