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Hirsch B.T.,Smithsonian Tropical Research Institute | Hirsch B.T.,Cec Inc. | Morrell L.J.,University of Leeds | Morrell L.J.,University of Hull
Behavioral Ecology | Year: 2011

Predation is a major pressure that shapes animal sociality, but predation risk is not homogenous within groups. Animals located on the group edge typically face an increased threat of predation, although different patterns have been reported. We created a simulation model to determine how changes in predator attack distance and prey density influence predation in relation to within-group spatial position. At large attack distances, peripheral animals were attacked far more than central animals. At relatively short attack distances, central individuals were attacked almost as often as peripheral animals. We used 6 different methods to classify within-group spatial position in our simulations and tested which methods were the best predictors of predation risk at different parameter values. The minimum convex polygon and angle of vulnerability methods were the best predictors of predation risk at large and medium attack distances, respectively. At relatively short attack distances, the nearest neighbor distance and neighbor density methods were the best predictors of predation risk. These patterns demonstrate that the threat of marginal predation is dependent on the behavior of predators and that for some predator-prey systems, marginal predation is predicted to be insignificant. We predict that social prey animals should change antipredatory behavior, such as vigilance, within-group spacing, and within-group spatial choice based on the relative distances at which their predators attack. These results demonstrate the importance of incorporating the behavior of predators in empirical studies and predator-prey models. © The Author 2011. Source

Hirsch B.T.,Smithsonian Conservation Biology Institute | Hirsch B.T.,Smithsonian Tropical Research Institute | Hirsch B.T.,Cec Inc. | Maldonado J.E.,Smithsonian Conservation Biology Institute
Molecular Ecology | Year: 2011

The ring-tailed coati (Nasua nasua) is the only coati species in which social groups contain an adult male year round, although most males live solitarily. We compared reproductive success of group living and solitary adult male coatis to determine the degree to which sociality affects reproductive success. Coati mating is highly seasonal and groups of female coatis come into oestrus during the same 1-2 week period. During the mating season, solitary adult males followed groups and fought with the group living male. This aggression was presumably to gain access to receptive females. We expected that high reproductive synchrony would make it difficult or impossible for the one group living male to monopolize and defend the group of oestrous females. However, we found that group living males sired between 67-91% of the offspring in their groups. This reproductive monopolization is much higher than other species of mammals with comparably short mating seasons. Clearly, living in a group greatly enhanced a male's reproductive success. At the same time, at least 50% of coati litters contained offspring sired by extra-group males (usually only one offspring per litter); thus, resident males could not prevent extra-group matings. The resident male's reproductive advantage may reflect female preference for a resident male strong enough to fend off competing males. © 2010 Blackwell Publishing Ltd. Source

Hirsch B.T.,Smithsonian Tropical Research Institute | Hirsch B.T.,Cec Inc.
Behavioral Ecology and Sociobiology | Year: 2011

The location of an animal within a social group has important effects on feeding success. When animals consume quickly eaten food items, individuals located at the front edge of a group typically have greater foraging success. When groups feed at large clumped resources, dominant individuals can often monopolize the resource, leading to higher feeding success in the center of the group. In order to test these predictions, behavioral data relating foraging success to within-group spatial position were recorded from two habituated groups of ring-tailed coatis (Nasua nasua) in Iguazu, Argentina. Foraging success did not fit expected patterns. When feeding on small ground litter invertebrates, coatis had the same foraging success at all spatial positions. This pattern likely resulted from an abundance of invertebrates in the ground litter. When feeding on fruit, individuals in the front of the group had greater feeding success, which was driven by the relatively quick depletion of fruit trees. Dominant juveniles were often located in the front of the group which led to increased access to food. This resulted in higher feeding success on fruits but simultaneously increased their risk of predation. Although groups typically became more elongated and traveled faster when feeding on fruit, it did not appear that the coatis were drastically changing their spacing strategies when switching between the two food types. Paradoxically, spatial position preferences during invertebrate foraging appeared to be driven by fruit trees. Because fruit trees were encountered so frequently, juveniles ranging at the front edge of the group during invertebrate foraging were the first to arrive at fruit trees and thus had higher foraging success. This study demonstrates the importance of how food patch size and depletion rate affect the spatial preferences of individuals. © 2010 Springer-Verlag. Source

Hirsch B.T.,Smithsonian Tropical Research Institute | Hirsch B.T.,Cec Inc.
Behavioral Ecology and Sociobiology | Year: 2011

A variety of factors can influence an individual's choice of within-group spatial position. For terrestrial social animals, predation, feeding success, and social competition are thought to be three of the most important variables. The relative importance of these three factors was investigated in groups of ring-tailed coatis (Nasua nasua) in Iguazú, Argentina. Different age/sex classes responded differently to these three variables. Coatis were found in close proximity to their own age/sex class more often than random, and three out of four age/sex classes were found to exhibit within-group spatial position preferences which differed from random. Juveniles were located more often at the front edge and were rarely found at the back of the group. Juveniles appeared to choose spatial locations based on feeding success and not predation avoidance. Since juveniles are the most susceptible to predation and presumably have less prior knowledge of food source location, these results have important implications in relation to predator-sensitive foraging and models of democratic group leadership. Subadults were subordinate to adult females, and their relationships were characterized by high levels of aggression. This aggression was especially common during the first half of the coati year (Nov-April), and subadults were more peripheralized during this time period. Subadults likely chose spatial positions to avoid aggression and were actively excluded from the center of the group by adult females. In the Iguazú coati groups, it appeared that food acquisition and social agonism were the major determinants driving spatial choice, while predation played little or no role. This paper demonstrates that within-group spatial structure can be a complex process shaped by differences in body size and nutritional requirements, food patch size and depletion rate, and social dominance status. How and why these factors interact is important to understanding the costs and benefits of sociality and emergent properties of animal group formation. © 2010 Springer-Verlag. Source

Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2014

The current state-of-the art technology for CO2 capture from point- source emitters such as coal and natural-gas fired power plants is amine scrubbing. It is not clear that this single technology will be adequate, affordable, and environmentally sound at the scale required for significant mitigation of negative effects of climate change. It is imperative that other technologies are investigated. The main objective of the proposed technology is the development of a N2-selective catalytic membrane for application to CO2 capture from natural gas and coal-fired power plants. The N2-selective membrane technology benefits from the driving force of N2 in flue gas (~73 vol.%). Application of a membrane separation technology to CO2 capture simplifies a conventional separation process (i.e., amine scrubbing) by removing the need of regeneration, thereby motivating submission into the subcategory of Process Intensification in the primary category Carbon Capture. This proposal represents the first attempt to synthesize and test membranes that selectively separate N2 from gas mixtures. The proposed efforts will focus on the computational design, synthesis, characterization and testing of alloys of V and Nb with Ru for enhanced N2 flux. Experiments will take place in a custom-built high temperature reactor available to the PI. Commercial Applications and Other Benefits: In addition to CO2 capture, there are other benefits associated with this technology. For instance, metallic membranes of the type described in the proposed work may also be applicable for air separation processes, which will lead to advances in oxycombustion and gasification technologies. Through the application of selective- N2 membrane technology, ammonia could be produced at a lower energy cost than the traditional high-pressure Haber-Bosch process and the ammonia can also be used directly as a fuel to source for the agriculture industry. Finally, this membrane technology may be applied to natural gas purification.

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