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Animal personalities range from individuals that are shy, cautious, and easily stressed (a "reactive" personality type) to individuals that are bold, innovative, and quick to learn novel tasks, but also prone to routine formation (a "proactive" personality type). Although personality differences should have important consequences for fitness, their(More)
Telomeres are DNA-protein complexes at the ends of chromosomes that control genomic integrity but appear to become shorter with age and stress. To test whether stress causes telomere attrition, we exposed the offspring of wild-caught house mice (Mus musculus) to stressful conditions and examined the changes in telomere length over six months. We found that(More)
The large variation in brain size that exists in the animal kingdom has been suggested to have evolved through the balance between selective advantages of greater cognitive ability and the prohibitively high energy demands of a larger brain (the "expensive-tissue hypothesis"). Despite over a century of research on the evolution of brain size, empirical(More)
Flexible or innovative behavior is advantageous, especially when animals are exposed to frequent and unpredictable environmental perturbations. Improved cognitive abilities can help animals to respond quickly and adequately to environmental dynamics, and therefore changing environments may select for higher cognitive abilities. Increased cognitive abilities(More)
unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Brain size varies dramatically among vertebrates, and selection for increased cognitive abilities is thought to be the key force underlying the evolution of a large brain. Indeed, numerous comparative studies suggest positive relationships between(More)
Selection pressures that act differently on males and females produce numerous differences between the sexes in morphology and behaviour. However, apart from the controversial report that males have slightly heavier brains than females in humans, evidence for substantial sexual dimorphism in brain size is scarce. This apparent sexual uniformity is(More)
The presence of fat stores in fish is widely used as a correlate of fish health and fitness. Techniques to measure fat content with some accuracy are available for medium-sized and large fish, but apart from morphometric indices, a noninvasive method to determine fat content in small fish has hitherto been lacking. In this study, we introduce a novel method(More)
Vertebrate brain size is thought to evolve through a balance between positive selection on cognitive abilities and evolutionary costs (Striedter 2005). In a recent study we tested this hypothesis experimentally by investigating the costs and benefits of evolving a larger brain (Kotrschal et al. 2013). We selectively bred guppies, Poecilia reticulata, for(More)
Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups, the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny, depending on early social experience.(More)