We could not detect regionally increased [(18)F]FDDNP binding and regionally decreased FDG binding in the brains of Tg2576 transgenic versus wild-type mice. However, small group differences in signal might have been masked by inter-animal variability. In addition, technical limitations of the applied method (partial volume effect, spatial resolution) for measurements in such small organs as mouse brain have to be taken into consideration.

Knowledge of the genetic mating system of animal species is essential for our understanding of the evolution of social systems and individual reproductive strategies. In recent years, genetic methods have uncovered an unexpected diversity of paternal genetic contributions across diverse animal social mating systems, but particularly in pair-living species. In most pair-living birds, for example, genetic and behavioral observations have confirmed a previously unknown significance of extra-pair copulations (EPCs) and extra-pair paternity. Among mammals, white-handed gibbons (Hylobates lar) are also known to live in pairs and are traditionally believed to be single-male single-female breeders. However, at Khao Yai National Park, Thailand, behavioral observations have confirmed the occurrence of both EPCs and functional multi-male grouping, but knowledge about the genetic mating system is still unavailable. In this study, we genotyped 89 white-handed gibbons of the Khao Yai population based on fecal samplings and were able to determine paternity for 41 offspring through short tandem repeat analysis. We found that females' stable social partners sired the majority (90.5%) of offspring (N = 38), while only a few (7.1%) offspring (n = 2 confirmed cases; n = 1 inferred case) were conceived with extra-pair partners. The paternity of one offspring remained inconclusive (2.4%), because the offspring's genotype did not mismatch with the genotypes of two potential sires. Like other predominantly pair-living species, gibbons appear to follow a mixed-reproductive strategy. The genetic mating system of wild white-handed gibbons is best described as flexible, primarily monogamous and opportunistically promiscuous. Inc.

Measuring energetic condition of wild animals is of major importance in ecological research, as it is profoundly linked to fitness. However, noninvasive monitoring of energetic condition in wild-living animals is methodologically challenging. Measuring urinary C-peptide levels is a suitable method to noninvasively assess energy balance in wild-living animals. As collecting urine is not always feasible in the wild, it is essential to establish alternative biomarkers for other sample types to assess energy balance. Thyroid hormones (TH) are potential candidates as they are involved in the regulation of metabolic processes. During periods of low energy intake, serum TH levels are reduced, leading to a decrease in metabolic activity. To investigate whether fecal TH can serve as a biomarker for energy balance, we validated a total T3 ELISA to measure immunoreactive T3 (iT3) in fecal samples of yellow-breasted capuchins. We restricted caloric intake of seven males, assessed daily group caloric intake and determined daily individual fecal iT3 levels. Analytical validation of the assay showed that fecal iT3 levels can be reliably measured; however, proper storage conditions must be implemented and possible degradation to be accounted for. IT3 levels were significantly higher on days with high group caloric intake. However, individual iT3 levels varied substantially, resulting in an overlap across individuals between conditions. Our results indicate that fecal iT3 levels can serve as a useful biomarker to detect changes in energy intake of yellow-breasted capuchins. Overall, measuring fecal iT3 levels may present a suitable method for monitoring energy balance when urine collection is impossible.

One of the primary sources of perceived stress is the social environment of an animal and the interactions with conspecifics. An essential component of the response to a stressor is the activation of the hypothalamic-pituitary-adrenocortical axis, which results amongst others in a temporal increase in circulating glucocorticoid (GC) levels. Giraffes occur in a highly flexible fission-fusion social system and group compositions can change on a daily basis, with bulls establishing an age-related dominance hierarchy and showing a roaming strategy in the search for fertile females. The aim of this study was to non-invasively monitor the influence of different group compositions (mixed sex groups vs. all-male groups) on GC concentrations in free ranging giraffe bulls of different age classes. We collected fecal samples from free-ranging giraffe bulls for 12months in a South African Private Game Reserve to examine age- and social context-related patterns of fecal GC metabolite (fGCM) concentrations. We found that fGCM levels in giraffe bulls are age-class dependent, as well asassociated with changes in the social environment. Independently of the social setting, bulls of the youngest age class exhibited the highest fGCM levels compared to bulls of the other two older age-classes, with differences most pronounced when the bulls are associated in all-male groups. In contrast, an almost reversed picture appears when looking at the fGCM levels of sexually active individuals in mixed sex groups, where highest levels were found for the bulls in the oldest age-class, and the lowest for the bulls in the youngest age-class. The study stresses the importance to taking factors such asage-related status and social settings into account, when interpreting fGCM levels in free ranging giraffes.