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Exploitation by humans impacts wildlife in many ways. Selective harvesting regimes affect demography of the remaining population, and increased mortality shortens life expectancy affecting optimal life-history strategies. We studied this in a Finnish moose (Alces alces) population using harvest data on age, carcass weight, antler spread and tine number, and compared the growth in body weight and that of antlers in male moose after adult-biased and mixed age class harvesting. According to our results, both body weight and antler growth of young males increased after mixed age class harvesting. Changes in growth patterns were affected by population density and sex ratio, but as the period effect still remained in the growth patterns after removing the effects of density and sex ratio, we suggest that the change in male moose growth patterns might have resulted from the harvest-induced young-male age structure and higher harvest pressure among young male moose.
Predation on artificial ground nests placed along four transects (alderwood, fallow, pine forest and fallow-forest edge) was studied in 1998–2009. On average, a 25.4% increase in overall predation rate was observed over the study period and increasing predation occurred at all sites. Mean multiannual predation rate differed up to 2.3-fold between transects and was highest in the alderwood and lowest in the fallow area. Despite that share of particular predators in depredation of nests was not random with respect to the studied habitats, high year-to-year variation in the pattern of predation was recorded. Between-year and between-transect changes in predation pressure were responsible for 48% of overall predation variability. Predation in one, randomly selected year was weakly related to averaged data from all 12 years, which indicates that short-term studies employing artificial nests can significantly over- or underestimate the contribution of particular species to overall predation.
Nest size and nest building behaviour affect individual fitness and thus, selection may act on these traits. Most data on nesting behaviour come from species that build a nest for each new breeding attempt, whereas almost nothing is known regarding nest reusers. Here, the association between nest size and nest building behaviour, and occupation date as well as breeding success of the white stork Ciconia ciconia, a migratory species with nest reuse, is presented. Large nests were occupied earlier and showed higher breeding success, even accounting for the confounding effect of the breeder's age. In addition, nest size increased steadily over the entire breeding season and only ceased when reproduction failed. However, this increase was not related to breeding success variables. Finally, nest size was related to the number of times that it was used in the past and thus, to the probability of successful reproduction. These results suggest that storks may seek and compete for bigger nests and that nest size could be an indicator of individual and/or nest-site quality.
Seed dispersal by vertebrates is one of the main plant-animal interactions, especially in the Mediterranean region where fleshy fruits are, at least seasonally, one of the main food resources for birds and carnivores. To effectively assess the role of these predators as seed dispersers, we need to demonstrate the viability of ingested seeds. We therefore compared germination rates of seeds from freshly collected fruits with those of seeds collected from carnivore scats. We detected that several species (e.g. badgers, foxes, genets) had a significant positive effect on germination rates of seed of at least one fruit pland and one species (stone marten) had deleterious effects on most seeds. Seed size (e.g. weight, width, etc.) was correlated with seed survival, germination time and germination rate.
Eurasian woodcock (Scolopax rusticola) over-wintering in northern Spain follows a pattern of daily movement from diurnal sites in woodlands to nighttime sites in grazed fields, congruent with previous reports on other European populations. Fields have a much higher abundance and biomass of earthworms, the main prey of woodcock, than woodlands, but are only used by birds at night, when they emerge about 30 minutes after sunset. Emergence time was quite uniform among fortnightly periods except for the second half of November when it was earlier, probably reflecting extended activity resulting from the higher energy requirements of migrating birds. Woodcock emergence time relative to sunset was negatively related to illumination, so that birds moved earlier when the sky was overcast. Also, birds tended to move earlier at low air temperatures, a pattern which is to be predicted since woodcock have higher energy requirements at low temperatures because of the increased cost of thermoregulation. Emerging late, at low light intensity, avoids exposure to raptors but results in reduced energy gains and therefore the timing of moving to feeding fields may be modified by energy considerations. We discuss the idea that there is a divergent spatio-temporal gradient of food and safety between woodlands and fields and, therefore, that predation risk is an important determinant of the timing of evening emergence of over-wintering woodcock. Thus, their daily activity cycle would reflect a trade-off between feeding and predator avoidance. Special features of the visual fields of the woodcock, allowing detection of predators at long distances, and chemoreceptors in the bill enabling detection and capture of prey by probing using non visual cues, comprise adaptations that facilitate successful feeding at night with reduced predation risk.
Plants show rapid adaptation towards resistance against heavy metals. In contrast, tests examining the local adaptation of insect herbivores to heavy metal pollution are lacking. Here we test whether the autumnal moth Epirrita autumnata, living in a heavy metal contaminated area, shows local adaptation in the growth rate and immune function. We gathered male moths from control and polluted areas for use in paternal half-sib crossings in order to ensure that we measure genotypic variation in addition to phenotypic variation. We found genotype × environment interactions in the growth of the larvae suggesting potential local adaptation in the growth of pollution-exposed moths. However, adaptation appears to incur a cost, because we observed reduced performance of the heavy metal adapted strain in a non-polluted environment. Finally, we found that pollution enhanced the immune function in female moths but not in males.