Survival of male Tengmalm’s owls increases with cover of old forest in their territory

The loss and fragmentation of forest habitats have been considered to pose a worldwide threat to the viability of forest-dwelling animals, especially to species that occupy old forests. We investigated whether the annual survival of sedentary male Tengmalm’s owls Aegolius funereus was associated with the cover of old coniferous forests in Finland. Survival and recapture probabilities varied annually with density changes in populations of the main prey (Microtus voles). When this variation was controlled for, and relationships between survival and proportions of the three different forest age classes (old-growth, middle-aged, and young) were modeled separately, the old-growth model was the most parsimonious. Survival increased with the cover of old forest, although the extent of old forest within owl territories was relatively small (mean ∼12%, range 2–37%). This association, however, varied among years and appeared especially in years of increasing vole abundance. At such times, old forests may sustain high populations of bank voles Clethrionomys glareolus, shrews and small passerines. In addition, old forests may serve as refuges against large avian predator species, such as Ural owls Strix uralensis and goshawks Accipiter gentilis. Our results suggest that changes in habitat quality created by agriculture and forestry may have the potential to reduce adult survival, an essential component of fitness and population viability.     

Nonhelical,fibronectin-binding basement-membrane collagen from endodermal cell culture

A novel method of affinity chromatography on insolubilized collagen-binding fragments of fibronectin was utilized to isolate a random-coil collagenous protein from culture media of mouse teratocarcinoma-derived endodermal cells. These cells also produced another collagenous protein, which did not bind to fibronectin but could be isolated by differential salt precipitation. The affinity-purified collagen differs from its conventionally isolated counterpart in that it is not triple-helical in structure, its polypeptides are not disulfide-crosslinked and it has affinity for fibronectin in its native state. Both collagens resemble previously characterized type IV basement-membrane collagens with respect to their amino acid composition, cyanogen bromide peptides, chain size, immunological reactivity and tissue localization. The random-coil collagen is directly active in promoting the attachment of some lines of cells, but for attachment of the endodermal cells addition of fibronectin is required. This suggests that the presence of nonhelical, fibronectinbinding collagen may have biological significance in the interaction of cells with the extracellular matrix.     

Birch leaves as a resource for herbivores: Seasonal occurrence of increased resistance in foliage after mechanical damage of adjacent leaves

Summary Seasonal occurrence of such wound-induced reaction in birch foliage which deteriorates the quality of nearby leaves for herbivores was tested by means of bioassays. Length of the larval period was protracted in two early and mid-summer (larval period!) lepidopteran species as well as in two mid-summer hymenopteran species when larvae were reared on birch leaves whose adjacent leaves had earlier been damaged mechanically. This response was not found for two late-summer hymenopteran species. In a lepidopteran species whose larval period lasts through the whole season, retardation in growth was significant in the beginning of August but notl later. Hence such response of leaves, interpreted as defensive on the part of the birch, was not efficient after leaves had gained their final size. The potential consequences of wound-induced responses of leaves for herbivores are discussed.     

The effect of aeration intensity on the biochemical composition of Baker's yeast: Activities of enzymes of the glycolytic and pentose phosphate pathways

A series of baker's yeast continuous cultivations were made using different intensities of aeration. The experimental conditions were such as to eliminate the effects caused by high glucose concentrations in the medium on the formation of enzymes. The variation in activity of several enzymes was investigated and distinct changes were noted. The activities of hexokinase and alcohol dehydrogenase characterize the actual rate of glycolysis in yeast, the same being true, in part, for pyruvate decarboxylase. The activity of phosphofructokinase is nearly insensitive to the oxygen level at normal tensions. The activity of the cell to the phosphofructokinase can be limited in anaerobic conditions by its scarcity. The insensitivity of glucose-6-phosphate dehydrogenase to the oxygen tension together with its low activity suggests that this enzyme plays primarily a biosynthetic role and that the function of the pentose phosphate pathway as an energy-producing route is negligible.     

Higher nest predation risk in association with a top predator: mesopredator attraction?

Breeding close to top predators is a widespread reproductive strategy. Breeding animals may gain indirect benefits if proximity to top predators results in a reduction of predation due to suppression of mesopredators. We tested if passerine birds gain protection from mesopredators by nesting within territories of a top predator, the Ural owl (Strix uralensis). We placed nest boxes for pied flycatchers (Ficedula hypoleuca) in Ural owl nest sites and in control sites (currently unoccupied by owls). The nest boxes were designed so that nest predation risk could be altered (experimentally increased) after flycatcher settlement; we considered predation rate as a proxy of mesopredator abundance. Overall, we found higher nest predation rates in treatment than in control sites. Flycatcher laying date did not differ between sites, but smaller clutches were laid in treatment sites compared to controls, suggesting a response to perceived predation risk. Relative nest predation rate varied between years, being higher in owl nest sites in 2 years but similar in another; this variation might be indirectly influenced by vole abundance. Proximity to Ural owl nests might represent a risky habitat for passerines. High predation rates within owl territories could be because small mesopredators that do not directly threaten owl nests are attracted to owl nest sites. This could be explained if some mesopredators use owl territories to gain protection from their own predators, or if top predators and mesopredators independently seek similar habitats.