bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogenetic shifts in habitat use and activity in a stream‐dwelling isopod
Authors: Holomuzki Joseph R. , Short Terry M.
Published: July 2006

We examined ontogenetic changes in diel patterns of habitat use and activity of the lotic isopod Lirceus fontinalis in relation to differences in predation risk from green sunfish, Lepomis cyanellus. Juveniles are ≤5 mm total length (TL), individuals 6‐9 mm TL are mature females (c. 90%) and immature males, and mature males are ≥10 mm TL. Isopods of all sizes were far more dense in Cladophora, a filamentous green algae, than in open silt/sand substrates in fish pools. Densities of each size did not increase in open areas at night in fish pools when risk of predation presumably decreases. Few individuals of any size class occurred in open silt/sand areas in fish pools. However, habitat use did not depend on fish presence. Densities and relative abundances of all sizes were similar between algal and open habitats in fishless pools both day and night, except for mature males which were more abundant in open areas during daylight. All sizes of isopods were significantly more dense in fishless versus fish pools, and density of a size class was influenced by fish presence. Densities of size classes were typically juveniles > individuals 6‐9 mm TL > mature males. Green sunfish are size selective feeders on isopods, thus demography of isopods within pools may be partially influenced by the size structure of the fish population.

Isopods reduced their activity, as measured by captures in benthic traps, in the presence of caged green sunfish only at night. This behavior coupled with relatively high activity levels during daylight regardless of fish presence suggests other predators or factors may influence diel activity. Mature males were overrepresented in traps relative to their occurrence in fish runs, indicating high activity levels. Mature males were also more active than gravid and nongravid females and juveniles in the presence of fish in laboratory aquaria. Number of male encounters with nongravid females depended on activity level.
Tidal dispersal of salt marsh insect larvae within the Westerschelde estuary
Authors: Hemminga M. A. , van Soelen J. , Koutstaal B. P.
Published: July 2006

In the Westerschelde estuary, salt marshes are present as isolated patches fringing the estuary. In the present paper tidal transport of stem‐boring larvae of Agapanthia villosoviridescens (Coleoptera) from salt marshes of the upper reaches of the Westerschelde estuary to marshes of the lower reaches is demonstrated. The evidence for the origin of the larvae is based on comparisons of growth and development characteristics of larvae found in flood debris belts and resident larval populations. These characteristics are different on the various salt marshes along the Westerschelde, probably as a result of estuarine gradients. Additional evidence for the larval origin comes from the plant composition of the flood debris. The occurrence of upward tidal transport is discussed. Considering the comparatively large area of salt marshes in the upper estuary, tidal dispersal of larvae probably will be dominated by transport in seaward direction. So far, very little is known on the role of tidal currents with regard to the exchange between salt marsh populations. The present results suggest that tidal transport may not only be important for dispersal of aquatic organisms in an estuary, but also for organisms inhabiting the semi‐terrestrial estuarine salt marshes.
Summer grazing by voles and lemmings upon subarctic snow‐bed and tall herb meadow vegetation – an enclosure experiment
Authors: Moen Jon
Published: July 2006

Ther hypothesis of the exploitation of ecosystems predicts that plant communities in productive habitats should experience a low grazing pressure, while communities in less productive habitats should be structured by intense grazing. Thus, if a high population density of rodents was to be established in these communities and they could graze without predation, the plant community in the productive habitat should be more affected than the community in the less productive habitat. This was tested by building enclosures for grey‐sided voles Clethrionomys rufocanus and lemmings Lemmus lemmus in a productive tall herb meadow and a less productive snow‐bed on Finnmarksvidda, northern Norway. The simulated rodent population densities varied from 150 to 750 ind. ha‐1, and the rodents were allowed to graze for 18 to 55 d. The shoot mortality of relatively abundant plant species were monitored together with plant community structure, and the above‐ground biomass were harvested at the end of the experiment. The shoot mortality were generally low, the significantly grazed species were either known preferred species or species with a grazing‐sensitive morphology. The community structure did not show any major changes. The aboveground biomass of woody plants was significantly lower in the enclosures on the snow‐bed, but not in the tall herb meadow. The total biomass did not differ significantly. These results are somewhat ambiguous with reference to the predictions from the food chain hypothesis, and the conclusion were drawn that intense grazing by voles and lemmings during 18 to 55 d during the growing season does not seem to be sufficient to greatly influence shoot mortality and structure of the studied plant communities.
Population dynamics of the coprophilous moss Tayloria tenuis in a Pyrenean forest
Authors: Lloret Francisco
Published: July 2006

Three populations of Tayloria tenuis (Splachnaceae) growing on three isolated cattle droppings in coniferous forests of the Eastern Pyrenees were sampled by permanent grids through three years. Each population was initially in a different stage of the dung colonization process. At first, T. tenuis developed a conspicuous protonema on the dropping surface. After one or two years, the moss completed development and fruited abundantly. Eventually, the populations were covered by larger pleurocarpous mosses, which were common on the forest soil.

There were important differences between the two stages of development of the T. tenuis gametophyte: the protonema stage exhibited high mortality but rapidly covered nearly all the free surface of the dropping. Afterwards, the gametophore stage established more permanently.

Pleurocarpous mosses growing over Tayloria tenuis gametophores produced changes in the vegetative and reproductive pattern of this species. Tayloria tenuis disappeared gradually from the places covered by pleurocarps, although these larger species exhibited high rates of mortality at a micro‐scale level.
Insect‐related differences in growth of birch and pine at northern treeline in Swedish Lapland
Authors: Eckstein Dieter , Hoogesteger Jan , Holmes Richard L.
Published: July 2006

The tree‐ring patterns of birch and pine in the Torneträsk area of Swedish Lapland were compared. In order to dendrochronologically identify years of major insect attacks on birch, pine being unaffected by these outbreaks, served as control. The sharp growth increase in birch following the historically confirmed, heavy outbreak in 1954–55 is discussed and evidence pointing to possible earlier outbreaks is presented.
The sensitivity of phenological events to changes in nutrient availability for several plant growth forms in the arctic
Authors: Larigauderie Anne , Kummerow Jochen
Published: July 2006

The purpose of the experiment was to see whether a change in nutrient availability resulting from perturbations might alter rates of development of the major plant growth forms of an arctic tussock tundra slope. Slow release fertilizer pellets (NPK) were spread in June and July 1985 on the frost surface under an 8‐20 cm thick layer of thawed tundra in the northern foothills of the Brooks Range, Alaska. Initiation day of main phenological events, their duration and their intensity (% plants reaching a phenophase in a plot) were recorded during the 1985, 1986 and 1987 growing season. Variations in initiation day of phenophases were mainly due to environmental variations among years and to a lesser degree to fertilization; only timing of vegetative bud break of evergreen shrubs was significantly affected by fertilization, and occurred earlier than in the control. Flowering intensity varied significantly from one year to an other but was not significantly stimulated by fertilization.
Flower herbivory and seed predation in Silene vulgaris (Caryophyllaceae): effects of pollination and phenology
Authors: Pettersson Mats W.
Published: July 2006

Pollination and seed predation were studied in Silene vulgaris populations during two seasons, one with much lower pollinator abundance than the other. Among the pollinators, noctuid moths of the genus Hadena also acted as seed predators. Nectar‐foraging female moths oviposited in flowers, and their larvae consumed flowers and seed capsules.

Despite a lower percentage of pollinated flowers in the year of low pollinator abundance, similar numbers of flowers set fruit in both years, because fewer flower buds and flowers were eaten by Hadena larvae during the year of low pollinator visitation. The number of seed capsules preyed upon was also lower in the year with low pollinator abundance, resulting in a higher seed set. The positive correlation between the percentage of pollinated flowers and the percentage of seed capsules destroyed was also observed when comparing flowers opening in different parts of the season.

Early flowering plant individuals had the same pollination success but suffered higher seed predation than late flowering ones. Selection for maximized pollination success through synchronous flowering, is probably the main reason for the compressed flowering period in 5. vulgaris, but the high level of predation early in the season may further increase the reproductive success of synchronous flowering individuals.
Regenerative traits of tree species in a deciduous forest of northeastern North America
Authors: Houle Gilles
Published: July 2006

I studied the seed rain, seedling bank, newly emerged seedlings, and seed bank of tree species in a deciduous forest of northeastern North America (Québec, Canada). The main objective was to determine to what extent the tree species present on the site differed in some of their regenerative traits. All the species present on the quadrats as mature trees contributed to the annual seed rain, although seed rain was strongly dominated by yellow birch and sugar maple. The seedling bank was mostly composed of red maple and sugar maple, but inputs from the 1988 cohort were mostly red maple and yellow birch seedlings. Seedling mortality was high in general (from 60% to 100%), but sugar maple had the lowest mortality of the tree species present. Two species maintained a seed bank on the study site: yellow birch and american basswood. Some species not present on the quadrats, but having populations nearby, disseminated seeds onto the quadrats (i.e. white ash and grey birch). Other species, not present on the quadrats as mature individuals, had seeds in the seed bank although they did not participate in the seed rain, did not maintain a seedling bank, and did not establish seedlings in 1988 (i.e. pin‐ cherry and Rubus spp.). Red maple, sugar maple, and yellow birch showed contagion in the dispersion pattern of their seeds in the seed rain (and the seed bank for yellow birch), and of their seedlings in the seedling bank and the 1988 cohort. Seedlings of american beech and american basswood of the seedling bank and the 1988 cohort were randomly dispersed over the quadrats, although their seeds in the seed rain had a contagious dispersion pattern. It has often been proposed in the literature that regenerative traits come only in “compatible assemblages” and that, consequently, species may be grouped according to their strategy of regeneration: e.g. species that maintain a seed bank vs those with a seedling bank; species with either a seed or a seedling bank vs those with the ability to sprout. In the community studied, it appears that regenerative traits do not come in neatly packaged exclusive assemblages, although the species do seem to possess different combinations of regenerative traits. However, yearly variations in seed production, seed germination, and seedling survival may render difficult the identification of strategies of regeneration.
The relationship between body length, age and sexual maturity in the common toad, Bufo bufo
Authors: Reading C. J.
Published: July 2006

An investigation of the relationship between the onset of sexual maturity, age and body size in common toads Bufo bufo was started in 1984 at a pond in southern England. During the toad breeding seasons of 1984 and 1985, 7259 common toad‘metamorphs’were captured and permanently marked so that if captured as adults their true age would be known. Although a very small proportion of males and females reached sexual maturity at ages of two and four years respectively, most did so much later and asynchronously. The body size of toads breeding for the first time was relatively constant for each sex and not correlated with age. The rational behind our understanding of the mechanism of female choice is discussed in the light of these results.
Population dynamics of Clethrionomys and Peromyscus in southwestern Yukon 1973‐1989
Authors: Gilbert B. Scott , Krebs Charles J.
Published: July 2006

Clethrionomys rutilusandPeromyscus maniculatusoccur together in the boreal forest of southwestern Yukon and we studied their population dynamics on unmanipulated live‐trapping grids for 17 yr.Peromyscusshowed a regular seasonal change in numbers each year with little interannual variation.Clethrionomysby comparison, showed low density fluctuations during one period (1976‐1982) followed by changes in number in the next period that are consistent with a typical 3‐4 yr microtine cycle. During one of two years of peak numbers adult males had unusually heavy body weights. The sexual maturation of juvenileClethrionomysvaried inversely with density. In most yearsClethrionomysshowed higher rates of population increase from spring to late summer thanPeromyscusand this may be partly attributed to the vole's longer breeding season. Juvenile femaleClethrionomysoften reached sexual maturity during their first summer when population density was low butPeromyscusnever matured during their first summer. Finally, there was no correlation between the two species in year to year changes in overwinter survival rates. This is the first report of a cyclic Norh American population ofClethrionomysand it underlines the need to search for hypotheses of population regulation that explain both annual and multi‐annual cycles within the same population.
Operation of dichogamy and herkogamy in five taxa of Pulsatilla
Authors: Jonsson Olle , Rosquist Gabrielle , Widén Björn
Published: July 2006

Dichogamy in five taxa of Pulsatilla (P. patens, P. pratensis, P. vernalis, P. vulgaris ssp. gotlandica and P. vulgaris ssp. vulgaris) is incomplete with overlap between the female and male phases of a flower. The species are protogynous with the duration of the obligate female phase lasting 0 to 10 d and the duration of stigma receptivity of unpollinated flowers lasting 3.5 to 32 d in the greenhouse. The pollen presentation time varied between 1.5 and 10 d. There were significant differences among species in duration of both female and male phases. Hand pollination decreased the duration of stigmatic receptivity and pollen presentation significantly. The spatial separation of pollen presentation and receptive surfaces in a flower changed with time due to the continuing growth of the androecium and the gynoecium, and due to the temporal pattern of pollen presentation within the androecium. Hand pollination experiments indicate that seed set may be partly pollen‐limited in a natural population of P. vulgaris ssp. vulgaris. The level of cross‐pollination was high in this population as shown by high levels of pollen deposition on the stigmas during the obligate female phase.
Carbohydrate and lipid levels in two Polytrichum moss species growing on the Alaskan tundra
Authors: Sveinbjörnsson Bjartmar , Oechel Walter C.
Published: July 2006

Two tundra Polytrichum moss species were sampled in the field near Barrow, Alaska, three times during the growing season. Lipid, sugar, and starch concentrations of the green above ground shoots and below ground rhizomes were analyzed. Lipid and TNC (sugar + starch) concentrations were higher in Polytrichum commune growing on raised polygon rims than in Polytrichum alpinum. There were no significant differences between the two populations of P. alpinum. Green parts had significantly higher lipid concentrations than rhizomes in P. commune but not in P. alpinum. Both species had significantly higher sugar concentration in green shoots and higher starch concentrations in the rhizome and sugar concentration varied significantly in both species. Seasonal variation of TNC concentration levels were significant only in P. commune. A statistically significant positive relationship was found between lipid and TNC concentration while a stronger statistically significant negative relationship was found between sugar and starch concentration. The first is interpreted as an adaptation to drought in surface waxes and osmoticum while the second is interpreted as conversion indicator depending on tissue and use. Polytrichum mosses resemble evergreen vascular plants in their seasonal stability of these compound groups.
Dynamic and temporal structure of the troglobitic beetle Speonomus hydrophilus (Coleoptera: Bathyscimae)
Authors: Crouau‐Roy Brigitte , Crouau Yves , Ferre Claire
Published: July 2006

The population ecology of the beetle Speonomus hydrophilus, occurring both in caves (reduced fluctuations in many abiotic parameters) and under the deepest layer of soil in mountains (MSS, more exposed to climatic variations), was studied in four habitats in the French central Pyrenees We have assessed some of the characteristics of the environment where these populations occur c g physical data (altitude and exposure), geologic data (nature of the parent‐rock) and abiotic parameters (temperature with its seasonal fluctuations) and we investigated the relative importance of environmental structure and ecological characteristics on the temporal organization of S hydrophilus and the troglobitic fauna which cohabits The climatic study shows the existence of an annual thermal cycle which is regular and well marked for the MSS habitats but slightly out of phase with the surface cycle These periodic variations however slight may be stressful for troglobitic species In the MSS populations, the phenology of the entire community is reflected in the pattern seen in Speonomus The analysis of faunal profiles shows that samples follow the same seasonal succession during the annual cycle A potential seasonal rhythm of emergence may reflect a seasonal rhythm of vitellogenesis which produces a rhythm of egg‐laying
Mechanisms regulating bird predation on a herbivorous Larva guild in boreal coniferous forests
Authors: Atlegrim Ola
Published: July 2006

Bird predation was previously found to considerably reduce the abundance of the herbivorous insect larva guild feeding on bilberry Vacanium myrtillus within boreal coniferous forests In this follow‐up study, interest was focused on determining whether female pied flycatchers Ficedula hypoleuca tend to use the field layer more frequently than other types of feeding niches In addition, the degree to which the conspicuousness of a larva increases the risk of its being preyed upon by birds was evaluated in order to further understand the mechanisms regulating the bird predation effect Larval predation risks were measured by presenting larvae with contrasting characteristics to seven captured female flycatchers

Female flycatchers hunted more frequently in the tree and field layers than in the air However, the relative degree of utilization of the tree and field layer varied considerably between years, with use of field layer being positively related to the abundance of insect larvae on bilberry

Large larvae did not suffer higher bird predation than small larvae when both size classes were presented to the birds on bilberry Larvae that crawl on leaves and stems during feeding (high degree of exposure) were preyed upon more than larvae that feed between leaves they have spun together (low degree of exposure) No difference in larval predation risk was found between sawflies and geometrids, the two taxa represented in the exposed feeder group However, dark geometrids suffered higher predation than green sawflies and green geometrids

My findings suggest that the herbivorous larva guild constitutes an abundant food resource frequently utilized by small bird predators However, certain members of the guild appeared to be preyed upon more than other members Thus the risk for predation seems to be highest for dark geometnds followed in decreasing order by green geometrids. sawflies pyralids, and tortricids
Dry matter economy and reproduction of a temperate forest spring geophyte, Allium ursinum
Authors: Eggert Andreas
Published: July 2006

For a natural population of Allium ursinum age states are defined on the basis of morphological criteria Differences in the dry matter economy of these age states illustrate the underlying life history

Most seeds rest several years m dormancy after maturity It takes on average more than 6 yr until juvenile plants attain the dry matter threshold level for the production of an inflorescence Flowering plants divert 41% of their dry matter gain during spring to reproductive parts (7% to the seeds) Since flowering plants show a marked negative annual dry matter balance, c 81% of them are not able to flower again the next year

At the same expense of carbon reserves the formation of daughter bulbs results in a considerably higher number of new ramets than the production of seeds Nevertheless, the investment in seed production is extraordinarily high in relation to other woodland perennials This might be explained by the lack of an effective dispersal of the daughter bulbs By vegetative propagation dense groups of adult ramets develop, which will finally undergo mutual shading
Rodent seed predation in cereal crop areas of central Spain: effects of physiognomy, food availability, and predation risk
Authors: Diaz Mario
Published: July 2006

Patterns of rodent seed predation in extensive cereal croplands of central Spain were investigated by measuring rodent predation rates on artificial seed patches, together with seed availability, rodent abundance and habitat physiognomy Sampling was designed to cope with the spatial and temporal variability of factors potentially affecting rodent activity (natural and man‐made habitat features, season and moonlight) Rodent predation was unpredictably distributed in summer In winter, rodents foraged on average in the patches least used by man. moonlight, however, did alter this pattern, so that rodent predation was closely associated with shrubs in the bright nights and evenly distributed in the dark ones I conclude that the need of stable underground refuges and predation risk in the winter period seemed to be the mam factors constraining rodent foraging activity in the man‐made ecosystem studied
Food habits and foraging of the brown bear Ursus arctos in central south Norway
Authors: Elgmork Kåre , Kaasa Jon
Published: July 2006

Analysis of 134 excrement samples from the brown bear Ursus arctos L in boreal forests m central south Norway found volumes to be largest for Vaccinium spp, herbage Empetrum spp, and Formicidae The most important plant material in volume uptake were herbage, leaves, and mosses, closely followed by berries and seeds All together, plant material amounted to c 85% by volume, Formicidae to c 8%, and domestic sheep to c 7% These values were radically changed by applying correction factors for different nutritional value of food items The importance of large mammals then increased substantially, while the importance of herbage was reduced There was a drastic shift in food composition through the seasons Formicidae and flowers of deciduous trees were prevalent in spring, herbage in early summer, Vaccinium spp and sheep in late summer, and Vaccinium spp and Empetrum spp in autumn
Apparent decline in the harbour seal Phoca vitulina population near Hvaler, Norway, following an epizootic
Authors: Hedlund Markussen Nina
Published: July 2006

From 1986‐90 we tagged 98 harbour seal pups at Hvaler, Norway Fifteen were recovered later the same year of which 10 were recovered in 1988, when the seal population was infected by a morbillivirus The epizootic in 1988 resulted in a population decline of c 75% Predicted birth weight did not vary significantly before and after the epizootic Newborn harbour seals have antibodies against the morbillivirus two years after the outbreak of the disease
The reproductive behaviour of a clonal herbaceous plant, the longleaved sundew Drosera intermedia, in different heathland habitats
Authors: De Ridder Filip , Dhondt André A.
Published: July 2006

The reproductive behaviour of the longleaved sundewDrosera intermediaHayne was studied in three hydrologically differing heathland habitats a pool edge, an old path through the wet heath and a seepage area

Sexual reproductive allocation (SRA) (the slope of the regression of sexual biomass on vegetative biomass m a given season) differed strongly between years (related to temperature and precipitation) and habitats Averaged over years, path plants had a higher SRA than plants in the seepage area and at the pool edge

Asexual reproductive allocation, expressed as the size‐dependent probability of reproducing asexually, did not differ between habitats in most years

The observations agreed with general life history theory SRA was high in the path habitat where adult survival chances were low and juvenile (= seed, first year seedling) survival was high SRA was lower in the seepage area where adult survival chances were higher and juvenile survival lower At the pool edge, a habitat with high adult mortality and low juvenile establishment, the predicted optimal reproductive behaviour, a high SRA, was not observed due to environmental constraints (inundation)
Diversity and evenness of Hemiptera communities on naturally vegetated derelict land in NW England
Authors: Sanderson R. A.
Published: July 2006

Samples of Hemiptera were collected at sixteen naturally vegetated derelict sites using both suction apparatus and beating bags Sample sites were chosen to provide a broad range of vegetation types, representing changes in successional stage and soil pH Hemipteran diversity indices were significantly correlated with site area, but not with soil pH or site age Vegetation species diversity and evenness indices were not significantly correlated with site age, area or soil pH Hemipteran and vegetation evenness (using both Shannon evenness, J, and Heip's evenness, F10) were significantly correlated Similar evenness correlations were found when sub‐order Homoptera and vegetation were compared No significant correlations were found between the diversities of sub‐order Heteroptera and vegetation Factors determining Hemiptera and vegetation diversity on these sites are discussed It is suggested that rare plant species are of importance in determining the presence of rare species of Hemiptera on the sites It is proposed that diversity as a concept is of most value in ecological studies when its two components, species richness and evenness are considered separately
Influence of weather conditions on pallid swift Apus pallidus breeding success
Authors: Cucco Marco , Malacarne Giorgio , Orecchia Gualtiero , Boano Giovanni
Published: July 2006

The reproductive ecology of three colonies of pallid swift in a warm continental climate (Piedmont, NW‐Italy) was studied over a ten years period About 60% of the clutches were laid in late May and June, but continued until late August and September, when some females laid a second clutch Clutch size and the mean number of fledged young decreased progressively from spring to autumn

Laying dates were influenced by rain and temperature unfavourable weather conditions during May induced most females to postpone egg laying until June Clutch size was not related to the rain or temperature parameters considered

These observations differ from the findings about the common swift studied in cool temperate areas, where a very short stay in the breeding colonies does not allow a delay in laying, and spring weather conditions therefore have a strong influence on clutch size There are also differences about the effect of weather on chick rearing In warmer climates, typical of our colonies, fledging success is hindered both by too dry or too rainy seasons, even if these situations very rarely occur and the three‐egg clutch is always the most productive In colder climates the breeding success of the common swift depends primarily on the climatic conditions of May. and in bad weather a two‐egg clutch is more productive than a clutch of three In summary, the annual breeding success of the pallid swift appears little influenced by weather changes, due to a lesser impact of adverse conditions in Southern climates and the possibility, for this species, of shifting the laying period in response to a temporary worsening of climatic conditions
The diet of the parti‐coloured bat Vespertilio murinus in Sweden
Authors: Rydell Jens
Published: July 2006

Food habits of the parti‐coloured bat in southern Sweden were investigated by analysis of fecal samples collected from three maternity roosts used in summer and, in addition, one roost used by a male during the mating season m autumn Small (c 3‐10 mm) dipterans dominated all samples, representing 64‐82% by volume, but larger flying insects like moths, caddis‐flies and dung beetles were also eaten, together representing 14‐33% At the family level, midges (Chironomidae) were by far the most common prey items, compnsing 12‐67% of the diet The dominance of small prey items in the diet of the parti‐coloured bat in Sweden contrasts with other bat species of similar size and foraging habits, but agrees with observations on parti‐coloured bats in Ukrama and Poland
The influence of weather on habitat use by small mammals
Authors: Vickery William L. , Rivest Daniel
Published: July 2006

Summer habitat use by three species of forest small mammals was determined using tracking stations Nocturnal weather influenced habitat selection by deer mice and woodland jumping mice but not by red‐backed voles Deer mice used all habitats equally on clear nights but were most active in mixed forest on cloudy, rainless nights and most active in a coniferous habitat on rainy nights Jumping mice were most active in mixed forest on clear and rainy nights but shifted to coniferous forest on cloudy dry nights Red‐backed voles were most active in the coniferous habitat regardless of weather Microhabitat references within habitats reflected the same preferences as habitat selection Microhabitat selection by jumping mice also changes with weather The mechanism most likely responsible for the observed habitat selection changes is changing insect abundance associated with cloud cover and rainfall
Foraging and diet of the red fox Vulpes vulpes in relation to variable food resources in Biatowieza National Park, Poland
Authors: Jędrzejewski Wlodzimierz , Jędrzejewska Bogumila
Published: July 2006

Feeding ecology of red fox Vulpes vulpes was studied by scat analysis and snow‐tracking m primeval temperate forest and adjacent meadows during four years (1985/86‐1988/89) Winters varied from mild to unusually severe Main food resources for foxes were rodents of open meadows and river valleys (root vole Microtus oeconomus). forest rodents (bank vole Clethrionomys glareolus and yellow‐necked mouse Apodemus flavicollis), hare Lepus europaetis and carcasses of wild boar Sus scrofa and red deer Cervus elaphus either killed by wolves and lynx or that had died from inanition Composition of fox diet m four cold seasons (autumn‐winter) was compared to the abundance of main food resources Prolonged, sharp decline of Microtus was followed by only a twofold decrease of its share in fox diet Foxes continued to prey on declining Microlus The changes in the proportions of forest rodents and hare in fox diet clearly followed the fluctuations in numbers of these two prey Carcasses were alternative, buffer food to foxes and were taken considerably when Microlus and other prey were in low numbers or poorly accessible The depth of snow was the most important factor restricting foxes access to rodents Snow‐tracking revealed that foxes dwelling in the forest widely used adjacent open areas In open meadows foxes mainly hunted for rodents, while in the forest the most significant foraging activity was scavenging Seasonal analysis of fox diet revealed that consumption of Microlus by foxes was stable throughout the year (37‐47% of biomass consumed) Bank vole significantly contributed to fox diet in autumn, and hare in summer only Scavenging was most pronounced in winter and spring when carcasses made up 30% of biomass taken
Reproduction and growth in bank voles Clethrionomys glareolus: the effect of food‐quality and density manipulations in a laboratory colony
Authors: Kviljo Tor , Anker Ims Rolf , Stenseth Nils Chr. , Bondrup‐Nielsen Søren
Published: July 2006

Young laboratory raised bank voles Clethrionomys glareolus, originating from a cyclic population at low phase, were experimentally subjected to manipulations of food and density This was done to assess possible effects of the juvenile environment on later breeding success Juveniles were exposed to the expenmental treatments for 40 d previous to pairing

The study revealed that a high population density in itself can increase future breeding success as compared to low density This effect was only found m females There were also indications that high density led to arrested growth in subordinate females
Habitat use of small mustelids in north Fennoscandian tundra: a test of the hypothesis of patchy exploitation ecosystems
Authors: Oksanen Tarja , Oksanen Lauri , Norberg Mats
Published: July 2006

The habitat use of small mustelids in a tundra area in Norwegian Lapland was studied chiefly by means of snow‐tracking 1986‐89 Stoats showed strong peference to a habitat complex immediately beneath the thrust line of the Scandes, with exceptional abundance of luxuriant habitats, whereas weasel activity was more evenly spread over the lowland tundra Mustelid activity on the high tundra above the thrust line was consistently low Within each subarea. stoat activity was concentrated to the most luxuriant habitats Similar preferences were shown by weasels on the lowland but not in the vicinity of the thurst cliff Daily movements of both species varied from local (c 200 m) to extensive (up to 4 km), no consistent interspecific differences in travel distances could be observed

The results largely conform to the hypothesis of patchy exploitation ecosystems (T Oksanen 1990a), according to which predator activity tends to “spill over’ from luxuriant habitats, capable of supporting predator populations, to adjacent barren ones, due to despotic behavior within and between species and due to opportunistic predation by transient predators However, predator activity in barren habitats during the crash winter could not be explained by these mechanisms alone A third mechanism ‐ breakdown of habitat preferences of predators during crash phases of a cyclic prey population ‐ was thus introduced
Bat community structure in an urban park
Authors: Kurta Allen , Teramino Joseph A.
Published: July 2006

In summer 1990, we mist‐netted bats on 35 net‐nights, for 4 h each night, along tributaries of the River Rouge in surburban Detroit, Michigan, USA The floodplains of these nvers are preserved as parkland We compared elements of bat community structure in these urbanized park areas to that of rural areas For the rural data set, we used mist‐netting data obtained previously on 53 net‐nights in southern Michigan using a similar protocol Mean number of bats captured per night was lower in urban compared to rural areas (13 vs 46) Species diversity (Simpson Index) was lower in the city (0.53 vs 0.28) as was species evenness (0.66 vs 0.36) The big brown bat Eptesicus fuscus made up 65% of the catch m rural areas but 83% in the city The red bat Lasirus borealis represented 18% of all bats m rural areas and 13% in the city The proportion of sites where the big brown bat was captured was significantly lower in the city (51% vs 74%) The proportion of sites that yielded red bats also declined, from 52% along rural nvers to only 14% in the city Sex ratio of adult big brown bats did not differ between urban (43% male) and rural (32% male) sites The ratio of juvenile big brown bats to adult females was significantly lower in the city (1.21 vs 30.77) Our data suggest that urbanization is a threat to insectivorous bat communities and leads to decreased overall abundance, decreased species diversity, and possibly lower reproductive success of those that are present
Variability in timing of larval season in an amphibian community in SW Spain
Authors: Díaz‐Paniagua Carmen
Published: July 2006

Timing of larval periods of 9 species of amphibians (Hyla meridionalis, Pelobates cultripes, Discoglossus galganot, Bufo calamita, Bufo bufo, Rana perezi, Triturus marmoratus, Triturus boscat, Pleurodeles waltl) was followed in 7 different years Total larval season may last from autumn to summer, whereas in low rainy years it may last from late winter to summer In rainy years, two species are early breeders, starting to breed m autumn, six species commonly start in mid‐winter and one species always breeds later, in spring The widest interannual variability m the onset and duration of larval season occurs in the earliest breeders In general, the more rainy the autumn and the higher temperatures were reached, the earlier the season started In contrast, duration of the season was not correlated with rainfall and temperature Interannual variability is interpreted as the possibility of adjusting the reproduction of the species to the availability of breeding habitats, constrained by physiological features of the species and interspecific relationships
Spatial and temporal feeding segregation of two Icelandic goose species during the spring pre‐nesting period
Authors: Fox A. D. , Boyd Hugh , Warren Stephanie M.
Published: July 2006

The pre‐nesting feeding behaviour of greylag Anser anser and pink‐footed geese A brachyrhynchus was studied on agricultural land at low altitude in southern Iceland from 10 April to 8 May 1990 Greylag geese were already present on 12 April increased to 4580 birds by 24 April, but declined to 1300 by 3 May Pink‐footed geese arrived around 20 April and numbers continued to increase to a peak count of 11340 on 3 May Over 60% of greylag geese initially used stubble fields on the coast where this habitat was most frequent, but increasingly resorted to grassland and wetland habitats during late April Later‐arriving pink‐feet predominantly used managed grassland, away from coastal areas At inland grassland sites, greylag numbers peaked on 20 April, pink‐feet m early May The early exploitation by greylags was associated with grass growth initiated under protective snow‐patches Greylags spent 90 times more time feeding within 1 m of snow patches with enhanced grass growth than expected by chance and their feeding rates near snow patches were faster and their step rates slower than further away By early May, grass growth was uniform and, although snow‐patches persisted, no difference in forage quality, goose feeding rates or step rates could be detected It is concluded that, in spring 1990 at least, habitat segregation during spring migration in southern Iceland minimised competition between these two closely related goose species within the same geographical area In areas where both species exploit the same habitat, a two week difference m timing of breeding (and hence phenology of migration) further assures minimal overlap in feeding exploitation
Effects of burial in sand on the growth and reproduction of Cakile edentula
Authors: Zhang Jianhua , Maun M. A.
Published: July 2006

Studies were conducted to examine the effects of sand burial on the growth and reproduction of Cakile edentula under controlled greenhouse conditions Sand burial enhanced both the vegetative growth and reproduction of plants Within one week after burial, plants showed a significant increase in the length of the internode just below the current sand surface This response was not mediated by the dark conditions imposed by sand burial About two weeks after burial, adventitious roots grew upwards into the deposited sand Plants buried in washed sand did not differ in their dry weight whereas those buried in unwashed sand were significantly taller, produced greater biomass and larger number of seeds per plant than control However, the mean mass per fruit and per seed were not altered The frequency distribution of fruit and seed was only slightly modified by the burial treatments
Year‐to‐year changes in the age structure of a caddisfly population following loss and recovery of a springbrook habitat
Authors: Resh Vincent H.
Published: July 2006

A severe drought in 1977 resulted in cessation of normally permanent flow m a northern California (USA) springbrook, and no individuals of the numerically dominant macroinvertebrate, the caddisfly Gumaga nigricula (McL), survived Prior to habitat loss (1976) this population was multiple cohort, two years after habitat recovery (1979) a single‐cohort population was present The shift m age structure back to pre‐drought conditions occurred gradually median head capsule width in 1976 (pre‐drought) 0 39 mm, 1981 (post‐drought) 0 95 mm, 1982 0 99 mm, 1983 0 59 mm, 1984 0 63 mm, 1985 0 63 mm, 1986 0 45 mm Age structure from 1981‐1985 was significantly different (p < 0.001) from that occurring before habitat loss in 1976, age structure m 1986 was not significantly different from that in 1976 The ten‐year time for return to the original population age structure could be influenced by the isolation of the springbrook from other colonization sources, gradual increases in population density, and differential growth reflecting food availability
Environmental parameters and estivation of Rhyacodrilus (Tubificidae, Oligochaeta) in Lake Suwa, Japan
Authors: Takada Kaori , Kato Kenji , Okino Tokio
Published: July 2006

We confirmed that Rhyacodrilus spp of Yasuda and Okino (1987) (Tubificidae, Oligochaeta) migrated entirely downward below 15 cm into the sediment from June to September m Lake Suwa, a shallow eutrophic lake in Japan In October, Rhyacodrilus spp began to return to the upper layer and immediately attained sexual maturity They tended to show reduced body weight and respiratory activity during summer The results indicate that an oligochaete of Rhyacodrilus spp estivated in the deeper layer during summer The estivation ostensibly occurred at 15°C and the species died off at 20°C, so it is evident that they must migrate from the surface to the deeper layer of sediment during summer in order to escape high temperature Furthermore, physiological experiment suggested that this behavior is accelerated by low oxygen concentration with high temperature
Spatial structure and niche patterns of a rodent community in the south Bukhara desert (Middle Asia)
Authors: Shenbrot Georgiy I.
Published: July 2006

The distribution of niches in resource space and the niche patterns of a 13 species community of Middle Asian desert rodents were studied by use of discriminant function analysis Nineteen quantitative parameters of the environment (soil structure and vegetation), measured at 600 sample plots within twenty four one ha grids, were considered The first three canonical axes of resource space account for 83% of the variance, the first axis represents a general landscape gradient from sand to clay soils, the second axis reflects a gradient of increasing productivity, and the third axis reflects a gradient of increasing protectability of the environment The distribution of niches in resource space is not even, there are two distinct spatial guilds consisting of psammophilous and sclerophilous species There is a negative correlation between niche position (distance from species centroid to the center of the resource space) and maximal population biomass At the same time there are no correlations between the niche breadth and the niche position due to the absence of species with really broad niches Rodent biomass increases along the productivity axis and reaches a peak in the middle part of the substrate axis Rodent species diversity increases along the substrate axis from sand to clay soils Changes of species diversity along productivity axis have humpshaped patterns Maximum species diversity was recorded at low level of productivity on the sandy soils and shifted to intermediate levels of productivity on sandy‐loam and clay soils
Niche overlap of two sympatric‐nesting hawks Accipiter spp. in the New Jersey‐New York Highlands
Authors: Bosakowski T. , Smith D. G. , Speiser R.
Published: July 2006

The food and habitat niches of two nesting species of hawksAccipiterspp were studied in an extensively forested area of the Eastern Deciduous Forest Biome Nesting habitat was quantitated at 19 Cooper s hawkA cooperunests and 16 northern goshawkA gentilisnests There was no significant trend for Cooper's hawks to nest in less mature forests than northern goshawks as reported previously for western North America Forest habitats did not differ markedly except that shrub cover was greater at Cooper's hawk nest sites, which were also on flatter terrain and closer to roads, forest openings, and human habitation However, these few differences resulted m reducing habitat‐niche overlap considerably (0 538), as was calculated using principal components analysis Mean prey weight was significantly larger for the northern goshawk which follows its 2 2‐fold body weight advantage over Cooper's hawk Although bird prey was of primary importance to bothAccipiter,goshawks took twice the proportion of mammals compared to their smaller congener Food‐niche overlap was lowest by prey species overlap (0 470), followed by prey size class overlap (0 529), and highest by vertical foraging zone overlap (0 816) The Cooper's hawk showed the greatest niche breadth for both food and habitat niches indicating it as more of a generalist Overall, niche complementarity of food and habitat dimensions resulted in niche overdispersion along food and habitat dimensions with a total niche overlap (0 504) that was below the competition threshold These results suggested that competition (past and current) was responsible for segregating niches