bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temporal changes in key factors and key age groups influencing the population dynamics of female red deer
Authors: Albon S. D. , Coulson T. N. , Brown D. , Guinness F. E. , Pemberton J. M. , Clutton‐Brock T. H. 
Published: September 2010

Summary 1. We use structured demographic accounting to decompose the contribution to the variance in relative population growth between 1971 and 1997 in female red deer on Rum, Scotland, in terms of different fitness components and age categories. 2. During the first 10 years (1971–80) the variance in relative population growth was small (0·00246) as the population grew from 58 to 148 having been culled previously. After this the relative variance in population growth increased to 0·00575 between 1981 and 1989, and increased again to 0·00848 between 1990 and 1997. 3. In the first phase of population growth (1971–80) changes in the birth rate contributed most to the variance in relative population growth (30%), then adult winter survival (23%), with calf summer and calf winter survival contributing less than 10%. Birth rate tended to covary strongly with adult winter survival, and to a lesser extent with calf winter survival. 4. The contribution of birth rate to the variance in relative population growth diminished to less than 5% in both the periods 1981–89 and 1990–97. In contrast, the contribution of adult winter survival increased to 36% in 1980s and 40% in 1990s. At the same time, the covariation of adult winter survival with calf winter survival increased successively to reach 40% in 1990–97. 5. Changes in population age structure were small and contributed little to the variance in relative population growth (≈ 1% over the entire study). In the 1970s the 5–7‐year‐old group contributed most (23%) to the variance in relative population growth, though this covaried with 8–12‐year‐olds. In the 1980s the 8–12‐year‐olds contributed most (27%) and now the covariation was with older animals (> 12‐year‐olds). This pattern persisted in the 1990s, though there was covariation with 5–7‐year‐olds too. 6. Birth rate, calf winter survival and adult winter survival were all density‐dependent. The strength of density dependence within each vital rate did not differ between the 1970s, 1980s and 1990s; however, there were differences in the means of these vital rates relative to population size between the three periods. 7. The implications of temporal changes in the most important vital rates, the ‘key factors’, contributing to the variance in relative population growth rate are discussed.
Life path analysis: scaling indicates priming effects of social and habitat factors on dispersal distances
Authors: Kenward R. E. , Walls S. S. , Hodder K. H. 
Published: September 2010

Abstract

Movements of many animals along a life‐path can be separated into repetitive ones within home ranges and transitions between home ranges. We sought relationships of social and environmental factors with initiation and distance of transition movements in 114 buzzards Buteo buteo that were marked as nestlings with long‐life radio tags.
Ex‐natal dispersal movements of 51 buzzards in autumn were longer than for 30 later in their first year and than 35 extra‐natal movements between home ranges after leaving nest areas. In the second and third springs, distances moved from winter focal points by birds that paired were the same or less than for unpaired birds. No post‐nuptial movement exceeded 2 km.
Initiation of early ex‐natal dispersal was enhanced by presence of many sibs, but also by lack of worm‐rich loam soils. Distances travelled were greatest for birds from small broods and with relatively little short grass‐feeding habitat near the nest. Later movements were generally enhanced by the absence of loam soils and short grassland, especially with abundance of other buzzards and probable poor feeding habitats (heathland, long grass).
Buzzards tended to persist in their first autumn where arable land was abundant, but subsequently showed a strong tendency to move from this habitat.
Factors that acted most strongly in ½‐km buffers round nests, or round subsequent focal points, usually promoted movement compared with factors acting at a larger scale. Strong relationships between movement distances and environmental characteristics in ½‐km buffers, especially during early ex‐natal dispersal, suggested that buzzards became primed by these factors to travel far.
Movements were also farthest for buzzards that had already moved far from their natal nests, perhaps reflecting genetic predisposition, long‐term priming or poor habitat beyond the study area.
Rate‐maximizing optimality models predict when oystercatchers exploit a cohort of the bivalveScrobicularia planaover a 7‐year time span
Authors: Wanink Jan H. , Zwarts Leo 
Published: September 2010

AbstractThe timing of prey exploitation by oystercatcherHaematopus ostralegusL. was predicted from detailed knowledge of the characteristics of its prey, the clamScrobicularia planada Costa.Growth, mortality and depth distribution of a single cohort ofScrobiculariawere monitored on a tidal flat in the Dutch Wadden Sea during a period of 7 years.A random search model predicted for every sampling date the encounter rate with buried clams providing oystercatchers vary the depth at which they probe their bill into the substrate. The time needed to handle encountered prey was estimated from experimentally determined relationships of handling time with clam size and handling time with burying depth. Encounter rate, handling time and body weight of the potential prey items were used in an optimal prey choice model to predict the average intake rate of an oystercatcher as a function of probing depth.The predicted intake rate reached a profitable level only during three restricted periods. During the first period, a relatively high intake rate could only be achieved by probing extremely deeply, and the mortality rate of the clams remained at a low level. During the other two periods, maximal intake rate was reached by probing only the upper few cm of the substrate, and this time there was a high mortality in the prey population.Although the observed peaks in clam mortality coincided with the predicted exploitation periods, they could not be explained fully by the estimated predation pressure.Prey switching was predicted and confirmed during several exploitation periods.Oystercatcher densities during winter peaks in bird abundance showed a tight relationship with predicted maximum intake rates.
Healthy wrinkles for population dynamics: unevenly spread resources can support more users
Authors: C. Patrick Doncaster 
Published: September 2010

AbstractResource users have a curvilinear relation of abundance to the richness of their limiting resource, with richness defined by the carrying capacity of renewing resource in the absence of exploitation. The non‐linearity means that local unevenness in the distribution of resources can directly influence the overall abundance of users. This effect is entirely independent of overall resource abundance.Outcomes are demonstrated for a classical model of consumer aggregations under conditions of ideal and free exploitation. Consumers that make little impact on the stock of their limiting resource can benefit directly from environmental heterogeneity. They can sustain higher abundance in an environment with unevenly spread resources than in one of equivalent richness with an even spread. Positive effects of heterogeneity are reduced by density dependence in the exploitation rate, for example caused by mutual interference between users. Heterogeneity may have a negative impact on abundance for consumers with a more efficient exploitation of resources.Similar outcomes are predicted for classical models of consumer breeding populations as for consumer aggregations. At still larger scales, unevenness in the distribution of resource patches in metapopulations, and of niches in communities, can increase the abundances of populations and species. Species or communities most likely to benefit from unevenness in their resource carpet are those most vulnerable to local extinction from loss or degradation of their habitat.These effects illustrate applications of non‐spatial models to spatial contexts. They show how steady‐state predictions are likely to be biased by ignoring any underlying heterogeneity in the environment.
Scale invariant spatio‐temporal patterns of field vole density
Authors: Mackinnon James L. , Petty Steve J. , Elston David A. , Thomas Chris J. , Sherratt ToM. N. , Lambin X. 
Published: September 2010

AbstractRecent characterizations of the spatial scale of population dynamics have typically considered patterns at a single scale and ignored the possibility that different patterns may arise at different scales. In this study we assessed population densities of field voles with cyclic dynamics in northern England at 147 sites from three spatial scales on five occasions over a 2·5‐year period.The scale over which densities were similar was estimated by comparing the variance of density at the three scales (< 1 km2, 10 km2, and 70 km2) and by using autocorrelation techniques. Closer sites were more similar in density than more distant sites and the autocorrelations suggested that sites up to within 8–20 km had more similar densities and higher population synchrony than the average similarity for all the sampling sites.A generalized additive model fitted to all the data showed that the data supported the hypothesis of a travelling wave of vole densities moving through the study area. The model assumed that the wave moved at a constant speed and in a uniform direction. Estimates of the wave’s speed (14 km year−1) and direction (travelling in a direction of 66° from north) were consistent with the estimates which had previously been calculated from a time series of vole densities covering a much smaller spatial area but a longer temporal scale.The spatio‐temporal pattern of vole densities detected over a small spatial scale therefore appears to extend over much larger scales and occurs despite the fragmentation of suitable vole habitat at local (a few square kilometres) and regional (hundreds of square kilometres) scales.
Constraints on body‐size distributions: an experimental test of the habitat architecture hypothesis
Authors: Leaper Rebecca , Raffaelli Dave , Emes Chas , Manly Bryan 
Published: September 2010

Summary

Holling (1992) has claimed that a range of mechanisms, including habitat architecture, may be responsible for discontinuities in body‐size distributions across a broad range of spatial and temporal scales.
We tested this proposition in the marine benthos by manipulating habitat architecture directly. Specifically, we constructed artificial sediments (using glass beads) of uniform large or small particles, to change interstitial pore diameters at two estuarine sites.
A combination of kernel estimation and smoothed bootstrap re‐sampling showed that there was a high and varaible degree of modality in body‐size (1–5 modes) in the experimental bead treatments and controls and no obvious evidence for a trough at organism size 0·5–1 mm ESD.
We propose that habitat architecture may not be as intimately related to body‐size patterns as originally claimed, at least at smaller scales where experimental tests are tractable.
Field experiments testing for apparent competition between primary parasitoids mediated by secondary parasitoids
Authors: Morris Rebecca J. , MÜller Christine B. , Godfray H. Charles J. 
Published: September 2010

Summary

Two field manipulation experiments were performed to look for apparent competition between primary parasitoids of aphids, mediated by shared secondary parasitoids. In each case the frequency of secondary parasitism on a ‘focal’ species was compared in the presence or absence of a ‘treatment’ species and its aphid host.
In both experiments the focal species was Aphidius ervi (Haliday) attacking Acyrthosiphon pisum (Harris) (pea aphid). In the first experiment the treatment species was Aphidius rhopalosiphi (De Stefani‐Perez) attacking Sitobion avenae (Fabricius) (a grass aphid) and in the second Aphidius microlophii (Pennachio & Tremblay) attacking Microlophium carnosum (Buckton) (nettle aphid).
No significant effects of either the presence of A. rhopalosiphi or of its host on secondary parasitism of A. ervi were detected in the first experiment.
In the second experiment, rates of secondary parasitism were estimated twice: a significant effect of treatment was found on the first occasion but not the second. In the former, parasitism was highest in the presence of the treatment species and its host, intermediate when just the host was present, and lowest when both were absent.
We discuss the evidence for apparent competition in host‐parasitoid communities.
Invasion of a stream food web by a new top predator
Authors: Woodward Guy , Hildrew Alan G. 
Published: September 2010

Summary

A new top predator, the dragonfly Cordulegaster boltonii Donovan, ‘invaded’ a stream with a well‐described food web.
The pre‐invasion web was species‐poor but complex, with prevalent intraguild predation, cannibalism and omnivory. Such characteristics differ from expectations based upon the early food web literature, but are consistent with more recent empirical webs and theoretical developments.
Exhaustive sampling was necessary to describe web structure, with the gut contents of several hundred individuals being required to reach the asymptote of the total number of links for individual species. There was no single ‘standard’ sample size that was applicable for estimating the number of links: sampling ‘x’ guts gave a different fraction of the asymptotic value for different species. Smaller predators were more prone to underestimation of links than larger species higher in the web.
The number of feeding links, trophic status and the degree of omnivory increased progressively with predator body size, both within and among species. The diet of each predator species (or instar) was effectively a subset of the diet of the next largest predator.
The invader was extremely polyphagous and fed at all trophic levels. Mean chain length increased by half a link following the invasion. Web complexity, and omnivory in particular, also increased. Pre‐ and post‐invasion webs displayed intervality and rigid circuitry. The resident predators were frequently eaten by the invader, but the only significant predators of C. boltonii were larger conspecifics. Although no species have yet been deleted, there has been a 21% increase in links for a 6% increase in species since the invasion, suggesting that the members of the web had become more tightly packed within niche space. Most prey species were eaten by every predator species (including C. boltonii), indicating the potential for strong apparent competition within the web.
Experimentally fragmented communities are more aggregated
Authors: HOYLE MARTIN 
Published: September 2010

Summary

I investigated the effect of habitat fragmentation on species richness, aggregation and community dominance and composition for predators and non‐predators at two spatial scales. Two independent experiments were considered, both using a microecosystem of microarthropods inhabiting moss patches.
In the study at a larger spatial scale, species richness was lower in the more fragmented habitats, due possibly to the lack of a metapopulation ‘rescue effect’. In the smaller‐scale study, species richness was again lower in the fragmented habitats, but did not depend on whether a connecting moss ‘corridor’ was complete or broken. Fragmentation affected predators more than non‐predators in both studies.
The degree of aggregation both within and among habitat patches was greater in the fragmented species‐poor communities, especially for predators. Theory suggests that lower migration in the fragmented communities may either (a) lead to greater aggregation and lower species richness simultaneously, or (b) greater aggregation, leading to increased dominance and hence lower species richness.
There was no clear association between community dominance and species richness.
Community composition was affected by fragmentation in both studies, but knowledge of trophic level and mite developmental stage was insufficient to predict these effects.
Are kernels the mustard? Data from global positioning system (GPS) collars suggests problems for kernel home‐range analyses with least‐squares cross‐validation
Authors: HEMSON GRAHAM , JOHNSON PAUL , SOUTH ANDY , KENWARD ROBERT , RIPLEY RUTH , MACDONALD DAVID 
Published: September 2010

Summary

Kernel‐density estimation (KDE) is one of the most widely used home‐range estimators in ecology. The recommended implementation uses least squares cross‐validation (LSCV) to calculate the smoothing factor (h) which has a considerable influence on the home‐range estimate.
We tested the performance of least squares cross‐validated kernel‐density estimation (LSCV KDE) using data from global positioning system (GPS)‐collared lions subsampled to simulate the effects of hypothetical radio‐tracking strategies.
LSCV produced variable results and a 7% failure rate for fewer than 100 locations (n = 2069) and a 61% failure rate above 100 points (n = 1220). Patterns of failure and variation were not consistent among lions, reflecting different individual space use patterns.
Intensive use of core areas and site fidelity by animals caused LSCV to fail more often than anticipated from studies that used computer‐simulated data.
LSCV failures at large sample sizes and variation at small sample sizes, limits the applicability of LSCV KDE to fewer situations than the literature suggests, and casts doubts over the method's reliability and comparability as a home‐range estimator.
Individual quality mediates trade‐offs between reproductive effort and immune function in tree swallows
Authors: ARDIA DANIEL R. 
Published: September 2010

SummaryIndividual variation in the trade‐off between self‐maintenance and offspring quality was assessed in tree swallows,Tachycineta bicolor, by manipulating reproductive effort while simultaneously immunochallenging breeding females.An experimental manipulation of parental effort was conducted by creating broods of, on average, three, five and eight nestlings. Breeding females were immunochallenged to mount a humoral immune response to sheep red blood cells (SRBC) and a cell‐mediated response to phytohaemagglutinin (PHA). The consequences of adult decisions on offspring quality were assessed through immune responses to PHA, growth rates and residual body mass of nestlings.Clutch initiation date, a strong measure of individual quality in tree swallows, was linked with immune responses, with earlier‐nesting, presumably higher quality, females mounting stronger immune responses than did later‐nesting birds. Increased reproductive effort led to decreased parental immune responses. There was a significant interaction between individual quality and reproductive effort treatment, with lower‐quality individuals showing greater depression of humoral immune response to SRBC while raising enlarged broods, suggesting individual‐level variation in trade‐offs.Breeding females raising enlarged broods tended to raise offspring of similar quality to control females, with only growth rate decreasing with increasing brood size, but not residual nestling body mass or nestling immunocompetence. This suggests that females are maintaining offspring quality at the cost of their own immune system maintenance.
Examination of the large white and small white butterflies (Pierisspp.) for the presence of mustard oils and mustard oil glycosides
Authors: APLIN R. T. , D'ARCY WARD R. , ROTHSCHILD MIRIAM 
Published: September 2010

ABSTRACTSinigrin and mustard oils were identified in the pupae of the large white butterfly (Pieris brassicae) and the small white (P. rapae). It is assumed that these substances are sequestered by the larvae from its foodplant and stored. The large white is apparently the more efficient storer of the two, and mustard oils could be detected in the adults, as well as the larvae.
Orcadian rhythm ofOecophylla longinodain relation to territoriality and predatory behaviour
Authors: DEJEAN A. 
Published: September 2010

AbstractCircadian rhythms of activity in four societies ofOecophylla longinoda(Latreille) have been studied. Activity is continuous, but diurnal activity is greater than the nocturnal activity. This species is characterized by a strong sense of territoriality and the workers occupy: central territories, trees and immediate surroundings occupied by the society; secondary territories, used for hunting purposes, in natural conditions located on the ground; and intermittent territories in the forest zone (diurnal), scarcely used for hunting, but mainly in relation to the tending of homopterans.The circadian rhythm of activity can be reversed by artificially lighting certain territories at night (reinforcement by attraction of numerous prey). This reversal can only be obtained progressively. By permanent surveillance of the territories and efficient recruitment, the societies rapidly adapt to fluctuations in the quantity of prey. There is a close correlation between agressive territoriality and predation.
Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: I. Respiratory metabolism and energy consumption of unloaded and loaded workers during locomotion
Authors: NIELSEN MOGENS GISSEL , BARONI‐URBANI CESARE 
Published: September 2010

Abstract The respiratory metabolism of workers of Messor capitatus (Latreille) was measured using standard micro‐Warburg techniques on single individuals. The experiments were carried out at 10, 20, 25, 30 and 40oC, and the respiratory quotient (RQ), measured for the same individuals at 30oC, was found to be 0.77. The specific respiratory rate (y, in μl O2/mg dry weight/h) could be described by the following equation: Iny = ‐2.24 + 0.098r ‐0.258 In W; where T is temperature and W is the dry weight in mg. The Q10 for M. capitatus in the temperature interval 20–30oC was 3.4, a higher value than for other ants.The energy costs of movement and carrying were determined by using the RQ to convert the continuous measurement of CO2 produced at 30oC by Enfiuran anaesthetized workers (‘resting metabolism’), by running workers and by workers loaded with a 20 mg weight to units of energy. The resting metabolism was 10.0±1.0 mJ/mg fresh weight/h. The cost of running (Y in joule per km) could be described by: Y = 3.865 + 0.363 Wf, where Wf is fresh weight in mg. The cost of transport for all experiments could be expressed as 0.64 × the cost of running.
Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: II. Do ants optimize their harvesting?
Authors: BARONI‐URBANI CESARE , NIELSEN MOGENS GISSEL 
Published: September 2010

Abstract The preference in seed selection by Messor capitatus (Latreille) was studied with artificial seeds (weighted styropore spheres) in the laboratory and with natural seeds in the field. The laboratory experiments showed no strong preference for size of the artificial seeds in the range 3–8 mm (diameter). A mass of about 400 mg was selected when artificial seeds of 5‐5.5 mm were offered at different distances from the nest.In the field experiments, crushed seeds were placed 2 m from the nest and ants showed a clear preference for the size class 2.0–3.0 mm in diameter, which is much smaller and lighter than the preference for the artificial seeds. The preference of seeds from different plants showed very big variability. There was no correlation between the preference and any of the following variables of the seeds: fresh mass, dry mass, water content, energy content, and nitrogen content. No evidence for energy optimizing in food selection in Messor capitatus was found.The energetic reward of bringing any seed back to the nest will, under all normal conditions, be much higher than the energetic expenditure. For example, the energetic content in a wheat seed is about 650 Joule, which is sufficient energy for a worker ant of Messor capitatus to carry the seed for a distance of 6.5 km at a temperature of 30oC.