Winter severity modulates the benefits of using a habitat temporally uncoupled from browsing

Resources whose abundance is not affected by the density of the consumer population, namely donor-controlled resources, are ubiquitous. Donor-controlled resources can act as food subsidies when they sustain consumer populations at higher densities than what would be predicted without donorcontrolled dynamics. Herbivore populations that have access to food subsidies may reach and maintain high densities, with potential major ecological and economic consequences. A better understanding of the roles of food subsidies on temperate herbivores will likely be achieved by simultaneously taking into account other drivers of demographic variations such as winter severity. Here, we tested the hypothesis that the use of a donor-controlled food resource that may act as a food subsidy, namely balsam fir (Abies balsamea), and winter severity act together to shape the patterns of overwinter mass loss in a large herbivore population (white-tailed deer, Odocoileus virginianus). We monitored weather conditions, diet, habitat use, and mass loss of female deer during two highly contrasted winters. During an exceptionally milder winter, characterized by shallower snow depth and warmer windchill temperatures, female deer shifted their diet toward resources usually covered by snow during typical winters. Surprisingly, the rate of body mass loss remained similar during the milder and the harsher winter. The rate of body mass loss rather decreased with the use of balsam fir stands during the harsher winter, but increased with that same variable during the milder winter. Our study revealed that deer can alleviate overwinter mass loss by using a donor-controlled habitat type temporally uncoupled from browsing, but that this benefit is climate dependent. This study represents an additional step to address the largely unexplored concept of how temporal uncoupling between resources and consumer dynamics may contribute to sustain consumer populations at higher densities than predicted without considering donor-controlled dynamics

Reduced rapid eye movement sleep in late middle-aged and older apolipoprotein E ɛ4 allele carriers

Study Objectives Apolipoprotein E ɛ4 (APOE4) is the strongest genetic risk factor for Alzheimer’s disease (AD). In addition, APOE4 carriers may exhibit sleep disturbances, but conflicting results have been reported, such that there is no clear consensus regarding which aspects of sleep are impacted. Our objective was to compare objective sleep architecture between APOE4 carriers and non-carriers, and to investigate the modulating impact of age, sex, cognitive status, and obstructive sleep apnea (OSA). Methods A total of 198 dementia-free participants aged >55 years old (mean age: 68.7 ± 8.08 years old, 40.91% women, 41 APOE4 carriers) were recruited in this cross-sectional study. They underwent polysomnography, APOE4 genotyping, and a neuropsychological evaluation. ANCOVAs assessed the effect of APOE4 status on sleep architecture, controlling for age, sex, cognitive status, and the apnea–hypopnea index. Interaction terms were added between APOE4 status and covariates. Results Rapid eye movement (REM) sleep percentage (F = 9.95, p = .002, ηp2 = 0.049) and duration (F = 9.23, p = .003, ηp2 = 0.047) were lower in APOE4 carriers. The results were replicated in a subsample of 112 participants without moderate-to-severe OSA. There were no significant interactions between APOE4 status and age, sex, cognitive status, and OSA in the whole sample. Conclusions Our results show that APOE4 carriers exhibit lower REM sleep duration, including in cognitively unimpaired individuals, possibly resulting from early neurodegenerative processes in regions involved in REM sleep generation and maintenance

Altered resting-state functional connectivity patterns in late middle-aged and older adults with obstructive sleep apnea

IntroductionObstructive sleep apnea (OSA) is increasingly recognized as a risk factor for cognitive decline, and has been associated with structural brain alterations in regions relevant to memory processes and Alzheimer’s disease. However, it is unclear whether OSA is associated with disrupted functional connectivity (FC) patterns between these regions in late middle-aged and older populations. Thus, we characterized the associations between OSA severity and resting-state FC between the default mode network (DMN) and medial temporal lobe (MTL) regions. Second, we explored whether significant FC changes differed depending on cognitive status and were associated with cognitive performance.MethodsNinety-four participants [24 women, 65.7 ± 6.9 years old, 41% with Mild Cognitive Impairment (MCI)] underwent a polysomnography, a comprehensive neuropsychological assessment and a resting-state functional magnetic resonance imaging (MRI). General linear models were conducted between OSA severity markers (i.e., the apnea-hypopnea, oxygen desaturation and microarousal indices) and FC values between DMN and MTL regions using CONN toolbox. Partial correlations were then performed between OSA-related FC patterns and (i) OSA severity markers in subgroups stratified by cognitive status (i.e., cognitively unimpaired versus MCI) and (ii) cognitive scores in the whole sample. All analyzes were controlled for age, sex and education, and considered significant at a p < 0.05 threshold corrected for false discovery rate.ResultsIn the whole sample, a higher apnea-hypopnea index was significantly associated with lower FC between (i) the medial prefrontal cortex and bilateral hippocampi, and (ii) the left hippocampus and both the posterior cingulate cortex and precuneus. FC patterns were not associated with the oxygen desaturation index, or micro-arousal index. When stratifying the sample according to cognitive status, all associations remained significant in cognitively unimpaired individuals but not in the MCI group. No significant associations were observed between cognition and OSA severity or OSA-related FC patterns.DiscussionOSA severity was associated with patterns of lower FC in regions relevant to memory processes and Alzheimer’s disease. Since no associations were found with cognitive performance, these FC changes could precede detectable cognitive deficits. Whether these FC patterns predict future cognitive decline over the long-term needs to be investigated

Le travail domestique et le travail du sexe dans les migrations internationales

En 1996, l’Organisation internationale du travail reconnaissait que la féminisation de la migration internationale pour le travail représentait un des phénomènes économiques et sociaux les plus impressionnants des temps récents (Lepp, 2002). En effet, ces 25 dernières années, la migration féminine a augmenté de façon spectaculaire. Désormais, les femmes constituent presque la moitié des migrant-e-s sur une population migrante totale d’environ 175 millions de personnes, dont 36 millions d’émig..

Data_WithinHomeRangeScale_Windchill

Data used in the within-home-range scale analysis describing wind-chill dat

Data from: Coping with strong variations in winter severity: plastic habitat selection of deer at high density

Few empirical studies on large herbivores considered how behavioral plasticity could enhance their capacity to cope with rapid and extreme changes in weather conditions at several spatiotemporal scales. During winter, large herbivores living under low predation pressure mainly trade-off benefits of forage acquisition with the costs of exposure to harsh weather conditions. We assessed the changes in this trade-off for white-tailed deer adult females on Anticosti Island (Canada) at different scales during 2 contrasted winters (i.e., a harsher and a milder winter). We hypothesized that deer should adjust their foraging decisions to avoid cold wind-chill temperatures and high locomotion costs in deep snow as winter severity increased. We compared habitat selection at the home-range scale, habitat selection relative to thermal conditions within the home range, and selection for foraging sites relative to snow conditions along the foraging tracks between winters. Home-range selection of deer was similar between winters. Deer adjusted their within-home-range selection relative to thermal conditions: they selected thermal cover during cold-stress periods while their selection for open areas increased during the warmer periods. Deer showed high behavioral plasticity along their foraging tracks: they selected tracks with different forage resources between winters and traded-off the locomotion costs in deep snow cover with the benefits of forage availability as winter severity increased. We discuss how behavioral plasticity of deer in their thermoregulatory behavior and foraging site selection allows them to cope with varying winter conditions, in a system where their short-term behavioral adaptations were already strongly constrained by intraspecific competition

Data_HomeRangeScale

Data used in the home-range scale analysis

Data_WithinHomeRangeScale

Data used in the within-home-range scale analysis

Data_ForagingTrackScale

Data used in the foraging track scale analysis

A New Way of Assessing Foraging Behaviour at the Individual Level Using Faeces Marking and Satellite Telemetry

<div><p>Heterogeneity in foraging behaviour can profoundly influence ecological processes shaping populations. To scale-up from individual foraging behaviour to processes occurring at the population scale, one needs to sample foraging behaviour at the individual level, and over large temporal scales or during critical seasons known to influence life-history traits. We developed an innovative technique to monitor foraging behaviour at the individual level in secretive species, a technique that can be ultimately used to investigate the links between foraging behaviour and life-history traits. First, the technique used a novel approach, namely the combination of telemetry tracking and biomarking of faeces with food dyes to locate fresh signs of presence left by individuals equipped with GPS collars. Second, the technique is based on the simultaneous or successive sampling of life-history traits and individual foraging behaviour, using tracks with high probabilities of recovery of dyed faeces. We first describe our methodological approach, using a case study of a large herbivore, and then provide recommendations and guidelines for its use. Sampling single snow tracks of individuals equipped with a GPS collar was a reliable way to assess individual winter foraging behaviour in a white-tailed deer (<em>Odocoileus virginianus</em> Zimmermann) population. During that period, the probability of recovery of dyed faeces within the range of the collar precision was very high for single snow tracks of equipped deer (97%). Our approach is well suited to study individual foraging behaviour, and could ultimately be used to investigate the interplay between intra-population heterogeneity in foraging behaviour, life-history traits, and demographic processes.</p> </div