Marginal populations usually have low densities and are considered to be particularly vulnerable to environmental stochasticity. Using data collected in nest boxes, we analyzed the breeding performance of the edible dormouse (Glis glis), an obligate hibernating rodent and a seed predator in deciduous forests, in two populations at the distribution range\'s edge. Despite being only 20 km apart from each other, Montseny is a large patch of mixed deciduous forests (oaks and beech), whereas Montnegre would be the harshest habitat, that is, a small, isolated patch with only oaks. First, we studied the differences in climate and tree cover change in the two populations. Second, we analyzed the direct and indirect roles of local climate conditions and seed availability on breeding performance over 10 years in each population. Finally, we explored the influence of tree cover change on the occupancy dynamics in the two populations. Our results showed contrasting responses between populations: in Montseny, asynchronous seed production between oaks and beech precluded skip breeding, and breeding performance increased with seed availability. Furthermore, dormice in Montseny may use pollen production to anticipate the amount of beech nut resources and adjust their breeding effort. Boxes showed higher occupancy and colonization and fewer extinctions in Montseny than in Montnegre, where seed availability did not drive breeding performance. Results from Montnegre suggest that skip breeding was an adaptive response to a more pulsed, harsher environment. Here, females produced a similar number of pups than at Montseny. Long-term studies dealing with population responses in marginal habitats can lead to a deeper understanding of the capacities of organisms to adapt to harsh environments. Although local adaptation is frequently documented across various taxa, studies at the distribution edge may shed light on our still limited comprehension of the underlying mechanisms responsible for its occurrence.

The aim of the present study was to critically analyze operational definitions of food deserts and food swamps included in empirical studies published in peer-reviewed journals. A scoping review was conducted following the recommendations of the Joanna Briggs Institute and PRISMA Extension for Scoping Reviews. A search of the scientific literature was performed on August 2023 to identify empirical studies including operational definitions of food deserts and/or food swamps in three databases: Scopus, PubMed, and Scielo. A total of 932 scientific articles were identified in the three databases, from which 157 articles, published between 2002 and 2023, were included in the review. The included studies were mainly conducted in WEIRD (Western, Educated, Industrilaized, Rich and Democractic) countries. They presented a total of 107 operational definitions of food deserts and 30 operational definitions of food swamps. Large heterogeneity in the operational definitions of food deserts and food swamps was found. Published studies differed in all the elements of the operational definitions analyzed in the present work. Results stress the need for standardization and the development of more objective and multivariate continuous measures of physical food accessibility that reflect the complexity of modern food environments globally. A series of recommendations to advance food environment research are derived.

Golden-winged Warblers (Vermivora chrysoptera) have become rare across much of their historic breeding range and response to conservation efforts is variable. Evidence from several recent studies suggests that breeding output is a primary driver explaining responses to conservation and it is hypothesized that differences in food availability may be driving breeding output disparity between two subpopulations of the warbler\'s Appalachian breeding range. Herein, we studied two subpopulations: central Pennsylvania (\"central subpopulation\"), where breeding productivity is relatively low, and eastern Pennsylvania (\"eastern subpopulation\"), where breeding productivity is relatively high. To test the food-availability hypothesis in this system, we measured density of caterpillars, plasma lipid metabolites (triglycerides [TRIG; fat deposition] and glycerol [GLYC; fat breakdown]), body mass of adults males, and acquired body mass data for fledglings at 38 sites managed for nesting habitat. Consistent with our prediction, leaf-roller caterpillar density, the group upon which Golden-winged Warblers specialize, was 45× lower in the central subpopulation than the eastern subpopulation. TRIG concentrations were highest within the eastern subpopulation during breeding grounds arrival. The change in TRIG concentrations from the breeding-grounds-arrival stage to the nestling-rearing stage was subpopulation dependent: TRIG decreased in the eastern subpopulation and was constant in the central subpopulation, resulting in similar concentrations during the nestling-rearing stage. Furthermore, GLYC concentrations were higher in the eastern subpopulation, which suggests greater energy demands in this region. Despite this, adult male warblers in the eastern subpopulation maintained a higher average body mass. Finally, fledgling body mass was 16% greater in the eastern subpopulation than the central subpopulation before and after fledging. Collectively, our results suggest that poor breeding success of Golden-winged Warblers in the central subpopulation could be driven by lower availability of primary prey during the breeding season (leaf-roller caterpillars), and this, in turn, limits their response to conservation efforts.

Maintenance metabolism as the minimum energy expenditure needed to maintain homeothermy (a high and stable body temperature, T b), reflects the magnitude of metabolic machinery and the associated costs of self-maintenance in endotherms (organisms able to produce heat endogenously). Therefore, it can interact with most, if not all, organismal functions, including the behavior-fitness linkage. Many endothermic animals can avoid the costs of maintaining homeothermy and temporally reduce T b and metabolism by entering heterothermic states like torpor, the most effective energy-saving strategy. Variations in BMR, behavior, and torpor use are considered to be shaped by food resources, but those conclusions are based on research studying these traits in isolation. We tested the effect of ecological contexts (food availability and predation risk) on the interplay between the maintenance costs of homeothermy, heterothermy, and exploration in a wild mammal-the yellow-necked mouse. We measured maintenance metabolism as basal metabolic rate (BMR) using respirometry, distance moved (exploration) in the open-field test, and variation in T b (heterothermy) during short-term fasting in animals captured at different locations of known natural food availability and predator presence, and with or without supplementary food resources. We found that in winter, heterothermy and exploration (but not BMR) negatively correlated with natural food availability (determined in autumn). Supplementary feeding increased mouse density, predation risk and finally had a positive effect on heterothermy (but not on BMR or exploration). The path analysis testing plausible causal relationships between the studied traits indicated that elevated predation risk increased heterothermy, which in turn negatively affected exploration, which positively correlated with BMR. Our study indicates that adaptive heterothermy is a compensation strategy for balancing the energy budget in endothermic animals experiencing low natural food availability. This study also suggests that under environmental challenges like increased predation risk, the use of an effective energy-saving strategy predicts behavioral expression better than self-maintenance costs under homeothermy.

An understanding of thermal limits and variation across geographic regions is central to predicting how any population may respond to global change. Latitudinal clines, in particular, have been used to demonstrate that populations can be locally adapted to their own thermal environment and, as a result, not all populations will be equally impacted by an increase in temperature. But how robust are these signals of thermal adaptation to the other ecological challenges that animals commonly face in the wild? Seasonal changes in population density, food availability, or photoperiod are common ecological challenges that could disrupt patterns of thermal tolerance along a cline if each population differentially used these signals to anticipate future temperatures and adjust their thermal tolerances accordingly. In this study, we aimed to test the robustness of a cline in thermal tolerance to simulated signals of seasonal heterogeneity. Experimental animals were derived from clones of the Australian water flea, Daphnia carinata, sampled from nine distinct populations along a latitudinal transect in Eastern Australia. We then factorially combined summer (18 h light, 6 h dark) and winter (6 h light, 18 h dark) photoperiods with high (5 million algal cells individual-1 day-1) and low (1 million algal cells individual-1 day-1) food availabilities, before performing static heat shock assays to measure thermal tolerance. We found that the thermal tolerances of the clonal populations were sensitive to both measures of seasonal change. In general, higher food availability led to an increase in thermal tolerances, with the magnitude of the increase varying by clone. In contrast, a switch in photoperiod led to rank-order changes in thermal tolerances, with heat resistance increasing for some clones, and decreasing for others. Heat resistance, however, still declined with increasing latitude, irrespective of the manipulation of seasonal signals, with clones from northern populations always showing greater thermal resistance, most likely driven by adaptation to winter thermal conditions. While photoperiod and food availability can clearly shape thermal tolerances for specific populations, they are unlikely to overwhelm overarching signals of thermal adaptation, and thus, observed clines in heat resistance will likely have remained robust to these forms of seasonal heterogeneity.

Recent evidence suggests that individuals differ in foraging tactics and this variation is often linked to an individual\'s behavioural type (BT). Yet, while foraging typically comprises a series of search and handling steps, empirical investigations have rarely considered BT-dependent effects across multiple stages of the foraging process, particularly in natural settings. In our long-term sleepy lizard (Tiliqua rugosa) study system, individuals exhibit behavioural consistency in boldness (measured as an individual\'s willingness to approach a novel food item in the presence of a threat) and aggressiveness (measured as an individual\'s response to an \'attack\' by a conspecific dummy). These BTs are only weakly correlated and have previously been shown to have interactive effects on lizard space use and movement, suggesting that they could also affect lizard foraging performance, particularly in their search behaviour for food. To investigate how lizards\' BTs affect their foraging process in the wild, we supplemented food in 123 patches across a 120-ha study site with three food abundance treatments (high, low and no-food controls). Patches were replenished twice a week over the species\' entire spring activity season and feeding behaviours were quantified with camera traps at these patches. We tracked lizards using GPS to determine their home range (HR) size and repeatedly assayed their aggressiveness and boldness in designated assays. We hypothesised that bolder lizards would be more efficient foragers while aggressive ones would be less attentive to the quality of foraging patches. We found an interactive BT effect on overall foraging performance. Individuals that were both bold and aggressive ate the highest number of food items from the foraging array. Further dissection of the foraging process showed that aggressive lizards in general ate the fewest food items in part because they visited foraging patches less regularly, and because they discriminated less between high and low-quality patches when revisiting them. Bolder lizards, in contrast, ate more tomatoes because they visited foraging patches more regularly, and ate a higher proportion of the available tomatoes at patches during visits. Our study demonstrates that BTs can interact to affect different search and handling components of the foraging process, leading to within-population variation in foraging success. Given that individual differences in foraging and movement will influence social and ecological interactions, our results highlight the potential role of BT\'s in shaping individual fitness strategies and population dynamics.

Food availability determines the amount of energy animals can acquire and allocate to reproduction and other necessary functions. Female animals that are food limited thus experience reduced energy available for reproduction. When this occurs, females may reduce frequency of reproductive events or the number or size of offspring per reproductive bout. We assessed how maternal diet affects reproductive output in adult female Murray River short-necked turtles, Emydura macquarii, from four wetlands in Victoria. We previously found that turtle diets differ in the composition of plants and animals between our study wetlands. In this study, we tested whether differences in turtle diet composition (i.e. plants and animals) at these wetlands were associated with differences in clutch mass, individual egg mass, bulk egg composition and hatching success. We found total clutch mass increased with maternal body size at each site. At sites where filamentous green algae were scarce and E. macquarii were carnivorous, females produced smaller clutches relative to body size compared to females from sites where algae were abundant, and turtles were more herbivorous. Individual egg mass, bulk egg composition and hatching success did not differ across wetlands. Isotopic analysis revealed significant positive relationships between the carbon and nitrogen isotopes (δ13C, δ15N) of the eggs and those of the mothers, indicating that mothers allocated ratios of carbon and nitrogen isotopes to their eggs similar to those present in their tissues. Our study suggests that at sites where females are more carnivorous due to a relative absence of algae, females produce smaller clutches, but other aspects of their reproduction are not significantly impacted. The reduction in clutch size associated with differences in the availability of dietary plants and animals may have long-term consequences for E. macquarii and other freshwater turtle species that are experiencing population declines.

BACKGROUND: The number of globally food-insecure people is increasing since 2017. Sub-Saharan Africa has the highest proportion of severely food-insecure people in the world. Tigray region of Ethiopia is one of the food-insecure regions, which, over the past many decades has been affected by recurrent food insecurities. In the drought-prone rural areas of Tigray, many people are living under the condition of chronic hunger. Proper food security studies are vital for proper intervention mechanisms. Yet, previous food security studies have rarely addressed the four pillars of food security: availability, access, utilization, and stability. In this study, all components are duly considered to assess the food insecurity status in the drought-prone rural areas of Tigray, Ethiopia. Of the 34 rural districts in Tigray, 363 households from three drought-prone rural districts were studied.
RESULTS: Household Food Insecurity Access Scale and Food Insecurity Experience Scale were adapted to measure the food availability, access to food, and stability components of food security; and, Household Dietary Diversity Score (HDDS), Food Consumption Score (FCS), mid-upper arm circumference, and Bitot\'s spot were used to analyze the food utilization aspect. Findings show that 68% of the studied community frequently ate less food than they felt they needed and 82.1% of the households have experienced hunger because of lack of food. The study rural districts were unconnected to road networks; hence, 87.9% of the elderly and 20.4% of the women and girls had no access to food markets. Regarding the food utilization, 81.5% of the studied households had poor FCS; and the average HDDS and FCS for the study areas were 2.47 and 18.9, respectively. The prevalence of Global acute malnutrition, severe acute malnutrition (SAM), and moderate acute malnutrition (MAM) for 6-59 months of age children in the study areas were 50.3, 4.2, and 46.1%, respectively. More notably, the prevalence of SAM for children from the food-insecure households was 21.2%. The prevalence of MAM for pregnant and lactating women (PLW) in the study areas was 59.5. Further, the prevalence of Bitot\'s spot among 6-59 months of age children was 1.9%. On the other hand, all the rural households had anxiety about their future food demands.
CONCLUSIONS: The rural households living in the studied areas were critically food-insecure. All the measurements implied that the food insecurity situation in the study areas was unacceptably worrisome and life-threatening. This calls for an instant action to avert the occurrence of famine and starvation in the drought-prone rural areas of Tigray region. Thus, interventions should primarily target the vulnerable rural people and need to be planned based on attaining food availability first rather than concurrently addressing all components of food security. Further, due emphasis should be given to diversifying livelihood strategies of the vulnerable villagers.

BACKGROUND: In Africa, approx. 675 million people were at risk of food insecurity. COVID-19 pandemic is likely to have exacerbated this situation, by damaging populations\' access to and affordability of foods. This study is aimed at estimating the impacts of the COVID-19 pandemic on availability and prices of essential food commodities at 20 large markets in Ghana.
METHODS: Data on food availability and food retail prices collected through weekly market-level data during the period from July 2017 to September 2020 were used in this study. We performed interrupted time-series analyses and estimated the percentage increases between the observed and predicted food prices by food group and by region to assess the impact of COVID-19 pandemic on food prices.
RESULTS: As a result, the impact of COVID-19 on food availability was limited. However, the results of interrupted time-series analyses indicate a significant increase in overall mean food prices in Greater Accra, Eastern and Upper East regions. It was also found that mean price of starchy roots, tubers and plantains significantly increased across regions.
CONCLUSIONS: The impact of COVID-19 pandemic on food availability and prices was significant but varied by food type and regions in Ghana. Continuous monitoring and responses are critical to maintain food availability and affordability.

In birds, patterns of development of the adrenocortical response to stressors vary among individuals, types of stressors, and species. Since there are benefits and costs of exposure to elevated glucocorticoids, this variation is presumably a product of selection such that animals modulate glucocorticoid secretion in contexts where doing so increases their fitness. In this study, we evaluated hypothalamo-pituitary-adrenal (HPA) activity in first-hatched free-living seabird nestlings that engage in intense sibling competition and facultative siblicide (black-legged kittiwakes, Rissa tridactyla). We sampled 5 day old chicks (of the ∼45 day nestling period), a critical early age when food availability drives establishment of important parent-offspring and intra-brood dynamics. We experimentally supplemented parents with food (\"supplemented\") and measured chick baseline corticosterone secretion and capacity to rapidly increase corticosterone in response to an acute challenge (handling and 15 min of restraint in a bag). We also used topical administration of corticosterone to evaluate the ability of chicks to downregulate physiologically relevant corticosterone levels on a short time scale (minutes). We found that 5 day old chicks are not hypo-responsive but release corticosterone in proportion to the magnitude of the challenge, showing differences in baseline between parental feeding treatments (supplemented vs non-supplemented), moderate increases in response to handling, and a larger response to restraint (comparable to adults) that also differed between chicks from supplemented and control nests. Topical application of exogenous corticosterone increased circulating levels nearly to restraint-induced levels and induced downregulation of HPA responsiveness to the acute challenge of handling. Parental supplemental feeding did not affect absorbance/clearance or negative feedback. Thus, while endogenous secretion of corticosterone in young chicks is sensitive to environmental context, other aspects of the HPA function, such as rapid negative feedback and/or the ability to clear acute elevations in corticosterone, are not. We conclude that 5 day old kittiwake chicks are capable of robust adrenocortical responses to novel challenges, and are sensitive to parental food availability, which may be transduced behaviorally, nutritionally, or via maternal effects. Questions remain about the function of such rapid, large acute stress-induced increases in corticosterone in very young chicks.