Extra Nestlings That Are Condemned to Die Increase Reproductive Success in Hoopoes.

AbstractThe adaptive value of routinely laying more eggs than can be successfully fledged has intrigued evolutionary biologists for decades. Extra eggs could, for instance, be adaptive as insurance against hatching failures. Moreover, because recent literature demonstrates that sibling cannibalism is frequent in the Eurasian hoopoe (Upupa epops), producing extra offspring that may be cannibalized by older siblings might also be adaptive in birds. Here, directed to explore this possibility in hoopoes, we performed a food supplementation experiment during the laying period and a clutch size manipulation during the hatching stage. We found that females with the food supplement laid on average one more egg than control females and that the addition of a close-to-hatch egg at the end of the hatching period increased the intensity of sibling cannibalism and enhanced fledging success in hoopoe nests. Because none of the extra nestlings from the experimental extra eggs survived until fledging, these results strongly suggest that hoopoes obtain fitness advantages by using temporarily abundant resources to produce additional nestlings that will be cannibalized. These results therefore suppose the first experimental demonstration of the nutritive adaptive function of laying extra eggs in vertebrates with parental care.

Evidence for Policies and Practices to Address Global Food Insecurity.

Food insecurity affects an estimated 691-783 million people globally and is disproportionately high in Africa and Asia. It arises from poverty, armed conflict, and climate change, among other demographic and globalization forces. This review summarizes evidence for policies and practices across five elements of the agrifood system framework and identifies gaps that inform an agenda for future research. Under availability, imbalanced agriculture policies protect primarily staple food producers, and there is limited evidence on food security impacts for smallholder and women food producers. Evidence supports the use of cash transfers and food aid for affordability and school feeding for multiple benefits. Food-based dietary guidelines can improve the nutritional quality of dietary patterns, yet they may not reflect the latest evidence or food supplies. Evidence from the newer food environment elements, promotion and sustainability, while relatively minimal, provides insight into achieving long-term impacts. To eliminate hunger, our global community should embrace integrated approaches and bring evidence-based policies and practices to scale.

Resource manipulation reveals interactive phenotype-dependent foraging in free-ranging lizards.

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.

Corticosterone release in very young siblicidal seabird chicks (Rissa tridactyla) is sensitive to environmental variability and responds rapidly and robustly to external challenges.

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.

Longitudinal changes in home food availability and concurrent associations with food and nutrient intake among children at 24-48 months.

OBJECTIVES: To describe changes in home food availability during early childhood, including modified, developmentally sensitive obesogenic scores, and to determine whether home food availability is associated with food and nutrient intakes of children concurrently, over time. DESIGN: Data were drawn from the STRONG Kids 2 longitudinal, birth cohort to achieve the study objectives. Home food availability was assessed with the Home Food Inventory (HFI) and included fifteen food groups (e.g. fruit and vegetables) and three obesogenic scores (one original and two modified). Food and nutrient intakes were measured using the Block FFQ and included twenty-seven food groups and eighteen nutrients (e.g. vitamins A and C, protein). HFI and FFQ were completed by trained researchers or mothers, respectively, at 24, 36 and 48 months. Repeated-measures ANOVA and Spearman's correlations were used to achieve the study objectives. SETTING: Central Illinois, USA. PARTICIPANTS: Participants were 468 children at 24, 36 and 48 months of age. RESULTS: Availability of less nutritious foods and obesogenic foods and beverages increased as children aged, and availability of both nutritious and less nutritious foods were associated with child food and nutrient intake. The three obesogenic scores demonstrated similar, positive associations with the intake of energy, saturated fat, added sugars and kilocalories from sweets. CONCLUSION: These findings offer novel insight into changes in home food availability and associations with food and nutrient intake during early childhood. Additional attention is needed examining antecedents (e.g. built environments, purchasing behaviours) and consequences (e.g. child diet quality and weight) of home food availability.

Assessing food availability and healthier options in an urban Chinese university: a case study using the Chinese Nutrition Environment Measurement Survey for Stores (C-NEMS-S).

Young adults (18-24 years) in universities are frequently exposed to an environment that promotes unhealthy eating behaviors. Using a validated tool, the Chinese Nutrition Environment Measurement Survey for Stores (C-NEMS-S), we assess the food availability and healthier options in a large, urban Chinese university. We employed C-NEMS-S for scoring criteria and weighting. A total of 52 on-campus canteen outlets were audited in an urban university located in Shijiazhuang City, China. General food outlets (n 43) and self-served food outlets (n 7) were further categorized into eight subtypes. Beverage outlets (n 2) were discussed separately from food outlets. C-NEMS-S scores were significantly different across food outlet types (P = 0.0024), especially between noodle and rice outlets (P = 0.0415). Food availability scores for starchy tubers (P < 0.001), dry beans (P < 0.001), vegetables (P = 0.0225), and fruits (P < 0.001) were significantly different across food outlet subtypes. Healthier options were scarce and only appeared in "grains" (n 2) and "meat and poultry" (n 2) categories. Further research on improving the accustomed audit tool and assessing university student diet quality is warranted.

Impact of COVID-19 pandemic on food availability and affordability: an interrupted time series analysis in Ghana.

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. DISCUSSION: 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.

Consistency in Verreaux's sifaka home range and core area size despite seasonal variation in resource availability as assessed by Enhanced Vegetation Index (EVI).

Primates are adept at dealing with fluctuating availability of resources and display a range of responses to minimize the effects of food scarcity. An important component of primate conservation is to understand how primates adapt their foraging and ranging patterns in response to fluctuating food resources. Animals optimize resource acquisition within the home range through the selection of resource-bearing patches and choose between contrasting foraging strategies (resource-maximizing vs. area-minimizing). Our study aimed to characterize the foraging strategy of a folivorous primate, Verreaux's sifaka (Propithecus verreauxi), by evaluating whether group home range size varied between peak and lean leaf seasons within a seasonally dry tropical forest in Madagascar. We hypothesized that Verreaux's sifaka used the resource maximization strategy to select high-value resource patches so that during periods of resource depression, the home range area did not significantly change in size. We characterized resource availability (i.e., primary productivity) by season at Kirindy Mitea National Park using remotely-sensed Enhanced Vegetation Index data. We calculated group home ranges using 10 years of focal animal sampling data collected on eight groups using both 95% and 50% kernel density estimation. We used area accumulation curves to ensure each group had an adequate number of locations to reach seasonal home range asymptotes. Neither 95% home ranges nor 50% core areas differed across peak and lean leaf resource seasons, supporting the hypothesis that Verreaux's sifaka use a resource maximization strategy. With a better understanding of animal space use strategies, managers can model anticipated changes under environmental and/or anthropogenic resource depression scenarios. These findings demonstrate the value of long-term data for characterizing and understanding foraging and ranging patterns. We also illustrate the benefits of using satellite data for characterizing food resources for folivorous primates.

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northern Europe.

The availability of resources varies across a species distributional range, and a low-productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicates that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low-productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient-rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient-poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving the S. salar population in a nutrient-poor river.

Integrative biological analyses of responses to food deprivation reveal resilience mechanisms in sea urchin larvae.

A fundamental question in ecology is how organisms survive food deprivation. In the ocean, climate change is impacting the phenology of food availability for early life-history stages of animals. In this study, we undertook an integrative analysis of larvae of the sea urchin Strongylocentrotus purpuratus-an important keystone species in marine ecology and a molecular biological model organism in developmental biology. Specifically, to identify the mechanisms of resilience that maintain physiological state and the ability of organisms to recover from food deprivation, a suite of molecular biological, biochemical, physiological and whole organism measurements was completed. Previous studies focused on the importance of energy reserves to sustain larvae during periods of food deprivation. We show, however, that utilization of endogenous energy reserves only supplied 15% of the metabolic requirements of long-term survival (up to 22 days) in the absence of particulate food. This large energy gap was not supplied by larvae feeding on bacteria. Estimates of larval ability to transport dissolved organic matter directly from seawater showed that such substrates could fully supply metabolic needs. Integrative approaches allowed for filtering of gene expression signatures, linked with gene network analyses and measured biochemical and physiological traits, to identify biomarkers of resilience. We identified 14 biomarkers related to nutrition-responsive gene expression, of which a specific putative amino acid transporter gene was quantified in a single larva experiencing continuous nutritional stress. Advances in applications of gene expression technologies offer novel approaches to determine the physiological state of marine larval forms in ecological settings undergoing environmental change.

Thermoregulatory costs of the innate immune response are modulated by winter food availability in a small passerine.

In winter, a challenge to the immune system could pose a major energetic trade-off for small endotherms, whereby increasing body temperature (Tb ; i.e. eliciting fever) may be beneficial to fight off invading pathogens yet incur a cost for vital energy-saving mechanisms. Having previously shown that the availability and acquisition of energy, through manipulation of food predictability, influences the depth of rest-phase hypothermia in a wild bird in winter, we expected that the nocturnal thermoregulatory component of the acute-phase immune response would also be modulated by food availability. By manipulating winter food availability in the wild for great tits Parus major, we created an area offering a "predictable" and constant supply of food at feeding stations, while an unmanipulated area was subject to naturally "unpredictable" food. Birds were subject to an immune challenge shortly after dusk, and the thermoregulatory response was quantified via continuous recording of nocturnal Tb , using subcutaneous thermo-sensitive transponders. In response to immune challenge, all birds increased Tb above the level maintained prior to immune challenge (i.e. baseline). However, birds experiencing a naturally unpredictable food supply elevated Tb more than birds subject to predictable food resources, during the period of expected peak response and for the duration of the night. Furthermore, "unpredictable-food" females took longer to return to their baseline Tb . Assuming baseline nocturnal Tb reflects an individual's optimum, based on their available energy budget, the metabolic cost of eliciting an acute-phase response for "unpredictable-food" birds was more than double that of "predictable-food" birds. The absence of differences in absolute Tb during the peak response could support the idea of an optimal Tb for immune system activation. Alternatively, "predictable-food" birds could have acquired tolerance to endotoxin as a result of using feeding stations, thus affording them reduced costs associated with a smaller Tb increase. These findings shed new light on the trade-offs associated with food acquisition, thermoregulation and immune function in small-bodied endotherms. This knowledge is of increasing importance, given the predicted elevated pathogen risks associated with changes in climate and anthropogenic activities.

Examining the New Zealand school food environment: what needs to change?

Habitual dietary intakes and nutrition behaviours developed during childhood and adolescence pave the way for similar behaviours to manifest in adulthood. Childhood obesity rates have now reached a point where one in six children globally are classified as overweight or obese. Schools have the unique ability to reach almost all children during key developmental stages, making them an ideal setting for influencing children's nutrition behaviours. Evidence suggests the school food environment is not always conducive to healthy food choices and may be obesogenic. The aim of this narrative review is to explore factors that influence the healthy food and drink environment in and around schools in New Zealand. The review focused on evidence from New Zealand and Australia given the close resemblance in education systems and school food guidance. Using the Analysis Grid for Environments Linked to Obesity (ANGELO) framework, the school food environment was categorised into the following domains: economic, political, physical and socio-cultural factors. Findings suggest that food policies are not utilised within schools, and guidelines to improve the school food environment are not well implemented. Canteen profit models, lack of staff support and resources, and higher availability of low-cost unhealthy foods are among barriers that hinder implementation. This review highlights recommendations from existing evidence, including canteen pricing strategies, restriction of unhealthy foods and using peer modelling in a time-scarce curriculum to improve the school food environment. Key areas for improvement, opportunities to enhance policy implementation and untapped avenues to improve the food and nutrition behaviours of children are highlighted.

Change in hyper-palatable food availability in the US food system over 30 years: 1988-2018.

OBJECTIVE: To quantify the change in availability of hyper-palatable foods (HPF) in the US foods system over 30 years (1988-2018). DESIGN: Three datasets considered representative of the US food system were used in analyses to represent years 1988, 2001 and 2018. A standardised definition from Fazzino et al. (2019) that specifies combinations of nutrients was used to identify HPF. SETTING: Analysis of food-item level data was conducted. Differences in the prevalence of HPF were characterised by Cochran's Q and McNemar's tests. Generalised linear mixed models with a fixed effect for time and random intercept for food item estimated change in the likelihood that a food was classified as hyper-palatable over time. PARTICIPANTS: No participant data were used. RESULTS: The prevalence of HPF increased 20 % from 1988 to 2018 (from 49 % to 69 %; P < 0·0001). The most prominent difference was in the availability of HPF high in fat and Na, which evidenced a 17 % higher prevalence in 2018 compared with 1988 (P < 0·0001). Compared with 1988, the same food items were >2 times more likely to be hyper-palatable in 2001, and the same food items were >4 times more likely to be classified as hyper-palatable in 2018 compared with 1988 (P values < 0·0001). CONCLUSIONS: The availability of HPF in the US food system increased substantially over 30 years. Existing food products in the food system may have been reformulated over time to enhance their palatability.

Spawning time in adult polar cod (Boreogadus saida) altered by crude oil exposure, independent of food availability.

Fish early life stages are well known for their sensitivity to crude oil exposure. However, the effect of crude oil exposure on adults and their gametes during their spawning period is not well studied. Polar cod, a key arctic fish, may be at risk for crude oil exposure during this potentially sensitive life stage. Additionally, this species experiences lower food availability during their spawning season, with unknown combined consequences. In the present study, wild-caught polar cod were exposed to decreasing levels of a water-soluble fraction (WSF) of crude oil or control conditions and fed either at a low or high feed ration to assess the combined effect of both stressors. Samples were taken during late gonadal development, during active spawning (spawning window), and in the post-spawning period. Histology analysis of gonads from fish sampled during the spawning window showed that oil-exposed polar cod were more likely to have spawned compared to controls. Oil-exposed females had 947 differentially regulated hepatic genes, and their eggs had a higher polycyclic aromatic hydrocarbon body burden compared to controls. Feed ration did not consistently affect polar cod's response to oil exposure for the endpoints measured, however, did alone result in decreases in some sperm motility parameters. These results suggest that polar cod's spawning period is a sensitive life event to crude oil exposure, while feed limitation may play a minor role for this supposedly capital breeder. The effects of adult exposure to crude oil on gamete quality and the next generation warrant further investigation.

Children's food choices are highly dependent on patterns of parenting practices and food availability at home in families at high risk for type 2 diabetes in Europe: Cross-sectional results from the Feel4Diabetes study.

BACKGROUND: Food parenting practices, behaviours and food availability at home are associated with children's food choices; however, these associations have been mainly studied for each parenting practice separately and focused mostly on healthy populations. The aim of the study was to identify patterns of parenting practices (including data regarding food availability at home, food and physical activity-related behaviours and rewards) and to investigate their cross-sectional associations with children's food choices in families at high risk for type 2 diabetes (T2D). METHODS: Data of parents and children (n = 2278), from the Feel4Diabetes study conducted in six European countries, were collected using validated questionnaires. The data analysed included children's food choices, food availability at home and food and physical activity-related parenting practices. Four patterns of parenting practices were identified using principal component analysis, and associations between those components and children's food choices were assessed using adjusted, individual linear regressions. RESULTS: Parenting patterns focusing on unhealthy habits, such as allowing unhealthy snacks and unlimited screen time, providing higher availability of unhealthy foods at home, rewarding with snacks and screen time, were positively associated with children's unhealthy food choices (consumption of savoury/sweet snacks, fizzy drinks, etc.). The parenting patterns providing fruit/vegetables at home, consuming fruit, and being physically active with the child were positively associated with children's healthier food choices (consumption of fruit, vegetables, whole grain cereals, etc.). CONCLUSIONS: Public health initiatives should focus on high-risk families for T2D, assisting them to adopt appropriate parenting practices and behaviours to promote healthier food choices for children.

Food availability and food habits among Ghanaians: Tracking the dietary transition in Ghana.

Background: Although extreme hunger has reduced significantly, people are eating nutrient-poor cheap foods that are unhealthy and environmentally unsustainable. Even though dietary practices are changing in Ghana, there is minimal national-level analysis of the changes and their implication for population health. Aim: This study describes shifts in food availability and consumption in Ghana from 1983-2013. Methods: Data from the Food and Agriculture Organisation (FAO) food balance sheets and a scoping review were used. Descriptive analysis was conducted in excel for the FAO data, and Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews recommendation was followed for the scoping review. Results: The availability of total calories increased from 1527 kcal in 1983 to 3016 kcal in 2013, representing 608 kcal above the daily recommended allowance for women. Sugar and sweeteners was the food group with the highest increase of 1075%. Vegetables contributed the least to food availability, with less than 40 kcal a day. Rice contributed the most to food availability among cereals (56 kcal in 1983 to 304 kcal in 2013), replacing maise as the primary cereal. Conclusion: After the 1983 famine, there were significant increases in food availability in Ghana. The provision of rice, sugars and tubers meant to end hunger, changed dietary patterns and has resulted in low dietary diversity, high energy intake and overweight/obesity. Therefore, there is a need to intervene and increase the availability of other food groups.

Telomere length correlates with physiological and behavioural responses of a long-lived seabird to an ecologically relevant challenge.

Determinants of individual variation in reallocation of limited resources towards self-maintenance versus reproduction are not well known. We tested the hypothesis that individual heterogeneity in long-term 'somatic state' (i) explains variation in endocrine and behavioural responses to environmental challenges, and (ii) is associated with variation in strategies for allocating to self-maintenance versus reproduction. We used relative telomere length as an indicator of somatic state and experimentally generated an abrupt short-term reduction of food availability (withdrawal of food supplementation) for free-living seabirds (black-legged kittiwakes, Rissa tridactyla). Incubating male kittiwakes responded to withdrawal by increasing circulating corticosterone and losing more weight compared to continuously supplemented controls. Males with longer telomeres increased time in directed travel regardless of treatment, while experiencing smaller increases in corticosterone. Males with longer telomeres fledged more chicks in the control group and tended to be more likely to return regardless of treatment. This study supports the hypothesis that somatic state can explain variation in short-term physiological and behavioural responses to challenges, and longer-term consequences for fitness. Male kittiwakes with longer telomeres appear to have prioritized investment in self over investment in offspring under challenging conditions.

Not just females: the socio-ecology of social interactions between spider monkey males.

Male-male relationships are mostly characterized by competition. However, males also cooperate with one another if socio-ecological conditions are suitable. Due to their male philopatry, the need for cooperation in home range defence and high degree of fission-fusion dynamics, spider monkeys provide an opportunity to investigate how male-male interactions are associated with socio-ecological factors, such as the presence of potentially receptive females, the degree of food availability and the likelihood of home range defence. We tested predictions about changes in social interactions between wild spider monkey males in relation to these factors. First, males did not change their interaction patterns when potentially receptive females were in the subgroup compared to when they were absent. Second, males tended to be less tolerant of one another when feeding, but spent more time grooming, in contact and proximity with one another when food availability was lower than when it was higher. Third, males exchanged fewer embraces, spent less time grooming, in proximity and in contact with one another, and spent more time vigilant at the home range boundary area than at other locations. Our findings contribute to the understanding of social flexibility and the importance of considering males in socio-ecological models of any group-living species.

Habitat restoration weakens negative environmental effects on telomere dynamics.

Habitat quality can have far-reaching effects on organismal fitness, an issue of concern given the current scale of habitat degradation. Many temperate upland streams have reduced nutrient levels due to human activity. Nutrient restoration confers benefits in terms of invertebrate food availability and subsequent fish growth rates. Here we test whether these mitigation measures also affect the rate of cellular ageing of the fish, measured in terms of the telomeres that cap the ends of eukaryotic chromosomes. We equally distributed Atlantic salmon eggs from the same 30 focal families into 10 human-impacted oligotrophic streams in northern Scotland. Nutrient levels in five of the streams were restored by simulating the deposition of a small number of adult Atlantic salmon Salmo salar carcasses at the end of the spawning period, while five reference streams were left as controls. Telomere lengths and expression of the telomerase reverse transcriptase (TERT) gene that may act to lengthen telomeres were then measured in the young fish when 15 months old. While TERT expression was unrelated to any of the measured variables, telomere lengths were shorter in salmon living at higher densities and in areas with a lower availability of the preferred substrate (cobbles and boulders). However, the adverse effects of these habitat features were much reduced in the streams receiving nutrients. These results suggest that adverse environmental pressures are weakened when nutrients are restored, presumably because the resulting increase in food supply reduces levels of both competition and stress.

Effects of manipulated food availability and seasonality on innate immune function in a passerine.

The innate immune system is essential for survival, yet many immune traits are highly variable between and within individuals. In recent years, attention has shifted to the role of environmental factors in modulating this variation. A key environmental factor is food availability, which plays a major role in shaping life histories, and may affect resource allocation to immune function through its effect on nutritional state. We developed a technique to permanently increase foraging costs in seed-eating birds, and leveraged this technique to study the effects of food availability on the innate immune system over a 3-year period in 230 zebra finches housed in outdoor aviaries. The immune components we studied were haptoglobin, ovotransferrin, nitric oxide, natural antibodies through agglutination, complement-mediated lysis, and killing capacity of Escherichia coli and Candida albicans, covering a broad spectrum of the innate immune system. We explored the effects of food availability in conjunction with other potentially important variables: season, age, sex and manipulated natal brood size. Increased foraging costs affected multiple components of the immune system, albeit in a variable way. Nitric oxide and agglutination levels were lower under harsh foraging conditions, while Escherichia coli killing capacity was increased. Agglutination levels also varied seasonally, but only at low foraging costs. C. albicans killing capacity was lower in winter, and even more so for animals in harsh foraging conditions that were raised in large broods. Effects of food availability on ovotransferrin were also seasonal, and only apparent in males. Haptoglobin levels were independent of foraging costs and season. Males had higher levels of immune function than females for three of the measured immune traits. Innate immune function was independent of age and manipulated natal brood size. Our finding that food availability affects innate immune function suggests that fitness effects of food availability may at least partially be mediated by effects on the immune system. However, food availability effects on innate immunity varied in direction between traits, illustrating the complexity of the immune system and precluding conclusions on the level of disease resistance.