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Food supply is one of the major drivers of animal behavior, and the gut microbiome is an important mediator between food supply and its effects on physiology. However, predicting the outcome of diet change on microbiome and consequences for the animal has proven extremely challenging. We propose this reflects processes occurring at different scales. Inadequate accounting for the multi-level complexity of nutrition (nutrients, foods, diets) obscures the diet influence on microbiome and subsequently animal. Here, we present a detailed year-round, multi-level analysis of diet and microbiome changes in a wild population of a temperate primate, the rhesus macaque (Macaca mulatta). Total daily food and nutrient intake of 6 male and 6 female macaques was monitored in each of the 4 seasons (total 120 days observations). For each individual, we found significant variation in the microbiome between all 4 seasons. This response was more strongly correlated with changes in macronutrient intake than with food items and much of the response could be explained at the level of 6 ecological guilds-sets of taxa sharing similar responses to nutrient intake. We conclude that study of diet, microbiome, and animal performance in ecology will more effectively identify patterns if diet is recorded at the level of nutrient intake. Although microbiome response to diet does show variation in species-level taxa in response to food items, there is greater commonality in response at the level of guilds. A goal for microbiome researchers should be to identify genes encoding microbial attributes that can define such guilds.

At northern latitudes, large spatial and temporal variation in the nutritional composition of available foods poses challenges to wild herbivores trying to satisfy their nutrient requirements. Studies conducted in mostly captive settings have shown that animals from a variety of taxonomic groups deal with this challenge by adjusting the amounts and proportions of available food combinations to achieve a target nutrient balance. In this study, we used proportions‐based nutritional geometry to analyze the nutritional composition of rumen samples collected in winter from 481 moose (Alces alces) in southern Sweden and examine whether free‐ranging moose show comparable patterns of nutrient balancing. Our main hypothesis was that wild moose actively regulate their rumen nutrient composition to offset ecologically imposed variation in the nutritional composition of available foods. To test this, we assessed the macronutritional composition (protein, carbohydrates, and lipids) of rumen contents and commonly eaten foods, including supplementary feed, across populations with contrasting winter diets, spanning an area of approximately 10,000 km2. Our results suggest that moose balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available (and eaten) foods. Furthermore, we found that rumen macronutrient balance was tightly related to ingested levels of dietary fiber (cellulose and hemicellulose), such that the greater the fiber content, the less protein was present in the rumen compared with nonstructural carbohydrates. Our results also suggest that moose benefit from access to a greater variety of trees, shrubs, herbs, and grasses, which provides them with a larger nutritional space to maneuver within. Our findings provide novel theoretical insights into a model species for ungulate nutritional ecology, while also generating data of direct relevance to wildlife and forest management, such as silvicultural or supplementary feeding practices., This right‐angled mixture triangle depicts the relative components of macronutrient content in individual moose (Alces alces) rumen samples. Our results suggest that the 481 moose in our study balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available foods. Furthermore, we found that macronutrient balancing was dependent of rumen fiber content, for this large ruminant herbivore.

Reduced protein intake, through dilution with carbohydrate, extends lifespan and improves mid-life metabolic health in animal models. However, with transition to industrialised food systems, reduced dietary protein is associated with poor health outcomes in humans. Here we systematically interrogate the impact of carbohydrate quality in diets with varying carbohydrate and protein content. Studying 700 male mice on 33 isocaloric diets, we find that the type of carbohydrate and its digestibility profoundly shape the behavioural and physiological responses to protein dilution, modulate nutrient processing in the liver and alter the gut microbiota. Low (10%)-protein, high (70%)-carbohydrate diets promote the healthiest metabolic outcomes when carbohydrate comprises resistant starch (RS), yet the worst outcomes were with a 50:50 mixture of monosaccharides fructose and glucose. Our findings could explain the disparity between healthy, high-carbohydrate diets and the obesogenic impact of protein dilution by glucose-fructose mixtures associated with highly processed diets.

Apposite conceptualization and measurement of resource variation is critical for understanding many issues in ecology, including ecological niches, persistence and distribution of populations, the structure of communities and population resilience to perturbations. We apply the nutritional geometry framework to conceptualize and quantify the responses of a temperate-living primate, the golden snub-nosed monkey Rhinopithecus roxellana to variation in resource quality and quantity and in nutrient requirements associated with seasonal environments. We present a geometric model distinguishing qualitative constraint, quantitative constraint and 'pseudo-constraint' whereby nutrient intakes resemble response to qualitative resource constraint but are in fact driven by variation in nutrient requirements. The model is applied to analyse nutrient intakes recorded in 164 full-day observations of monkeys from two populations, one wild and the other captive, across seasons. Additionally, we recorded the diet of a single animal over 32 consecutive days in the wild. Despite considerable differences in available resources, the captive and wild populations showed marked similarities in nutrient intakes, including indistinguishable amounts and ratios of ingested macronutrients during summer and autumn and strong year-round maintenance of protein compared to seasonally variable fat and carbohydrate intakes. These similarities suggest homeostatically regulated nutritional targets and provide reference points to identify factors driving population differences in macronutrient intake in winter and spring. Our framework enabled us to distinguish examples of quantitative, qualitative and 'pseudo-constraint'. We suggest that this approach can increase the resolution at which resource constraint is conceptualized and measured in ecological studies.

Preventing malnutrition through consuming nutritionally appropriate resources represents a challenge for foraging animals. This is due to often high variation in the nutritional quality of available resources. Foragers consequently need to evaluate different food sources. However, even the same food source can provide a plethora of nutritional and non‐nutritional cues, which could serve for quality assessment. We show that bumblebees, Bombus terrestris , overcome this challenge by relying on lipids as nutritional cue when selecting pollen. The bees ‘prioritised’ lipid perception in learning experiments and avoided lipid consumption in feeding experiments, which supported survival and reproduction. In contrast, survival and reproduction were severely reduced by increased lipid contents. Our study highlights the importance of fat regulation for pollen foraging bumblebees. It also reveals that nutrient perception, nutrient regulation and reproductive fitness can be linked, which represents an effective strategy enabling quick foraging decisions that prevent malnutrition and maximise fitness.

Laboratory studies have demonstrated that, given plenty of food, many animals can achieve a species‐specific macronutrient intake target by selecting nutritionally balanced foods or combining complementary foods. Wild‐living, broad‐scope omnivorous species often face great heterogeneity in the composition of available resources. Hence they may be precluded, either locally or seasonally, from meeting their nutritional preferences. With the aim of shedding light on the nutritional niche breadth of a wild‐living omnivore, the European badger Meles meles, we reviewed available scat‐based studies on badger diet and applied right‐angled mixture triangles to examine the relationships between macronutrient availability and composition of diets. Moreover, to assess the potential of scat analysis to investigate nutritional balancing, we analysed badger diet in two habitats of NW Italy, focusing on identifying the total weight of each food item ‘as ingested’ as accurately as possible. The average macronutrient content of the European badger's diet comprised 40–45% protein‐energy, 30–35% lipid‐energy, and 20–25% carbohydrate‐energy. Macronutrient intake was not constant throughout the year, suggesting that, in some seasons, badgers may be unable to reach their macronutrient target, and that diet balancing is achieved over longer periods. The macronutrient selection strategy of badgers suggests that their feeding habits are close to those of obligate carnivorous mammals, although badgers were found to be more tolerant towards carbohydrates than obligate carnivores. Macronutrient ratios as assessed by scat analysis matched well with those obtained by reviewing available data, confirming that meta‐analyses of diet studies can provide useful information on the macronutrient requirements of elusive wild mammals.

Primate foraging is influenced by the spatial and temporal distribution of foods, which may facilitate or constrain optimal nutrient intakes. Chimpanzees are frugivorous primates that mainly subsist on ripe fruit that is typically low in available protein (AP) and high in easily digestible carbohydrates. Because chimpanzees prefer ripe fruit and often eat it in large quantities compared with other foods, we hypothesized that protein intake would be tightly regulated while non-protein energy (NPE) would vary with fruit intake. To test this hypothesis, we conducted all-day follows on female chimpanzees, recorded all types of food consumed (i.e., drupes, figs, and non-fruit foods), estimated the nutritional contributions of these foods to daily NPE and AP intake and investigated how the ratio of NPE to AP varied due to changes in the types of foods consumed. Although the proportions of drupes, figs, and non-fruit foods varied in their diets, female chimpanzees maintained a relatively stable intake of AP while intake of NPE varied depending on the daily diet, demonstrating that like other frugivorous primates studied to date, chimpanzees prioritize protein. The mean daily ratio of NPE to AP was 7:1, which is similar to that of other frugivorous primates studied. Our results support the hypothesis that frugivorous animals may generally prioritize AP, while maximizing NPE intake within that constraint, and could shed light on aspects of human dietary evolution.

Establishing diets and dietary generalism in marine top predators is critical for understanding their ecological roles and responses to environmental fluctuations. Nutrition plays a key mediatory role in species-environment interactions, yet descriptions of marine predators’ diets are usually limited to the combinations of prey species consumed. Here we combined stomach contents analysis (n = 40), literature prey nutritional data and a multidimensional nutritional niche framework to establish the diet and niche breadths of white sharks (Carcharodon carcharias; mean ± SD precaudal length = 187.9 ± 46.4 cm, range = 123.8-369.0 cm) caught incidentally off New South Wales (NSW), Australia. Our nutritional framework also facilitated the incorporation of existing literature diet information for South African white sharks to further evaluate nutritional niches across populations and sizes. Although teleosts including pelagic Eastern Australian Salmon (Arripis trutta) were the predominant prey for juvenile white sharks in NSW, the diversity of benthic and reef-associated species and batoids suggests regular benthic foraging. Despite a small sample size (n = 18 and 19 males and females, respectively), there was evidence of increased batoid consumption by males relative to females, and a potential size-based increase in shark and mammal prey consumption, corroborating established ontogenetic increases in trophic level documented elsewhere for white sharks. Estimated nutritional intakes and niche breadths did not differ among sexes. Niche breadths were also similar between juvenile white sharks from Australia and South Africa. An increase in nutritional niche breadth with shark size was detected, associated with lipid consumption, which we suggest may relate to shifting nutritional goals linked with expanding migratory ranges.

An organism’s fitness is tied closely to its ability to obtain food. However, many foods are nutritionally suboptimal on their own, forcing an individual to develop a feeding strategy that actively manages both type and amount of food consumed. Animals in captivity are additionally limited to human provisioned diets, which may be nutritionally inadequate and negatively affect behavior and health. We studied the nutritional intake of captive golden snub-nosed monkeys (Rhinopithecus roxellana) at two locations in China (132 days of continuous, sunrise to sunset focal samples of 7 individuals at each site) and used the Geometric Framework for nutrition to identify their feeding strategy and evaluate diet variation across sites, seasons, and age–sex classes. Captive golden snub-nosed monkeys had a mean nutrient intake of 75% carbohydrates (15% neutral detergent fiber, 60% total nonstructural carbohydrates), 12% fat, and 13% protein (by energy) that differed by location and season owing to differences in the type and amount of food items offered and consumed. Intake at one location differed from that of wild golden snub-nosed monkeys, suggesting that the captive diet was inadequate. These results highlight the importance of developing nutritionally adequate diets for captive animals based on an understanding of their nutritional requirements.

Diet regulation behavior can mediate the consequences of imbalanced diets for animal well-being, particularly for captive species that have little dietary choice. Dasyurids (carnivorous marsupials) are of conservation concern in Australia, and many species are in captive breeding programmes. However, their nutrient targets and dietary regulation behaviors are poorly understood, a limitation that may decrease the breeding success and well-being of captive animals. We tested how dietary protein content influenced the intake and utilization of nutrients, physical activity, and body mass of fat-tailed dunnarts Sminthopsis crassicaudata. Twelve adult dunnarts from six sibling pairs (one female and one male per pair) were provided ad libitum access to three diets in a repeated measures design: cat food, cat food supplemented with raw lean beef (1:1), and cat food supplemented with cooked lean beef (1:1). Food intake, activity level, and fecal output were measured daily. Dunnarts significantly decreased food intake, increased protein digestion, and physical activity, but body mass was unchanged when on the high-protein diet compared to the normal cat food diet. These observations suggest a capacity of dunnarts to maintain constant body mass using a dynamic balance of feeding, digestion, and activity. We also found a significant effect of family, with differences between families as large as the difference between the diet treatments, suggesting a genetic component to diet selection. The nutrient regulation responses of dunnarts to high-protein diets and the strong family effects provide important messages for the management of populations of small carnivores, including the aspects of dietary manipulation and conservation of genetic diversity.

We combine a recently developed framework for describing dietary generalism with compositional data analysis to examine patterns of omnivory in a large widely distributed mammal. Using the brown bear (Ursus arctos) as a model species, we collected and analyzed data from the literature to estimate the proportions of macronutrients (protein, carbohydrate, and lipid) in the diets of bear populations. Across their range, bears consumed a diversity of foods that resulted in annual population diets that varied in macronutrient proportions, suggesting a wide fundamental macronutrient niche. The variance matrix of pairwise macronutrient log‐ratios indicated that the most variable macronutrient among diets was carbohydrate, while protein and lipid were more proportional or codependent (i.e., relatively more constant log‐ratios). Populations that consumed anthropogenic foods, such agricultural crops and supplementary feed (e.g., corn), had a higher geometric mean proportion of carbohydrate, and lower proportion of protein, in annual diets. Seasonally, mean diets were lower in protein and higher in carbohydrate, during autumn compared to spring. Populations with anthropogenic subsidies, however, had higher mean proportions of carbohydrate and lower protein, across seasons compared to populations with natural diets. Proportions of macronutrients similar to those selected in experiments by captive brown bears, and which optimized primarily fat mass gain, were observed among hyperphagic prehibernation autumn diets. However, the majority of these were from populations consuming anthropogenic foods, while diets of natural populations were more variable and typically higher in protein. Some anthropogenic diets were close to the proportions selected by captive bears during summer. Our results suggest that omnivory in brown bears is a functional adaptation enabling them to occupy a diverse range of habitats and tolerate variation in the nutritional composition and availability of food resources. Furthermore, we show that populations consuming human‐sourced foods have different dietary macronutrient proportions relative to populations with natural diets.

Invasion success is dependent on the ability of a species to discover and exploit novel food resources. Within this context, individuals must be willing to taste novel foods. They must also be capable of evaluating the nutritional content of new foods, and selecting their relative intake in order to fulfil their nutritional needs. Whereas the former capacity is well studied, little is known about the latter capacity. First, using the common myna as a model avian invader species, we quantified the willingness of mynas to taste novel foods relative to familiar ones. Mynas readily tasted high protein (HP) novel foods and consumed them in higher quantities compared to a familiar food. Data showed that at three different levels – mixes, ingredients and macronutrients – intake could not be explained by a random model. In experiment 2, we confirmed that mynas were making their selection based on protein (P) content rather than a selection for novelty per se. When given the choice of three equally unfamiliar foods, mynas again ate disproportionately from the high protein relative to high lipid and high carbohydrate foods. Analysis revealed that mynas consumed amounts of protein that were closer to the ones in their natural diet. Finally, in experiment 3, we measured inter-individual variation in innovation and exploration propensities, and examined associations with inter-individual variation in consumption of specific macronutrients. This analysis revealed that individuals that selected HP pellets were more exploratory and individuals that selected HC pellets were quicker to solve the innovative foraging task. These findings indicate that not only the willingness to taste novel foods, but also the capacity to evaluate their nutritional content, might be central to the myna's substantial ecological success. This article is protected by copyright. All rights reserved.

Tasmanian devils (Sarcophilus harrisii) are the largest carnivorous marsupial in Australia. Currently many animals are being held in captivity as a management procedure to combat Devil Facial Tumor Disease. Only one published study thus far has investigated nutrition in Tasmanian devils, determining their maintenance energy requirements and digestibility on a rodent diet. More information is needed on Tasmanian devil nutritional and gastrointestinal function to aid in their management. Our study aimed to investigate the current nutritional status of Tasmanian devils in a captive population and functional morphology and histology of their gastrointestinal tract. Animals were maintained on a diet of kangaroo, rabbit, quail and chicken wings and digestibility of these items by the devils was high (>85% for dry matter, protein and lipid). Kangaroo and rabbit were high protein diet items while the quail and chicken wings provided high lipid to the diet, and carbohydrates were minimal (≤3% energy). Maintenance energy requirements were determined to be 620kJkg-0.75d-1 with no significant difference between males and females. Opportunistic samples for gastrointestinal morphology were obtained from captive specimens. Tasmanian devils have a simple digestive tract similar to other dasyurid species. Both the morphology and histology of the gastrointestinal tract show specialization for a high protein carnivorous diet.

Sex differences in foraging behavior are typically studied in size-dimorphic taxa. Data on sex-specific behavior in monomorphic taxa are needed to test theories of reproductive investment. It has been suggested that in seabirds foraging niche separation may be related to decreased intersexual competition for food between cooperating pair-bonded individuals. Alternatively, sex differences in foraging niches may be driven by different nutritional requirements of females associated with the reproductive costs of egg production and oviposition. To assess these possibilities, we studied a size-monomorphic colonial seabird, the Australasian Gannet (Morus serrator) at the Cape Kidnappers gannetry, New Zealand. We recorded maximum dive depths, and distinct diet composition of incubating females as indicated by stable isotopic signatures. Results suggested greater female foraging effort during early times of incubation, indicated by significantly deeper maximum dives. Sex-specific foraging patterns across...

Many animals consume foods that vary in all 3 macronutrients: carbohydrates, lipid, and protein. Yet most studies of diet regulation only consider pairs of nutrients (protein and carbohydrate or protein and lipid). Diet regulation also extends beyond nutrient and energy intake to include sources of energy expenditure, such as changes in activity level. We used a right-angled mixture triangle design to quantify the 3-dimensional intake target of fat-tailed dunnarts, Sminthopsis crassicaudata , and to test the consequences of free choice for energy intake, weight gain, and activity level relative to a standard maintenance diet. Dunnarts consistently preferred a relatively high-lipid, low-protein, and low-carbohydrate diet in 3 separate feeding experiments. Dunnarts also consumed a higher total energy intake during choice relative to no-choice periods. However, the weight of dunnarts was not consistently higher at the end of choice relative to no-choice periods, which is likely because dunnarts increased their activity level during periods of choice and decreased their activity when on no-choice diets. This shows that increases in the intake of lipid, which is an important component in the diet of dunnarts, does not necessarily lead to increases in weight gain because these animals can adjust energy expenditure to balance their energy budget. These results have important implications for the design of diets for animals in captivity and demonstrate that consideration of both energy intake and expenditure are needed for a more comprehensive and integrative understanding of diet regulation by animals.

The Tasmanian devil (Sarcophilus harrisii) is the largest extant carnivorous marsupial. The Tasmanian devil is currently listed as endangered and is under threat from a contagious cancer. The aims of the study were to determine hematology and blood chemistry reference intervals for captive Tasmanian devils and determine the influence of three biological factors on blood variables. Hematology and blood chemistry data were analyzed retrospectively from medical reports obtained from Taronga Zoo. Samples were analyzed using current technology at the time of collection. Thirty seven variables were analyzed for 104 blood samples from 1992 until 2015. Data were statistically analyzed for differences between age, gender and season. Generally Tasmanian devils have higher serum concentrations of albumin (ALB) and creatinine and lower alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and amylase (AMY) compared with other dasyurids. Younger animals tended to have significantly higher serum concentrations of ALP, AST and phosphorus, while total protein and globulin activity in younger animals was less than in older animals. Hemoglobin, total protein and AST concentrations were influenced by season, with higher concentrations observed in either spring or summer. Lymphocyte, and erythrocyte counts, and serum concentrations of lipase and AMY were significantly higher in females compared with males. The reference ranges determined here can be used in the health assessment of captive Tasmanian devils and for those used in translocation programs in the future.

It is widely believed that predators maximise their energy intake while foraging and consume prey that are nutritionally similar. We combined GPS data loggers, miniaturised cameras, dietary sampling and nutritional geometry to examine the nutritional variability in the prey and selected diet, and foraging performance, of the masked booby (Sula dactylatra tasmani), a wild carnivore and marine top predator. Data loggers also revealed no significant differences between sexes in the foraging performance of chick-rearing adults. Females provided more food to their chicks than the males and, regardless of the nutritional variability of prey consumed, both sexes showed similar amounts of protein and lipid in their diets. Miniaturised cameras combined with nutritional analysis of prey provided, for the first time, fine-scale detail of the amounts of macronutrients consumed in each plunge dive and the overall foraging trip. Our methodology could be considered for future studies that aim to contribute to th...

Territorial protandry, or early season male-biased settlement at breeding sites, is a widespread phenomenon in a range of animal breeding systems. While protandry is common across several avian lineages and has been linked with increased reproductive success of earlier breeding males in terrestrial species, the selective advantage of breeding protandry has only rarely been studied in seabirds. We assessed the seasonal changes in the sex ratio at the breeding site and sex-specific correlates of arrival date with reproductive success during 2 breeding seasons of a colonial seabird, the Australasian Gannet (Morus serrator), at Cape Kidnappers, New Zealand. We found no biases in overall sex ratios of adults and fledglings but detected a male sex bias during nest site establishment, and a significantly higher probability of reproductive success for earlier-settling males. In contrast, the reproductive success of females did not correlate with the timing of arrival. Our findings provide an assessment of the sex differences in reproductive correlates of the timing of breeding settlement in gannets and are consistent with selective advantages as suggested by indirect selection hypotheses. This study contributes to our understanding of the fitness benefits of protandry, and its linkages with sex differences in breeding philopatry and mate fidelity, in a long-lived seabird species with obligate and extended biparental care.

Generalist primates eat many food types and shift their diet with changes in food availability. Variation in foods eaten may not, however, match variation in nutrient intake. We examined dietary variation in a generalist-feeder, the blue monkey (Cercopithecus mitis), to see how dietary food intake related to variation in available food and nutrient intake. We used 371 all-day focal follows from 24 adult females (three groups) in a wild rainforest population to quantify daily diet over 9 months. We measured food availability using vegetation surveys and phenology monitoring. We analyzed >700 food and fecal samples for macronutrient content. Subjects included 445 food items (species-specific plant parts and insect morphotypes) in their diet. Variation in fruit consumption (percentage of diet and total kcal) tracked variation in availability, suggesting fruit was a preferred food type. Fruits also constituted the majority of the diet (by calories) and some fruit species were eaten more than expected based on relative availability. In contrast, few species of young leaves were eaten more than expected. Also, subjects ate fewer young leaves (based on calories consumed) when fruit or young leaves were more available, suggesting that young leaves served as fallback foods. Despite the broad range of foods in the diet, group differences in fiber digestibility, and variation that reflected food availability, subjects and groups converged on similar nutrient intakes (grand mean ± SD: 637.1 ± 104.7 kcal overall energy intake, 293.3 ± 46.9 kcal nonstructural carbohydrate, 147.8 ± 72.4 kcal lipid, 107.8 ± 12.9 kcal available protein, and 88.1 ± 17.5 kcal structural carbohydrate; N = 24 subjects). Thus, blue monkeys appear to be food composition generalists and nutrient intake specialists, using flexible feeding strategies to regulate nutrient intake. Findings highlight the importance of simultaneously examining dietary composition at both levels of foods and nutrients to understand primate feeding ecology.

Temperature fluctuations have caused considerable biological and ecological impacts on marine organisms and their communities. For example, increased temperatures in sub-tropical environments have led to the influx of tropical “vagrant” marine species into cooler temperate waters in a phenomenon called ‘tropicalisation’. Here we combine metabolic performance metrics, feeding manipulations and nutritional geometry models to examine the influence of temperature on macronutrient selection (energy amounts of protein, lipid and carbohydrates) in the Indo-Pacific damselfish Abudefduf vaigiensis and explore the role of temperature and macronutrient intake on individual performance (active and routine metabolic rate, and burst swim speed). Indo-pacific damselfish fed non-randomly from presented food blocks, showing selection for their macronutrient intake. In our high-temperature treatment we observed a significant increase in the intake of protein and lipid, but not carbohydrate. The fish in our low-temperature treatment had a significantly higher active metabolic rate and burst swim speed compared to our high-temperature treatment. Our findings provide evidence that the vagrant Indo-Pacific Damselfish in Sydney are able to select specific macronutrients in their diets ameliorating the effects on performance when thermally stressed. This work also suggests some underlying level of acclimation to or selection for colder water temperatures in these relatively recently recruited fish. Further studies should benefit from the approach proposed here, to better understand the ecological and evolutionary drivers that influence the survival of tropical species in marginal thermal habitats.

Marine top predators forage in environments that show potentially extreme temporal and spatial variation in prey availability, with reproductive success being crucially linked to food supply. Multiple factors of interannual and sexual variation, as well as variation across breeding stages, can shape patterns of spatial use in foraging seabirds, yet studies that address all of these variables simultaneously are rare. We present spatial assessment of foraging patterns by µGPS tracking of a sexually size monomorphic, long-lived species, the Australasian gannet (Morus serrator). The study spanned the incubation and chick-rearing stages in three consecutive breeding seasons. Our findings revealed high interannual variability in foraging distances and trip durations, but no consistent differences between birds across different breeding stages or the sexes. The exception was that core foraging areas were different for female and male Australasian gannets, although trip durations or distances were similar for both sexes. Our results also indicate bimodality in foraging distance and trip duration in this species, while highlighting interannual variability in the extent of bimodality. These findings contribute to a scarcely documented type of foraging behaviour in the seabird family of the Sulidae. Overall, these spatial use patterns provide a baseline for understanding the evolution of sex-specific foraging differences in biparental seabirds, and the extent to which these differences might help in securing breeding success across years of variable food availability.

Among aquatic organisms, nutritional requirements are historically assessed by evaluating formulated diets with changes in a single nutrient profile. These studies provide organisms with the option of regulating the total feed intake but do not enable individuals to regulate intake of specific nutrient ratios. An alternate experimental approach, known as the geometric framework (GF) for nutrition, tests whether organisms held under specific conditions have optimal target intake levels for particular nutrients and whether, when provided with diet choices, they will self-regulate nutrient intake to reach these specific targets. In this study, we used the GF to assess intake levels of dietary protein and carbohydrate in cultured adults of the sea urchin Lytechinus variegatus provided choices between diets varying in both dry matter and specific macronutrient concentrations. Adult urchins (ca. 120 g) held previously on formulated diets were offered moist gel-based diets in pairwise combinations. Diets varied in levels of fish meal isolate (as a protein source) and wheat starch (as a carbohydrate source) and in nutrient concentration (5 or 10% dry matter). Regardless of diet combination, individuals maintained an average dietary protein intake of ca. 0.047–0.061 g day − 1 . Dietary carbohydrate intake was not regulated to a specific level and ranged from 0.042–.0136 g day − 1 . These data suggest that large adult L. variegatus held in culture have a tightly regulated intake target for dietary protein but not carbohydrate. Regardless of nutrient ratios or macronutrient concentration, individuals adjusted intake patterns to defend this target. We suggest that the GF will be an important tool in evaluating macronutrient requirements in cultured sea urchins and other aquatic species.

Anthropogenic environments can offer rich sources of energy to urban wildlife, but little is known about how they impact on nutritional balance and food selection. Common mynas (Sturnus tristis) provide a powerful model system for testing the nutritional constraints and priorities of an invasive species that has successfully adapted to urban environments. Here, we use behavioral observations, field-based feeding trials, videography, and the right-angled mixture triangle model (RMT) to examine the macronutrient preferences of these invasive birds. Our behavioral observations showed that mynas consumed insects (40.6%), worms (33.2%), human discards (17.6%), and plants (8.6%). Our feeding trials using nutritionally defined foods showed that mynas had a clear preference for food dishes containing only high-protein (HP) pellets over high-lipid (HL) or high-carbohydrate (HC) pellets. In addition, mixed feeders were also presented in 2 combinations: 1) contained equal proportions of HP and HC pellets and 2) equal proportions of HP and HL pellets. HP pellets were selectively consumed from both mixed feeders, this involving an increase in feeding time. Overall, the RMT showed that mynas consumed a higher proportion of protein from the feeders than in their natural diet. Furthermore, the majority of our observations of birds feeding at the dishes containing HP foods ended in intraspecific aggression, suggesting that protein is a contestable resource. These results suggest that mynas at our urban study site are deficient in protein relative to fats and carbohydrates.

Food resources are often critical regulating factors affecting individual fitness and population densities. In the Himalayan Mountains, Bharal “blue sheep” (Pseudois nayaur) are the main food resource for the endangered snow leopard (Panthera uncia), as well as being preyed upon by other predators. Blue sheep, however, may face a number of challenges including food resource competition with other wild and domestic ungulates, and hunting pressure. Here, we characterized the diet of blue sheep in the Annapurna Conservation Area (ACA) of Nepal and conducted proximate nutritional analysis on a limited number of plants identified as foods. Furthermore, we investigated the macronutrient and fiber balance of these plants using nutritional geometry which is a state‐space approach to modeling multidimensional and interactive nutritional aspects of foraging. A total of 19 plant species/genera were identified in blue sheep pellets using microhistological analysis. On average, across seasons and regions of the study area, the two most frequently occurring plants in pellets were graminoids: Kobressia sp. and Carex spp. The macronutrient balance of Kobresia sp. was relatively high in carbohydrate and low in protein, while other plants in the diet were generally higher in protein and lipid content. Analysis of fiber balance showed that the two most consumed plants of blue sheep (i.e., Kobresia spp. and Carex spp.) contained the highest concentration of hemicellulose, which is likely digestible by blue sheep. The hemicellulose and lignin balance of plants ranged relatively widely, yet their cellulose contents showed less variation. Foraging by blue sheep may therefore be a balance between consuming highly digestible high‐carbohydrate plants and plants less‐digestible but higher in protein and/or lipid.

Most extant primates feed on insects to some degree, yet the nutritional contributions of insects to primate diets are poorly characterized. Like many small- bodied frugivorous primates, redtail monkeys (Cercopithecus ascanius) also eat insects. We quantified the nutritional contributions of insects to the diets of female redtail monkeys in Kibale National Park, Uganda, from July 2010 to June 2012 through full day follows (N = 64) using weight-based estimates of food intake. Female redtail monkeys targeted insects for 41 % of feeding bouts, plant reproductive parts (including ripe fruits, unripe fruits, flowers, seeds) for 15 % of feeding bouts, and leaves (including young leaves, mature leaves, leaf petioles, leaf buds) for 17 % of feeding bouts. However, females spent just under 10 % of feeding time on insects, in contrast to 42 % on plant reproductive parts and 39 % on leaves. Redtail monkeys fed primarily on

The Himalayan marmot (Marmota himalayana) occurs throughout the Himalayan alpine mountain ecosystem. We examined the characteristics of Himalayan marmot habitat, diet, and macronutrient consumption in the upper Mustang region of Nepal. Marmots inhabited warmer valleys close to water sources in areas between 2,900 and 4,800 m above sea level. Soil pH, organic matter, organic carbon, and phosphorus were not different in marmot use versus available habitat; however, potash levels significantly lower in marmot burrow habitat. Seventeen species of plants, including Primula spp., Potentilla fruticosa, Kobresia pygmaea, Anaphalis contorta, Lonicera spinosa, and Carex spp., were recorded in marmot scats over 3 seasons (summer 2010, autumn 2010, and spring 2011). Analysis showed a positive correlation between the total macronutrient content (dry matter protein + carbohydrate + fat) of plants and their occurrence in the diet. Analysis of the fiber and macronutrient balance of a limited number of plants consumed by ...

The Asiatic wild dog or dhole (Cuon alpinus) is an endangered, yet little-studied, species throughout its range in Nepal. We examined habitat selection and diet of the dholes by searching for dholes in the Dhorpatan Hunting Reserve (DHR), the only hunting reserve in Nepal, and developed a habitat selection model to determine their habitat preferences. We also collected anecdotal data on depredation events and attitudes toward the dholes from 89 local people. We collected each dhole scat encountered and conducted dietary analysis to calculate the percent frequency of occurrence of each prey item and to estimate the biomass consumed by dholes in the study area. The dholes used most habitat types and targeted a wide range of prey species and sizes, but avoided barren land, Juniperus spp. — and Abies spp.—dominated forests, and habitat under anthropogenic pressure. Eighty percent of the dhole's diet was represented by wild prey species; blue sheep (Pseudois nayaur) comprised 13.9% and livestock comprised 20% ...

SummaryIncreased salt intake has been found to boost egg production in Drosophila. Females develop a specific appetite for salt following mating. This is not triggered by demand for sodium from developing eggs, but by release of a Sex Peptide into the female’s reproductive tract by the male during mating.

Many animals consume mixed diets that maximize their fitness by optimizing macronutrient intake. We tested whether brown bears (Ursus arctos), generalist omnivores that hibernate, regulated their diet to a common nutrient target, achieved a nutrient target related to fitness, and selected a nutrient target that differed between seasons and from other species with differing life histories. When given unlimited access to 2 or 3 highly digestible foods containing primarily protein, carbohydrate, or lipid, brown bears selected mixed diets in which protein provided 17% ± 4% SD of the metabolizable energy and 22% ± 6% of the dry matter. This dietary protein content maximized the rate of gain per unit of energy consumed, is similar to the level preferred by other omnivores, and is less than that preferred by obligate carnivores. Between seasons, bears selected similar dietary protein levels, although the proportion of lipid was higher during the fall than during the spring. Bears strongly preferred lipids over carbohydrates, as did other carnivores, but they used lipids and carbohydrates with equal efficiency to produce a dietary protein content that maximized mass gain per unit of energy intake. Thus, dietary sources of lipids and carbohydrates play an interchangeable and important role in determining the productivity of bears that goes beyond their role in providing energy.

Human communities in the Trans-Himalayan region depend on the dynamics of the agro-pastoral system for survival. Humans, livestock and wild predators share common resources in the region, and this leads to human–wildlife interactions that have the potential to threaten the continued viability of this fragile ecosystem and impact the local economy. This study explored the interaction between livestock and predators in the upper Mustang region of Nepal in terms of economic and ecological impacts. A total of 1,347 km2 of pasture land were grazed by 30,217 livestock belonging to local people from six village development committees. It was found that the seasonal movement patterns of livestock, from higher to lower elevations (closer to villages), coincided with elevation movements of wild ungulate prey and snow leopards into this smaller land area. The number of livestock reported to have been killed by predators during the study period was 706, 75 % of which was attributed to snow leopards. An estimated US$ 44,213 was lost between October 2009 and June 2011 due to livestock predation. These losses of livestock to snow leopards and other carnivores provoked retaliatory killings by villagers, and this in turn may significantly affect the viability of predator populations in this region. We suggest four approaches to mitigate human–carnivore conflict in the region: (a) introduce a livestock insurance policy, (b) promote the use of predator-proof livestock corrals and sheds, (c) involve local people in alternative income generating activities, and (d) increase conservation education in these regions.

Lay Summary Birds that color their feathers with dietary carotenoid pigments are expected to seek out these pigments when they are molting. We show that molting male hihi, who express carotenoid-based plumage, seek out naturally occurring foods that are rich in carotenoid pigments. Female hihi, who do not express carotenoid-based plumage, do not seek out carotenoid-rich foods. This lends strength to the idea that carotenoid-based plumage reveals an individual’s foraging ability., Dietary access to carotenoids is expected to determine the strength of carotenoid-based signal expression and potentially to maintain signal honesty. Species that display carotenoid-based yellow, orange, or red plumage are therefore expected to forage selectively for carotenoid-rich foods when they are depositing these pigments during molt, but whether they actually do so is unknown. We set out to address this in the hihi (Notiomystis cincta), a New Zealand passerine where males, but not females, display yellow carotenoid-based plumage. We measured circulating carotenoid concentrations in male and female hihi during breeding and molt, determined the nutritional content of common foods in the hihi diet, and conducted feeding observations of male and female hihi during molt. We found that although male and female hihi do not differ significantly in plasma carotenoid concentration, male hihi have a greater proportion of carotenoid-rich foods in their diet than do females. This is a consequence of a greater fruit and lower invertebrate intake than females and an avoidance of low-carotenoid content fruit. By combining behavioral observations with quantification of circulating carotenoids, we present evidence that colorful birds forage to maximize carotenoid intake, a conclusion we would not have drawn had we examined plasma carotenoids alone.

International audience; Predators that forage on foods with temporally and spatially patchy distributions may rely on private or public sources of information to enhance their chances of foraging success. Using GPS tracking, field observations, and videography, we examined potential sites and mechanisms of information acquisition in departures for foraging trips by colonially breeding Australasian gannets (Morus serrator). Analyses of the bill-fencing ceremony between mated pairs of breeding gannets did not detect correlations between parameters of this reciprocal behavior and foraging trips, as would have been predicted if gannets used this behavior as a source of private information. Instead, 60 % of the departing birds flew directly to join water rafts of other conspecific en route to the feeding grounds. The departure of solitary birds from the water rafts was synchronized (within 60 s) with the arrival of incoming for-agers and also among departing birds. Furthermore, solitary departing birds from the rafts left in the same directional quadrant (908 slices) as the prior arriving (67 %) and also prior departing forager (79 %). When associated plunge dives of conspecific were visible from the colony, providing a public source of information, gannets more often departed from the water rafts in groups. Our study thus provides evidence for the use of water rafts, but not the nest site, as locations of information transfer, and also confirms the use of local enhancement as a strategy for foraging flights by Australasian gannets.

Primate field studies often identify "lean seasons," when preferred foods are scarce, and lower- quality, abundant foods (fallback foods) are consumed. Here, we quantify the nutritional implications of these terms for two diademed sifaka groups (Propithecus dia- dema) in Madagascar, using detailed feeding observa- tions and chemical analyses of foods. In particular, we sought to understand 1) how macronutrient and energy intakes vary seasonally, including whether these intakes respond in similar or divergent ways; 2) how the amount of food ingested varies seasonally (including whether changes in amount eaten may compensate for altered food quality); and 3) correlations between these variables and the degree of frugivory. In the lean season, sifakas shifted to non-fruit foods (leaves and flowers), which tended to be high in protein while low in other macronu- trients and energy, but the average composition of the most used foods in each season was similar. They also showed dramatic decreases in feeding time, food ingested, and consequently, daily intake of macronu- trients and energy. The degree of frugivory in the daily diet was a strong positive predictor of feeding time, amount ingested and all macronutrient and energy intakes, though season had an independent effect. These results suggest that factors restricting how much food can be eaten (e.g., handling time, availability, or intrinsic characteristics like fiber and plant secondary metabolites) can be more important than the nutritional composition of foods themselves in determining nutritional outcomes—a finding with rele- vance for understanding seasonal changes in behavior, life history strategies, competitive regimes, and conser- vation planning. Am J Phys Anthropol 153:78-91

Understanding why food chains are relatively short in length has been an area of research and debate for decades. We tested if progressive changes in the nutritional content of arthropods with trophic position limit the availability of a key nutrient, lipid, for carnivores. Arthropods at higher trophic levels had progressively less lipid and more protein in their bodies compared with arthropods at lower trophic levels. The nutrients present in arthropod bodies were directly related to the nutrients that predators extracted when feeding on those arthropods. As a consequence, nutrient assimilation shifted from lipid-biased to protein-biased as arthropods ascended trophic levels from herbivores to secondary carnivores. Successive changes in the nutritional consequences of predation may ultimately set an upper limit on the number of trophic levels in arthropod communities. Further work is needed to examine the influence of lipid and other nutrients on food web traits in a range of ecosystems.

Blue sheep (Pseudois nayaur) are the key prey of the endangered snow leopard (Panthera uncia) in the Himalayan region of Nepal. However, the snow leopard population has recently expanded back into the Sagarmatha (Mt. Everest) National Park where the blue sheep are currently absent, and the evidence of snow leopard depredation of livestock can be found. A solution to this prospective human–wildlife conflict is the translocation of blue sheep back into this area. The aims of this study are (1) to characterize the spatial and environmental factors related to current blue sheep distributions in three areas: Annapurna Conservation Area, Shey Phoksundo National Park and Kanchanjunga Conservation Area, and (2) to use these characteristics to assess the suitability of two areas: Sagarmatha (Mt. Everest) National Park and Langtang National Park for blue sheep translocation. Blue sheep were found to occur in 14,603 km2 of Nepal, with 7343 km2 (49%) inside protected areas. Blue sheep preferred the alpine meadow, pas...

Background Nepal provides habitat for approximately 100–125 wild Asian elephants (Elephas maximus). Although a small proportion of the world population of this species, this group is important for maintaining the genetic diversity of elephants and conservation of biodiversity in this region. Knowledge of foraging patterns of these animals, which is important for understanding their habitat requirements and for assessing their habitat condition, is lacking for the main areas populated by elephants in Nepal. This study investigates the feeding preferences of the Asian elephant in Parsa Wildlife Reserve (PWR) and Chitwan National Park (CNP), Nepal. Result Fifty-seven species of plants in 25 families were found to be eaten by Asian elephants, including 12 species of grasses, five shrubs, two climbers, one herb and 37 species of trees. The species that contributed the greatest proportion of the elephant’s diet were Spatholobus parviflorus (20.2%), Saccharum spontaneum (7.1%), Shorea robusta (6.3), Mallotus philippensis (5.7%), Garuga pinnata (4.3%). Saccharum bengalensis (4.2%), Cymbopogan spp (3.7%), Litsea monopetala (3.6) and Phoenix humilis (2.9%). The preference index (PI) showed that browsed species were preferred during the dry season, while browsed species and grasses were both important food sources during the rainy season. Elephants targeted leaves and twigs more than other parts of plants (P

Predators have been shown to alter their foraging as a regulatory response to recent feeding history, but it remains unknown whether trap building predators modulate their traps similarly as a regulatory strategy. Here we fed the orb web spider Nephila pilipes either live crickets, dead crickets with webs stimulated by flies, or dead crickets without web stimulation, over 21 days to enforce spiders to differentially extract nutrients from a single prey source. In addition to the nutrients extracted we measured web architectures, silk tensile properties, silk amino acid compositions, and web tension after each feeding round. We then plotted web and silk “performance landscapes” across nutrient space. The landscapes had multiple peaks and troughs for each web and silk performance parameter. The findings suggest that N. pilipes plastically adjusts the chemical and physical properties of their web and silk in accordance with its nutritional history. Our study expands the application of the geometric framework foraging model to include a type of predatory trap. Whether it can be applied to other predatory traps requires further testing.

The foraging challenge for predators is to find and capture food with adequate levels of energy and nutrients. Marine predators require particularly sophisticated foraging strategies that enable them to balance self- and offspring-feeding, and also in many circumstances simultaneously consider the nutritional constraints of their partners. Here we combined the use of dietary analysis, proximate composition and nutritional geometry (right-angled mixture triangle nutritional models) to examine the macronutrient preferences of Australasian gannets (Morus serrator) at Farewell Spit gannetry in New Zealand. Our results showed intra- and inter-specific variation in the protein, lipid and water composition of prey captured by our sample of 111 Australasian gannets. In addition, we observed significant differences in the Australasian gannets’ nutritional niche between seasons. We provide evidence of sex-specific macronutrient foraging strategies in a successful marine predator in the wild. We have shown that in spite of fluctuations in the nutritional composition of foods available to Australasian gannets, males consistently capture prey with higher protein-to-lipid ratios and lower lipid-to-water ratios than females. These results aid to better understand the evolutionary relationship between macronutrient selection and sex-specific traits in wild animals. They also suggest an incentive for these predators to combine individually imbalanced but nutritionally complementary foods to achieve dietary balance, further highlighting the likelihood that prey selection is guided by the balance of macronutrients, rather than energy alone.

Although many herbivores and omnivores have been shown to balance their intake of macronutrients when faced with nutritionally variable foods, study of this ability has been relatively neglected in carnivores, largely on the assumption that prey are less variable in nutrient composition than the foods of herbivores and omnivores and such mechanisms therefore unnecessary. We performed diet selection studies in 5 breeds of adult dog (Canis lupus familiaris) to determine whether these domesticated carnivores regulate macronutrient intake. Using nutritional geometry, we show that the macronutrient content of the diet was regulated to a protein:fat:carbohydrate ratio of approximately 30%:63%:7% by energy, a value that was remarkably similar across breeds. These values, which the analysis suggests are dietary target values, are based on intakes of dogs with prior experience of the respective experimental food combinations. On initial exposure to the diets (i.e., when naive), the same dogs self-selected a diet that was marginally but significantly lower in fat, suggesting that learning played a role in macronutrient regulation. In contrast with the tight regulation of macronutrient ratios, the total amount of food and energy eaten was far higher than expected based on calculated maintenance energy requirements. We interpret these results in relation to the evolutionary history of domestic dogs and compare them to equivalent studies on domestic cats. Key words: Canis lupus, carnivore nutrition, domestication, domestic dog, geometric framework, macronutrient regulation, predation, right-angled mixture triangles. [Behav Ecol]

We investigated the distribution and diet of brown bears (Ursus arctos) in the Upper Mustang Region (UMR) of the Annapurna Conservation Area (ACA) in Nepal by interviewing local residents (n = 166) and collecting bear sign (n = 109). Residents reported that brown bears predominantly used the Dhalung and Chungjung pastures and the Damodar Kunda Valley of the UMR from May to November, as well as the unprotected area between this region and Shey–Phoksundo National Park. We conducted dietary analyses on 56 bear scats; bears were predominately carnivorous in the UMR. Plant matter comprised 8% of fecal volume in scats. Small mammal hair was the most commonly identified item (75%), with marmots (Marmota himalayana; 46%) being the largest contributor. In addition, hair from ungulates (14%) and livestock (10%) were identified in scats. Few bear depredations occurred between 2003–10 in the UMR.

Australasian gannets ( Morus serrator ), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive. Here we address the question of whether gannets are capable of visually accommodating in the transition from aerial to aquatic vision, and analyse underwater video footage for evidence that gannets use vision in the aquatic phases of hunting. Photokeratometry and infrared video photorefraction revealed that, immediately upon submergence of the head, gannet eyes accommodate and overcome the loss of greater than 45 D (dioptres) of corneal refractive power which occurs in the transition between air and water. Analyses of underwater video showed the highest prey capture rates during WF phase when gannets actively pursue individual fish, a behaviour that very likely involves visual guidance, following the transition after the plunge dive's M phase. This is to our knowledge the first demonstration of the capacity for visual accommodation underwater in a plunge diving bird while capturing submerged prey detected from the air.

Evolutionary theory predicts that animals should forage to maximize their fitness, which in predators is traditionally assumed equivalent to maximizing energy intake rather than balancing the intake of specific nutrients. We restricted female predatory ground beetles ( Anchomenus dorsalis ) to one of a range of diets varying in lipid and protein content, and showed that total egg production peaked at a target intake of both nutrients. Other beetles given a choice to feed from two diets differing only in protein and lipid composition selectively ingested nutrient combinations at this target intake. When restricted to nutritionally imbalanced diets, beetles balanced the over- and under-ingestion of lipid and protein around a nutrient composition that maximized egg production under those constrained circumstances. Selective foraging for specific nutrients in this predator thus maximizes its reproductive performance. Our findings have implications for predator foraging behaviour and in the structuring of ecological communities.

A nectar diet is simple in nutritional composition and easily digested, but may vary greatly in its proportions of sugar and water. Here, we apply the geometric framework, a modelling approach for investigating how animals balance nutrient needs in multidimensional and dynamic nutritional environments, to captive whitebellied sunbirds (Cinnyris talatala). We address the question of how these small birds (~8 g) prioritise sugar and water intake, and how dietary salt content interacts with sugar and water intake. Sunbirds kept at 20°C and provided with moderate to high sucrose concentrations (≥1 M), together with supplementary water, converge on an intake target of 2.79 g day(-1) of sucrose and 7.72 g day(-1) of water: equivalent to 0.85 M sucrose. When the birds are given more dilute sucrose concentrations, they defend their sugar intake by over-ingesting water, up to a ceiling of 47 g day(-1). Sugar intake thus gets priority over water intake, but the birds have a finite capacity to over-ingest water to gain the target level of sugar. Regulation appears to be less precise when birds are given a choice between two sucrose solutions than when they choose between a sugar solution and supplementary water. Intake targets vary in response to internal and external factors, and sunbirds increase their sugar intake in response to increased activity and cold, irrespective of nectar concentration. They also compensate for interruptions in foraging activity, whether overnight or during the day. Interactive effects become evident when sodium is included as a third nutrient: on very dilute nectar (≤0.1 M), where sunbirds lose body mass, the addition of sodium to the diet helps to achieve the carbohydrate intake target, while raising the ceiling on water intake. This analysis provides a new perspective on nectarivory, while adding to the comparative database on nutrient regulation and emphasising water as a nutrient.

Gannets are specialist plunge divers that perform short and shallow V-shaped dives and long and deep U-shaped dives in pursuit of pelagic fish and squid. We used underwater video graphy to examine the patterns of behaviour and relative success rates of Vand U-shaped dives in Australasian gannets. A significantly greater proportion of U-shaped dives were associated with successful prey capture than V-shaped dives (95% vs. 43%, respectively). The maximum number of prey captured per dive by the gannets was higher than previously reported, reaching up to 5 fish in a single U-shaped dive. However, V-shaped dives were more efficient in terms of grams of prey captured per time spent underwater in successful dives. In contrast, a population-level comparison of the mass of fish captured per total time spent under water (i.e. including unsuccessful dives) suggested that the 2 dive profiles were equally efficient. We also found that gannets adjusted their dive shape in relation to the depth of their prey rather than prey type, as previously hypothesized. Further studies are needed to understand decisions made by gannets while plunge diving in complex marine environments.

Ultraviolet-sensitive vision (UVS), believed to have evolved from an ancestral state of violet-sensitive vision (VS), is widespread among terrestrial birds, where it is thought to play a role in orientation, foraging, and sexual selection. Less is known, however, about the distribution and significance of UVS in seabirds. To date UVS has been definitively demonstrated only in two families (Laridae and Sternidae), although indirect evidence has been used to argue for a more widespread occurrence. In this study we analyzed short-wavelength sensitive (SWS1) opsin DNA sequences to determine the distribution of ancestral (VS) and derived (UVS) amino acid spectral tuning sites in 16 seabird species representing 8 families with diverse ecological niches. Our results revealed sequences associated with UVS pigments (UVSs) in the Black-backed gull (Larus dominicanus), providing further evidence of its widespread occurrence within the Laridae. The Caspian tern (Hydroprogne caspia) and White-fronted tern (Sterna striata), however, were found to have VSs, suggesting an evolutionary reversion to the ancestral state within Sternidae. VSs were also detected in an additional six families. Our results raise interesting questions about the functions of UV vision in marine environments.

Plunge-diving is a highly successful strategy for dealing with the challenges confronting birds feeding on pelagic prey. We tested for evidence of fatal injuries due to collision between conspecifics in plunge-diving Australasian Gannets Morus serrator and Cape Gannets Morus capensis, respectively, by performing post-mortem examinations of carcasses recovered from New Zealand waters and analysing video footage of Cape Gannet foraging events from South Africa. We found evidence of accidental collisions between Gannets and also observed a case of attempted kleptoparasitism, in which a diving Cape Gannet targeted a previously captured fish in the beak of a conspecific.

Weuseda strainofdiamondback moth,PlutellaxylostellaL. (Lepidoptera: Plutellidae),that hadbeen reared for approximately 350 generations in a precisely characterised environment to test hypotheses regarding the influence of nutritional heterogeneity on the evolution of nutrient regulatory responses. Caterpillars were maintained with ad libitum access to a diet that emulated that of an extreme nutritional specialist, comprising a homogeneous food of fixed nutrient composition. We measured performance (survival, development rate, and pupal mass), as well as the protein and carbohydrate intake of individual caterpillars confined to one of a range of single foods differing in their protein, carbohydrate, and water content. In a separate experiment, we measured the amount and balance of protein and carbohydrate self-selected by caterpillars presented with nutritionally complementary foods. Results showed a close fit with three of four predictions about the nutritional responses of ‘nutrient specialist’ feeders: (1) survival, development rate, and pupal mass were highest for animals given diets with the protein:carbohydrate composition of the ancestral culture diet, and dropped off sharply with higher and lower protein:carbohydrate balance, (2) caterpillars coped poorly with dietary dilution by water, irrespective of the macronutrient balance, and (3) the self-selected intake point corresponded with the macronutrient balance that gave peak performance (i.e., that of the ancestral culture diet). The fourth prediction, that caterpillars would be disinclined to over-ingest nutrients on imbalanced diets, was at best weakly met. We hypothesise that the evolution and maintenance of the specialist strategy might, paradoxically, require some degree of environmental heterogeneity.

Evolutionary theories of aging predict that fitness-related traits, including reproductive performance, will senesce because the strength of selection declines with age. Sexual selection theory predicts, however, that male reproductive performance (especially sexual advertisement) will increase with age. In both bodies of theory, diet should mediate age-dependent changes in reproductive performance. In this study, we show that the sexes exhibit dramatic, qualitative differences in age-dependent reproductive performance trajectories and patterns of reproductive ageing in the cricket Teleogryllus commodus. In females, fecundity peaked early in adulthood and then declined. In contrast, male sexual advertisement increased across the natural lifespan and only declined well beyond the maximum field lifespan. These sex differences were robust to deviations from sex-specific dietary requirements. Our results demonstrate that sexual selection can be at least as important as sex-dependent mortality in shaping the signal of reproductive ageing.