Fluctuations In Food Availability Research Articles

Effect of starvation and subsequent feeding on glycogen concentration, behavior and mortality in the golden mussel Limnoperna fortunei (Dunker, 1857) (Bivalvia: Mytilidae

<p>The success of <em>Limnoperna fortunei</em> as an invasive species is related to its physiological plasticity that allows them to endure adverse environmental conditions. Starvation tolerance is considered to be an important trait associated with bivalve invasiveness. In natural ecosystems, food resources can vary during the year, exposing mussels to variable periods of starvation or limited food availability. Thus, mussels have developed physiological strategies to tolerate and survive fluctuations in food availability. Glycogen concentration has been used in different monitoring studies as an indicator of the nutritional condition of bivalves. The aim of this study was to investigate the physiological responses of <em>L. fortunei</em> based on the glycogen concentrations of specimens under four treatments, comprising different combinations of feeding and starvation, during 125 days. The experiment was carried out in two phases. In the phase I, mussels were divided in two treatments: starvation (S) and feeding (F). After 100 days, tissue samples were collected to quantify glycogen concentrations and, each phase I group was divided in two subgroups: starvation (S) and feeding (F), resulting in four treatments. In the phase II, that lasted 25 days, starvation specimens (S) from phase I were allowed to feed (starvation-feeding treatment , or S-F), or continued to undergo starvation (starvation-starvation treatment , or S-S) and the feeding specimens (F) continued feeding (feeding-feeding group, or F-F), or were subjected to starvation (feeding-starvation treatment , or F-S). Behavior (valve-closing) and mortality were recorded in 24 h intervals. After the 25 days (phase II) all specimens were killed, and their soft tissue was removed to quantify glycogen concentrations. The glycogen concentration of the S-F treatment was lower than that of the F-S treatment, which was initially allowed to feed (phase I) and then subjected to starvation (phase II). Stability in the glycogen concentrations was observed when the phase II feeding conditions were maintained during the experiments, as observed in the S-S (continued starvation) and F-F (continued feeding) treatments. Based on our glycogen concentrations results, the golden mussel shows a higher tolerance to starvation (125 days) than has previously been published, which suggests that its tolerance strongly influences its invasive behavior.<strong></strong></p>

Seasonally Consistent Small Home Range and Long Ranging Distance in Presbytis rubicunda in Danum Valley, Borneo

Seasonal fluctuation in food availability is a universal problem for wild animals. One common response to dietary changes is to modify ranging patterns. We studied the ranging pattern of one group (8–12 individuals) of red leaf monkeys (Presbytis rubicunda) in the lowland dipterocarp forest of Danum Valley, Borneo from December 2006 to December 2008. The seasonal availability of fruits varies significantly in this forest because of mast fruiting. We tested the hypothesis that changes in ranging pattern are linked with seasonal changes in diet in this species. We recorded activity, foods eaten, and location every 10 min from around 06:00 until 16:00 h, 5–10 days/mo. The home range size was 21.4 ha over the 25-mo study (95% kernel contour). There were no statistically significant relationships between feeding times on the four major nonexclusive dietary components (all species of seeds, all species of young leaves, young leaves of Spatholobus macropterus, and other species of young leaves) and either the home range (95% kernel contour) or the core area (50% kernel contour). The areas used in the seed-eating and non-seed-eating seasons overlapped to a large extent. The daily path length was 1160 ± 340 m (mean ± SD, range: 550–2140 m). Neither daily path length nor monthly mean travel rate was significantly related to feeding time on any of the four major dietary components. The group’s ranging patterns may be related to the unusual fallback strategy of this population, which depends on the young leaves of an abundant liana (S. macropterus), which are available in small patches. The monkeys need only a small home range because of the high abundance of these leaves. However, they range a relatively long distance because the patches of S. macropterus are easily depleted; thus the ranging distance does not decrease in non-seed-eating periods.

Feeding Strategies of Brown Howler Monkeys in Response to Variations in Food Availability.

Primates display varying degrees of behavioral flexibility that allow them to adjust their diet to temporal changes in food availability. This trait might be critical for the survival of folivorous-frugivorous species inhabiting small forest fragments, where the availability of food resources tends to be lower than in large fragments and continuous forests. However, the scarcity of studies addressing this issue hampers our understanding of the adaptive behaviors that favor the survival of these primates in low-quality habitats. We conducted a 36-mo study testing the hypothesis that brown howler monkeys (Alouatta guariba clamitans) are able to adjust their diet in response to local and seasonal changes in resource availability. We compared the diet of six free-ranging groups inhabiting three small (<10 ha) and three large (>90 ha) Atlantic forest fragments in southern Brazil and estimated the temporal availability of their top food species (i.e., those species that together contribute ≥80% of total feeding records). We found that brown howlers exploited similarly rich diets in small (45, 54, and 57 plant species) and large (48, 51, and 56 species) fragments. However, intermonth diet similarity was higher for groups in small fragments, where howlers also fed on plant items from nine alien species. Fruits and leaves were the most consumed plant items in both small (42% and 49% of feeding records, respectively) and large (51% and 41%, respectively) fragments. The consumption of young leaves was higher in small than in large fragments, whereas the consumption of other plant items did not show a pattern related to fragment size. Regarding the contribution of growth forms as food sources, only the exploitation of palms showed a pattern related to fragment size. Palms contributed more to the diet of groups inhabiting large fragments. The availability of seasonal food items–ripe fruits and young leaves–influenced their consumption in both habitat types. Therefore, brown howlers cope with local and seasonal fluctuations in food availability by opportunistically exploiting resources. We believe that this feeding flexibility is a key component of the phenotypic plasticity that enables howlers to thrive in disturbed habitat patches, where periods of scarcity of preferred foods shall be more common.

Eating locally: Australasian gannets increase their foraging effort in a restricted range.

ABSTRACTDuring the breeding season, seabirds adopt a central place foraging strategy and are restricted in their foraging range by the fasting ability of their partner/chick and the cost of commuting between the prey resources and the nest. Because of the spatial and temporal variability of marine ecosystems, individuals must adapt their behaviour to increase foraging success within these constraints. The at-sea movements, foraging behaviour and effort of the Australasian gannet (Morus serrator) was determined over three sequential breeding seasons of apparent differing prey abundance to investigate how the species adapts to inter-annual fluctuations in food availability. GPS and tri-axial accelerometer data loggers were used to compare the degree of annual variation within two stages of breeding (incubation and chick rearing) at a small gannet colony situated between two larger, nearby colonies. Interestingly, neither males nor females increased the total distance travelled or duration of foraging trip in any breeding stage (P>0.05 in all cases) despite apparent low prey availability. However, consistently within each breeding stage, mean vectorial dynamic body acceleration (an index of energy expenditure) was greater in years of poorer breeding success (increased by a factor of three to eight), suggesting birds were working harder within their range. Additionally, both males and females increased the proportion of a foraging trip spent foraging in a poorer year across both breeding stages. Individuals from this colony may be limited in their ability to extend their range in years of low prey availability due to competition from conspecifics in nearby colonies and, consequently, increase foraging effort within this restricted foraging area.

Gut fat signaling and appetite control with special emphasis on the effect of thylakoids from spinach on eating behavior.

The metabolic controls of eating are embedded in a neural system that permits an interaction with the environment. The result is an integrated adaptive response that coordinates the internal milieu with the prevailing environment. Securing adequate amounts of fat and optimizing its storage and use has an evolutionary basis. By generating neuronal and endocrine feedback signals, behavior and metabolism could then adapt to fluctuations in food availability. However, in modern society, foods that appeal to the palate are neither in shortage nor are they difficult to procure. These foods can activate brain reward circuitry beyond their evolved 'survival advantage' limits. Many foods high in fat invoke an undeniably pleasurable sensation and could excessively stimulate the brain's reward pathways leading to overeating. However, the high appeal and potential for being eaten in excess notwithstanding, fat has the added distinction of inducing powerful signals in the gut that are transduced to the brain and result in the regulation of appetite. Fatty acids are sensed by G-protein-coupled receptors on enteroendocrine cells which trigger the release of peptides involved in appetite regulation. Lipid sensing may also occur through the fatty acid translocase, CD-36, on enterocytes. Additionally, fat can activate dopaminergic systems affecting reward, to promote an inhibition over eating. Prolonging the presence of fats in the gastrointestinal lumen permits the activation of signaling mechanisms. Thylakoids, found within the chloroplasts of plants, are flattened disc-like membranous vesicles in which the light-dependent reactions of photosynthesis occur. By interacting with lipids and delaying fat digestion, thylakoid membranes promote the release of peptides involved in appetite regulation and may influence the reward system. This review explores gut lipid sensing and signaling in the context of appetite regulation. The effects of thylakoid membranes on eating behavior are also reviewed.

Food Spoilage, Storage, and Transport: Implications for a Sustainable Future

Human societies have always faced temporal and spatial fluctuations in food availability. The length of time that food remains edible and nutritious depends on temperature, moisture, and other factors that affect the growth rates of organisms that cause spoilage. Some storage techniques, such as drying, salting, and smoking, date back to ancient hunter–gatherer and early agricultural societies and use relatively low energy inputs. Newer technologies developed since the industrial revolution, such as canning and compressed-gas refrigeration, require much greater energy inputs. Coincident with the development of storage technologies, the transportation of food helped to overcome spatial and temporal fluctuations in productivity, culminating in today's global transport system, which delivers fresh and preserved foods worldwide. Because most contemporary humans rely on energy-intensive technologies for storing and transporting food, there are formidable challenges for feeding a growing and increasingly urbanized global population as finite supplies of fossil fuels rapidly deplete.

Exploiting the richest patch has a fitness pay-off for the migratory swift parrot.

1. Unlike philopatric migrants, the ecology of nomadic migrants is less well understood. This life-history strategy reflects responses to spatiotemporal variation in resource availability and the need to find resource rich patches to initiate breeding. The fitness consequences of movements between regions of patchily distributed resources can provide insight into ecology of all migrants and their responses to global change. 2. We link broad-scale data on spatiotemporal fluctuation in food availability to data on settlement patterns and fitness outcomes for a nomadic migrant, the endangered swift parrot Lathamus discolor. We test several predictions to determine whether facultative movements are adaptive for individual swift parrots in an environment where resources are patchily distributed over time and space. 3. Variation in the availability of swift parrot food resources across our study period was dramatic. As a consequence, swift parrots moved to breed wherever food was most abundant and did not resettle nesting regions in successive years when food availability declined. By moving, swift parrots exploited a variable food resource and reproduced successfully. 4. Exploiting the richest patches allowed swift parrots to maintain stable fitness outcomes between discrete breeding events at different locations. Unlike sedentary species that often produce few or lower quality offspring when food is scarce, nomadic migration buffered swift parrots against extreme environmental variation. 5. We provide the first detailed evidence that facultative movements and nomadic migration are adaptive for individuals in unpredictable environments. Our data support the widely held assumption that nomadic migration allows animals to escape resource limitation.

Did Children in Medieval and Post‐medieval Poland Suffer from Scurvy? Examination of the Skeletal Evidence

AbstractLate‐medieval and post‐medieval writings report that scurvy was a widespread condition in medieval and early historical Poland. Archaeological and historical data indicate that the diet of children was based on foods poor in vitamin C and contained small amounts of raw plant products. Also, historians emphasise that in medieval and post‐medieval Poland, there were seasonal fluctuations in food availability, frequently accompanied by poor harvests. Both resulted in long periods of poor nutrition, which affected children most severely. The aim of this study was to investigate skeletal manifestations of scurvy in subadult remains from medieval and post‐medieval Poland. Following standards described by Ortner and colleagues, anatomical sites pathognomonic of scurvy in subadults (&lt;17 years) were assessed for abnormal porosity and hypertrophic bone among skeletons excavated from three sites: Ostrów Lednicki (dated to the 11th–14th centuries AD), Cedynia (10th–14th centuries AD) and Słaboszewo (14th–17th centuries AD). In total, 3.6% of all examined children were found to bear traces of vitamin C deficiency. The prevalence of scorbutic lesions was 4.5% for Cedynia, 2.6% for Ostrów Lednicki and 3.6% for Słaboszewo. The majority of affected children were less than 7 years of age. Scurvy was likely more widespread in the living populations than it appears from the calculation of skeletal markers, because some individuals might have recovered or died before obvious traces became apparent. Also, in some children, scurvy might not have reached an advanced stage, identifiable in the skeletal material. The prevalence of scurvy reflects not only dietary patterns but also food storage and preparation techniques adopted in the Polish territories during the Middle Ages, which contributed to low intakes of vitamin C. Copyright © 2015 John Wiley &amp; Sons, Ltd.

A severe predator-induced population decline predicted for endangered, migratory swift parrots (Lathamus discolor)

Identifying the impact of introduced predators on endangered prey populations is critical for conservation management. Population viability analysis (PVA) becomes a valuable tool for quantifying such impacts when high quality life history data are available but, surprisingly, predictions from PVA of future population decline have seldom been used directly to assess conservation status. Here we synthesise new research on the unusual life history of the endangered swift parrot Lathamus discolor, an austral migrant that breeds in Tasmania, Australia. Swift parrots are challenging to monitor because (1) spatio-temporal fluctuation in food availability causes them to select entirely different breeding sites each year over a 10,000km2 range, and (2) they suffer high but variable rates of predation from introduced sugar gliders Petaurus breviceps depending on where they breed. 50.9% of nesting females on the main island of Tasmania were killed by sugar gliders while incubating eggs, but there was no predation from this source on offshore islands. Over four years 16.5% (0–29%) of the population bred on offshore islands. We use PVAs to examine the likely extent of future population decrease due to sugar glider predation, and demonstrate that the remaining swift parrot population is likely to decrease by 78.8–94.7% (mean over four models=86.9%) over only three generations (12–18years). Our models offer a rare example of the use of PVAs for assessing impending population decline and conservation status in species that are challenging to monitor. In this case they support a change of status for swift parrots from “Endangered” to ‘Critically Endangered’ under IUCN criteria.

Daily changes in food availability, but not long-term unpredictability, determine daily torpor-bout occurrences and frequency in stripe-faced dunnarts (Sminthopsis macroura)

Daily torpor, a short-term reduction in body temperature and metabolism, is an energy-saving strategy that has been interpreted as an adaptation to unpredictable resource availability. However, the effect of food-supply variability on torpor, separately from consistent food restriction, remains largely unexamined. In this study, we investigated the effect of unpredictable food availability on torpor in stripe-faced dunnarts (Sminthopsis macroura). After a control period of ad libitum feeding, dunnarts were offered 65% of their average daily ad libitum intake over 31 days, either as a constant restriction (i.e. as equal amount of food offered each day) or as an unpredictable schedule of feed offered, varied daily as 0%, 30%, 60%, 100% or 130% of ad libitum. Both feeding groups had increased torpor-bout occurrences (as a proportion of all dunnarts on a given day) and torpor-bout frequency (average number of bouts each day) when on a restricted diet compared with ad libitum feeding, but torpor frequency did not differ between the consistently restricted and unpredictably restricted groups. Most importantly, torpor occurrence and daily bout frequency by the unpredictably restricted group appeared to change in direct association with the amount of food offered on each day; torpor frequency was higher on days of low food availability. Our data do not support the interpretation that torpor is a response to unpredictable food availability per se, but rather that torpor allowed a rapid adjustment of energy expenditure to manage daily fluctuations in food availability.

食物限制对黑线仓鼠免疫功能的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 食物限制对黑线仓鼠免疫功能的影响 DOI: 10.5846/stxb201305241171 作者: 作者单位: 曲阜师范大学生命科学学院,曲阜师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31070332,31370427);山东省自然科学基金(ZR2013CM019);曲阜师范大学博士启动基金(bsqd20100204) Effect of food restriction on immune function in the striped hamster (Cricetulus barabensis) Author: Affiliation: College of Life Sciences,Qufu Normal University,Qufu,273165,Shandong Province Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:温带地区小型哺乳动物经常面临着食物资源的波动。食物对动物的免疫功能具有重要影响。将19只成年雄性黑线仓鼠(Cricetulus barabensis)随机分为自由取食组(n=9)和限食组(n=10)。注射植物血球凝集素(PHA)来测定细胞介导的免疫反应,用匙孔血蓝蛋白(KLH)免疫动物,然后测定抗KLH抗体的浓度以反映其体液免疫功能。旨在检验食物限制是否会抑制黑线仓鼠的细胞免疫和体液免疫功能。结果发现,与对照组相比,限食组黑线仓鼠具有较低的体重、体脂、脾脏鲜重、血清瘦素水平、免疫球蛋白IgG和IgM浓度。而限食对胸腺鲜重、白细胞数、皮质酮水平以及PHA反应没有显著影响。结果表明黑线仓鼠免疫系统的不同成分对限食反应存在差异,在食物资源短缺时,黑线仓鼠防御细胞外病原体的能力降低,从而导致生存能力的下降。 Abstract:The immune system protects animals against environmental pathogens, and hence it plays an important role in their survival and fitness. However, immune function is influenced by many factors including food availability. Small mammals in the temperate zone often face fluctuations in food availability, which is important to their survival. Changes in food availability may have a great influence on an animals' immunity. Some investigators have examined the effect of reduced food availability (i.e., food restriction) on the immune function in small rodents, but their results are often inconsistent. Food restriction could depress, enhance or have no effect on immunity in different species. In order to clarify the discrepancy between results, the striped hamster (Cricetulus barabensis) was used to examine the effect of food restriction on its immune function. The striped hamster is a major pest rodent in northern China. It is granivorous, nocturnal and feeds mainly on plant stems and leaves during summer and forages crop seeds in winter. The climate is arid and characterized by warm and dry summers and cold winters. Thus, the species experiences great seasonal fluctuations in temperature, photoperiod as well as food quality and availability. The question we focused on in the present study was how the immune function would vary in the face of reduced food availability for hamsters. Nineteen adult male hamsters were randomly divided into the fed ad libitum group (Fed, n=9) and food restricted group (FR, n=10) (90% of baseline food intake). The course of food restriction was 21 days. Hamsters were injected with phytohaemagglutinin (PHA) and keyhole limpet haemocyanin (KLH) solution to assess cellular and humoral immunity, respectively. Our goal was to test whether food restriction would suppress cellular and humoral immunity in striped hamsters. Body mass in the FR group decreased significantly after 21 days of food restriction, whereas body mass in the Fed group did not change significantly. Body mass in the FR group was significantly lower than that of the Fed group after 10 days of food restriction. Food restriction significantly reduced perirenal fat, perirenal fat content, retroperitoneal fat, total body fat, and wet spleen mass in the FR group compared with the Fed group. However, it had no significant effect on the wet thymus mass or white blood cells. Immunoglobulin (Ig) G and IgM concentrations were reduced significantly in the food restricted hamsters in contrast with the Fed control group, which indicated the suppressive role of food restriction on humoral immunity. PHA response did not differ between the two groups, suggesting cellular immunity was not influenced by food restriction. Food restricted hamsters had significantly lower serum leptin levels than that of the control group, while corticosterone levels were not affected by food restriction. Taken together, our results suggest that different components of the immune system respond differently to food restriction in striped hamsters. Humoral immunity was suppressed in food restricted hamsters, which might be due to their lower body fat mass and lower leptin levels. In the face of food shortage, striped hamsters might be more prone to extracellular pathogens and their survival capability would decrease. 参考文献 相似文献 引证文献

Magnitude of food overabundance affects expression of daily torpor

Many small mammal species use torpor as a strategy for reducing energy expenditure in winter. Some rodent hibernators also hoard food to provide reserves of energy, and individuals with large hoards express less torpor than those with smaller reserves. These facts imply that animals can recognize levels of food availability, but where food is very plentiful, it is unclear whether torpor expression is affected by temporal changes in the extent of food overabundance. Moreover, the relationship between daily torpor and excess food availability has not been clearly established. The large Japanese field mouse Apodemus speciosus caches food for use as a winter energy resource and exhibits daily torpor under artificial winter conditions. The present study examined whether individuals exposed to different magnitudes of overabundant food exhibited differences in expression of daily torpor, and secondly whether torpor expression varied in response to changes in the overall quantity of overabundant food. It was observed that while absolute quantities of overabundant food did not appear to affect daily torpor expression, the mice did respond to changes in food availability, even when food remained overabundant. This suggests that the mice respond to fluctuations in food availability, even where these changes do not place any constraint on energy budgets. Thus recognition of changing food availability cannot be a purely physiological response to shortage or plenty, and may contribute to predictions of future energy availability. The expression of torpor was inhibited in response to increasing food availability, and the mice used shallower torpor when food availability increased to superabundance. These findings suggest that daily torpor may be regulated not only physiologically in response to energy constraints but also psychologically, via recognition of food availability.

Differences in growth rate, body condition, habitat use and food availability between island and mainland lizard populations ofAnolis nebulosusin Jalisco, Mexico

Abstract:Lizards of the genusAnolishave been widely studied, however, little is known about the effects of environmental seasonality, food availability and geographic isolation on body condition, growth rate and habitat use of lizards. The existence of an insular and a continental population ofAnolis nebulosus(clouded anole), separated by only 0.47 km, represents an ideal opportunity to address this topic. We compared seasonal fluctuations in food availability (arthropod density) for anoles, as well as body condition, growth rate and habitat use in the two populations. Food availability throughout the year was sampled every 2 mo by trapping arthropods at each site. Lizards were also monitored and measured every 2 mo by surveying three quadrats in each site over 2 y giving a total of 30 visits for each quadrat. Results suggested that composition and density of food supply was similar for the two populations. Nevertheless, food supply responded to seasonality of rainfall, with an increase of 1.5 times during the rainy season. Despite similarity in food availability, insular anoles had body condition that was 5–10 times better, with growth rate twice as fast, and used similar perches. The role of predation, and inter- and intraspecific competition are discussed as possible drivers.

Niche partitioning among frugivorous fishes in response to fluctuating resources in the Amazonian floodplain forest

In response to temporal changes in the quality and availability of food resources, consumers should adjust their foraging behavior in a manner that maximizes energy and nutrient intake and, when resources are limiting, minimizes dietary overlap with other consumers. Floodplains of the Amazon and its lowland tributaries are characterized by strong, yet predictable, hydrological seasonality, seasonal availability of fruits, seeds, and other food resources of terrestrial origin, and diverse assemblages of frugivorous fishes, including morphologically similar species of several characiform families. Here, we investigated how diets of frugivorous fishes in the Amazon change in response to fluctuations in food availability, and how this influences patterns of interspecific dietary overlap. We tested predictions from classical theories of foraging and resource competition by estimating changes in diet breadth and overlap across seasons. We monitored fruiting phenology to assess food availability, and surveyed local fish populations during three hydrological seasons in an oligotrophic river and an adjacent oxbow lake in the Colombian Amazon. We analyzed stomach contents and stable isotope data to evaluate temporal and interspecific relationships for dietary composition, breadth, and overlap. Diets of six species of characiform fishes representing three genera changed according to seasonal fluctuations in food availability, and patterns of diet breadth and interspecific overlap during the peak flood pulse were consistent with predictions of optimal foraging theory. During times of high fruit abundance, fishes consumed items to which their functional morphological traits seemed best adapted, potentially enhancing net energy and nutritional gains. As the annual flood pulse subsided and availability of forest food resources in aquatic habitats changed, there was not a consistent pattern of diet breadth expansion or compression. Nonetheless, shifts in both diet composition and stable isotope ratios of consumer tissues during this period resulted in trophic niche segregation in a pattern consistent with competition theory.

Change in paternal grandmothers´ early food supply influenced cardiovascular mortality of the female grandchildren

BackgroundThis study investigated whether large fluctuations in food availability during grandparents' early development influenced grandchildren's cardiovascular mortality. We reported earlier that changes in availability of food - from good to poor or from poor to good - during intrauterine development was followed by a double risk of sudden death as an adult, and that mortality rate can be associated with ancestors´ childhood availability of food. We have now studied transgenerational responses (TGR) to sharp differences of harvest between two consecutive years´ for ancestors of 317 people in Överkalix, Sweden.ResultsThe confidence intervals were very wide but we found a striking TGR. There was no response in cardiovascular mortality in the grandchild from sharp changes of early exposure, experienced by three of the four grandparents (maternal grandparents and paternal grandfathers). If, however, the paternal grandmother up to puberty lived through a sharp change in food supply from one year to next, her sons´ daughters had an excess risk for cardiovascular mortality (HR 2.69, 95% confidence interval 1.05-6.92). Selection or learning and imitation are unlikely explanations. X-linked epigenetic inheritance via spermatozoa seemed to be plausible, with the transmission, limited to being through the father, possibly explained by the sex differences in meiosis.ConclusionThe shock of change in food availability seems to give specific transgenerational responses.

Influence of Developmental Conditions on Immune Function and Dispersal-Related Traits in the Glanville Fritillary (Melitaea cinxia) Butterfly

Organisms in the wild are constantly faced with a wide range of environmental variability, such as fluctuation in food availability. Poor nutritional conditions influence life-histories via individual resource allocation patterns, and trade-offs between competing traits. In this study, we assessed the influence of food restriction during development on the energetically expensive traits flight metabolic rate (proxy of dispersal ability), encapsulation rate (proxy of immune defence), and lifespan using the Glanville fritillary butterfly, Melitaea cinxia, as a model organism. Additionally, we examined the direct costs of flight on individual immune function, and whether those costs increase under restricted environmental conditions. We found that nutritional restriction during development enhanced adult encapsulations rate, but reduced both resting and flight metabolic rates. However, at the individual level metabolic rates were not associated with encapsulation rate. Interestingly, individuals that were forced to fly prior to the immune assays had higher encapsulation rates than individuals that had not flown, suggesting that flying itself enhances immune response. Finally, in the control group encapsulation rate correlated positively with lifespan, whereas in the nutritional restriction group there was no relationship between these traits, suggesting that the association between encapsulation rate on adult lifespan was condition-dependent. Thus stressful events during both larval development (food limitation) and adulthood (forced flight) induce increased immune response in the adult butterflies, which may allow individuals to cope with stressful events later on in life.

From breeding pairs to fox towns: the social organisation of arctic fox populations with stable and fluctuating availability of food

Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox (Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming (Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a ‘fox town’ with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation.

Divergence in chick developmental patterns among wedge-tailed shearwater populations

Mechanisms of population divergence in seabirds are poorly understood. We evaluated whether divergent patterns of chick development among wedge-tailed shearwater Puffinus pacificus populations are facultative responses to short-term fluctuations in food availability, or fixed colony-specific phenomena potentially associated with differences in local resource availability. Supplementary feeding at Heron Island increased food intake to levels equal to, or greater than, those observed at Lord Howe Island. In supplemented chicks, mass accumulation per gram of food received was inversely related to current body stores, up to a maximum storage level set by body size. Significantly, maximum storage was lower for Heron Island than for Lord Howe Island chicks at equivalent body size. In contrast, relative allocation to skeletal growth did not differ between supplemented and control chicks, was not influenced by body condition and did not increase to levels observed at Lord Howe Island. Overall, the present study showed that supplemented chicks were unable to use short-term increases in food availability to increase relative mass stores or rates of skeletal development, implying that both life-history parameters have some colony-specific components that are divergent between the locations of this study. Our findings add weight to previous studies suggesting that phenotypic plasticity and/or genetic drift due to philopatry cannot fully explain patterns of morphological, behavioural and physiological divergence among these 2 shearwater colonies.

More ecological ERA: Incorporating natural environmental factors and animal behavior

We discuss the importance of selected natural abiotic and biotic factors in ecological risk assessment based on simplistic laboratory bioassays. Although it is impossible to include all possible natural factors in standard lower-tier ecotoxicological testing, neglecting them is not an option. Therefore, we try to identify the most important factors and advocate redesigning standard testing procedures to include theoretically most potent interactions. We also point out a few potentially important factors that have not been studied enough so far. The available data allowed us to identify temperature and O2 depletion as the most critical factors that should be included in ecotoxicity testing as soon as possible. Temporal limitations and fluctuations in food availability also appear important, but at this point more fundamental research in this area is necessary before making decisions on their inclusion in risk assessment procedures. We propose using specific experimental designs, such as Box-Behnken or Central Composite, which allow for simultaneous testing of 3 or more factors for their individual and interactive effects with greater precision and without increasing the effort and costs of tests dramatically. Factorial design can lead to more powerful tests and help to extend the validity of conclusions. Finally, ecological risk assessment procedures should include information on animal behavior, especially feeding patterns. This requires more basic studies, but already at this point adequate mechanistic effect models can be developed for some species.

A leopard ate a chimpanzee: First evidence from East Africa

Fission-fusion societies are social systems in which individuals belonging to the same community are rarely all together but rather spend most of their time in temporary parties. This flexible social organization is assumed to be an adaptation that balances advantages and costs of group living in a fluid way as resources and constraints shift through space and time. It has been argued that this flexibility freed hominins from the foraging constraints caused by living in large groups. Given their close genetic relationship to humans and because they represent the classic case of a fission-fusion society, chimpanzees have often been used as referential models to understand human social evolution. Determinants of chimpanzee party size have been widely studied for decades across several communities. However, we lack data from open and dry sites—which closely resemble those reconstructed for Plio-Pleistocene hominins—on communities that potentially face similar environmental constraints as early hominins did. We investigated chimpanzee (Pan troglodytes schweinfurthii) grouping patterns on a recently habituated community living in the savanna-woodland mosaic landscape of the Issa Valley, western Tanzania, by following chimpanzees daily and recording party size every hour. Our results revealed that party size at Issa 1) followed seasonal fluctuations in food availability, 2) increased in the presence of swollen females, and 3) was higher in open vegetation, which potentially presents a high predation risk. Furthermore, we found the Issa community to be highly cohesive compared with the majority of other communities, possibly due to a combination of its small size and potential threats characterizing its home range. Our study fills a gap in our knowledge of chimpanzee sociality by exploring grouping pattern determinants in an East African understudied biome and highlights what elements of early hominin social behavior may have evolved in Late Pliocene landscapes.