Fluctuations In Food Availability Research Articles

AgRP neuron cis-regulatory analysis across hunger states reveals that IRF3 mediates leptin’s acute effects

AgRP neurons in the arcuate nucleus of the hypothalamus (ARC) coordinate homeostatic changes in appetite associated with fluctuations in food availability and leptin signaling. Identifying the relevant transcriptional regulatory pathways in these neurons has been a priority, yet such attempts have been stymied due to their low abundance and the rich cellular diversity of the ARC. Here we generated AgRP neuron-specific transcriptomic and chromatin accessibility profiles from male mice during three distinct hunger states of satiety, fasting-induced hunger, and leptin-induced hunger suppression. Cis-regulatory analysis of these integrated datasets enabled the identification of 18 putative hunger-promoting and 29 putative hunger-suppressing transcriptional regulators in AgRP neurons, 16 of which were predicted to be transcriptional effectors of leptin. Within our dataset, Interferon regulatory factor 3 (IRF3) emerged as a leading candidate mediator of leptin-induced hunger-suppression. Measures of IRF3 activation in vitro and in vivo reveal an increase in IRF3 nuclear occupancy following leptin administration. Finally, gain- and loss-of-function experiments in vivo confirm the role of IRF3 in mediating the acute satiety-evoking effects of leptin in AgRP neurons. Thus, our findings identify IRF3 as a key mediator of the acute hunger-suppressing effects of leptin in AgRP neurons.

Boldness suppresses hoarding behavior in food hoarding season and reduces over-wintering survival in a social rodent.

The "pace-of-life" syndrome (POLS) framework can encompass multiple personality axes that drive important functional behaviors (e.g., foraging behavior) and that co-vary with multiple life history traits. Food hoarding is an adaptive behavior important for an animal's ability to adapt to seasonal fluctuations in food availability. However, the empirical evidence for the relationships between animal personality and hoarding behavior remains unclear, including its fitness consequences in the POLS framework. In this study, the Mongolian gerbil (Meriones unguiculatus), a social rodent, was used as a model system to investigate how boldness or shyness is associated with food hoarding strategies during the food hoarding season and their impact on over-winter survival and reproduction at both individual and group levels. The results of this study showed that, compared with shy gerbils, bold gerbils had a lower effort foraging strategy during the food hoarding season and exhibited lower over-winter survival rates. However, bold-shy personality differences had no effect on over-winter reproduction. These findings suggest that the personality is a crucial factor influencing the foraging strategy during the food hoarding season in Mongolian gerbils. Personality may be related to energy states or the reaction to environmental changes (e.g., predation risk and food availability) in bold or shy social animals. These results reflect animal life history trade-offs between current versus future reproduction and reproduction versus self-maintenance, thereby helping Mongolian gerbils in adapting to seasonal fluctuations in their habitat.

DNA-metabarcoding supports trophic flexibility and reveals new prey species for the Galapagos sea lion.

Tropical ecosystems are challenging for pinnipeds due to fluctuating food availability. According to previous research, the Galapagos sea lion (GSL, Zalophus wollebaeki) adopts trophic flexibility to face such conditions. However, this hypothesis comes from studies using traditional methods (hard-parts analysis of scat and isotopic analysis from tissue). We studied the diet of five rookeries in the southeastern Galapagos bioregion (which harbors the highest GSL density), via DNA-metabarcoding of scat samples. The DNA-metabarcoding approach may identify consumed prey with a higher taxonomic resolution than isotopic analysis, while not depending on hard-parts remaining through digestion. Our study included five different rookeries to look for evidence of trophic flexibility at the bioregional level. We detected 98 prey OTUs (124 scats), mostly assigned to bony-fish taxa; we identified novel prey items, including a shark, rays, and several deep-sea fish. Our data supported the trophic flexibility of GSL throughout the studied bioregion since different individuals from the same rookery consumed prey coming from different habitats and trophic levels. Significant diet differentiations were found among rookeries, particularly between Punta Pitt and Santa Fe. Punta Pitt rookery, with a more pronounced bathymetry and lower productivity, was distinguished by a high trophic level and consumption of a high proportion of deep-sea prey; meanwhile, Santa Fe, located in more productive, shallow waters over the shelf, consumed a high proportion of epipelagic planktivorous fish. Geographic location and heterogeneous bathymetry of El Malecon, Española, and Floreana rookeries would allow the animals therein to access both, epipelagic prey over the shelf, and deep-sea prey out of the shelf; this would lead to a higher prey richness and diet variability there. These findings provide evidence of GSL adopting a trophic flexibility to tune their diets to different ecological contexts. This strategy would be crucial for this endangered species to overcome the challenges faced in a habitat with fluctuating foraging conditions.

Hypothalamic AMP-Activated Protein Kinase as a Whole-Body Energy Sensor and Regulator.

5´-Adenosine monophosphate (AMP)-activated protein kinase (AMPK), a cellular energy sensor, is an essential enzyme that helps cells maintain stable energy levels during metabolic stress. The hypothalamus is pivotal in regulating energy balance within the body. Certain neurons in the hypothalamus are sensitive to fluctuations in food availability and energy stores, triggering adaptive responses to preserve systemic energy equilibrium. AMPK, expressed in these hypothalamic neurons, is instrumental in these regulatory processes. Hypothalamic AMPK activity is modulated by key metabolic hormones. Anorexigenic hormones, including leptin, insulin, and glucagon-like peptide 1, suppress hypothalamic AMPK activity, whereas the hunger hormone ghrelin activates it. These hormonal influences on hypothalamic AMPK activity are central to their roles in controlling food consumption and energy expenditure. Additionally, hypothalamic AMPK activity responds to variations in glucose concentrations. It becomes active during hypoglycemia but is deactivated when glucose is introduced directly into the hypothalamus. These shifts in AMPK activity within hypothalamic neurons are critical for maintaining glucose balance. Considering the vital function of hypothalamic AMPK in the regulation of overall energy and glucose balance, developing chemical agents that target the hypothalamus to modulate AMPK activity presents a promising therapeutic approach for metabolic conditions such as obesity and type 2 diabetes mellitus.

Peasants and food security in England and Wales c.1300

ABSTRACT Food security is discussed with a particular focus on the decades either side of 1300, years characterised by poor weather and significant fluctuations in food availability, evident especially in the varied performance of grain harvests. Examining access to food and the vulnerability of the food supply in a period of particular pressure on food resources allows reflection on stresses on food availability in these decades as well as the range of approaches that individuals and institutions could employ in seeking to respond to them. The article discusses relative entitlement and contemporary perceptions of the same. While its focus is upon rural society and the experience of the peasantry, there will necessarily be some reference to the urban context, which cannot be separated from the experience of the countryside, and the attempts of institutions such as government to respond to issues relevant to food security in this period.

Small-scale farmer responses to the double exposure of climate change and market integration.

Anthropologists have long studied how small-scale societies manage climate variation. Here, we investigate how Yucatec Maya subsistence farmers respond to climate stress, and the ways in which market integration may enhance or disturb response stategies. Using information on harvest returns, climate perceptions, household economics and helping networks, modelling results show that as farmers rely more on market inputs (e.g. seed, tractors, fertilizer) for a successful yield, the reasons given for a bad harvest shift from climate variables to access to quality inputs. We also find that social and economic diversification is key to mediating a household's experience of climate and market shocks. The Maya are astute stewards of climate knowledge, and have effective social and economic means to mitigate potential fluctuations in food availability. In the transition from a subsistence to a market integrated economy, these traditional strategies become strained. Reliance on market inputs forges a more rigid food production system that conflicts with the diversity and flexibility on which traditional strategies depend to manage climate variation. Moving forward, the best policies would be those that facilitate maintaining an equal footing in both a subsistence maize economy, while incorporating new market opportunities. This article is part of the theme issue 'Climate change adaptation needs a science of culture'.

Strong seasonality in diets and alarming levels of food insecurity and child malnutrition in south-eastern Madagascar

Rural areas of Madagascar face a tense food and nutrition security situation. The country reports some of the highest rates of undernourishment and malnutrition worldwide. Evidence is scant, however, about how the rural people’s diets vary over the course of the agricultural year, and how different household types deal with fluctuating food availability. This lack of detailed understanding of the food and nutrition security situation across time and social strata currently limits development stakeholders’ ability to tailor interventions to local needs. Using randomly sampled survey data from Farafangana District in south-eastern Madagascar, this study analyzes rural households’ diets across three time points within one year (minor lean period, major lean period, main post-harvest period). In addition, anthropometric data on children aged 6–59 months were collected during the major lean period to determine levels of chronic and acute child malnutrition. Overall, food insecurity stood at high levels at all times, but with substantial variation across the year. Shortly before the main rice harvest, the prevalence of moderate and severe food insecurity was 78%, twice as high as shortly after harvest. With 57% of children stunted and a 17% prevalence of wasting, the observed levels of chronic and acute child malnutrition exceed levels reported previously. By studying what households eat and how they source it (own production vs. purchases), we found distinct patterns of food acquisition between the three periods. Diminishing food security is reflected by substituting rice by cassava, unripe jackfruit (minor lean period), and local tuber tavolo (major lean period), as well as by lower diversity of side dishes. Our results underline the need for long-term agricultural development strategies that contribute to greater household food self-sufficiency especially during the lean periods. But the alarming level of acute child malnutrition also calls for more immediate humanitarian aid and public health interventions.

On the paradox of thriving cold-water coral reefs in the food-limited deep sea.

The deep sea is amongst the most food-limited habitats on Earth, as only a small fraction (<4%) of the surface primary production is exported below 200 m water depth. Here, cold-water coral (CWC) reefs form oases of life: their biodiversity compares with tropical coral reefs, their biomass and metabolic activity exceed other deep-sea ecosystems by far. We critically assess the paradox of thriving CWC reefs in the food-limited deep sea, by reviewing the literature and open-access data on CWC habitats. This review shows firstly that CWCs typically occur in areas where the food supply is not constantly low, but undergoes pronounced temporal variation. High currents, downwelling and/or vertically migrating zooplankton temporally boost the export of surface organic matter to the seabed, creating 'feast' conditions, interspersed with 'famine' periods during the non-productive season. Secondly, CWCs, particularly the most common reef-builder Desmophyllum pertusum (formerly known as Lophelia pertusa), are well adapted to these fluctuations in food availability. Laboratory and in situ measurements revealed their dietary flexibility, tissue reserves, and temporal variation in growth and energy allocation. Thirdly, the high structural and functional diversity of CWC reefs increases resource retention: acting as giant filters and sustaining complex food webs with diverse recycling pathways, the reefs optimise resource gains over losses. Anthropogenic pressures, including climate change and ocean acidification, threaten this fragile equilibrium through decreased resource supply, increased energy costs, and dissolution of the calcium-carbonate reef framework. Based on this review, we suggest additional criteria to judge the health of CWC reefs and their chance to persist in the future.

Epibenthic faunal community dynamics and seasonal species turnover in a deep-sea coral ecosystem

Deep-sea coral ecosystems represent oases of life in the deep ocean, often hosting abundant and diverse faunal communities. Although mounting evidence indicates that deep-sea benthic communities are highly dynamic and can change over scales of a few hours to seasons or years, such dynamics have never been characterized in deep-sea coral ecosystems. We used a time-lapse camera deployed for a year at a depth of 1230 m on Sur Ridge (Monterey Bay National Marine Sanctuary) to characterize hourly changes in megafaunal abundance and diversity in a deep-sea coral assemblage. The response of community dynamics to variation in environmental factors, including surface net primary production as well as current speed/direction, temperature and acoustic backscatter (a proxy for particle and zooplankton density) at depth, was also evaluated. Overall, 33 taxa from 6 phyla, including multiple commercially valuable species, were observed throughout the study period. The strong seasonal pattern and periodicities in the occurrence of the most abundant taxa likely drove the observed temporal trends in overall abundance and diversity. Fluctuations in food availability may have, at least partially, driven these trends, as indicated by the significant relationship between community dynamics, surface net primary production and acoustic backscatter at depth. However, the low explanatory power of environmental parameters tested here suggest that biotic factors such as individual behaviors and species interactions had a strong influence on community dynamics. This study emphasizes the role of deep-sea coral as habitat and the need for monitoring to better understand how environmental and biological processes interact to shape associated faunal communities.

Diet disparity and diversity predict extinction risk in primates

AbstractSpecies vary in their vulnerability to extinction according to their biology, ecology, environmental factors and threats to which they are exposed. Diet is an important ecological trait that affects many aspects of a species' biology, including its vulnerability to extinction. Despite the importance of diet as a species' trait, its influence on extinction risk has only been studied in a coarse way, in part due to a lack of detailed diet data covering a large breadth of species or geographic areas. We examined the association between diet and extinction risk in primates, using a high‐resolution dataset covering all major primate lineages and habitats on a global scale. The resolution of the dataset allowed us to calculate multiple biologically informative metrics for diet composition and diversity, allowing us to tease apart what aspects of diet were most important for predicting the risk of extinction, whilst accounting for phylogeny, body mass and geographic range size. Our results showed that both diet disparity and diet diversity predict primate extinction risk, showing that primates that are able to consume more types of items, and items that are more disparate from one another, are less prone to extinction. Furthermore, we found that although closely related species tend to have similar dietary diversity and disparity, these metrics vary widely amongst primate families. Primates with a high diet diversity and disparity may be able to cope better with fluctuations in food availability than species with homogeneous diet items, through a portfolio effect. Understanding the degree of dietary specialization of the species may help guide new studies relating to extinction risk and threats and be useful in future species assessments.

Foraging behaviour of an omnivorous bird varies in mixed-species groups

In mixed-species groups (MSGs), individuals from different species may locate and communicate about the presence of predators and prey quickly and accurately but may compete for food and favourable positions in the flock. Thus, foraging behaviour is likely to change when individuals participate in MSGs compared with single-species groups (SSGs). In a highly seasonal tropical environment, the foraging behaviour of omnivorous birds may also vary with fluctuations in food availability, weather, and breeding conditions. Here, we observed the foraging behaviour (food item consumed and foraging substrate) of an insectivorous-granivorous songbird, the Coal-crested finch (Charitospiza eucosma), in a savanna in central Brazil, while simultaneously sampling the grass seed production. Birds were more likely to consume grass seeds and forage on lower vertical strata (i.e., ground or herbaceous layers) in MSGs than in other social contexts (SSGs, pair or alone), suggesting they are facing interference competition from other species in MSGs or obtaining antipredator benefits in MSGs that enable them to explore preferred food resources in microhabitats more exposed to predators. As expected, Coal-crested finches were more likely to feed on grass seeds and forage on lower vertical strata when grass seed production is abundant, suggesting that they switch their diet according to the availability of their main food items: grass seeds and invertebrates. Weather and breeding seasonalities had small effects on foraging behaviour. Our results show that MSGs may have a major role in the foraging behaviour of omnivorous birds even considering the seasonal mismatching of their main food items.

Relative food abundance predicts greater binge-eating symptoms in subsequent hours among young adults experiencing food insecurity: Support for the “feast-or-famine” cycle hypothesis from an ecological momentary assessment study

Food insecurity (FI) may increase risk for binge eating through a “feast-or-famine” cycle, where fluctuations in food availability correspond to alternating periods of food restriction and opportunities for binge eating, but research on this topic is limited. To clarify the relationship between food availability and binge eating in the context of FI, this study examined the association between momentary food security level and subsequent binge-eating symptoms among individuals in food-insecure households and investigated how this association differs by factors that may modify the extent to which food availability fluctuates. Ecological momentary assessment data were collected in 2020–2021 from 75 young adults (Mage = 25.3 ± 1.8 years; 72% female; 72% Black, Indigenous, or a Person of Color) in the United States who had experienced past-month household FI. For 14 days, participants reported four times per day on food security and eating episodes, and binge-eating symptoms were assessed for each reported eating episode. About 35% of the variance in momentary food security ratings was accounted for by within-person variability over time. A significant within-person association was observed in multilevel analyses, indicating that instances of greater food security relative to one's average level predicted greater subsequent binge-eating symptoms. Moderation analyses revealed that this association was significant only among individuals reporting use of food assistance programs, high engagement in resource trade-off coping strategies (e.g., skipping bill payments to buy food), or low food security-related self-efficacy. Overall, findings offer support for the “feast-or-famine” cycle hypothesis as an explanation for the link between FI and binge eating, emphasize the importance of identifying approaches to promote more stable access to adequate food, and suggest potential intervention targets to reduce risk for binge eating in populations experiencing FI.

Long-term demographic dynamics of a keystone scavenger disrupted by human-induced shifts in food availability.

Scavenging is a key ecological process controlling energy flow in ecosystems and providing valuable ecosystem services worldwide. As long-lived species, the demographic dynamics of vultures can be disrupted by spatiotemporal fluctuations in food availability, with dramatic impacts on their population viability and the ecosystem services provided. In Europe, the outbreak of bovine spongiform encephalopathy (BSE) in 2001 prompted a restrictive sanitary regulation banning the presence of livestock carcasses in the wild on a continental scale. In long-lived vertebrate species, the buffering hypothesis predicts that the demographic traits with the largest contribution to population growth rate should be less temporally variable. The BSE outbreak provides a unique opportunity to test for the impact of demographic buffering in a keystone scavenger suffering abrupt but transient food shortages. We studied the 42-year dynamics (1979-2020) of one of the world's largest breeding colonies of Eurasian griffon vultures (Gyps fulvus). We fitted an inverse Bayesian state-space model with density-dependent demographic rates to the time series of stage-structured abundances to investigate shifts in vital rates and population dynamics before, during, and after the implementation of a restrictive sanitary regulation. Prior to the BSE outbreak the dynamics was mainly driven by adult survival: 83% of temporal variance in abundance was explained by variability in this rate. Moreover, during this period the regulation of population size operated through density-dependent fecundity and subadult survival. However, after the onset of the European ban, a 1-month delay in average laying date, a drop in fecundity, and a reduction in the number of fledglings induced a transient increase in the impact of fledgling and subadult recruitment on dynamics. Although adult survival rate remained constantly high, as predicted by the buffering hypothesis, its relative impact on the temporal variance in abundance dropped to 71% during the sanitary regulation and to 54% after the ban was lifted. A significant increase in the relative impact of environmental stochasticity on dynamics was modeled after the BSE outbreak. These results provide empirical evidence on how abrupt environmental deterioration may induce dramatic demographic and dynamic changes in the populations of keystone scavengers, with far-reaching impacts on ecosystem functioning worldwide.

Fish thieves: An alternative tactic of food capture in a Neotropical frugivorous species (Brycon falcatus)

AbstractFrugivorous fishes switch their diets seasonally in response to fluctuating food availability; a strategy that maximizes energy and nutrient intake and reduces competition for food. Kleptoparasitism is a form of competition that involves the stealing of already‐procured items, for which the host has invested energy in prey capture. We did not find previous studies on kleptoparasitism among Neotropical fish. Here we contribute the first record of kleptoparasitism among a frugivorous fish species. The matrinxã (Brycon falcatus) is a member of an iconic genus of broadly distributed frugivorous fishes. We made focal daylight underwater observations (by snorkeling) of frugivorous fish behavior in an Amazonian stream. Opportunistic feeding interactions between a school of juvenile matrinxã, (B. falcatus) and an individual of threespot leporinus (Leporinus friderici) were observed. The matrinxã stole the fruit that was captured in the substrate by the leporinus. Brycon falcatus usually lives between the middle of the water column to the surface of rivers and streams while Leporinus friderici occupies the lower portion of the water column and it actively forages close to the substrate. This suggests that stealing food from a benthic feeder is an opportunistic ecological interaction to take advantage of scarce resources during the period of food scarcity. This alternative technique of capturing fruits may be advantageous (i.e., save energy expenditures related to searching) for young matrinxã who do not eat fruit as frequently as adults. Our results reflect the trophic plasticity and foraging opportunism characteristic of most tropical freshwater fish. We believe that the hydrological period in which the observations were made, when a few trees were bearing fruit, can favor fruit stealing by Brycon falcatus.

The effects of feeding ration and cheliped autotomy on the growth and expression of ecdysteroid receptor in early juvenile mud crabs, Scylla paramamosain

This study investigated the combined effects of feeding ration and cheliped autotomy on the intermolt duration, molting success, molt increments in size and weight, and ecdysteroid receptor gene (SpEcR) expression of early juvenile mud crab Scylla paramamosain. Newly molted second stage juvenile crabs (C2) were subjected to four feeding conditions; optimal, suboptimal (1/2 optimal), low (1/4 optimal) ration and starvation, and autotomy (intact vs. cheliped autotomy) in a 4 × 2 factorial design until all crabs successfully molted or died. A significant interaction of feeding ration and cheliped autotomy on intermolt duration was identified. With reduced feeding ration, both intact and cheliped autotomized crabs showed increased time and desynchrony of molting, but decreased carapace size and body weight. Importantly, all crabs with different feeding rations even the low ration had high rates of molting success (> 95%), while the crabs subjected to starvation died without molting. When fed optimal ration, the mean intermolt duration of the cheliped autotomized crabs was significantly prolonged, while no such effect was found between autotomized and intact crabs subjected to suboptimal or low feeding ration. The qRT-PCR revealed that the expression of SpEcR showed a general trend of inhibited by reduced feeding ration, which was consistent with observed significantly increased intermolt duration. Interestingly, the transcript level of SpEcR was only significantly affected by cheliped autotomy under the optimal and suboptimal feeding rations but not for the low feeding ration. Together, the results of this study suggest that the S. paramamosain early juveniles have a strong tolerance for fluctuations in food availability. In addition, the availability of food and limb autotomy could significantly affect growth, molting duration and synchrony of the crabs, which appeared to reflect in SpEcR expression level that involved in the regulation of molting and limb regeneration process of the juvenile crabs.

Resource Availability, Sex, and Individual Differences in Exploration Drive Individual Diet Specialization.

AbstractIndividual diet specialization (IDS) is widespread and can affect the ecological and evolutionary dynamics of populations in significant ways. Extrinsic factors (e.g., food abundance) and individual variation in energetic needs, morphology, or physiology have been suggested as drivers of IDS. Behavioral traits like exploration and boldness can also impact foraging decisions, although their effects on IDS have not yet been investigated. Specifically, variation among individuals in exploratory behavior and their position along the exploration/exploitation trade-off may affect their foraging behavior, acquisition of food items, and home range size, which may in turn influence the diversity of their diet. Here, we analyzed stable carbon and nitrogen isotopes in hair of wild eastern chipmunks, Tamias striatus, to investigate the influence of individual differences in exploration on IDS. We found that exploration profile, sex, and yearly fluctuations in food availability explained differences in the degree of dietary specialization and in plasticity in stable carbon and stable nitrogen over time. Thus, consistent individual differences in exploration can be an important driver of within-population niche specialization and could therefore affect within-species competition. Our results highlight the need for a more thorough investigation of the mechanisms underlying the link between individual behavioral differences and diet specialization in wild animal populations.

Food restriction delays breeding and affects insulin‐like growth factor‐1, oxidative damage and haematocrit value before egg‐laying in female canaries

Environmental challenges, such as fluctuations in food availability, could influence reproductive investment. If resource availability is poor, individuals need to decide in which life‐history process they invest more energy and vital compounds, which determine the cost of reproduction. In resource allocation, the physiological pathways have important roles. The aim of our study was to examine whether food availability influenced physiological traits (insulin‐like growth factor‐1 (IGF‐1) concentration, antioxidant capacity (OXY), level of oxidative damage (ROM) and haematocrit value) prior to egg‐laying in female canaries Serinus canaria. We also tested whether these physiological traits were associated with traits reflecting the reproductive investment in egg macro‐ (egg mass and yolk mass) and micronutrient content (eggshell biliverdin‐ and protoporphyrin‐based colouration). To test these questions we conducted a food restriction experiment with control and food‐restricted (72% of control food) groups. Our study showed that food‐restricted canary females delayed egg‐laying and the physiological traits differed between the groups. At the pre‐laying period, after 9–11 days of treatment, a reduction in plasma IGF‐1 concentration, ROM level and haematocrit value was detected in the control group, whereas in the food‐restricted group plasma IGF‐1 concentration increased, while ROM level and haematocrit value did not change. Plasma level of OXY was not influenced by treatment or breeding period. Plasma concentration of IGF‐1, haematocrit value and oxidative status before egg laying did not affect the egg characteristics. Our study highlights the importance of breeding stage when studying and interpreting the effects of food restriction on physiological traits of breeding birds. Moreover, our data suggest that nutritional limitation had an effect on the timing of egg‐laying that could be mediated by changes in physiological variables.

Seasonal patterns in behavior and glucocorticoid secretion of a specialist Holarctic tree squirrel (Sciurus aberti).

Seasonally breeding mammals must make constant adjustments in behavior and physiology to manage energetic trade-offs between survival and reproduction. Despite encountering high levels of climate and resource variability across the year, specialist Abert's squirrels (Sciurus aberti), lack the capacity to express hibernation or pronounced morphological adaptations to seasonality. Using accelerometer and GPS devices, we assessed how abiotic environmental factors, reproduction, and resource abundance influenced levels of activity and daily range size in a rural and food-supplemented suburban population of squirrels. We also quantified fecal cortisol metabolites (FCM) in squirrels to assess patterns of glucocorticoid secretion. While changes in weather predicted activity levels in both populations, seasonal variation in activity levels were reduced in food-supplemented compared to rural squirrels. In contrast to activity, daily range size was not affected by weather but was a better predictor of sex-specific reproductive investment. Comparisons between populations suggest that food-supplemented squirrels forage more efficiently within smaller areas. Across both sexes and populations, squirrels showed no sexual dimorphism in body size, no major patterns of seasonal weight change, and no associations between body mass and FCM concentrations; however, FCMs were lower in the food-supplemented compared to rural population during late-spring. Taken together, activity levels and FCM concentrations appear primarily influenced by weather and seasonal fluctuations in food availability, whereas daily range size reflects sexual asymmetries in seasonal reproductive investment. Overall, squirrels appear to rely largely on behavioral adjustments to cope with novel environmental heterogeneity, rather than changes in morphology or GC secretion.

Chimpanzee (Pan troglodytes schweinfurthii) grouping patterns in an open and dry savanna landscape, Issa Valley, western Tanzania

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.

First report of the order Mysida (Crustacea) in Antarctic marine ice caves, with description of a new species of Pseudomma and investigations on the taxonomy, morphology and life habits of Mysidetes species.

SCUBA diving explorations of three islands off Dumont d’Urville Station at the coast of Adélie Land, East Antarctica, enabled the observation of marine ice caves. Sampling in this unusual habitat yielded a total of three species of Mysidae, altogether previously poorly known or unknown to science. Pseudommakryotroglodytumsp. nov. is described, based on the structure of the antennal scale, telson and on cornea-like lateral portions set off against the main body of eyeplates. Mysidetesilligi is re-established at species level after almost a century in synonymy. Re-descriptions are provided for M.illigi and M.hanseni, based on types and ice cave materials. Keys to the Southern Ocean species of Pseudomma and to the world-wide species of Mysidetes are given.Phylogenetic trees are provided for the genera Pseudomma and Mysidetes. 18S rDNA sequences of P.kryotroglodytum differ from GenBank sequences of other Pseudomma species. First sequence data are given for species of the genus Mysidetes: 18S differs between the two examined species and COI is quite diverse between and within species.We found previously unknown, probably sensorial structures in these ice cave species: in P.kryotroglodytum, the basal segment of the antennula shows a pit-like depression with striated pad on the bottom and a median cyst, connected with the bottom of the eyeplate cleft. M.illigi shows a female homologue of the appendix masculina bearing a field of modified setae. Subsequent investigations demonstrated these structures also in species from other habitats.The feeding apparatus and stomach contents of the three ice cave species point to brushing of small particles (detritus, microalgae) from available surfaces, such as sediment, rock and the ice surface. Differences in the feeding apparatus are very subtle between the two Mysidetes species. The high content of fat bodies in M.hanseni could help it to survive periods of starvation. The large storage volume of the foregut in P.kryotroglodytum points to the collection of food with low nutritional quality and could help to balance strongly fluctuating food availability.Summer specimens of M.hanseni showed a bimodal frequency of developmental stages in the marsupium and bimodal size-frequency distribution of free-living stages. The females with younger brood (embryos) were, on average, larger and carried more marsupial young than those with older brood (nauplioid larvae). All examined incubating and spent females showed (almost) empty foreguts and empty ovarian tubes, suggesting possible semelparity and death following the release of young. The absence of juveniles and immature females from summer samples suggests that growth and accumulation of fat and yolk occur outside ice caves, while such caves could be used by fattened adults as shelter for brooding. A provisional interpretation proposes a biannual life cycle for M.hanseni, superimposed with shifted breeding schedules, the latter characterised by early breeding and late breeding females, probably in response to harsh physical and trophic conditions along the continental coast of Antarctica.