Periods Of Food Scarcity Research Articles

Isoniazid-associated pellagra during mass scale-up of tuberculosis preventive therapy: a case-control study

Pellagra is caused by niacin (vitamin B3) deficiency and patients with pellagra present with a characteristic rash. Isoniazid disrupts intracellular niacin synthesis and might induce niacin deficiency. In 2017, Malawi scaled up continuous isoniazid preventive treatment (IPT) for tuberculosis prevention among people living with HIV. In addition, an under-diversified diet based on subsistence maize, as is commonly the case in Malawi, is a risk factor for pellagra. We aimed to investigate whether large-scale isoniazid exposure in Malawi contributed to the cumulative risk for pellagra in a nutritionally vulnerable population. We did a matched case-control study to evaluate the association between daily, continuous isoniazid exposure and pellagra. We matched sequentially enrolled patients with pellagra each with four control participants by sex and age from referral dermatology centres in three IPT scale-up districts in Malawi (Lilongwe, Blantyre, and Zomba) to evaluate isoniazid as a risk for pellagra using multivariable conditional logistic regression. We established a community clinic referral system surrounding the dermatology clinic in each district to enhance case-finding and included all patients with pellagra, regardless of referral status. The primary outcome was dermatologist-diagnosed pellagra. We calculated the interval between isoniazid initiation and rash onset and assessed 30-day clinical outcomes after multi-B vitamin treatment containing 300 mg nicotinamide daily. Between Feb 5 and Aug 9, 2019, we enrolled 197 patients with pellagra and 781 matched controls. Isoniazid exposure was associated with an increased risk of pellagra (adjusted odds ratio 42·6 [95% CI 13·3-136·6]). Significant covariates included HIV infection, referral status, food insecurity, underweight, excess alcohol consumption, and, among women, lactation. The median time from isoniazid initiation to rash onset was shorter during the season of food scarcity (5 months [IQR 3-7]) compared with the harvest season (9 months [8-11]; hazard ratio 7·2 [95% CI 3·2-16·2], log-rank p<0·0001). Those with isoniazid-associated pellagra who discontinued isoniazid and adhered to multi-B vitamin treatment showed 30-day clinical improvement. Continuous IPT scale-up and the annual period of food scarcity both increased the risk of pellagra in Malawi. Use of shorter rifamycin-based regimens for tuberculosis prevention and food fortification in populations with undernutrition might reduce this risk. Niacin-containing multi-B vitamin co-administration with isoniazid as pellagra prevention is worth exploring further. This study was supported by the President's Emergency Plan for AIDS Relief through the US Centers for Disease Control and Prevention under project 7173.

Routes matter: the effect of seasonality on bamboo lemur navigational strategies

Seasonal environments challenge animals, increasing the complexity of locating resources. Navigation may rely on ‘habitual routes’ or ‘Euclidean’ maps: following established routes or computing novel paths, respectively. Folivores are presumed to rely on evenly distributed resources and thus have a reduced reliance on navigation. We tested whether the navigation strategy of southern bamboo lemurs, Hapalemur meridionalis , a primarily folivorous strepsirrhine that periodically consumes fruit, varies across seasons. We recorded behaviour and location of three social groups during full-day, focal follows during January–December 2013. We analysed the macronutrient components of food items. Bamboo lemurs travelled through habitual routes during periods of food scarcity but relied on nodes (i.e. intersections where directional decisions are made) to navigate throughout the year. Likely, habitual route navigation promoted an energy-saving strategy during lean periods by easing lemur locomotion across the forest. In contrast, lemurs relied on Euclidean navigation during food abundant periods. The continuous use of nodes suggest that nodes may act as cognitive anchors to support efficient directional decisions across seasons. Linearity increased during periods of resource abundance when feeding on energy-rich items and during periods of scarcity to reach latrines. By travelling increasingly linearly towards energy-rich items, lemurs maximized energy intake during periods of food abundance. Overall, bamboo lemurs' combination of both Euclidean and route-based navigational strategies demonstrates a cognitive adaptation for coping with seasonal resource variability in a way that challenges previous research postulating constrained spatial skills in folivorous strepsirrhines. • Route navigation and Euclidean skills are not necessarily exclusive. • Seasonal landscapes likely favour the combination of both navigation strategies. • Bamboo lemurs relied on habitual routes during food scarcity periods. • Bamboo lemurs travelled more linearly off-route during food abundant periods. • Cognitive evidence from lemur navigation supports the energy frugality hypothesis.

Neural Circuits Involved in Torpor and Hibernation and Prospects for Artificial Hibernation Technology

Mammals and birds are categorized as thermostatic animals and consume significant quantities of energy to maintain their body temperature. Body temperature in mammals is usually maintained within a narrow range of 36-37℃ despite fluctuations in the external temperature. However, during periods of food scarcity, which leads to a diminished source of energy, such as in winter, some species adopt a strategy to overcome the energy shortage by lowering their body temperature, which significantly reduces their basal metabolism (energy demand). This phenomenon is referred to as hibernation or torpor. Although physiological functions are greatly reduced, the animals can safely recover from prolonged periods of hibernation. This function is not only biologically interesting but also has potential applications in medicine, including in emergency medicine and in future human space exploration. In this paper, I have discussed the mechanisms underlying hibernation with regard to neural circuits that induce hypothermia, which currently remain unclear and the possibility of artificial hibernation in the future.

Evaluating adaptive hypotheses for female-led infanticide in wild chimpanzees

Although rare among group-living primates, infanticide by females has been reported in several chimpanzee, Pan troglodytes, populations. We examined 13 infanticidal attacks over 47 years at Gombe National Park, Tanzania to evaluate three adaptive hypotheses. (1) Exploitation of the infant as a food resource – by eating a vulnerable neonate, attackers gain calories that may be important during periods of food scarcity or energetic stress. (2) Resource competition – Gombe females concentrate their foraging in overlapping core areas and dominance rank influences foraging success. By killing the infant of a female with high core area overlap, the perpetrator removes a current and future competitor, improving her access to food. (3) Low cost – female chimpanzees mature and reproduce slowly, and longevity increases reproductive success. Physical aggression causes risk of severe injury or death, so females will only mount attacks when risks to the perpetrator are low. In support of hypothesis 1, females usually consumed the carcass. However, attacks were not more likely in times of resource or energy scarcity. In support of hypothesis 2, females attacked others with whom they shared core areas, but attacks did not cause shifts in ranging patterns. In support of hypothesis 3, one or more attackers always outranked the victim, the attacks often involved coalitions and victims usually lacked kin support. Attacks were more likely to be successful when attackers were not hindered by clinging infants and victims could not retreat. Our results provide further evidence for female competition and the adaptive value of female-led infanticide in this species.

Consumption of insect and plant exudates by mouse lemurs

While exploring Isalo National Park in southcentral Madagascar, we observed numerous nymphs and adults of the endemic flatid leaf bug (Phromnia rosea). As in many other hemipterans (including aphids, scale insects, and leafhoppers), nymphs of these leaf bugs feed on phloem and expel a liquid endearingly termed “honeydew” from their anuses. This sugary substance drops onto leaves and stems. In northwestern Madagascar, the gray mouse lemur (Microcebus murinus), golden-brown mouse lemur (Microcebus ravelobensis), Madame Berthe’s mouse lemur (Microcebus berthae, the world’s smallest primate, found only in a small area in western Madagascar), and ring-tailed lemur (Lemur catta, which are in a different family from the others) mostly consume honeydew and plant-based exudates such as gums during the dry season. Honeydew could be a critical resource during periods of food scarcity (Joly-Radko and Zimmerman 2010; doi.org/10.1007/978-1-4419-6661-2_7), and lemurs are the only mammals ever documented to eat honeydew. Precious little is known about most of the mouse lemurs, and until the late 20th century only one species was recognized – now, more than 20 are known. However, collecting field data on flatid leaf bugs and mouse lemurs is challenging. Future studies could determine whether exudates account for a substantial fraction of their calories in the dry season, and if dietary shifts are accompanied by changes in the lemurs’ gut microbiota.

Dental microwear textures differ in pigs with overall similar diets but fed with different seeds

The thick-enameled, bunodont dentition shared by most early hominins has traditionally been interpreted as reflecting durophagy, especially in the robust genus Paranthropus. However, subsequent works on dental microwear textures (DMT) and biogeochemical compositions have challenged this hypothesis. Some authors argued that their robust morphology might have been driven by the consumption of mechanically challenging resources during periods of food scarcity. An experimental baseline using a model taxon with bunodont, thick-enameled cheek teeth, could help better interpret DMT and test hypotheses regarding the consumption of mechanically challenging foods that could be fallback foods. Besides, earlier studies have shown that DMT can track subtle dietary variations in extant taxa. This study aims at testing the hypothesis that the consumption of various seeds has an impact on DMT of bunodont mammals despite similar overall diets. Trials were conducted on four groups of domestic pigs (Sus scrofa) all fed on mixed cereal and soy flours: the control group received only flours (n = 12), and the three others were supplemented with either 20% corn kernels (n = 6), 30% barley seeds (n = 5), or 10 hazelnuts in shell per day (n = 6). We studied phases I and II facets on first molars and on fourth deciduous premolars, and applied a subsampling surface strategy to identify discriminative parameters among dietary groups. Principal Component Analyses show that DMT differ between pigs fed on different types of seeds. Our results also demonstrate that combining both crushing and shearing facets into analyses improves dietary discriminations. This study shows that variables that contribute most to dietary discriminations as selected from the subsampling strategy are mainly height parameters. These results thus support the idea that the consumption of seeds has an impact on the relief of surface textures.

Quality of hydroponic forage corn cultivated on different by-product substrates

Abstract Hydroponic corn cultivation is an efficient, fast, and feasible alternative for periods of food scarcity; however, there is still little information on the qualitative and quantitative parameters of the produced biomass, especially with regard to substrates. This study aimed to evaluate the productive and qualitative aspects of hydroponic feed corn grown on different substrates with a cultivation period of 15 days. Four substrates were evaluated: 1) fermented whole açaí seeds, 2) crushed açaí seeds, 3) sugarcane bagasse, and 4) ground Tifton hay, with five replications under a randomized block design. Substrate temperature was monitored during the production period. After harvesting on day 15, roots length (RL), shoot length (SL), biomass dry matter content (BDM), dry biomass yield, forage dry mass productivity, crude protein (CP), and ash content were assessed. There was no correlation of growth period and substrate temperature. RL was not affected by substrates, BDM was lower in treatment 3, CP was not influenced, and ash content was higher in treatment 1. In general, the best development was observed in treatment 1 because of the absence of distinction regarding qualitative parameters (CP and ash) and higher granulometry of whole açaí seeds which affects mass density and substrate aeration, thus allowing higher dry biomass yield.

Acclimation temperature affects thermal reaction norms for energy reserves in Drosophila

Organisms have evolved various physiological mechanisms to cope with unfavourable environmental conditions. The ability to tolerate non-optimal thermal conditions can be substantially improved by acclimation. In this study, we examined how an early-life acclimation to different temperatures (19 °C, 25 °C and 29 °C) influences thermal reaction norms for energy stores in Drosophila adults. Our results show that acclimation temperature has a significant effect on the amount of stored fat and glycogen (and their relative changes) and the optimal temperature for their accumulation. Individuals acclimated to 19 °C had, on average, more energy reserves than flies that were initially maintained at 25 °C or 29 °C. In addition, acclimation caused a shift in optimal temperature for energy stores towards acclimation temperature. We also detected significant population differences in this response. The effect of acclimation on the optimal temperature for energy stores was more pronounced in flies from the temperate climate zone (Slovakia) than in individuals from the tropical zone (India). Overall, we found that the acclimation effect was stronger after acclimation to low (19 °C) than to high (29 °C) temperature. The observed sensitivity of thermal reaction norms for energy reserves to acclimation temperature can have important consequences for surviving periods of food scarcity, especially at suboptimal temperatures.

Seabird‐induced natural mortality of forage fish varies with fish abundance: Evidence from five ecosystems

AbstractForage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top‐down processes exerted by seabirds on forage fish stocks in five contrasted marine ecosystems, compiling numerous data sets on seabird counts, diets, energetic needs and prey energy content and abundance. Off Norway, South Africa, Peru, Sweden and Scotland, we found that predation pressure—estimated as the proportion of a fish stock consumed by seabirds—was generally low (median = 1%), but increased sharply at low levels of prey abundance. When prey biomass decreased below 15–18% of its maximum recorded value, predation by seabirds became a source of important additional pressure on prey stocks (~20% of prey biomass is consumed by seabirds). An earlier empirical study advocated for keeping forage stocks from falling below a threshold of 33% of long‐term maximum prey biomass in order to safeguard seabird breeding success, but here we further suggest that a threshold of 18% should be considered as a limit not to be exceeded for the sake of the forage fish themselves, and below which extra cautious management of fisheries may be required. Nevertheless, despite exceptionally high rates of predation on some occasions, predation pressure was not correlated with prey dynamics, suggesting an absence of prey entrapment due to seabirds alone in these five ecosystems.

Exogenous ethanol induces a metabolic switch that prolongs the survival of Caenorhabditis elegans dauer larva and enhances its resistance to desiccation.

The dauer larva of Caenorhabditis elegans, destined to survive long periods of food scarcity and harsh environment, does not feed and has a very limited exchange of matter with the exterior. It was assumed that the survival time is determined by internal energy stores. Here, we show that ethanol can provide a potentially unlimited energy source for dauers by inducing a controlled metabolic shift that allows it to be metabolized into carbohydrates, amino acids, and lipids. Dauer larvae provided with ethanol survive much longer and have greater desiccation tolerance. On the cellular level, ethanol prevents the deterioration of mitochondria caused by energy depletion. By modeling the metabolism of dauers of wild‐type and mutant strains with and without ethanol, we suggest that the mitochondrial health and survival of an organism provided with an unlimited source of carbon depends on the balance between energy production and toxic product(s) of lipid metabolism.

Capacités cognitives associées aux stratégies de recherche de nourriture chez les hominines plio-pléistocènes : vers de nouvelles perspectives à partir du cortex préfrontal ventromédian

Feeding and foraging behaviors can exert selective pressures among heterotrophic organisms that lead to morphological, physiological, and/or behavioral adaptations. Several studies showed that primates use complex cognitive abilities to adjust foraging strategies taking into account specific spatio-temporal context and already experienced events. Thus, it has been suggested that complex foraging strategies had a strong influence on the evolution of some cognitive abilities among primates, such as value-based decision-making. Following recent results showing that a cortical area, the ventromedial prefrontal cortex (VMPFC), is strongly associated with value-based decision-making, we previously explored the relationship between this region and ecological parameters (such as daily path length, mean group size, dietary quality) in extant primates. Among the five species studied (Macaca mulatta, M. fuscata, Gorilla gorilla, Pan troglodytes and Homo sapiens), those with broader diets and more complex foraging strategies exhibit a bigger VMPFC than species with a less diversified diet. We suggested that the capacity to switch foraging behaviors using memorized information may have been particularly favored among hominins of the Late Pliocene and especially Early Pleistocene, a period marked by several time intervals of increased climatic instability. Indeed, as these hominins faced critically changing environments, the ability to switch foraging behaviors and to fall back on alternative resources during periods of food scarcity probably played a strong influence on their diversity and evolution. This paper discusses the potential of a focus on the VMPFC to provide new insights into the evolution of foraging strategies and associated cognitive abilities (such as value-based decision-making) among hominins. As endocranial casts are the only available material to study brain anatomy on fossils, possible ways to measure this region from external cerebral markers are discussed.

Sustainable Peeling of Kapok Tree (Ceiba pentandra) Bark by the Chimpanzees (Pan troglodytes verus) of Como\xe9 National Park, Ivory Coast

Primates often consume either bark or cambium (inner bark) as a fallback food to complete their diet during periods of food scarcity. Wild chimpanzees exhibit great behavioral diversity across Africa, as studies of new populations frequently reveal. Since 2014, we have been using a combination of camera traps and indirect signs to study the ecology and behavior of wild chimpanzees (Pan troglodytes verus) in Comoé National Park, Ivory Coast, to document and understand the behavioral adaptations that help them to survive in a savanna–forest mosaic landscape. We found that Comoé chimpanzees peel the bark of the buttresses of kapok tree (Ceiba pentandra) trees to eat the cambium underneath. Individuals of all sex/age classes across at least six neighboring communities peeled the bark, but only during the late rainy season and beginning of the dry season, when cambium may represent an important fallback food. Baboons (Papio anubis) also target the same trees but mainly eat the bark itself. Most of the bark-peeling wounds on Ceiba trees healed completely within 2 years, seemingly without any permanent damage. We recorded chimpanzees visiting trees in early stages of wound recovery but leaving them unpeeled. Only 6% of peeled trees (N = 53) were reexploited after a year, suggesting that chimpanzees waited for the rest of the trees to regrow the bark fully before peeling them again, thus using them sustainably. Many human groups of hunter-gatherers and herders exploited cambium sustainably in the past. The observation that similar sustainable bark-peeling behavior evolved in both chimpanzees and humans suggests that it has an important adaptive value in harsh environments when other food sources become seasonally scarce, by avoiding the depletion of the resource and keeping it available for periods of scarcity.

Potential of Neglected and Underutilized Yams (Dioscorea spp.) for Improving Nutritional Security and Health Benefits.

Food and nutritional security are the major concerns in many countries of the world and may have potential to contribute to sustainable food systems under climate change. To address the food and nutritional insecurity, it has become extremely important to diversify the present-day agricultural system as well as to search for alternative food and feed ingredients. Some wild root and tuber crops occupy a remarkable position toward food security of the developing world due to their high calorific value and superior carbohydrate content. Yam (Dioscorea spp.) provides food and medicines to millions of people in the world especially in the tropics and sub tropics. It is recognized as the fourth most important tuber crop after potatoes, cassava, and sweet potatoes. It contributes about 10% of the total root and tubers production around the world. Yams also considered as famine food and plays a prime role in the food habit of small and marginal rural families and forest-dwelling communities during the food scarcity periods. These species are unique for their food, medicinal and economic values but their wider utilization is limited due to the presence of anti-nutritional compositions. This paper describes the ethnobotany of yam species in relation to their nutritional, anti-nutritional and pharmacological properties and highlights the potentiality for food and nutritional security for combating the “hidden hunger” caused by micronutrient deficiencies.

Stingless Bees (Melipona subnitida) Overcome Severe Drought Events in the Brazilian Tropical Dry Forest by Opting for High-Profit Food Sources.

In the Brazilian Tropical Dry Forest, the Caatinga, stingless bees (Apidae, Meliponini) need to adjust their foraging behavior to a very short and unpredictable blooming period. Melipona subnitida Ducke 1910 is one of the few meliponine species adapted to the environmental peculiarities of this biome. To get an insight into how these highly eusocial bees are able to maintain their perennial colonies despite extended periods of food scarcity, we asked the following questions: (1) At which plant species do colonies of M. subnitida collect their food during the rainy season? And (2) are there any plant species during the dry season, from which the colonies may profit for replenishing their food stores? During 1year, we collected monthly honey and pollen samples from recently built storage pots of five colonies of M. subnitida and identified the botanical origin of the collected resources. In the course of our study, the colonies foraged at native trees, shrubs, and herbaceous species, demonstrating the importance of all plant strata for the bees' diet. Profitable plants, which bloom mainly during the rainy season and usually produce a great number of flowers, were frequently sampled in new pots throughout the entire study, even during the dry season. From our results, we compiled a list of the most important plant species providing floral resources for bees throughout the year, including periods of drought. We recommend these plants for restoration areas to improve the conservation of native bee species and local beekeeping in the Brazilian Tropical Dry Forest.

Responses to Spatial and Temporal Variation in Food Availability on the Feeding Ecology of Proboscis Monkeys (Nasalis larvatus) in West Kalimantan, Indonesia

Folivorous primates have long been assumed to experience food competition less acutely than frugivores due to their ability to eat leaves, an abundant resource in most forest systems. Consequently, the behavioural responses of leaf-eating primates to variation in food availability are less well characterised than those of frugivores. Recent empirical studies have demonstrated that many colobine species are more affected by food availability and distribution than previously thought; they employ multiple strategies to survive during periods of food scarcity. We studied a population of proboscis monkeys (Nasalis larvatus) over 16 months in three forest types in West Kalimantan, Indonesia, to examine their responses to temporal fluctuation and spatial variation in food availability. We examined how feeding behaviour was influenced by the availability of plants in botanical plots to identify important and preferred foods of proboscis monkeys across months and in different forest types. Proboscis monkeys consumed foods from 68 genera, comprising 35% young leaves, 27% unripe fruit, 12% flowers and 6% mature leaves. Consumption of plant parts and genera by proboscis monkeys varied in response to monthly changes in food availability but did not vary among forest types despite substantial differences in phenology and floristics among them. The monkeys preferred unripe fruits and flowers and used young and mature leaves as fallback foods in mangrove forests. Documentation of proboscis monkey responses to variation in food availability contributes to our understanding of how monkeys respond to changes in their environments due to climate change and habitat degradation.

Re-examination of the effects of food abundance on jaw plasticity in purple sea urchins

Morphological plasticity is a critical mechanism that animals use to cope with variations in resource availability. During periods of food scarcity, sea urchins demonstrate an increase in jaw length relative to test diameter. This trait is thought to be reversible and adaptive by yielding an increase in feeding efficiency. We directly tested the hypotheses that (1) there are reversible shifts in jaw length to test diameter ratios with food abundance in individual urchins, and (2) these shifts alter feeding efficiency. Purple sea urchins, Strongylocentrotus purpuratus, were collected and placed in either high or low food treatments for 3 months, after which treatments were switched for two additional months in La Jolla, CA (32.8674°N, 117.2530°W). Measurements of jaw length to test diameter ratios were significantly higher in low compared to high food urchins, but this was due to test growth in the high food treatments. Ratios of low food urchins did not change following a switch to high food conditions, indicating that this trait is not reversible within the time frame of this study. Relatively longer jaws were also not correlated with increased feeding efficiency. We argue that jaw length plasticity is not adaptive and is simply a consequence of exposure to high food availability, as both jaw and test growth halt when food is scarce.

Diets of native and introduced tree squirrels in Washington

ABSTRACTCompetition for food resources can be a primary mechanism for displacement of native species by introduced species. Investigation of dietary partitioning between potential competitors and spatiotemporal variability in food resources can reveal contested food items and intensity of competition. Introduced eastern gray squirrels (Sciurus carolinensis) have been implicated as competitors with western gray squirrels (S. griseus) and Douglas’ squirrels (Tamiasciurus douglasii), but little is known about interactions among these species. We collected foraging observations and fecal pellets of sympatric gray and Douglas’ squirrels trapped and radio‐tracked in western Washington, USA, from 2007 to 2012. We compared food resources consumed across species, seasons, and years to evaluate dietary overlap and the potential for competitive interactions. All squirrel species ate hypogeous fungi throughout all seasons; spores of several genera were present in 272 of 275 fecal samples and observed in all months. Rhizopogon, Geopora, and Melanogaster spp. occurred in most fecal pellets for all squirrels, but the diet of the Douglas’ squirrels had slightly lower richness of hypogeous fungi than gray squirrels. Although foraging observations suggest that eastern and western gray squirrels shared important dietary items such as acorns, strong differences in consumption of seeds of a common conifer may facilitate their coexistence. Our results suggest that dietary overlap among arboreal squirrels could lead to competitive interactions during periods of food scarcity, but subtle differences may be sufficient to permit long‐term coexistence. Tree squirrels in Washington would likely benefit from forest management practices that promote or sustain robust crops of hypogeous fungi. © 2019 The Wildlife Society.

Seasonal Shifts in Gut Microbiota‐Mediated Nitrogen Recycling in 13‐Lined Ground Squirrels

Hibernation is a complex phenotype that enables animals to fast for several months during periods of food scarcity. During this time, less of the hibernator's protein is degraded than would be predicted and, in the 13‐lined ground squirrel (Ictidomys tridecemlineatus), muscle volume and protein synthesis rise near the end of the hibernation season despite continued fasting and loss of body mass. With no exogenous nitrogen intake, one nitrogen source to support protein synthesis in late winter could be from urea nitrogen salvage (UNS), a nitrogen recycling process mediated by the ureolytic activity of the hibernator's gut microbiota. We hypothesized that the contribution of UNS to skeletal muscle growth in 13‐lined ground squirrels increases over the hibernation season, and tested this by comparing UNS processes in summer, early hibernation (1 month), and late hibernation (&gt;3 months) squirrels. Data collected thus far suggest that expression of the urea transporter (UT‐B) in cecal tissue is 3‐fold greater in late winter than in summer squirrels (P&lt;0.001; n=12 per group), indicating a greater capacity for transport of urea into the cecum during winter fasting. Real‐time measurement of microbial ureolytic activity using cavity ring‐down spectrometry on squirrels I.P.‐injected with 13C,15N‐labeled urea confirmed the bacterial origin of UNS, because δ13C in breath is substantially reduced in antibiotic‐depleted microbiotas. Isotope ratio mass spectrometry showed that tissues of squirrels treated with 13C,15N‐urea accumulated up to 200x more 15N as saline‐treated control squirrels, confirming that urea‐derived nitrogen is recycled and incorporated into host tissues. Together, these results corroborate UNS in active and hibernating 13‐lined ground squirrels and suggest that this mechanism for nitrogen recycling is a key aspect of the host‐microbe symbiosis in hibernating mammals that helps prepare the squirrels for spring emergence.Support or Funding InformationThis work is supported by NSF award IOS1558044This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Seed harvest by scatter-hoarding yellow pine chipmunks (Tamias amoenus)

Seed-caching rodents store large quantities of seeds during the summer and autumn but the number of stored seeds has rarely been estimated. Understanding how many seeds each individual stores has implications for energetics during the period of food scarcity, and the number of seeds scatter hoarded has implications for how well animals disperse the seed of plants and thereby effect ecological processes. The number of seeds of antelope bitterbrush (Purshia tridentata) and Jeffrey pine (Pinus jeffreyi) scatter hoarded by yellow pine chipmunks (Tamias amoenus) was estimated in a year of good seed production. Both of these plant species are adapted for seed dispersal by scatter-hoarding animals. Individual chipmunks scatter hoarded an estimated 29,629 bitterbrush seeds and 5,945 Jeffrey pine seeds each year. These estimates are likely underestimates and do not include the many thousands of seeds eaten during the harvest period. Combined, the number of seeds of these two species that chipmunks scatter hoard in soil provided 2.8 times more energy than required to survive the autumn and winter. Populations of yellow pine chipmunks have the potential to scatter hoard nearly a million seeds per hectare in good seed years.

The effect of fasting on nutritional status, organs size and isotopic composition in a Neotropical fish species (Jenynsia multidentata)

Digestive flexibility is considered an adaptive response that allows individuals to minimise maintenance costs during periods of food scarcity. Here, we evaluated changes in body condition and digestive (and energy storage) organs size during short-term (7 days) fasting in Jenynsia multidentata. Also, we analysed changes in the isotopic composition and C:N ratio (a proxy of lipids content) in the intestine, liver and muscle. Fasted animals were compared against two feeding groups: field animals and animals fed ad libitum in the laboratory. We found that intestinal length was larger in feeding and field animals than in fasting fish, while intestine and liver masses were heavier in feeding animals, followed by field animals and then by fasting individuals. Liver and intestine δ15N was higher in fasting fish than in field animals, but δ13C did not differ between both groups. Finally, body condition, C:N ratios and perivisceral fat mass, were greater in feeding and field individuals than in fasting animals. This way, our results indicate that (i) changes in digestive and energy storage organs size during fasting in fish are ubiquitous and noticeable, and (ii) nutritional status of animals should be taken in account for a proper interpretation of stable isotope results, particularly for splanchnic tissues (such as intestine and liver).