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Jorge E. Schondube - One of the best experts on this subject based on the ideXlab platform.
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Gut reaction! Neotropical Nectar-Feeding bats responses to direct and indirect costs of extreme environmental temperatures
Journal of Comparative Physiology B, 2020Co-Authors: Stephanie Ortega-garcía, Daniel Ferreyra-garcía, Jorge E. SchondubeAbstract:One of the consequences of anthropogenic climate change is an increase in the frequency and intensity of extreme weather events. These events have caused mass mortality of different species of wildlife, including bats. In this study, we exposed two species of neotropical Nectar-Feeding bats that live in contrasting environmental conditions ( A. geoffroyi and L. yerbabuenae ) to extreme high and low temperatures while offering them diets with different energy content. This experimental approach allowed us to determine their thermal and behavioral responses, and to identify environmental conditions that impose high physiologic costs to these species. To determine how bats' responded, we monitored both changes in their body masses and skin temperatures. Both bat species responded differently, with L. yerbabuenae spending more time in normothermia at high temperatures than A. geoffroyi . While both species presented torpor, they used it differently. Torpor allowed A. geoffroyi to maintain and increase body mass at intermediate and low ambient temperatures. At the same time, L. yerbabuenae used torpor only when facing cold ambient temperatures and low-quality food. Understanding the mechanisms that allow species to face changes in their environment is essential given the current climate trends and the fact that the loss of these species could have significant negative consequences in tropical and subtropical ecosystems.
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The thermal niche of Neotropical Nectar-Feeding bats: Its evolution and application to predict responses to global warming.
Ecology and evolution, 2017Co-Authors: Stephanie Ortega-garcía, Lázaro Guevara, Joaquín Arroyo-cabrales, Roberto Lindig-cisneros, Enrique Martínez-meyer, Ernesto Vega, Jorge E. SchondubeAbstract:The thermal niche of a species is one of the main determinants of its ecology and biogeography. In this study, we determined the thermal niche of 23 species of Neotropical Nectar-Feeding bats of the subfamily Glossophaginae (Chiroptera, Phyllostomidae). We calculated their thermal niches using temperature data obtained from collection records, by generating a distribution curve of the maximum and minimum temperatures per locality, and using the inflection points of the temperature distributions to estimate the species optimal (STZ) and suboptimal (SRZ) zones of the thermal niche. Additionally, by mapping the values of the STZ and SRZ on a phylogeny of the group, we generated a hypothesis of the evolution of the thermal niches of this clade of Nectar-Feeding bats. Finally, we used the characteristics of their thermal niches to predict the responses of these organisms to climate change. We found a large variation in the width and limits of the thermal niches of Nectar-Feeding bats. Additionally, while the upper limits of the thermal niches varied little among species, their lower limits differ wildly. The ancestral reconstruction of the thermal niche indicated that this group of Neotropical bats evolved under cooler temperatures. The two clades inside the Glossophaginae differ in the evolution of their thermal niches, with most members of the clade Choeronycterines evolving "colder" thermal niches, while the majority of the species in the clade Glossophagines evolving "warmer" thermal niches. By comparing thermal niches with climate change models, we found that all species could be affected by an increase of 1°C in temperature at the end of this century. This suggests that even nocturnal species could suffer important physiological costs from global warming. Our study highlights the value of scientific collections to obtain ecologically significant physiological data for a large number of species.
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Effect of diet quality and ambient temperature on the use of torpor by two species of neotropical Nectar-Feeding bats.
The Journal of experimental biology, 2017Co-Authors: Jorge Ayala-berdon, Rommy Vázquez-fuerte, René Beamonte-barrientos, Jorge E. SchondubeAbstract:Neotropical bats use torpor as a strategy to save energy when they experience a low energy intake and/or low ambient temperature (Ta). Digestive physiology limits the energy intake of several glossophaginid bats, and could play an important role in the onset of torpor in these tropical animals. We measured the effect that diet quality and Ta had on the use of torpor by the Nectar-Feeding bats Glossophaga soricina and Leptonycteris yerbabuenae Captive bats were fed with 5% (low) or 35% (high) sucrose solutions while exposed to two different Ta (17.7 and 23.2°C; low Ta and high Ta) in four different treatments: (1) high sucrose:high Ta, (2) high sucrose:low Ta, (3) low sucrose:high Ta and (4) low sucrose:low Ta We measured their energy intake, changes in body mass (ΔMb) and skin temperature (Tskin) as response variables. Energy intake (in 10 h) was limited when both species fed on 5% sucrose, but body mass gain was only affected in G. soricina. Energy intake and Ta had a negative effect on the minimum Tskin of both species, and ΔMb affected the time that G. soricina used torpor. Both species remained normothermic on the high sucrose:high Ta treatment, but used torpor on the other three treatments. Bats used torpor during their resting and activity periods. Leptonycteris yerbabuenae spent more time in torpor in the low sucrose:high Ta treatment, while G. soricina used this strategy for longer periods of time in the high sucrose:low Ta treatment. We found that diet quality and Ta played an important role in the use of torpor by Nectar-Feeding bats.
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A Physiological Perspective on Nectar-Feeding Adaptation in Phyllostomid Bats
Physiological and biochemical zoology : PBZ, 2011Co-Authors: Jorge Ayala-berdon, Jorge E. SchondubeAbstract:AbstractNectar-Feeding animals increase their food intake when Nectar sugar concentration decreases. However, some species present physiological constraints that limit their energy intake when Nectar is diluted. We hypothesized that gut capacities of bats affect the ability of these animals to acquire and store energy, modifying how they use food resources in the field. We measured the food intake and changes in body mass of the members of an assemblage of Nectar-Feeding bats (Choeronycteris mexicana, Leptonycteris yerbabuenae, and Glossophaga soricina) Feeding on sucrose solutions of different concentrations (146, 292, 438, 584, 730, 876, and 1,022 mmol L−1). The three bat species presented differences in their food intake and their capacity to store energy. While C. mexicana was able to maintain a constant energy intake at all concentrations tested, G. soricina and L. yerbabuenae decreased their sugar/energy intake at the lowest sugar concentrations. Choeronycteris mexicana also increased body mass inde...
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Seasonal intake responses in the Nectar-Feeding bat Glossophaga soricina
Journal of Comparative Physiology B, 2009Co-Authors: Jorge Ayala-berdon, Jorge E. Schondube, Kathryn E. StonerAbstract:Food intake in Nectar-Feeding animals is affected by food quality, their energetic demands, and the environmental conditions they face. These animals increase their food intake in response to a decrease in food quality, a behavior named “intake response”. However, their capacity to achieve compensatory Feeding, in which they maintain a constant flux of energy, could be constrained by physiological processes. Here we evaluated how both a seasonal change in environmental conditions and physiological constraints affected the food ingestion in the bat Glossophaga soricina . We measured food intake rate during both the wet/warm and dry/cool seasons at sucrose solutions ranging from 146 to 1,022 mmol L^−1. We expected that food intake and metabolic demands would be greater during the dry/cool season. Bats ingested ~20% more food in the dry/cool than in the wet/warm season. Regardless of season, bats were unable to achieve a constant flux of energy when facing the different sugar concentrations that we used in our experiments. This suggests that the rate of food intake is physiologically constrained in G. soricina . Using the digestive capacity of bats we modeled their food intake. The analytic model we used predicts that digestive limitations to ingest energy should have an important effect on the ecology of this species.
Christian C. Voigt - One of the best experts on this subject based on the ideXlab platform.
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Efficiency of facultative frugivory in the Nectar-Feeding bat Glossophaga commissarisi: the quality of fruits as an alternative food source
Journal of Comparative Physiology B, 2008Co-Authors: Detlev H. Kelm, Juliane Schaer, Sylvia Ortmann, Gudrun Wibbelt, John R. Speakman, Christian C. VoigtAbstract:The efficiency of food exploitation correlates positively with the extent of dietary specialization. Neotropical Nectar-Feeding bats (Glossophaginae) have one of the most specialized diets among mammals, as floral Nectar constitutes a sugar-rich and highly digestible but protein and fiber depleted food source. However, dietary constraints, such as a temporary scarcity of Nectar, or protein demands may sometimes require the uptake of alternative food items. We investigated the influence of a diet switch from Nectar to fruit on intestinal morphology, body mass, and energy budget in the Nectar-Feeding bat Glossophaga commissarisi and quantified Feeding efficiency. We hypothesized that these Nectar specialists depend on a constant supply of Nectar, if they were lacking the ability for morphological and physiological plasticity in response to a fiber-rich diet. Although capable of harvesting infructescences of Piper hispidum , G. commissarisi was less efficient in extracting energy from fruits (48% digestive efficiency of total fruit energy content) than from Nectar (c. 99% digestive efficiency). The intestinal morphology and organ masses did not change after bats were switched from Nectar to fruits. Captive bats exhibited lower daily energy expenditures and flight activity when Feeding on fruits than during Nectarivory. Possibly, this may have been a deliberate regulation to balance reduced Feeding efficiency, or simply the consequence of extended digestive pauses. The low digestibility of Piper, in combination with slow digestion and the bats’ inability for morphological and physiological plasticity may cause Nectar-feeders to reduce their maximum energy expenditure when Feeding on fruits. We argue that although fruits may substitute for Nectar, they may cause restricted maximum energy assimilation compared with Nectar.
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The power requirements (Glossophaginae: Phyllostomidae) in Nectar-Feeding bats for clinging to flowers
Journal of Comparative Physiology B, 2004Co-Authors: Christian C. VoigtAbstract:Nectar-Feeding bats are the heaviest pollinators exploiting flowers in a hovering foraging mode. As hovering flight is considered to be energetically costly, clinging to flowers would be beneficial from an energetic perspective. I examined the rate of oxygen consumption and carbon dioxide release during clinging flower visitation in two 10-g Glossophaga soricina (Glossophinae: Phyllostomidae) to evaluate the potential energetic benefit of clinging versus hovering. In addition, I measured the duration of flower visits of free-ranging glossophagine bats to Markea neurantha (Solanaceae), a bat-pollinated plant that allows both hovering and clinging flower visitation. After 20 s of clinging to an artificial respiratory mask, the bats’ respiratory exchange ratio did not significantly deviate from 1, indicating the combustion of sugar. The average oxygen uptake rate equaled 1.39 ml min^−1 (±0.38 SD, STPD) and the carbon dioxide release rate equaled 1.33 ml min^−1 (±0.20 SD, STPD) for feeder visits longer than 20 s ( n =79). Converting the oxygen uptake rate into power input yielded 0.49 W, less than a third of the power requirements for hovering for a 10-g bat. Free-ranging 10-g glossophagine bats exploited flowers of M. neurantha for, on average, 0.32 s ( ±0.14 SD, n =273) during hovering and for 0.39 s (±0.18 SD, n =152) during clinging visitations. A comparison between the power requirements of flower exploitation in differently sized bats indicates that clinging would benefit larger Nectar-Feeding bats to a greater extent than smaller species.
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Nitrogen stress causes unpredictable enrichments of 15N in two Nectar-Feeding bat species.
Journal of Experimental Biology, 2004Co-Authors: Christian C. Voigt, Felix MattAbstract:SUMMARY We estimated the effect of nitrogen stress on the nitrogen isotope enrichments in wing membrane and blood of two Nectar-Feeding bats ( Glossophaga soricina and Leptonycteris curasoae ) by offering a nitrogen-poor diet with a high δ 15 N andδ 13 C. Before the experiment, bats were sustained on a normal diet with a low δ 15 N and δ 13 C. Under this first food regime, the fractionation of nitrogen isotopes averaged 3.1‰δ 15 N for blood and 4.4‰ δ 15 N for wing membrane, which was almost twice as high as the corresponding fractionation of carbon isotopes. After switching to the nitrogen-poor diet, the enrichment of heavy isotopes increased for both elements in all tissues under study. The recently published estimates of half-life of carbon isotopes indicated a low turnover rate of carbon in wing membrane and blood and an almost constant half-life over varying losses of body mass. The estimates of half-life of nitrogen were two to six times higher than those of carbon. We argue that this discrepancy was caused by the mixing of nitrogen isotopes from internal and external sources. The mixing effect was probably negligible for carbon as the amount of ingested carbon outweighed the amount of mobilized carbon from internal sources. A correlation between the estimated turnover rates of nitrogen and losses of body masses was probably obscured by the additional fractionation of nitrogen isotopes in catabolic animals. We conclude that the interpretation of nitrogen isotope data of free-ranging animals is difficult when the animal9s diet is changing to a critical nitrogen content.
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Low turnover rates of carbon isotopes in tissues of two Nectar-Feeding bat species
Journal of Experimental Biology, 2003Co-Authors: Christian C. Voigt, Felix Matt, Robert H. Michener, Thomas H. KunzAbstract:SUMMARY Stable isotopes of carbon are commonly used to characterize dietary preferences in animals. Because turnover rates of carbon isotopes are related to metabolic rate, we wanted to determine the rates at which carbon isotopes are exchanged in tissues of two species of Nectar-Feeding bats ( Leptonycteris curasoae and Glossophaga soricina ), both of which have relatively high mass-specific metabolic rates. To test the hypothesis that isotope turnover is higher in Nectar-Feeding bats, because of their high mass-specific metabolic rates, than in other eutherian mammals, we conducted diet-switching experiments and chose three target tissues (hair, wing membrane and blood) to evaluate the isotopic turnover rates. We made the following predictions: (1) isotopic composition should change towards higherδ 13 C-values due to the turnover of carbon isotopes of C 3 origin with those of C 4 /CAM origin; (2) the turnover rates of carbon isotopes would differ between the three types of tissues in the following order of decreasing turnover rates: blood>wing membrane>hair; and (3) turnover rates of Nectar-Feeding bats should exceed those reported for other small mammals because of the high mass-specific metabolic rate of Nectar-Feeding bats. Compared to the initial diet, target tissues were enriched in heavy carbon isotopes by 2.8‰ in L. curasoae and by 2.6‰ in G. soricina . After changing the diet from C 3 to C 4 /CAM origin we found an increase in abundance of 13 C in blood and wing membrane in all experimental subjects. The estimated half life of carbon isotope turnover ranged from 100 to 134 days and did not differ significantly between blood and wing membrane, nor did it differ between the two species. The low turnover rate in wing membrane may reflect its specific composition and the relatively low temperature of this tissue, and long-lived erythrocytes in bat blood may be responsible for the low turnover rate of carbon isotopes in blood. The turnover rate of stable carbon isotopes in hair was low in L. curasoae and undetectable in G. soricina , which may be explained by the seasonal growth of the hair in these two species. Because both species are small (10 and 25 g, respectively) and Nectar-Feeding bats have higher mass-specific metabolic rates than bats in temperate regions or similar sized terrestrial mammals, our findings of low turnover rates were unexpected.
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Reproductive energetics of the Nectar-Feeding bat Glossophaga soricina (Phyllostomidae).
Journal of comparative physiology. B Biochemical systemic and environmental physiology, 2003Co-Authors: Christian C. VoigtAbstract:Pregnancy and lactation are energetically demanding periods for female mammals. Unique amongst mammals, bats have to allocate considerable amounts of energy into their offspring because juveniles cannot be weaned until they are capable of flying at almost adult size. Similar to other bat species, female Nectar-Feeding bats should increase their energy intake after parturition to meet the energy demands of offspring growth. However, previous studies have shown that Nectar-Feeding bats differ from other similar-sized bats in having a much higher metabolic rate. Therefore, I examined how Nectarivorous bats respond to the energetic challenge of reproduction. In this study, the daily energy intake of pregnant and lactating Glossophaga soricina was measured during a 6-week period prior to and a 10-week period after parturition. Body mass of G. soricina increased linearly until parturition. Within the same time period, daily flight time decreased and daily energy intake remained constant. Probably, the reduced flight activity of pregnant bats compensated for the increased power requirements of flight, thus resulting in an almost constant daily energy turnover. During 35 days after parturition, neither flight time, body mass nor daily energy intake of lactating females changed significantly. On average, the daily energy intake of pregnant, lactating or non-reproducing G. soricina was not significantly different. Possibly, for unknown reasons, female G. soricina maintain a daily energy intake of a constant high level during and beyond reproduction.
Marco Tschapka - One of the best experts on this subject based on the ideXlab platform.
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Discrimination of small sugar concentration differences helps the Nectar-Feeding bat Leptonycteris yerbabuenae cover energetic demands.
The Journal of Experimental Biology, 2020Co-Authors: Michael Walter, Aaron Verdong, Vanessa Olmos, Christina C. Weiss, Lisa-ruth Vial, Ahilan Putra, Jan Müller, Marco Tschapka, Hans-ulrich SchnitzlerAbstract:ABSTRACT Every day Nectar-Feeding animals face an energetic challenge during foraging: they must locate and select flowers that provide Nectar with adequate amounts of sugar to cover their very high energy needs. To understand this decision-making process, it is crucial to know how accurately sugar concentration differences can be discriminated. In a controlled laboratory setting, we offered the Nectar-specialist bat Leptonycteris yerbabuenae the choice between different sugar solutions covering the entire concentration range of bat-pollinated plants (3–33%). When Feeding on solutions below 10% sugar concentration, L. yerbabuenae were unable to cover their energetic demands because of physiological constraints. Their ability to discriminate sugar concentrations was better than that of any other Nectar-Feeding animal studied to date. At sugar concentrations below 15%, L. yerbabuenae can discriminate solutions differing by only 0.5%. The bats may utilize this fine-tuned ability to select Nectar from flowers with reward qualities that provide them with the necessary amount of energy to survive.
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Bats and bananas: Simplified diet of the Nectar-Feeding bat Glossophaga soricina (Phyllostomidae: Glossophaginae) foraging in Costa Rican banana plantations
Global Ecology and Conservation, 2020Co-Authors: Priscilla Alpízar, Julian Schneider, Marco TschapkaAbstract:Abstract Habitat loss for food production is a problem strongly affecting wildlife. However, some species may adapt their behavior and use these habitats, such as the neotropical Nectar-Feeding bats (Phyllostomidae: Glossophaginae) occurring in banana monocultures. We assessed the diet of the common Nectar-Feeding bat Glossophaga soricina, foraging in two habitats with different levels of alteration and land use intensities, conventional and organic banana plantations, and compared it to that from bats living in native forest patches. We collected pollen from the fur of captured bats and identified it under a microscope to the lowest taxonomical level possible. We found that bats foraging in forests have a richer diet, since they feed in more heterogeneous areas with more plant species. Additionally, bats foraging in conventional banana plantations generally showed a less diverse pollen load. One hectare of banana plantation provides an energy density that easily supports five bat individuals per night throughout the year, so plantations might be ideal foraging grounds. However, bats also require proteins, and banana cultivars produce very little or no pollen at all and additionally pesticide use makes insects a scarce resource in most plantations. Such a simplified and incomplete diet and agrochemical exposure might negatively affect the bats, but we still do not understand to what extent. Thus, we conclude that, although banana plantations represent a high Nectar availability habitat, they might be less-than-perfect foraging grounds for Nectarivorous bats.
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How Nectar-Feeding Bats Localize their Food: Echolocation Behavior of Leptonycteris yerbabuenae Approaching Cactus Flowers.
PloS one, 2016Co-Authors: Tania P. Gonzalez-terrazas, Theodore H. Fleming, Hans-ulrich Schnitzler, Elisabeth K. V. Kalko, Jens C. Koblitz, Rodrigo A. Medellín, Marco TschapkaAbstract:Nectar-Feeding bats show morphological, physiological, and behavioral adaptations for Feeding on Nectar. How they find and localize flowers is still poorly understood. While scent cues alone allow no precise localization of a floral target, the spatial properties of flower echoes are very precise and could play a major role, particularly at close range. The aim of this study is to understand the role of echolocation for classification and localization of flowers. We compared the approach behavior of Leptonycteris yerbabuenae to flowers of a columnar cactus, Pachycereus pringlei, to that to an acrylic hollow hemisphere that is acoustically conspicuous to bats, but has different acoustic properties and, contrary to the cactus flower, present no scent. For recording the flight and echolocation behaviour we used two infrared video cameras under stroboscopic illumination synchronized with ultrasound recordings. During search flights all individuals identified both targets as a possible food source and initiated an approach flight; however, they visited only the cactus flower. In experiments with the acrylic hemisphere bats aborted the approach at ca. 40–50 cm. In the last instant before the flower visit the bats emitted a long terminal group of 10–20 calls. This is the first report of this behaviour for a Nectar-Feeding bat. Our findings suggest that L. yerbabuenae use echolocation for classification and localization of cactus flowers and that the echo-acoustic characteristics of the flower guide the bats directly to the flower opening.
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Finding flowers in the dark: Nectar-Feeding bats integrate olfaction and echolocation while foraging for Nectar.
Royal Society open science, 2016Co-Authors: Tania P. Gonzalez-terrazas, Carlos Martel, Paulo Milet-pinheiro, Manfred Ayasse, Elisabeth K. V. Kalko, Marco TschapkaAbstract:Nectar-Feeding bats depend mainly on floral Nectar to fulfil their energetic requirements. Chiropterophilous flowers generally present strong floral scents and provide conspicuous acoustic echoes to attract bats. While floral scents are assumed to attract bats over long distances, acoustic properties of flower structures may provide detailed information, thus supporting the localization of a flower at close ranges. So far, to our knowledge, there is no study trying to understand the relative importance as well as the combination of these generally coupled cues for detection (presence) and localization (exact position) of open flowers in nature. For a better comprehension of the significance of olfaction and echolocation in the foraging behaviour of Nectar-Feeding bats, we conducted two-choice experiments with Leptonycteris yerbabuenae . We tested the bats' behaviour in three experimental scenarios with different cues: (i) olfaction versus echolocation, (ii) echolocation versus echolocation and olfaction, and (iii) olfaction versus echolocation and olfaction. We used the floral scent of the bat-pollinated cactus Pachycereus pringlei as olfactory cue and an acrylic paraboloid as acoustic cue. Additionally, we recorded the echolocation behaviour of the bats and analysed the floral scent of P. pringlei . When decoupled cues were offered, bats displayed no preference in choice for any of the two cues. However, bats reacted first to and chose more often the coupled cues. All bats echolocated continuously and broadcast a long terminal group before a successful visit. The floral scent bouquet of P. pringlei is composed of 20 compounds, some of which (e.g. methyl benzoate) were already reported from chiropterophilous plants. Our investigation demonstrates for the first time to our knowledge, that Nectar-Feeding bats integrate over different sensory modes for detection and precise localization of open flowers. The combined information from olfactory and acoustic cues allows bats to forage more efficiently.
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First records of day roosts of the Nectar-Feeding bat Lichonycteris obscura (Phyllostomidae: Glossophaginae)
Caribbean Journal of Science, 2013Co-Authors: David Villalobos-chaves, Bernal Rodríguez-herrera, Marco TschapkaAbstract:Abstract. We describe for the first time the day roost of the rare Lichonycteris obscura, a small specialized NectarFeeding bat that shows seasonal movements. Roosts were easily accessible cavities at or under fallen trees. As these structures occur frequently on slopes along streams, they are widely distributed, somewhat predictable and may be easily found by migrating bats. The use of such very common structures for roosting permits these small Nectar-Feeding species the seasonal access to areas with only temporarily high Nectar resource availability.
Carlos Martínez Del Rio - One of the best experts on this subject based on the ideXlab platform.
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A Nectar-Feeding mammal avoids body fluid disturbances by varying renal function
American journal of physiology. Renal physiology, 2008Co-Authors: Bradley Hartman Bakken, Jorge Ayala-berdon, Jorge E. Schondube, Robert M. Carroll, Carlos Martínez Del RioAbstract:To maintain water and electrolyte balance, Nectar-Feeding vertebrates oscillate between two extremes: avoiding overhydration when Feeding and preventing dehydration during fasts. Several studies ha...
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Concentration‐dependent sugar preferences in Nectar‐Feeding birds: mechanisms and consequences
Functional Ecology, 2003Co-Authors: Jorge E. Schondube, Carlos Martínez Del RioAbstract:Summary 1Specialised Nectar-Feeding birds tend to prefer sucrose over glucose-fructose mixtures or to be indifferent when tested at concentrations close to 584 mmol L−1 sucrose equivalents. The role of the potential interaction between sugar composition and concentration on the sugar preferences of these birds, however, has not been explored. 2We tested the hypothesis that sugar preferences in Nectar-Feeding birds are concentration-dependent. We predicted that at high concentrations they would prefer sucrose over hexoses, whereas at low sugar concentrations they would prefer hexoses. We expected birds to show differences in food intake that matched their sugar preferences when they fed on equicaloric solutions of sucrose and 1 : 1 mixture of glucose and fructose. Consequently, the curves describing the relationship between food intake and sugar concentration for these two sugar solutions should cross. We tested these hypotheses in two species of Nectar-Feeding birds: the Cinnamon-bellied Flowerpiercer, Diglossa baritula (Wagler) and the Magnificent Hummingbird, Eugenes fulgens (Swainson). 3The sugar preferences of both species were concentration dependent. At lower concentrations they preferred hexoses, whereas at higher concentrations they shifted their preference to sucrose. However, these concentration-dependent preferences were not matched by parallel differences in intake. 4Although Nectar composition and concentration are often discussed as two different floral traits, our results show that they have a synergistic effect on the sugar preferences of Nectar-Feeding birds.
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Intake Responses in Nectar Feeding Birds: Digestive and Metabolic Causes, Osmoregulatory Consequences, and Coevolutionary Effects
American Zoologist, 2001Co-Authors: Carlos Martínez Del Rio, Jorge E. Schondube, Todd J. Mcwhorter, L. Gerardo HerreraAbstract:Nectar-Feeding vertebrates respond to variation in Nectar sugar content by modulating volumetric intake. In some Nectar Feeding animals, the intake response to sugar concentration can be accurately predicted from simple mathematical models that rely on knowledge of gut morphology, in vitro rates of sugar digestion, and daily energy expenditures. Because most of the floral Nectars consumed by vertebrates are dilute, these animals ingest large amounts of water while Feeding. The water turnover rates of hummingbirds Feeding on dilute Nectar are more similar to those of amphibious and aquatic organisms than to those of terrestrial vertebrates. Dilute Nectars can pose osmoregulatory challenges for Nectarivores. Nectarivorous birds exhibit renal traits that are well suited to dispose of large water loads and that appear inadequate to produce concentrated urine. Nectar-Feeding birds prefer concentrated over dilute sugar solutions. However, the concentration difference that they can discriminate is smaller at low than at high concentration. We hypothesize that this pattern is a consequence of the functional form of intake responses that often results in decelerating sugar intakes with increasing sugar concentration. The diminishing returns in floral attractivity that may result from increased Nectar concentration may be one of the reasons why the Nectars of hummingbird pollinated flowers are dilute in spite of the preference of birds for higher concentrations. The intake responses of Nectar-Feeding birds capture the integration of a behavioral response with the physiological processes that shape it. Because the behavior of Nectar-Feeding birds can have consequences for the plants that they visit, the intake response may also have coevolutionary effects.
Y. Winter - One of the best experts on this subject based on the ideXlab platform.
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Weber's law, the magnitude effect and discrimination of sugar concentrations in Nectar-Feeding animals.
PloS one, 2013Co-Authors: Vladislav Nachev, Kai Petra Stich, Y. WinterAbstract:Weber’s law quantifies the perception of difference between stimuli. For instance, it can explain why we are less likely to detect the removal of three nuts from a bowl if the bowl is full than if it is nearly empty. This is an example of the magnitude effect – the phenomenon that the subjective perception of a linear difference between a pair of stimuli progressively diminishes when the average magnitude of the stimuli increases. Although discrimination performances of both human and animal subjects in various sensory modalities exhibit the magnitude effect, results sometimes systematically deviate from the quantitative predictions based on Weber’s law. An attempt to reformulate the law to better fit data from acoustic discrimination tasks has been dubbed the “near-miss to Weber’s law”. Here, we tested the gustatory discrimination performance of Nectar-Feeding bats (Glossophaga soricina), in order to investigate whether the original version of Weber’s law accurately predicts choice behavior in a two-alternative forced choice task. As expected, bats either preferred the sweeter of the two options or showed no preference. In 4 out of 6 bats the near-miss to Weber’s law provided a better fit and Weber’s law underestimated the magnitude effect. In order to test the generality of this observation in Nectar-feeders, we reviewed previously published data on bats, hummingbirds, honeybees, and bumblebees. In all groups of animals the near-miss to Weber’s law provided better fits than Weber’s law. Furthermore, whereas the magnitude effect was stronger than predicted by Weber’s law in vertebrates, it was weaker than predicted in insects. Thus Nectar-Feeding vertebrates and insects seem to differ in how their choice behavior changes as sugar concentration is increased. We discuss the ecological and evolutionary implications of the observed patterns of sugar concentration discrimination.
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OPERATIONAL TONGUE LENGTH IN PHYLLOSTOMID Nectar-Feeding BATS
Journal of Mammalogy, 2003Co-Authors: Y. Winter, O. Von HelversenAbstract:Abstract Glossophagine bats (Phyllostomidae, Glossophaginae) are specialized visitors to the flowers of several hundred species of neotropical plants. They are able to exploit flowers in hovering flight by imbibing Nectar with a highly protrusile brush-tip tongue. As tongue extension is achieved by muscular and vasohydraulic mechanisms, its operational length can be inferred only from actively Feeding animals. For this study, we measured maximum tongue extensions during Nectar Feeding in 9 species of glossophagine bats. We trained bats to feed from vertically oriented glass test tubes (9- and 15-mm inside diameter). The maximum depth of Nectar drainage by a bat was recorded as maximum operational tongue length. Measured operational tongue lengths were in the range of the total body length of bats. The record length was 77 mm (in tubes with 15-mm inside diameter) in the 17-g flower specialist Choeronycteris mexicana. This compares with only 11–24 mm in the nonglossophagine frugivorous bat Carollia perspici...
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Gas exchange during hovering flight in a Nectar-Feeding bat Glossophaga soricina.
The Journal of Experimental Biology, 1998Co-Authors: Y. Winter, Christian C. Voigt, O. Von HelversenAbstract:Glossophagine Nectar-Feeding bats exploit flowers while hovering in front of them. Aerodynamic theory predicts that power output for hovering flight in Glossophaga soricina is 2.6 times higher than during horizontal flight. We tested this prediction by measuring rates of gas exchange during hover-Feeding. Five individuals of Glossophaga soricina (mean mass 11.7 g) were trained to feed from a Nectar dispenser designed as a flow-through respirometry mask. Single hover-Feeding events lasted for up to 4.5 s. Measured rates of gas exchange varied as a function of hovering duration. O2 and CO2 during short hovering events (up to 1 s) were 20.5+/-6.7 ml g-1 h-1 (N=55) and 21.6+/-5.6 ml g-1 h-1 (N=39) (means +/- S.D.), respectively. These values are in the range of a previous estimate of the metabolic power input for level forward flight (23.8 ml O2 g-1 h-1). However, during hovering events lasting longer than 3 s, oxygen uptake was only 16.7+/-3.5 ml g-1 h-1 (N=73), which is only 70 % of the value expected for forward flight. Thus, bats reduced their rate of oxygen uptake during longer periods of hovering compared with level forward flight. This result is in contrast to the predicted hovering cost derived from aerodynamic theory. The exact metabolic power input during hovering remains uncertain. During longer hovering events, bats were probably not in respiratory steady state, as indicated by the deviation of the respiratory exchange ratio from the expected value of 1 (oxidization of Nectar sugar) to the measured value of 0.8.
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Flight cost and economy of Nectar-Feeding in the bat Glossophaga Soricina (Phyllostomidae; Glossophaginae)
1993Co-Authors: Y. Winter, O. Von Helversen, Ulla M. Norberg, Thomas H. Kunz, John F. SteffensenAbstract:The cost of forward flight for a 11.7 g Nectar-Feeding bat Glossophaga soricina (Phyllostomidae; Glossophaginae) was estimated to be 5.888 kJ h -1 (1.63 W). To obtain this estimate, we quantified the amount of time allocated to specific activities and the animal´s daily energy intake in captivity for 17 separate 24-hour-periods. These data were arrangedin a set of daily energy-balance equations with the energy coefficients for each activity as unknown parameters. These equations were solved for the unknown coefficients b ymultiple lonear regression analysis. Using our estimate of flight cost and values for daily energy expenditure from the literature, we estimated how a free-ranging Nectar-Feeding bat allocates time and energy among different activities.
