However, during post-hoc testing, no comparisons were significant within pre-flight (p>0.12). The Monkey Bar is a version of the Pro X Series Cage which uses our traditional cable system attached to the bow of the boat for stability. While this decreases the power output required for flight in thin air, birds at high altitude still need to flap harder than lowland birds. Metabolic rate during flight increased 16-fold from rest, supported by an increase in the estimated amount of O2 transported per heartbeat and a modest increase in heart rate. Flight is very metabolically costly at high-altitudes because birds need to flap harder in thin air to generate lift. High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose J Exp Biol. Mixed venous PO2, on the other hand, tended to decrease during the initial portion (first minute) of flights in hypoxia (Figure 3 and Figure 4), indicative of increased tissue O2 extraction. Thank you for submitting your article "Reduced metabolism and increased O2 pulse support hypoxic flight in the bar-headed goose (Anser indicus)" for consideration by eLife. documented an increase in heart rate with increasing altitude. Your article has been reviewed by three peer reviewers, and the evaluation has been overseen by a Reviewing Editor and Harry Dietz as the Senior Editor. ), with only two of their five bar-headed geese achieving flight in the wind tunnel, and flights remaining relatively short. Ward et al. We are indebted to Gordon Gray and the staff of the UBC Centre for Comparative Medicine for their tireless support and expertise in animal care. of Mechanical Engineering for use of the wind tunnel; Marty Loughry and Tom Wright of UFI for design and construction of the recorders; Bob Shadwick for use of his rad scooter and transport van; Yvonne Dzal for her mad chauffeur skills; James Whale for flight kinematic data and video; Graham Scott for manuscript review; and Erika Hale for assistance with statistics. Discover releases, reviews, credits, songs, and more about Bar-Kays - Flying High On Your Love at Discogs. Why did the authors not mix nitrogen with ambient air upstream of delivery to the mask? This video cannot be played in place because your browser does support HTML5 video. Heart rate and metabolic rate of bar-headed geese at rest in normoxia in this study were remarkably similar to those obtained by Ward et al. Asterisks indicate significant difference from normoxia (* indicates p<0.05; ** indicates p<0.01; *** indicates p<0.001, § indicates difference from pre-flight value, # indicates difference from recovery value, and $ indicates difference from start value). Determining how these results relate to the multi-hour migratory flights of this species at high altitude will require further work measuring physiological variables in the wild, or during longer flights in both normobaric and hypobaric conditions. The birds also wore a breathing mask that could simulate the limited oxygen availability at altitudes of roughly 5,500 and 9,000 meters, and measure the oxygen consumed and the carbon dioxide produced by the geese. Complete your Bar-Kays collection. Bar-tailed godwit - 20,000 feet . O2 pulse was also estimated during normoxic flights to calculate putative V˙O2 during hypoxic flights, assuming an RER of 1.0 to convert V˙CO2 into V˙O2. Interestingly, these values are equivalent to the mean minimum arterial PO2 values obtained near the end of dives in elephant seals, and are similar to the range exhibited by diving emperor penguins (Ponganis et al., 2007; Fedak et al., 1981). CO2 pulse in moderate hypoxic flight was significantly higher (t = −3.666, p=0.0008) than in severe hypoxia (EMM = 0.514 ± 0.034 mL CO2 beat−1 kg−1). Seven bar-headed geese (2.21 ± 0.26 kg) managed steady, stationary, and prolonged flight in the wind tunnel while fully instrumented. For example, when converting venous PO2 values (Figures 3,4, Supplementary file 2) into Hb-O2 saturation (Meir and Milsom, 2013), the corresponding temperature drop in hypoxia results in a substantial increase in O2 content, indicating an even larger venous reserve than that inferred from the PO2 values alone. This is further evidenced by the low success rate in flying instrumented birds under hypoxic conditions. Mind-blowing experience. Consent has been obtained by all subjects in the photo and videos used in this manuscript. Temperature profiles also reveal a transient spike in temperature immediately following each flight, perhaps due to a release of warm blood from exercising muscle or other areas. As the temperature probes were inserted through the jugular vein and advanced to the level of the heart, these records should reflect true mixed venous temperature. Arterial Po2 was maintained throughout flights. The authors state that they flowed nitrogen directly into the mask at a rate that brought O2 levels approximately to FiO2 of 0.105 and 0.07. Descriptive statistics are reported in Table 1 and supplementary files, mean ± SEM is reported here unless estimated marginal mean (EMM ± SEM) or median is indicated. We have reworded this point throughout the manuscript as “maintaining the increase in O2 pulse also measured in normoxia”, which more accurately reflects the data. CO2 pulse in normoxic flight (EMM = 0.722 ± 0.021 mL CO2 beat−1 kg−1) was significantly higher (t = −5.818, p<0.0001) than CO2 pulse in moderate hypoxic flight (EMM = 0.627 ± 0.022 mL CO2 beat−1 kg−1). The reduction in metabolism in hypoxia observed in the current study could represent O2 limitation, selective suppression of metabolism to specific tissues or increased efficiency of flight pattern and thus O2 utilization. 3) There should be discussion of the issue of the minimum cost of flight and the possibility that hypoxic birds "cheated" to remain aloft, since the major finding was that metabolic rate decreased during forward flight in hypoxia. Features: Your board bag currently does not contain any items. We have also attempted to emphasize the strengths pointed out here. Flybar, the Original Pogo Stick Company, has been around since 1918. Given that birds underwent considerable training, including outdoor flights, and that wind tunnel flights were short even in normoxia, it would appear that the birds were reluctant to fly for long once instrumented in the conditions of the wind tunnel. Briefly, bar-headed goose (Anser indicus) eggs were obtained from the Sylvan Heights Bird Park (Scotland Neck, North Carolina). This species migrates biannually across the Himalayan Mountains and Tibetan Plateau, wintering in India and breeding in China and Mongolia, typically flying through passes 5,000 to 6,000 m above sea level, where partial pressures of oxygen are only half of those at sea level. As opposed to indicating carbohydrate use during flight, an RER near 1 may reflect hyperventilatory CO2 loss. However, this should be taken into consideration especially in comparisons of moderate versus severe hypoxia. Thus the moderately hypoxic birds appear to have met the hypoxic challenge by a combination of a reduced metabolism, maintaining heart rate, and maintaining the increase in CO2/estimated O2 pulse. Twice a year, these amazing birds migrate over the Himalayas, the tallest mountains on the planet. Venous PO2 values as low as 2–10 mmHg have been reported during dives in elite divers like elephant seals and emperor penguins (Ponganis et al., 2007; Meir et al., 2009), or in hypoxemic extremes of race horses performing strenuous exercise (Manohar et al., 2001; Butler et al., 1993; Bayly et al., 1989). Note that only one bird flew consistently in severe hypoxia (red trace in panel A). VI. They were then housed in the University of British Columbia Animal Care Facility with constant access to water (small ponds) and ad libitum mixed grain pellets supplemented with lettuce for the duration of the project. The only exception is that the method for producing hypoxia (mixing N2 and air in the mask) was unable to create a stable background, so VO2 was not measured in hypoxia. RER in flight (EMM of 1.00 ± 0.034) was significantly higher than pre-flight (EMM of 0.87 ± 0.035; t=7.026, p<0.0001) and rest (EMM of 0.80 ± 0.035; t=10.073, p<0.0001). found that bar-headed geese could indeed fly at these simulated extreme altitudes in the wind tunnel, and that the birds largely achieved this by reducing their metabolism to match low oxygen conditions. Because incurrent CO2 levels remained close to zero throughout, any increase in CO2 must come from the bird and therefore our V˙CO2 data were considered robust. This characteristic spike is followed by a second bout of cooling, and then a slow warming to levels at rest (Figure 4). Bishop et al. It would benefit the lay reader to have this, and the reason for this study, explained in the Abstract. (2011) (running, filled triangles), Ward et al. Despite possible instrumentation effects or the short flight durations, flights were repeatable, of similar length under all conditions, and most importantly, produced stable levels of the measured variables, allowing us to make robust comparisons between flight in normoxia vs. hypoxia, thus examining the effects of hypoxia on flight physiology under similar conditions. Person three operated the tunnel and equipment. In moderate hypoxia, venous temperature in steady state (steady state EMM = 39.998 ± 0.509°C) was significantly lower than both preflight (preflight EMM = 41.473 ± 0.509°C; t = 3.139, p=0.0247) and the start of the flight (start EMM = 41.373 ± 0.509°C; t=−2.926, p=0.0460). So, this seems to remain a distinct problem. At these heights, the air is so thin that it contains only about 30–50% of the oxygen available at sea-level. The High Flyer Sports Bar is a favourite with locals and travellers alike, with a variety of drinks available, from ice cold beer and cider to spirits and delicious wine hailing from Australia and beyond. Lift and power requirements, One-step N2-dilution technique for calibrating open-circuit VO2 measuring systems, https://doi.org/10.1152/jappl.1981.51.3.772, Cardiopulmonary function in exercising bar-headed geese during normoxia and hypoxia, https://doi.org/10.1016/0034-5687(89)90010-8, Elevation and the morphology, flight energetics, and foraging ecology of tropical hummingbirds, The trans-Himalayan flights of bar-headed geese (, The paradox of extreme high-altitude migration in bar-headed geese, Maximum running speed of captive bar-headed geese is unaffected by severe hypoxia, https://doi.org/10.1371/journal.pone.0094015, Wind tunnel as a tool in bird migration research, Measuring Metabolic Rates: A Manual for Scientists, https://doi.org/10.1093/acprof:oso/9780195310610.001.0001, Effect of prior high-intensity exercise on exercise-induced arterial hypoxemia in thoroughbred horses, https://doi.org/10.1152/jappl.2001.90.6.2371, Flying, fasting, and feeding in birds during migration: a nutritional and physiological ecology perspective, https://doi.org/10.1111/j.0908-8857.2004.03378.x, Heart rate regulation and extreme bradycardia in diving emperor penguins, Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals, https://doi.org/10.1152/ajpregu.00247.2009, High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose, Guts Don't fly: small digestive organs in obese Bar-Tailed godwits, How bar-headed geese fly over the himalayas, https://doi.org/10.1152/physiol.00050.2014, Control of breathing and adaptation to high altitude in the bar-headed goose, https://doi.org/10.1152/ajpregu.00161.2007, Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates, https://doi.org/10.1038/scientificamerican1061-68, Creative Commons CC0 public domain dedication, Physiology: The highs and lows of bird flight, Listen to Jessica Meir talk about the amazing abilities of bar-headed geese, Listen to Jessica Meir talk about her trip to space, NASA Johnson Space Center, Houston, United States, University of Texas at Austin, Austin, United States, Harry C Dietz, Howard Hughes Medical Institute and Institute of Genetic Medicine, Johns Hopkins University School of Medicine, United States, Iain D Couzin, Max Planck Institute for Ornithology, Germany, Jon Harrison, Arizona State University, United States. We would expect during longer flights that RER would fall close to 0.7, assuming the birds are preferentially metabolizing lipids. We have added a discussion of this possibility to the text, and have added Supplementary file 4 (which contains the flight kinematic data from the Whale reference). To better understand how the bar-headed goose accomplishes its remarkable, high altitude migration, Meir et al. Social Entertainment Ventures, the company running the U.S. In the interests of transparency, eLife includes the editorial decision letter and accompanying author responses. Both moderate hypoxia (EMM=28.96 ± 3.18 mmHg; t=−5.579, p=0.0001) and severe hypoxia (EMM=23.36 ± 3.44 mmHg; t=7.001, p<0.0001) were significantly lower than normoxia (EMM=46.51 ± 3.18 mmHg), but not significantly different from each other (t=-1.694, p=0.3238). The findings will be valuable to researchers studying animals living at extreme altitudes. Tubes ran from mask out of the tunnel, one introducing a calibrated amount of dry nitrogen into the mask, and the other pulling from the mask by way of an air pump. Previous studies have documented wild, migrating geese flying regularly between 5,000–6,000 m above sea-level and as high as 7,290 m (Bishop et al., 2015; Hawkes et al., 2013), with earlier anecdotal reports suggesting that these birds may even fly as high as the summit of Mt. Without instrumentation, birds flew for up to 45 min in the wind tunnel, however, once fully instrumented, experimental flights were much shorter. This further increase in metabolic cost is concordant with the increased biomechanical costs of flying in the thinner air at high altitude (requiring increased flight speeds to offset reductions in lift; Pennycuick, 2008) but may also arise in part from increased metabolic demands on the cardiorespiratory system associated with flight in hypoxia. We therefore hypothesize that bar-headed geese reduce oxygen demand in hypoxic flight by limiting oxygen supply to less essential metabolic processes and/or maximizing the mechanical efficiency of flight. I suggest you A) discuss this possible problem in the text and B) add some supplementary figures and tables that show only the directly comparable data. A lightly edited version of the letter sent to the authors after peer review is shown, indicating the most substantive concerns; minor comments are not usually included. Although wing-beat frequencies of our birds were higher than those of bar-headed geese in the wild (Bishop et al., 2015), values were similar between normoxic vs. hypoxic and instrumented vs. uninstrumented flights (Supplementary file 4; Whale, 2012). Therefore, V˙O2 data are not reported for flights in hypoxia. The tubes sampling air and delivering nitrogen to the mask exited the tunnel to the respirometry set-up at an access point (Figure 5). Dashed line shown to indicate 300 beats per minute in each plot (for aid in visual comparison only). Venous PO2 did not significantly differ between exposed oxygen levels during pre-flight (preflight normoxia EMM = 47.68 ± 2.52 mmHg, preflight moderate hypoxia EMM = 44.47 ± 3.16 mmHG, preflight severe hypoxia EMM = 38.68 ± 4.21 mmHg), but then was maintained in normoxia (start EMM = 50.00 ± 2.52 mmHg) while dropping in both levels of hypoxia such that both moderate hypoxia (start EMM = 34.71 ± 3.16 mmHg, t = −4.360, p=0.0001) and severe hypoxia (start EMM = 33.61 ± 4.21; t = −3.705, p=0.0012) were significantly different from normoxia at the start of flight, but did not differ from each other (t = −0.236, p=1.0).
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