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). 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. Similar problems were encountered in a previous study (Hawkes et al., 2014). Complete your Bar-Kays collection. 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). 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). Animals recovered overnight from surgical procedures before experimental sessions in the wind tunnel were conducted. 9. Mind-blowing experience. In normoxia, venous temperature was significantly higher in preflight (preflight EMM = 41.37 ± 0.402°C) compared to steady state (steady state EMM = 39.99 ± 0.441°C; t = 4.342, p=0.0005) and the end of the flight (end EMM = 40.38 ± 0.421°C; t=−3.404, p=0.0110), as well as in steady state compared to recovery (recovery EMM = 41.04 ± 0.403°C; t = 3.311, p=0.0146) and the start of the flight (start EMM = 41.10 ± 0.406°C; t=−3.443, p=0.0097). Features: Your board bag currently does not contain any items. Time points shown along x-axis: 'pre-flight' is steady state before flight begins, 'start' at the start of the flight, 'steady state' is steady state in flight, 'end' at the end of the flight, 'recovery' is steady state after the bird lands. One concern of mine that appeared repeatedly is a sort of survivor bias in the presentation of the results, where summary data from the moderate and severe hypoxia treatments are shown together. Asterisks indicate significant difference from normoxia (linear mixed model ANOVA; * indicates p<0.05; ** indicates p<0.01; *** indicates p<0.001). This suggests to me that the only demonstrated mechanism for hypoxic flight is the ability to fly at lower metabolic rate. Flyheight.com is a leading online video website that brings you the latest and most entertaining viral contents from America and around the world. (A) Schematic and (B) photo showing the set up in the wind tunnel. We also discovered that mixed venous temperature decreased during flight, which may significantly increase oxygen loading to hemoglobin. This is further evidenced by the low success rate in flying instrumented birds under hypoxic conditions. The range of wind tunnel flight speeds selected was similar to that measured during natural migratory flight (14 to 21 m s−1; Hawkes et al., 2013; Hawkes et al., 2011) and the speed selected for each individual was that which allowed steady, stationary, and prolonged flight. Video credit: J. Whale. Why did the authors not mix nitrogen with ambient air upstream of delivery to the mask? Hopefully, further gains made in the field of bio-logging systems directly measuring PO2 or SO2 will elucidate these variables in wild, migrating birds in the future. 4) There should be discussion of the possibility of anaerobic metabolism occurring in the hypoxic experiments, which cannot be discounted with the data provided to date. Respiratory exchange ratios (RER) were calculated by dividing V˙CO2 by V˙O2 and could therefore only be calculated for data collected in normoxia. (2002) also concluded that their wind tunnel data could not be used directly to calculate the metabolic rate of wild migratory geese from measurements of heart rate alone. RER in pre-flight was also significantly higher than at rest (t=3.453, p=0.0019). For arterial deployments, Po2 electrodes were inserted in the aorta via the carotid artery using peel-away catheters (3.5 FR Peel-Away Denny Sheath Introducer Set, Cook Medical Inc, Bloomington, IN, USA or Arrow 17 Ga, Teleflex Medical) after exposing the vessel via a shallow incision. Flow turbulence in the tunnel, the presence of the experimenters and the presence of the mask and tubing all will have increased flight costs and may have contributed to this (Hedenström and Lindström, 2017). High thermal sensitivity of blood enhances oxygen delivery in the high-flying bar-headed goose J Exp Biol. Lift and power requirements, One-step N2-dilution technique for calibrating open-circuit VO2 measuring systems, https://doi.org/10.1152/jappl.1922.214.171.1242, 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. How do bar-headed geese cope with low oxygen levels when flying over the Himalayas? The technical work to produce this study is admirable and must have been exceptionally challenging. This is consistent with results from both ruby-throated hummingbirds (Archilochus colubris) and the South American hummingbird (Colibri coruscans), a montane species capable of hovering at altitudes over 6000m (Chai and Dudley, 1996; Berger, 1974). The bar-headed goose can flap to heights of 21,120 feet on its migration over the Himalaya, a new study finds. Flight Clubs, also runs AceBounce, a game venue; Puttshack, a high-tech mini golf experience; and Wonderball, a ping-pong bar. In the end, only one bird's arterial PO2 was successfully recorded. When normality of data was not achieved, groups were compared using Kruskal-Wallis one-way ANOVA on ranks with post-hoc Dunn’s test assuming significance at p<0.05. Thirty-eight-year-old executive chef Jon Cropf has only been living in the Maggie Valley area for a few weeks, but he already feels at home. High in the sky fly bar-headed gese. This product has not been reviewed yet. The geese have … The arterial PO2 of geese flying at 0.105 FiO2 was similar to that of geese running on a treadmill in a previous study at 0.07 FiO2 (Figure 4; Hawkes et al., 2014). We conclude that flight in hypoxia is largely achieved via the reduction in metabolic rate compared to normoxia. 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. Fly Fishing For the total experience...Book lodging with our bar fly rate at the Safety Harbor Resort & Spa, grab lunch at Bar fly Saltwater grill, enjoy your day fishing then head back to the Bar fly bar for fish stories & celebration brews! Twice a year, these amazing birds migrate over the Himalayas, the tallest mountains on the planet. (2015) (B). The thermistor could not be deployed simultaneously with the arterial Po2 electrode due to aortic size. The effect of timepoint was due to a drop in venous temperature between preflight and the steady state portion of the flight: the minimum drop was 1.22 °C and the maximum drop was 2.72 °C. We measured heart rate (fH), the rate of oxygen consumption (V˙o2) and the rate of CO2 production (V˙CO2) under conditions at rest and during flight in bar-headed geese in both normoxia and two levels of hypoxia (moderate: 0.105 and severe: 0.07 FiO2 equivalent to altitudes of roughly 5,500 m and 9,000 m respectively). We obtained the first measurements of arterial and venous PO2 and temperature records in this species, and that of any equivalently sized bird, during flight. This bird is capable of incredible air time which is why it is such a successful scavenger. Flying requires ten to … Figures and tables where presentation appears to be affected by a survivor bias: Figure 2, Figure 3A, Figure 4, Table 1, Supplementary file 2. (2002) (open circles are flight and open triangles are walking), and the present study (filled circles are flight data, filled squares are rest). During the steady state portion of the flight, PO2 in normoxia (steady state EMM = 42.30 ± 2.49 mmHg) dropped slightly so moderate hypoxia (steady state EMM = 33.59 ± 3.40 mmHg) was marginally non-significant (t = −2.373, p=0.0600) while PO2 in severe hypoxia (steady state EMM = 29.61 ± 4.21) remained significantly different from normoxia (t = −2.881, p=0.0152). There was a significant effect of oxygen level on flight duration (F2, 363.35=6.55, p=0.0016). 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. The bar-headed goose is famous as it is widely believed to make the highest altitude migration on earth. Bar-headed geese lower their flight metabolic rates to fly in low-oxygen conditions. Note that only one bird flew consistently in severe hypoxia (red trace in panel A). At the end of the experiments the cannulae were removed and the animals inspected by veterinary surgeons and recovered in outdoor aviaries. Wing-beat frequencies of bar-headed geese in this study were similar in both normoxia and hypoxia. Inspired by racing, driven by adventure, and crafted to performance, FLY Racing has been working hard since 1998 to bring you the best gear in the market. Filmed at 125 frames per second, shown here at 7.5 frames per second playback. We misunderstood the Data Dryad system and neglected to provide the temporary DOI link rather than the DOI itself (the data were available in Dryad at the time of submission). There was a significant effect of activity on RER (F2, 301.95=54.37, p<0.0001, ICC=0.254). Twice a year, these amazing birds migrate over the Himalayas, the tallest mountains on the planet. These High-Flying Geese Are ‘the Astronauts of the Bird World’ Bar-headed geese migrate above 26,000 feet. As opposed to indicating carbohydrate use during flight, an RER near 1 may reflect hyperventilatory CO2 loss. Increases in heart rate contributed less (between 2 and 3-fold), with large variations in heart rate at any level of CO2 production and vice versa. At these heights, the air is so thin that it contains only about 30–50% of the oxygen available at sea-level. Despite a constant wing beat frequency, flight biomechanics of the geese in our study were altered in response to hypoxia, with increased upstroke duration (T) and decreased upstroke wingtip speed (Utip), upstroke plane amplitude (FSP), and mid-upstroke angle of inclination (a) (Supplementary file 4; Whale, 2012) As the downstroke produces the majority of lift and all forward thrust, by increasing the ratio of the duration of upstroke to downstroke, the duration of activation of the pectoralis major muscle group is decreased (responsible for the majority of downstroke power). Arterial values in the range measured in 0.07 FiO2 are strikingly low (Supplementary files 1 and 3), particularly given the need to support the metabolically costly activity of flight. In the post-hoc comparison, severe hypoxia (0.07 FiO2, equivalent to ~ 9,000 m) was significantly shorter with an estimated marginal mean (EMM) of 79.1 ± 36.6 s compared to an EMM of 187.7 ± 20.7 s in normoxia (t = −3.245, p=0.0039). The intraclass correlation coefficient (ICC) for this model was 0.141. The gas analyzer was calibrated to account for sensor drift using: 1) two point calibration for CO2, 0% and 1.0% CO2 balance air (Praxair Canada, Scarborough, ON, Canada); 2) a single point calibration for O2 at a baseline of 20.95% for dried room air at experimental flow rates since zero is extremely stable (Fedak et al., 1981). For the one bird for which we have adequate data flying in FiO2 = 0.07, V˙CO2 was 20% lower under this severe hypoxic condition than in normoxia. Google has many special features to help you find exactly what you're looking for. Bar-headed geese have a slightly larger wing area for their weight than other geese, which is believed to help them fly at high altitudes. 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. 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). They may also be relevant to those looking to understand how humans respond to situations where oxygen is limited, such as during medical conditions like a heart attack or stroke, or procedures like organ transplants. 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. We have added discussion of this issue to the Results, as well as to the figure legends for the figures indicated. Bioclusive transparent film dressing (Henry Schein, Melville, NY, USA) was placed over the insertion site of the electrodes and Elastinet stocking placed over the neck to protect the insertion site, secured by Bioclusive at each end. These measurements suggest that the anecdotes of bar-headed geese flying over some of the highest mountains in the world are indeed physiologically plausible. (2011) (running, filled triangles), Ward et al. 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. As such, it remains unclear whether these birds would even be able to fly where the oxygen is as limited as it is above the summits of the world’s highest mountains. The Po2 electrode and thermistor, calibration procedures and verification testing have been described previously (Meir et al., 2008; Ponganis et al., 2007; Meir et al., 2009; Ponganis et al., 2009). With venous O2 values decreasing to only around 25–30 mmHg in the present study, even under extreme hypoxia, these high fliers may yet retain a venous O2 reserve, also suggesting that these birds were not O2 limited in hypoxic flight. Another weakness is that the sample sizes were quite low, especially in hypoxia, where it was difficult to get the birds to fly. V˙CO2 was calculated as: The start and end of each flight was determined from the data trace by an obvious change in CO2 production. 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). Important conclusions are based on the data obtained from only a small few (e.g. Normoxia and moderate hypoxia data from this study shown in (A), inset shows expansion of data at rest. FeO2 and FeCO2 were determined as the average across this entire portion of the trace. Briefly, bar-headed goose (Anser indicus) eggs were obtained from the Sylvan Heights Bird Park (Scotland Neck, North Carolina). When directly comparing at the same level of hypoxia (0.07 FiO2 for both studies), arterial PO2 during flight was about 20% lower than while running Hawkes et al. There was a significant effect of oxygen level on venous Po2 at rest (F2, 17.33=27.775, p<0.0001). We used the afex package in RStudio (R version 3.5.1) for generating the models, the emmeans package for post-hoc comparisons with Bonferroni adjustment where appropriate, and calculated the adjusted intraclass correlation coefficient (ICC) by dividing the variance of the random intercept by the sum of the random effect variances (a value closer to 1 indicates a greater effect of the individual bird). Resting heart rate in moderate hypoxia (EMM = 107.3 ± 10.1) did not differ significantly from normoxia (t = 2.077, p=0.1151). Only one site, either arterial or venous, was targeted per surgery and subsequent flights (n=5 birds). We were very straightforward in elucidating these limitations and fully describing the inferences we made throughout the study. Alternatively, they may increase efficiency by "cheating" and taking advantage of turbulence or lower-speed regions created by the operator and experimental apparatus, a possibility you should also note. They have been documented flying at altitudes as high as 7,290 m (Bishop et al., 2015; Hawkes et al., 2013). The work is made available under the Creative Commons CC0 public domain dedication. In general, preflight arterial PO2 levels were maintained throughout flights. But, they did not derive VO2 data from hypoxic flights (and do not present such data for the recovery period). There are several striking and interesting results. Measurements of temperature at the lung and at the muscle in wild, migrating birds would help determine if modulating blood temperature might increase oxygen flux during flight. For arterial deployments in which temperature data could not be obtained, temperature was assumed to be stable at baseline body temperature (41°C). digestion, birds are known to undergo atrophy of gut tissue prior to migration; McWilliams et al., 2004; Piersma and Gill, 1998), or that they may be altering their flight behavior and biomechanics to fly with maximal efficiency. In post-hoc testing, no comparisons among preflight arterial PO2 were significant (p>0.05). In (B) oxygen consumption versus heart rate for bar-headed geese from three studies, Hawkes et al. Only one bird (bird 45) flew in severe hypoxia consistently, with a median duration of 100 s. This was significantly shorter (one-way ANOVA on ranks; H(2)=14.911, p<0.001; post-hoc Dunn’s method Q = 3.815, p<0.05) than this bird would fly in normoxia (median = 232.5 s) but not moderate hypoxia (median = 158 s, Q = 2.113, p>0.05; Supplementary file 1). 2013 Jun 15;216(Pt 12):2172-5. doi: 10.1242/jeb.085282. We assume that RER remains close to 1.0 in hypoxia (as measured in normoxia) since durations between flights in normoxia and moderate hypoxia were not significantly different (we also added this point to this section in the manuscript). This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. Wing-beat frequency was measured in a separate biomechanical study and was similar regardless of oxygen level (mean 4.97 ± 0.27 Hz in normoxia and 4.91 ± 0.28 Hz in moderate hypoxia, Supplementary file 4; Whale, 2012).