Altitude matters: differences in cardiovascular and respiratory responses to hypoxia in bar-headed geese reared at high and low altitudes

Abstract

Bar-headed geese (Anser indicus) fly at high altitudes during their migration across the Himalayas and Tibetan plateau. However, we know relatively little about whether rearing at high altitude (i.e. phenotypic plasticity) facilitates this impressive feat because most of what is known about their physiology comes from studies performed at sea level. To provide this information, a comprehensive analysis of metabolic, cardiovascular and ventilatory responses to progressive decreases in the equivalent fractional composition of inspired oxygen (FI O2 : 0.21, 0.12, 0.09, 0.07 and 0.05) was made on bar-headed geese reared at either high altitude (3200 m) or low altitude (0 m) and on barnacle geese (Branta leucopsis), a low-altitude migrating species, reared at low altitude (0 m). Bar-headed geese reared at high altitude exhibited lower metabolic rates and a modestly increased hypoxic ventilatory response compared with low-altitudereared bar-headed geese. Although the in vivo oxygen equilibrium curves and blood-oxygen carrying capacity did not differ between the two bar-headed goose study groups, the blood-oxygen carrying capacity was higher than that of barnacle geese. Resting cardiac output also did not differ between groups and increased at least twofold during progressive hypoxia, initially as a result of increases in stroke volume. However, cardiac output increased at a higher FI O2 threshold in bar-headed geese raised at high altitude. Thus, bar-headed geese reared at high altitude exhibited a reduced oxygen demand at rest and a modest but significant increase in oxygen uptake and delivery during progressive hypoxia compared with barheaded geese reared at low altitude.

Respiratory mechanics of eleven avian species resident at high and low altitude

“…Despite this, high-altitude avian species such as the bar-headed goose (Anser indicus) and Andean goose (Chloephaga melanoptera) have been shown to preferentially increase V t over f R (Scott and Milsom, 2007;Lague et al, 2016; S.L.L., B.A.C., L.A., Y. Zhong, A. P. Farrell, K.G.M., Y. Wang and W.K.M., unpublished data). We wondered whether this deeper, slower breathing pattern might be found in other high-altitude species, and whether the mechanical design of the respiratory systems of high-altitude species might be altered to reduce the metabolic cost of potentially employing this higher tidal volume strategy.…”

Control of breathing and ventilatory acclimatization to hypoxia in deer mice native to high altitudes

“…High-altitude deer mice appear much like Tibetan humans, plateau pika and bar-headed geese, which breathe as much or more than hypoxia-acclimated lowlanders. [16][17][18][19][20][21] This strategy contrasts the blunted HVR of Andean humans, guinea-pigs and Andean geese. [22][23][24] These differences have previously been suggested to reflect divergent evolutionary outcomes arising from tradeoffs between O 2 uptake vs. CO 2 /pH homeostasis and the metabolic costs of breathing.…”

“…12,14,15 In some high-altitude populations or species, including Tibetan humans, plateau pika (Ochotona curzoniae), and bar-headed geese (Anser indicus), total and/or alveolar ventilation is similar or enhanced compared to lowlanders. [16][17][18][19][20][21] In contrast, some other highland taxa exhibit a blunted HVR, including Andean humans, guinea-pigs (Cavia porcellus) and Andean geese (Chloephaga melanoptera). [22][23][24] With some exceptions, 24 the underlying mechanisms of these evolved changes in the control of breathing are poorly understood.…”

Effects of experimental manipulation of hematocrit on avian flight performance in high and low altitude conditions

“…However, most studies investigating the physiology of migration have been conducted at low altitude and have largely ignored this transient but potentially important altitude component. Outside of a few species adapted to high altitude (Barve et al, 2016;Fedde et al, 1989;Lague et al, 2016;Scott and Dawson, 2017;Scott et al, 2015), physiological responses to exercise at high altitude in many passerines are still poorly understood. Borras et al (2010) found that citril finches (Carduelis citronella) increased Hct in response to increases in altitude, but these birds were transported passively to high elevation by the researchers.…”