title: 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 (FiO2 : 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-altitude-reared 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 FiO2  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 bar-headed geese reared at low altitude.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 lague@zoology.ubc.ca.
authors.forename: Sabine L
authors.identifier: 0000-0002-8724-7297
authors.initials: SL
authors.lastname: Lague
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Beverly
authors.initials: B
authors.lastname: Chua
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: William K
authors.initials: WK
authors.lastname: Milsom
mesh_terms: D000531:Altitude; D000693:Anaerobiosis; D025041:Animal Migration; D000818:Animals; D000835:Animals, Wild / Q000254:growth & development / Q000502:physiology; D005426:Flight, Animal; D005777:Geese / Q000254:growth & development / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D013045:Species Specificity
chemical_list: D010100:Oxygen
keywords: Anser indicus; Barnacle goose; Branta leucopsis; Cardiac output; Metabolic rate; Oxygen uptake; Stroke volume; Ventilation