Last Word on Point:Counterpoint: High altitude is/is not for the birds!

to the editor: We would like to thank the scientists who commented on this Point:Counterpoint. We originally argued that high altitude is for the birds because of several unique features that should improve their ability to exercise at extremely high altitudes (4). Many authors agreed with our Point, but several others highlighted the impressive ability of other vertebrates to tolerate hypoxia. These animals are indeed exceptional [Casey (1) in fact cites work by one of us (Meir) on these animals!], and we do not dispute the striking tolerance of acute, transient hypoxia by diving mammals (or by some birds, like penguins) or of chronic hypoxia/anoxia by carp, turtles, or hibernators. However, these animals use entirely different strategies in hypoxia, such as metabolic suppression, and they cannot compare with flying birds in their ability to sustain high rates of aerobic metabolism during prolonged exercise in hypoxia.