Any animal ascending a mountain experiences a double whammy of
impediments: the air gets thinner as it also becomes colder, which is particularly problematic for creatures struggling to keep warm when
less oxygen is available. For tiny animals with the highest-octane
lifestyles, such as hovering hummingbirds, the challenges of
relocating to higher levels to evade climate change may be too much,
but no one knew whether these extraordinary aviators may have more gas
in the tank to keep them aloft at higher altitudes.
As Anna's hummingbirds (Calypte anna) are comfortable up to elevations
of ~2800 m, Austin Spence from the University of Connecticut, USA, and
Morgan Tingley from the University of California, Los Angeles, USA,
were curious to find out how hummingbirds that originated from close
to sea level and those that live at the loftier end of the range would
cope when transported well above their natural habitat to an altitude
of 3800m. They publish their discovery in Journal of Experimental
Biology (
https://journals.biologists.com/jeb) that the birds struggle
to hover and suffer a 37% drop in their metabolic rate at that height
- in addition to becoming torpid for most of the night to conserve
energy - making it unlikely that they can relocate to higher
altitudes.
https://www.eurekalert.org/news-releases/953331
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