10.5061/DRYAD.T4B8GTHZH
Shankar, Anusha
0000-0002-3043-6126
Stony Brook University
Schroeder, Rebecca J.
George Fox University
Wethington, Susan M.
Hummingbird Monitoring Network
Graham, Catherine H.
Swiss Federal Institute for Forest, Snow and Landscape Research
Powers, Donald R.
George Fox University
Hummingbird torpor in context: duration, more than temperature, is the key
to nighttime energy savings
Dryad
dataset
2020
adaptive thermoregulation
avian torpor
Arizona
Comparative Physiology
Ecuador
tropics
National Aeronautics and Space Administration
https://ror.org/027ka1x80
NNX11AO28G
Tinker Foundation
https://ror.org/01sv5w039
National Geographic Society
https://ror.org/04bqh5m06
9506-14
Stony Brook Department of Ecology and Evolution*
George Fox University*
Faculty Development Grant GFU2014G02
George Fox University*
Richter Science Scholar Grant
Stony Brook Department of Ecology and Evolution
George Fox University
Faculty Development Grant GFU2014G02
2020-04-14T00:00:00Z
2020-04-14T00:00:00Z
en
77731 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Torpor is an important energy saving strategy in some small birds, but it
has rarely been studied in natural field conditions. We compared torpor
use across 43 wild-caught individuals of eight hummingbird species across
sites with different natural temperature regimes. Most laboratory studies
focus on the relationship between metabolic rate and temperature, but our
aim was to evaluate what environmental factors most influence hummingbird
nighttime energy management under natural conditions. We found that the
probability of an individual entering torpor was weakly correlated with
mass but unrelated to nighttime temperature and that hummingbirds at both
warm, tropical and cooler, temperate sites used torpor. Energy savings in
torpor were maximized as ambient temperatures approached a species’
minimum body temperature, consistent with laboratory studies; energy
savings ranged between 65-92% of energy per hour in torpor compared to
normothermy. However, regardless of the degree of energy savings in
torpor, variation in total nighttime energy expenditure was most
significantly influenced by torpor bout duration. Lab studies largely
assess the effect of temperature on torpor use, but our findings indicate
that other environmental conditions are more important in determining
hummingbirds’ total nighttime energy expenditure under natural temperature
cycles. Our results show that a small endotherm’s nighttime energy
management in its natural habitat is more affected by torpor bout
duration, which is linked to photoperiod, than by temperature. This result
suggests that in their natural environments hummingbirds are able to save
energy in torpor across a range of nighttime temperatures, indicating that
they may have sufficient physiological flexibility to tolerate climatic
variation.
Energy expenditure data collected via open-flow respirometry, in the field
in Arizona and Ecuador.
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