Published January 11, 2022 | Version v1
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A heterothermic spectrum in hummingbirds

  • 1. Cornell University
  • 2. George Fox University
  • 3. Swiss Federal Research Institute WSL*

Description

Many small endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g. arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37 &[deg]C, while others can only enter shallow torpor (e.g., pigeons, 3-10 &[deg]C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders. Although the literature hints that some bird species can use both shallow and deep torpor, little empirical evidence of such an avian torpor spectrum exists. We infrared imaged three hummingbird species that are known to use deep torpor, under natural temperature and light cycles, to test if they were also capable of shallow torpor. All three species used both deep and shallow torpor, often on the same night. Depending on the species, they used shallow torpor for 5-35% of the night. The presence of a bird torpor spectrum indicates a capacity for fine-scale physiological and genetic regulation of avian torpid metabolism.

Notes

See metadata for detailsĀ andĀ code on github (https://github.com/nushiamme/TorporShallowDeep).

Funding provided by: National Aeronautics and Space Administration
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100000104
Award Number: NNX11AO28G

Funding provided by: Tinker Foundation
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100006038
Award Number:

Funding provided by: National Geographic Society
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100006363
Award Number: 9506-14

Funding provided by: American Philosophical Society
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100001461
Award Number:

Funding provided by: European Research Council
Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100000781
Award Number: ERC-2017-ADG 787638

Funding provided by: Swiss Federal Institute for Forest, Snow and Landscape Research
Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100015742
Award Number:

Funding provided by: George Fox University*
Crossref Funder Registry ID:
Award Number: GFU2014G02

Funding provided by: George Fox University*
Crossref Funder Registry ID:
Award Number: Richter Scholar grant

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Additional details

Related works

Is derived from
10.5061/dryad.cc2fqz65h (DOI)