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The coldest hummingbird (~3º C) is getting headlines, but...
1) it wasn't the most exciting result of the paper
2) it wasn't unexpected
3) the 'record' won't last long
(thread)
https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0428
1) it wasn't the most exciting result of the paper
2) it wasn't unexpected
3) the 'record' won't last long
(thread)
https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0428
In a community of 6 hummingbird species, each had a different 'lower critical body temp' in nightly torpor.
e.g.
Black Metaltails tended to track air temps, dropping body temps to near-freezing, ~5º C
Sparkling Violetears spent energy keeping body temp's higher, ~10ºC
etc.
e.g.
Black Metaltails tended to track air temps, dropping body temps to near-freezing, ~5º C
Sparkling Violetears spent energy keeping body temp's higher, ~10ºC
etc.
Closely related hummingbird species had similar lower critical body temps, so depth of torpor was conserved during evolution.
Evolutionary history predicts whether a species uses extreme or moderate torpor depth.
And deep torpor allows more energy savings during cold nights.
Evolutionary history predicts whether a species uses extreme or moderate torpor depth.
And deep torpor allows more energy savings during cold nights.
It follows that some clades of hummingbirds are 'better' at torpor than others.
One hummingbird clade, the coquettes, exhibited deeper (colder) torpor than other clades (mangoes, brilliants, giant).
Coquettes have also diversified into the highest & coldest parts of the Andes.
One hummingbird clade, the coquettes, exhibited deeper (colder) torpor than other clades (mangoes, brilliants, giant).
Coquettes have also diversified into the highest & coldest parts of the Andes.
Is torpor ability a cause or consequence of evolutionary success in high-elevation cold environments?
YES.
(*This* was the most exciting finding of the paper)
More species-sampling & experimentation could tease apart cause from consequence.
<submit grant proposal!>
YES.
(*This* was the most exciting finding of the paper)
More species-sampling & experimentation could tease apart cause from consequence.
<submit grant proposal!>
Why was the ~3º result expected?
In the 1970's, F. Lynn Carpenter measured an Andean Hillstar hummingbird at 5º C, when ambient temp was 3º C
...since then, nobody has really looked, even though several Andean hummingbird species routinely experience ambient temperatures < 0ºC
In the 1970's, F. Lynn Carpenter measured an Andean Hillstar hummingbird at 5º C, when ambient temp was 3º C
...since then, nobody has really looked, even though several Andean hummingbird species routinely experience ambient temperatures < 0ºC
Why will the record be short-lived?
We took these measurements during the relatively warm, rainy season (March, see photo of lush green hillsides), but ambient temperatures drop lower during July-August, and hummingbird body temps probably do too.
We took these measurements during the relatively warm, rainy season (March, see photo of lush green hillsides), but ambient temperatures drop lower during July-August, and hummingbird body temps probably do too.
This study was always intended as preliminary—there's much more about torpor to discover! (e.g. see outstanding recent work by @nushiamme)
@UrSchmittinMe did both fieldwork & stats, & (along w/ other coauthors) deserves major kudos for the good parts of our paper.
8/end
@UrSchmittinMe did both fieldwork & stats, & (along w/ other coauthors) deserves major kudos for the good parts of our paper.
8/end
