Back

Numerous species of #mammals and #birds can respond to challenging periods (e.g., lack of food or water, extreme cold) through #torpor.

Photo: a torpid Eastern chipmunk. Taken by @dl_levesque / @daniellelevesque.bsky.social, the 2nd author of this paper.

2/12

#Torpor involves programmed and reversible decreases in metabolic rate, along with a drop in body temperature. Based on its duration, torpor in endotherms can be classified as daily torpor (<24 hours) or #hibernation (from days or weeks up to several months).

3/12

A wide range of #mammals can enter #torpor, including , , , , and .

Similarly, many clades of #birds include torpor-capable species. Yet, only a single bird species (the common poorwill; public domain picture by Louis Agassiz Fuertes) is known to hibernate.

4/12

To address 3 key questions regarding #torpor #evolution, we compiled a #dataset of a) torpor capabilities and b) 21 ecophysiological variables for 1,338 species of #mammals and #birds.

We then analysed this dataset using a series of #phylogenetic comparative methods.

5/12

Q: Are daily torpor and #hibernation evolutionarily distinct #torpor types or parts of a continuum?

Our results strongly support the continuum hypothesis. That is, evolutionary transitions between no torpor and hibernation generally require an intermediate daily torpor step.

6/12

Q: Can we predict whether a given species is capable of torpor based on its physiological and ecological characteristics?

Features associated with torpor include low body mass, nocturnality, and a resource-poor environment. Nevertheless, such associations are quite weak.

7/12

Furthermore, torpor-capable species cover a wide range of physiological and ecological parameter space. The distribution of daily heterotherms and hibernators in this space is primarily taxonomically structured rather than environmentally structured.

8/12

Q: Was #hibernation present in early mammalian ancestors or did it evolve multiple times independently?

The argument for a single origin of hibernation in #mammals stems from its high degree of complexity, which would make multiple gains of hibernation difficult to occur.

9/12

Some have also suggested that #hibernation might have been instrumental to the survival of #mammals during the K-Pg boundary.

In contrast to these, we estimated a low probability for hibernation in ancestral mammals, with multiple gains of hibernation being more likely.

10/12

A scenario of several independent gains of #hibernation is also consistent with:

a) the pattern of evolutionary transitions among #torpor states (post 6 above), and

b) the fact that variation among torpor-capable species is predominantly taxonomically structured (post 8 above).

11/12

I would like to thank #EMBO and my coauthors for this very cool collaboration which allowed us to shed light on the origins of the amazing diversity in #torpor patterns of endotherms!

Stay tuned for more related work soon!

12/12

Here's also a link to a Plain Language Summary of our study: https://fesummaries.wordpress.com/2024/12/20/repeated-evolution-of-torpor-throughout-the-evolutionary-history-of-mammals-and-birds/

13/12

The Senckenberg Society for Nature Research @SenckenbergWorld / @sgn.one also made a press release for our paper: https://www.senckenberg.de/en/pressemeldungen/just-five-more-minutes-news-on-the-evolution-of-hibernation/

14/12