Shrews have been found to shrink and regenerate tissue in their heads in response to seasonal variations:
Common shrews shrink their heads — including their skulls — in winter, researchers have found. They believe that this dramatic example of downsizing may help the animals to survive when food is scarce.
Individual wild common shrews (Sorex araneus) captured and tagged in Germany showed large reductions in skull size and body mass over the winter. Their spines also got shorter, and major organs, including the heart, lungs and spleen, shrank. Even their brain mass dropped by 20–30%, according to Javier Lázaro, a biologist at the Max Planck Institute for Ornithology in Radolfzell, Germany. In spring, the animals started to regrow.
"We hypothesize that these seasonal changes could have adaptive value," says Lázaro, who led the work. Shrews have an extremely fast metabolism, he points out, and reducing their body mass during winter might increase their chances of survival, because they wouldn't need so much food. In particular, he adds, "reducing brain size might save energy, as the brain is energetically so expensive".
Also at The Guardian.
Profound reversible seasonal changes of individual skull size in a mammal (DOI: 10.1016/j.cub.2017.08.055) (DX)
(Score: 3, Interesting) by frojack on Friday October 27 2017, @08:07PM (2 children)
Is this just another fancy name for living off the fat and other body mass while in hibernation?
They make it sound like something the shrew does intentionally, where it could just be surviving on a starvation diet while in hibernation.
Similar processes are known in bears during hibernation:
https://www.ncbi.nlm.nih.gov/pubmed/26157160 [nih.gov]
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480364/ [nih.gov]
https://phys.org/news/2015-07-hibernating-bones-resorption.html [phys.org]
Although in bears, the object seems to be to preserve bone mass by shutting down the normally occurring bone re-absorption that all land mammals undergo - even humans.
No, you are mistaken. I've always had this sig.
(Score: 2) by bob_super on Friday October 27 2017, @09:46PM (1 child)
Which leads us to a variant of the eternal question: Do Bear/Shrew females know about shrinkage?
(Score: 1) by Ethanol-fueled on Saturday October 28 2017, @12:36AM
I think a more important question would be, do they regenerate that lost brain mass, and what is the mechanism for that regeneration?