Stony Brook scientists study the tiny, mysterious shrew for clues to brain health

What can be learned from a shrew — the tiny, furry, high-strung creature that needs to eat the equivalent of its body weight in food every day to survive?

More than you might expect, including possible clues to neurodegenerative diseases such as Alzheimer’s, according to two Stony Brook University scientists who have spent years studying the extraordinary way shrews live through the winter.

They don’t migrate to warmer climates and they don’t hibernate. A shrew’s brain and other organs can shrink by as much as 30% and then grow back in the spring. Once the brain of a human being shrinks, it remains in that state.

Researchers believe unraveling the biological processes that allow the shrew to make this transformation without losing brain cells or cognitive abilities could eventually help treat humans.

Liliana M. Dávalos, an evolutionary biologist and professor at Stony Brook who runs a lab focused on natural history, and William Thomas, a postdoctoral researcher specializing in molecular and computational biology, are part of a team of researchers behind a new study published this month in Genome Research, the journal published by Cold Spring Harbor Laboratory Press. Working with scientists who trapped and examined wild shrews in Germany — and following ethics guidelines, shipped samples of the animals to Long Island — they explored the molecular pathways that allow shrews to control their metabolism and change their body size according to the season.

Newsday spoke with Dávalos and Thomas about their work. The interviews are edited for space and clarity.

What exactly happens to shrews in the winter?

Dávalos: Small mammals have more difficulty than larger mammals dealing with the winter because the smaller you are, the greater the rate you need to consume energy to keep your body warm. Shrews don’t migrate or hibernate. They become smaller so the total amount of energy needed goes down. This is their strategy for when resources are not abundant, and the temperature is lower.

[Other researchers have found] they do this in anticipation of the winter, starting in October. It’s a combination of environmental cues that have to do with temperature and, to some extent, food availability. Then in the spring the situation is reversed, and they started growing back.

It’s well-established shrews undergo this transformation, but not how. What have you learned?

Thomas: Our research is into the biochemistry of how shrews change their size. In our paper that came out in 2024, we looked at mRNA in the hypothalamus, a region of the brain that helps the body maintain body temperature, metabolism, growth, reproduction and so on. We found that shrews show unusually high activity in genes that help balance energy use in the brain.

In humans, this same process is linked to neuroinflammation and neurodegenerative diseases. But shrews avoid these harmful neurodegenerative effects, like not losing brain cells or cognitive abilities, suggesting they may have evolved unique protective mechanisms that allow their brains to function normally even under extreme energetic stress.

In our new paper, shrews coordinate these dramatic seasonal changes across the body. We analyzed both the chemical composition of their blood and gene activity in the liver across seasons. The results show that shrews continuously burn through fatty acids as they shrink and regrow, instead of saving them as hibernators do. This constant turnover likely helps keep their metabolism running during winter shrinkage without damaging neural function.

Why is it important?

Dávalos: I want to make a case for natural history for the sake of natural history. There is something about learning about the limits of what a mammal can do, especially a tiny mammal, that is interesting for its own sake, and this is really fascinating from a human perspective because when our brains shrink, they don't recover. Human brains and shrew brains share a common ancestry. We found there was no key molecular signal that suddenly says the shrew’s brain shrinks and regrows. The data is showing us there is a complex web of interaction across multiple genes.

There is no neuronal death in the shrinkage phase. We want to discover how these neuroprotective mechanisms can work across all mammals.

How could this lead to discoveries about human brain health?

Thomas: Metabolism, body size and life span are all interconnected, and when metabolism is disrupted by diet, exercise, aging, inflammation or disease, this can have cascading effects across the body and brain. This is why environmental factors like diet are linked to conditions such as obesity, diabetes and even neurodegenerative disorders like Alzheimer’s disease. By studying shrews, we can gain insights into understanding how these processes are coordinated at a molecular level in shrews whose unique traits would result in pathological states in humans.

We did find some genes similar to those associated with neurological diseases, such as one that is a protein recycling gene. What you see in diseases like Alzheimer’s is an accumulation of proteins in the brain that should not be there.

A gene called CCDC22 plays a pivotal role in protein recycling in the brain. Shrews have an overabundance of this gene compared to other mammals, including humans. Improper recycling can lead to the buildup of undesirable proteins, which has been implicated in neurodegenerative diseases.

Understanding how shrews remodel their bodies provides new clues for protecting brain health, managing metabolism and understanding life span in humans.