The challenge of being small
I study the common shrew (Sorex araneus), a tiny mammal with a metabolism so extreme that even a few hours without food can be fatal.
This high metabolism makes them particularly vulnerable to seasonal changes, and it makes it impossible for them to hibernate during winter. Their solution? They shrink.
Unlike animals that grow steadily over years, shrews undergo a radical transformation within a single lifetime.
This dramatic change, Dehnel’s Phenomenon, reduces their brain, bones, and organs to save energy in winter scarcity, regrowing them in spring for breeding.
How does it work?
Born in summer, shrews rapidly reach peak brain size. This is the largest their brains will ever be.
As winter sets in, the shrew shrinks their brains and bodies, reducing energy needs.
By spring, they double their winter mass, gearing up to reproduce.
Shrews live only about a year, so this transformation happens just once.
What happens cognitively when brains shrink and regrow?
My research explores what happens when their brain changes size:
How does brain size affect cognitive abilities?
Does a smaller brain lead to simpler decision-making?
These questions go beyond just shrews. Understanding how an animal maintains function despite physical changes in the brain helps us explore broader ideas in neurodegeneration and energy efficiency.
Does captivity influence learning?
Brain size is of course only part of the story… environment shapes behavior too.
In captivity, animals face new challenges. Do shrews kept in captivity learn differently than those in the wild?
I tested the ability of shrews to associate an odor cue with a reward in a Y-maze associative learning task.
Each dot represents an individual shrew’s decision in a trial. The x-axis represents the trial number, from 1 to 10. The y-axis shows whether they made the correct choice (1) or the wrong one (0).
Summer wild (orange) shrews had the highest and earliest success rates.
Winter wild (dark blue) shrews showed a similar learning curve, but they learned at a slower rate and did not reach the Summer success rate.
Winter captive (light blue) shrews showed no learning, never deviating from chance.
📄 This work is published in Royal Society Open Science: Captivity alters behaviour but not seasonal brain size change in semi-naturally housed shrews
Project Collaborators
I conduct this research supervised by Dr. Dina Dechmann at the Max Planck Institute of Animal Behaviour
Collaborators:
Prof. Dominik von Elverfeldt, University of Freiburg, Germany
Prof. Liliana Dávalos, Stony Brook University, New York
Prof. John Nieland, University of Aalborg, Denmark