Despite being one of the smallest mammals on the planet, shrews have a big role to play in the study of evolution and adaptation. Not only have shrews been around for millions of years, but there are also almost 400 known species around the world, making them one of the most species-diverse mammal families.  

Trent Environmental and Life Sciences Ph.D. candidate, Marie-Laurence Cossette (Gzowski College) is studying these fascinating creatures to gain a better understanding of how mammals adapt and evolve to different environments.  

In a recently published paper in Molecular Ecology, Marie shares new insights on the epigenetic variations between masked shrews (Sorex cinereus) living in mainland and island populations. 

“Shrews are really interesting animals and have adapted to their various environments over the years. Not many people know how fascinating these mammals are; that’s why I want to develop genomic resources on them,” Marie explains. “My research is just a little piece of the puzzle to better understand the very complicated topic of evolution.” 

Honing in on a tiny shrew population

A shrew population living off the southern coast of Nova Scotia has been isolated from the mainland for thousands of years and has evolved to adapt to their specific environment. For her study, Marie trapped shrews in two island locations, as well as two mainland locations, to compare epigenetic markers and morphology between the populations. 

Epigenetics is the study of how behaviors or the environment can change the way an organism’s genes work. Without changing anything in the DNA sequence, epigenetic markers can change how DNA is read and expressed. 

Findings from Marie’s study indicate that the island shrews were different than their mainland counterparts: they were smaller, and their digestive systems seem to have adapted to the food resources available on the island. Based on the epigenetic marker data she collected, Marie also found that the island shrews might also be aging faster than their mainland counterparts. 

Taking a look at the bigger picture

Marie has shifted her research to give a broader perspective of why shrews are so special. With the fastest rate of resting energy expenditure (I.e. metabolic rate) per unit body of mass of all mammals and living for only around 17 months, shrews are an important organism to study from an aging perspective. 

“We already know that shrews are masters of adapting and evolving,” Marie says. “I’m now doing a comparative analysis of shrews versus other mammals to see if they have specific mutations or gene duplications that make them so adaptable.” 

Working alongside forensic wildlife expert Dr. Aaron Shafer, Marie is looking at how shrew genomic data can inform the creation of more accurate non-invasive tools for aging wild animals.  

“Professor Shafer was one of my undergraduate research supervisors, and I found his wildlife genomics work really fascinating,” Marie explains. “When the opportunity came up to do my graduate studies with him, I jumped at the chance.” 

Learn more about the genomic tools that Marie and Professor Shafer are developing to age wild animals.