PIEN HUANG, HOST:
Adaptation and evolution can steer the trajectory of a species with the slightest environmental change. Scientists in Chicago are mapping some fascinating evolutionary changes to local animals and how humans have contributed to that change.
STEPHANIE SMITH: We have the shape information, and the new hypotheses that we can test based on our study are questions about how animals are adapting to sound in city life and questions about how animals are changing their diet.
HUANG: Stephanie Smith and co-author Anderson Feijo published their research on the changes in chipmunks and a mouselike creature called a vole in the Chicago area using skulls, bones and teeth collected at Chicago's Field Museum over decades.
SMITH: What we wanted to do was we wanted to do something that we could do only with museum specimens, and we wanted to learn a little bit about how city life is affecting animals in the city of Chicago.
ANDERSON FEIJO: We were able to find urbanization data for Chicago going back to the 1940s until recent day. So we used this information to provide a more precise information what - the level of urbanization those chipmunks and vole were exposed to by the time they were collected.
SMITH: We 3D scanned 82 skulls, and for the voles, we 3D scanned 54 skulls. In total, we took measurements - like, linear measurements using calipers - on 132 chipmunk skulls and 193 vole skulls. So it's a lot of skulls.
HUANG: Their team found a divergence in two types of animals.
FEIJO: For chipmunks, we found they're getting bigger over time, while for voles, they seem not to have changed much the size over the last century or so.
HUANG: The difference is human interaction.
FEIJO: With a shift in the diet that animals are eating towards a more soft, more processed, human-related food.
HUANG: Their research was published in the Society for Integrative and Comparative Biology.
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