Rat Universes

Jon Day and Thomas Jones

23 July 2025

The first true lab rat was the Wistar rat, a strain specifically bred for biomedical research. In his “rat universe” experiments, John B. Calhoun placed large numbers of these rats in a controlled environment for more than a year, and found evidence for the same anxieties sparked by their urban cousins: overpopulation and an ensuing ‘behavioural sink’.

Jon Day joins Tom to discuss lab rats, street rats and the ‘rat in the head’. They explore the reasons many found Calhoun’s rat utopias compelling, and why his conclusions do both rats and humans a grave disservice.

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