MI5's bizarre Cold War plan: Training gerbils as lie detectors

British intelligence has long relied on unusual allies—including animals—for its operations. During World War Two and the Cold War, creatures like homing pigeons played a role in secret missions. Now, newly released details reveal that even gerbils were once considered for detecting lies in interrogations.

Lady Manningham-Buller, mother of former MI5 chief Baroness Eliza Manningham-Buller, trained homing pigeons for the War Office. These birds were deployed on classified missions, though no specific operations have been confirmed. Baroness Manningham-Buller later acknowledged their use in wartime intelligence.

Decades later, MI5 explored another animal-based tactic. A classified dossier titled Gerbils Use in Counterintelligence outlined plans to train gerbils to sniff out stress hormones in human sweat. The idea was to create a 'rodent lie detector,' where the animals would signal deception through a mechanical system. Lord Jonathan Evans, who led MI5 from 2007 to 2013, reviewed the proposal but ultimately dismissed it. The technology, he confirmed, never worked.

Despite the failure, gerbils have now joined the list of animals linked to British intelligence efforts. Their inclusion follows a long tradition of unconventional methods in espionage.

The experiments with gerbils were abandoned, but the files remain part of MI5's history. Alongside pigeons and other animals, they highlight the creative—and sometimes bizarre—approaches intelligence agencies have tested. No further details on their effectiveness or operational use have been made public.