Breaking news (to me): "If wheel running is indeed caused by captive housing, wild mice are not expected to use a running wheel in nature. This however, to our knowledge, has never been tested. Here, we show that when running wheels are placed in nature, they are frequently used by wild mice, also when no extrinsic reward is provided. … Wheel movement not caused by mice was caused by shrews, rats, snails, slugs or frogs"
https://royalsocietypublishing.org/doi/10.1098/rspb.2014.0210
