Seasonal sleep-wake patterns of plateau zokors (Eospalax baileyi)

Plateau zokors (Eospalax baileyi), endemic to the Qinghai-Tibet Plateau (QTP), are solitary subterranean rodents that spend their lifespan within underground burrows. Although the activity rhythms of the plateau zokors have been slightly documented, their sleep-wake patterns and seasonal variations remain unclear. Here, we investigated the sleep-wake patterns of wild-caught plateau zokors during spring and autumn using polysomnographic (PSG) recordings in the lab, and compared the findings with those of Sprague-Dawley (SD) rats. We found that plateau zokors exhibit three clearly distinguishable brain states: wakefulness (W), non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Under complete darkness in spring, they showed rhythmic-like activity. Compared with daytime periods, they spent significantly more time in wakefulness (398.88 ± 15.02 min vs. 320.55 ± 23.69 min, P < 0.05), and less time both in NREM sleep (257.32 ± 11.28 min vs. 312.23 ± 18.18 min, P < 0.05) and REM sleep (63.80 ± 6.63 min vs. 87.22 ± 7.27 min, P < 0.05) during the nocturnal period (local time). Although the plateau zokors in autumn did not exhibit significant rhythmic-like activity, they showed higher levels of wakefulness in the awake state and shallower sleep during sleep. Notably, plateau zokors had longer and more stable REM sleep compared to SD rats. These findings provide new empirical evidence for adaptive strategies in sleep ecophysiology and help reveal the functions and evolutionary strategies of sleep.