Canine sleep behavior can exhibit variations, including instances where the eyelids do not fully close during rest. This phenomenon presents as the animal appearing to be asleep while the eyes remain partially or entirely open. The observed manifestation is generally harmless but can, in some instances, indicate underlying physiological or anatomical considerations.
This partial eyelid closure, or incomplete sleep, can stem from breed-specific characteristics, such as conformation of the facial structure, particularly in brachycephalic breeds. The depth of sleep also influences the completeness of eyelid closure; lighter sleep stages may not necessitate full ocular covering. Furthermore, persistence of certain ancestral behaviors, such as vigilance even during rest, may contribute to this observed phenomenon. This behavior afforded a level of protection in the wild.