The question of whether opossums blink is common, likely because the Virginia Opossum (Didelphis virginiana), often appears to have a perpetual, fixed gaze. Opossums do blink, as they are mammals equipped with the necessary anatomy. Blinking is a fundamental biological necessity for nearly all terrestrial vertebrates, and their nocturnal behavior makes their blinks less noticeable to human observers.
The Direct Answer: Opossums and Eyelid Function
Like all mammals, opossums possess upper and lower eyelids, and a lacrimal system that produces tears to maintain corneal health. The primary purpose of blinking is to distribute the tear film across the eye’s surface, which cleans the cornea and prevents it from drying out. Without this lubrication, the eye would suffer damage, affecting the animal’s vision.
The muscle groups responsible for eye movement and eyelid control, known as extraocular muscles, are present, allowing for the rapid closure and opening of the eye. However, an opossum’s blink is less frequent and more subtle than a human’s. Their small, dark eyes and nocturnal lifestyle mean the action of their eyelids is rarely observed clearly during brief encounters.
Vision and Nocturnal Adaptation
The appearance of the opossum’s eye is defined by its adaptation for life in low-light environments. Their eyes are structured to capture as much ambient light as possible during nighttime foraging. This adaptation results in perpetually widely dilated pupils, which makes the entire eye appear dark and fixed.
The retina, the light-sensitive tissue at the back of the eye, is dominated by rod cells, which are highly effective at detecting movement and contrast in dim conditions. They have a limited number of cone cells, meaning their vision is less acute and they perceive fewer colors compared to many diurnal animals. This focus on night vision means their gaze may seem unwavering because the visual system is optimized for broad light collection rather than fine, detailed focus that requires constant adjustment.
The Misconception: Eye Movement During Playing Possum
The most significant source of the misconception that opossums do not blink comes from their involuntary defense mechanism, often referred to as “playing possum.” This behavior is a physiological response known as tonic immobility or thanatosis, which is triggered by extreme threat. It is not a conscious act of feigning death but an automatic, catatonic state.
When an opossum enters tonic immobility, a physiological slowdown occurs, including a drop in heart rate and breathing. During this state, the animal’s reflexes are suspended, and the eyes may remain open, appearing glassy, fixed, and unblinking. This lack of movement and response, combined with a vacant stare, is convincing to predators that the animal is dead. This involuntary, temporary paralysis, which can last for minutes or even hours, is why the opossum’s eyes are commonly observed in an unblinking state.