Many people wonder if snakes truly lose their sight during the “dog days” of summer, a common belief passed down through generations. This idea suggests a specific period of the year renders these reptiles unable to see. Understanding the natural processes of snakes and the origins of this seasonal term can clarify this widespread notion.
Understanding Dog Days
The term “dog days” refers to the hottest, most humid part of summer. Its origin traces back to ancient times and the heliacal rising of Sirius, the “Dog Star.” When Sirius appeared to rise with the sun, ancient cultures associated this celestial event with intense heat. Historically, this period spans from early July to early September, marking a seasonal peak in warmth rather than an astronomical event influencing animal biology.
How Snakes See
Snakes possess unique visual adaptations. Unlike mammals, snakes lack movable eyelids; their eyes are covered by a transparent, fixed scale called a brille or spectacle. This clear scale protects the eye. Snake vision varies among species; some detect movement well, while others have sharper visual acuity. Many species are more sensitive to light and motion than to color, though some perceive two primary colors. Snakes also rely on other senses, such as their forked tongue for chemical cues via their Jacobson’s organ and, for some, heat-sensing pit organs to navigate and locate prey.
The Molting Process
Snakes periodically shed their outer layer of skin in a process known as molting. This natural event is necessary for growth and helps remove external parasites. Before shedding, a new skin layer forms underneath the old one, including a new brille over the eyes.
During this preparatory phase, a lubricating fluid accumulates between the old and new skin layers, beneath the old brille. This fluid causes the brille to become cloudy or opaque, often appearing milky or bluish, which temporarily impairs the snake’s vision. This cloudiness lasts for several days. Once the fluid is reabsorbed and the new skin is ready, the snake rubs against surfaces to peel off the old skin, including the cloudy brille, usually in one continuous piece.
Why Snakes Appear Blind
Snakes are not blind during the “dog days” due to the season itself. The perception of snakes being blind stems from their molting process, which can occur at any point throughout the year. Molting is more frequently observed during warmer months when snakes are more active. The temporary vision impairment caused by the cloudy brille during pre-shed makes snakes more vulnerable.
During this phase, snakes often exhibit behavioral changes. They may become more reclusive, seek hiding places, and appear less active or sluggish. They may also be more defensive or irritable due to their compromised sight. Once the old skin, including the opaque brille, is shed, the snake’s vision returns to its normal state.