How does the dorsal pattern of a Northern Water Snake change as it matures toward adulthood?

Darkening background pigments obscure the distinct dark blotches.

Physical appearance undergoes a significant transformation as the Northern Water Snake ages, which frequently causes misidentification. Juvenile snakes exhibit very clear, distinct markings, often involving reddish-brown or darker brown squarish blotches set against a lighter ground color. As the snake matures, an increase in melanism occurs, often exacerbated by time spent basking or algae accumulation. This darkening of the background coloration causes the original patterns to become faint, less defined, or almost completely obscured. In older specimens, especially those living in darker habitats, the snake can appear almost uniformly black due to this progressive darkening and pattern obscuring.