What is a key identification characteristic to determine the difference between a timber rattlesnake and a northern water snake?

A key identification characteristic that distinguishes a timber rattlesnake from a northern water snake is that the head of the rattlesnake abruptly swells from the neck. This pronounced difference in head shape is a reliable visual cue; rattlesnakes possess a distinctly larger and wider head compared to their neck, which contributes to their triangular-shaped profile. This feature is not present in northern water snakes, which have a more evenly tapered head that does not exhibit such a dramatic widening.

In contrast, while the northern water snake may display coloration variations, it does not have the same prominent head shape as a rattlesnake. The description of the coloration of the two snakes is not as reliable for identification as the head shape, as water snakes can have patterns and colors that may confuse identification. Additionally, stating that the rattlesnake is uniformly colored does not accurately reflect the diversity in its patterns and colors. By focusing on the distinct head shape, one can make a more accurate identification between these two species.