HerpIndiana

Northern Watersnake (Nerodia sipedon)

Description

A medium-sized gray and brown snake with banded dorsal pattern. These watersnake generally attain lengths of about 2 to 3.5 feet, with very large adults sometimes measuring nearly 4 feet. Ventral coloration varies greatly, but is usually light to dark tan with extremely variable reddish patterns of blotches and triangles. Juveniles are more heavily banded. These snakes have 7-9 upper labials and 10 lower labials, with 21-23 scale rows at midbody and a divided anal plate (Minton 2001, 266-268).

Distribution

The Northern Watersnake's range covers the entire state of Indiana. The sipedon subspecies generally occurs north of the Indianapolis area, while pleuralis exist in the southern third of the state. The central portion of the state contains intergrade populations (Minton 2001, 268).

Activity

Though Minton said he has observed this species in every month other than December, they are usually active from mid-spring to mid-fall. Like most snakes, Northern Watersnakes are generally most common in the spring and fall (Minton 269).

Taxonomy

Three species of the genus Nerodia occur in Indiana. Besides the Northern Watersnake, Plain-bellied Watersnakes (Nerodia erythrogaster) and Diamond-backed Watersnakes (Nerodia rhombifer) inhabit this state. Two subspecies of Northern Watersnake exist in the state, the Northern Watersnake (Nerodia sipedon sipedon) and the Midland Watersnake (Nerodia sipedon pleuralis).

Natural History

Northern Watersnakes can be found in most aquatic areas of the state, including rivers, lakes, ponds, and marshes. Watersnakes eat primarily fish, but will also take amphibians. Minton reported mating in this species throughout the month of May. Females give birth in late summer. Young Watersnakes are preyed upon by fish and Bullfrogs, while herons and some mammals will eat Watersnakes of varying sizes (Minton 2001, 268-269).