Nerodia rhombifer rhombifer - Northern Diamond-backed Watersnake
This stoutly-built aquatic species is generally brown to olive with a dark, chainlike pattern down the back. The belly is yellowish with dark, half-moon spots that occur irregularly but are concentrated at the sides.
Distinguishing this species from other nonvenomous watersnakes and, more importantly, from the venomous Cottonmouth takes a discerning eye that must be trained. Refer to each species account to learn the subtle differences.
This species occurs in a variety of wetland habitats: swamps, lakes, ponds, rivers, etc. It is mostly a lowland species and is uncommon in the Ozark and Ouachita Mountains.
Habits and Life History
This species can be observed during daylight hours basking along the banks of water. It is known to bask in branches and vines overhanging the water. (Cottonmouth are not known to exhibit this same tree-basking behavior.) Although this species may occasionally forage during the day, it is usually more active at night. The seasonal activity of this species correlates with the temperature of water and, to a lesser extent, ambient temperature. When the water and ambient temperatures reach their highs in late summer, this is also when you can expect the most activity from watersnakes.
Prey and Hunting Techniques
This species feeds primarily on fish. To hunt, it will find a spot with plenty of fish activity in and around rock crevices or submerged logs. It will sway from side to side with its mouth partially agape until a fish snags on its hook-like teeth. Then snap! If the prey is larger and unwieldy in the water, it may drag it to the shoreline for consumption.
Temperament and Defense
This species will make a hasty retreat into the nearest water when approached. If escape is not possible, it has quite an unsavory temperament. Like other watersnakes of the genus Nerodia, it will thrash, bite, and musk.
Many people mistake this species for a venomous Cottonmouth and kill it on sight. This is especially true at rural farm ponds and fish farms where people try to "protect" their fish stock. Despite persecution, populations of this species appear secure.
State Distribution and Abundance
This species is found throughout most of the southeastern half of the state and along the Arkansas and White Rivers. In its range, it is one of the most abundant and commonly encountered serpents.