Diamondback Watersnake
Nerodia rhombifer
Summary 5
Nerodia rhombifer, commonly known as the diamondback water snake, is a species of nonvenomous natricine colubrid endemic to the central United States and northern Mexico. There are three recognized subspecies of N. rhombifer, including the nominotypical subspecies.
Description 6
NOT venomous but may bite if harassed. Typically found in and around bodies of water. Head is only slightly wider than neck, keeled scales, round pupils. Stocky body with a diamond pattern down the back outlined in black or dark brown. Bold pattern when young, darkens with age, but can vary in individuals. Typically 30 to 48 inches (76 to 122cm) in length. (J. R. Dixon and J. E. Werler, Texas Snakes: A Field Guide, University of Texas Press, 2000.)
Behavior 7
When foraging for food the diamondback water snake will hang on branches suspended over the water, dipping its head under the surface of the water, until it encounters a fish or other prey. It is frequently found basking on branches over water, and when approached, it will quickly drop into the water and swim away. If cornered, it will often hiss, and flatten the head and body to appear larger. It only typically resorts to biting if physically harassed or handled. Its bite is known to be quite painful due to its sharp teeth meant to keep hold of slippery fish. Unfortunately, this defensive behavior is frequently misinterpreted as aggression and often leads to its being mistaken for the venomous cottonmouth (Agkistrodon piscivorus), with which it does share habitat in some places. The brown/tan coloration and diamond-shaped pattern also causes it to be mistaken for rattlesnakes, especially when encountered on land by individuals unfamiliar with snakes.
Habitat 7
The diamondback water snake is one of the most common species of snake within its range. It is found predominantly near slow-moving bodies of water such as streams, rivers, ponds, or swamps.
Geographic range 7
The diamondback water snake is found in the central United States, predominantly along the Mississippi River valley, but its range extends beyond that. It ranges within the states of Texas, Oklahoma, Kansas, Iowa, Louisiana, Arkansas, Missouri, Illinois, Indiana, Tennessee, Mississippi, Georgia, and Alabama. It is also found in northern Mexico, in the states of Coahuila, Nuevo León, Tamaulipas, and Veracruz.
This snake has been introduced to Lafayette Reservoir in Contra Costa County, California. It was first observed in the late 1980s and had reached high densities in the early 1990s, causing fisherman and other visitors to complain as they believed that the snakes were eating the reservoir's fish, frogs and, turtles—mostly stocked fish, American bullfrogs, and red-eared sliders—all non-native species too. In 1996 a contract was awarded to a wildlife control company to cull the snake population. Just when the control effort began in late 1997, dead watersnakes and turtles were observed in large numbers. The precise cause of the die-off is unknown, but a respiratory tract fungus was found in dissected snakes. A cause for the outbreak might have been an abnormally wet and cold El Niño weather system. There have been no confirmed observations of watersnakes at Lafayette Reservoir since late 1999, but sightings are occasionally reported, and the population may still continue to present in low numbers.
Conservation concerns 7
While not endangered or threatened, the main threat to N. rhombifer is human ignorance. The diamondback water snake is often mistaken for the cottonmouth or rattlesnakes and is killed out of fear. In actuality, the diamondback water snake and other species of water snakes are far more common than the venomous snakes in their range, especially in areas that are frequented by humans.
Sources and Credits
- (c) tomlott, some rights reserved (CC BY-NC), uploaded by tomlott
- (c) Sara Viernum, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/64920564@N03/6726765459
- (c) Stephen Ramirez, some rights reserved (CC BY-NC-ND), uploaded by Stephen Ramirez
- (c) Cullen Hanks, some rights reserved (CC BY-NC), uploaded by Cullen Hanks
- Adapted by Desmon M Dunn from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Nerodia_rhombifer
- (c) Amber Leung, some rights reserved (CC BY-SA), https://www.inaturalist.org/guide_taxa/494738
- (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Nerodia_rhombifer
