Species

Nerodia rhombifera grows to about 76 – 160 cm in length. Females tend to be slightly larger than males on average.  They are heavy bodied ranging from greenish brown to brown hues with a dark net-like pattern formed by dark blotches along the back. Blotches are connected by alternating dark bars on sides, leading to a yellow underbelly. Scales are keeled in rows of 25-31, with a divided anal plate. Males have pimple-like bumps on chin scales. The diamondback water snake is non-venomous but extremely aggressive, and often misidentified as poisonous cottonmouths. They release musk and fecal mater when defensive (Missouri Department of Conservation).

Status in Estuaries

Mating occurs in Spring producing live births of 14-62 young 23-33 cm in length between August and October (Behler and King, 1979).

Abundance and Range

Found as far north as Indiana and Southern Illinois, concentrated along the Mississippi River, as well as west into Texas and Mexico, east to Alabama, with smaller populations in Oklahoma, Kansas and Missouri. They inhabit marshes, rivers, swamps, streams, lake borders, canals, ditches, and ponds (Behler and King, 1979). 

Site Fidelity

No known site fidelity.

Ease of Census

Difficult. Partially terrestrial, without nesting, and easily misidentified.

Feeding Habits

A diurnal hunter, the diamondback water snake trolls shallow water, shorelines and deeper water for prey. The diet mostly consists of frogs, toads, slow moving and small fish, which are eaten live. Carrion is also a common part of diet. A nocturnal hunter on warm nights (Missouri Department of Conservation). 

Diamondback Water Snake Contaminant Exposure Data

  I.

Organochlorine Contaminants

1.

 Between April and September 1971, within 50 of water, 3 individuals were collected from the Navasota area (Fleet et al, 1972). Concentrations of DDE, DDT, DDD, and dieldrin, respectively, were 7.8, 0.7, 0.2, and <0.09 mg/g for the first individual, 14.6, 1.2, 0.2, and 0.1 mg/g for the second, and 14.3, 0.7, 0.2, and 0.2 mg/g for the third.

2.

Individuals (7-14) collected from two sites in central Texas between 1972 and 1973 were found to have 2.3 mg/g DDE in their fat bodies at the Navasota site and 16.4 mg/g DDE and 47.0 mg/g PCB at the Highway 21 area (Stafford et al, 1976).

3.

Seven to thirteen individuals were collected in south Louisiana from each of three sites between 1977 and 1979 (Sabourin, et al., 1984).  Lindane, endrin, and aldrin levels were all ≤0.02 mg/g wet weight for fat bodies, liver and muscle tissues except fat tissue from the Belle Helene site (1.47 mg/g).  Dieldrin and heptachlor epoxide levels ranged from 0.01 – 0.70 mg/g.  DDTs ranged from 0.01-0.23 mg/g with elevated levels in fat tissues of 5.02, 2.06, and 6.43 mg/g from the Thomas Point, Brusly, and Belle Helene sites respectively. PCBs were also higher in fat tissues, with measurements of 8.16, 5.15, and 13.65 mg/g from these sites, and concentrations of 0.02 - 0.66 mg/g in liver and muscle. PCBs, based on whole animal, were 0.58, 0.39, and 0.25 mg/g at the three sites. In embryos, high concentrations of heptachlor epoxide were found at Belle Helene (1.76 mg/g), and mean PCB (arochlor 1260) concentrations ranged from 0.80-1.33 mg/g at all three sites.

4.

Ten individuals collected from 1994-1995 in Old River Slough, Texas had DDE concentrations of 0.733 mg/g wet weight (Clark et al., 1999).

II.

Cholinesterase-Inhibiting Pesticides

No direct exposure data available

III.

Trace Elements, Metals, and Metalloids

1.

Thirty individuals were measured to have a mean Zn plasma concentration of 19.0 mg/ml (Lance et al., 1994).

 2.

Elements were measured in whole blood from two Texas sites from 1994-1995 in wet weight (Clark et al., 1999). Old River Slough: 0.648 mg/g Cu, 0.146 mg/g Hg, 0.352 mg/g Se, and 13.6 mg/g Zn. Private Lake: 0.586 mg/g Cu, 0.0613 mg/g Hg, 0.318 mg/g Se, and 13.9 mg/g Zn.

IV.

Petroleum

No residue data available 

Diamondback Water Snake Contaminant Response Data

I.

Organochlorine Contaminants

1.

N. rhombifera has a low activity for both detoxifying enzymes oxidases and alkyltranferases and was not present in the Brazos high residue area (Stafford, et al, 1976).  The authors suggest that the species may have been eradicated from this area due to its inability to detoxify insecticides.

2.

Males metabolize the fenitrothion significantly faster than females, 9.9 mg/g for males and 4.3mg/g for females (Stafford, et al, 1976).

3.

No relationships were found between half-coefficient of variation values of DNA damage (5.30 at both Old River Slough and Private Lake) and concentrations of DDE or toxic elements. (Clark et al., 1999).

II.

Cholinesterase-Inhibiting Pesticides

1. 

No significant differences in blood plasma cholinesterase activity were found in snakes from two Texas wetlands: 0.654 mmol/min/ml at Old River Slough and 0.881 mmol/min/ml at Private Lake (Clark et al., 1999).

III.

Trace Elements, Metals, and Metalloids

No response data available

IV.

Petroleum

No response data available 

References for Diamondback Water Snake

Fleet, R.F., D.R. Clark, and F.W. Plapp. 1972 Residues of DDT and Dieldrin in snakes from two Texas agro-systems. Bioscience. 22:664-665.

Behler, J.L. and W.F. King.  1979. Audubon Society Field Guide to North American Reptiles and Amphibians. Chanticleer Press, Inc., New York. 636 pp.

Clark, D.R., J.W. Bickham, D.L. Baker, and D.E. Cowman. 1999 Environmental contaminants in Texas, USA, wetland reptiles: evaluation using blood samples. Environ. Toxicol. Chem. 19:2259-2265.

Johnson, T.R. Missouri Department of Conservation

Lance, V.A., T. Cort, J. Masuoka, R. Lawson, and P. Saltman. 1994 Unusually high zinc concentration sin snake plasma, with observations on plasma zinc concentrations in lizards, turtles and alligators. J. Zool., London 235:577-585

Sabourin, T.D., W.B Stickle, T.C. Michot, C.E. Villars, D.W. Garton, and H.R. Mushinksy.  1984. Organochlorine residue levels in Mississippi River water snakes in southern Louisiana. Bull. Environ. Contam. Toxicol. 32:460-468.

Stafford, D.P., F.W. Plapp, and R.R. Fleet. 1976. Snakes as indicators of environmental contamination: relation of detoxifying enzymes and pesticide residues to species occurrence in three aquatic ecosystems. Arch. Environ. Contam. Toxicol. 5:15-27.