Concho Water Snake Scientific Name: Nerodia paucimaculata Federal Status: Threatened, 9/3/1986, with federally-designated critical habitat • State Status: not listed

Description whereas water snakes usually do not. stream to the FM 45 bridge over the The Concho Water Snake is small Also, an aroused cottonmouth will Colorado River (Mills and San Saba compared to most other water snakes, sometimes stand its ground, throw its Counties). This is a distance of about with adults rarely exceeding 3 feet in head upward and backward, and hold 233 river-miles. total length. This nonvenomous its mouth wide open, revealing a Apparently isolated lake popula- snake has four rows of alternating white “cotton-like” interior. tions have been found in E.V. Spence dark brown spots or blotches on its Reservoir and Ballinger Municipal back, two rows on each side. The Distribution Lake (formerly Lake Moonen). Con- coloration on its back is similar to a Historically, the Concho Water Snake cho Water Snakes have also been checkerboard of dark brown spots on occurred over about 276 river miles found at a number of sites in O.H. a gray, brown, or reddish-brown of the Colorado and Concho Rivers in Ivie Reservoir, and there are indica- color. The Concho Water Snake has a central Texas. The snake was first tions that this population is reproduc- light pinkish or orange belly that is collected from the South Concho ing. Scattered river populations unmarked or has somewhat indistinct River and Dove Creek, which are trib- occur along the Colorado River above spots along the sides. utaries to the Concho River west of Lake Buchanan, near the towns of San Angelo, Texas. When the sub- Regency, Harmony Ridge, Adams, and species was described in 1961, these records and one other on the Col- orado River south of Robert Lee in Coke County were the only known localities for this snake. The Concho Water Snake is endemic to Texas, which means it lives nowhere else in the world. It has one of the small- est distributions of any North American snake. The Concho Water Snake may once have been more widely distributed, but the E.V. Spence Reservoir upstream and Lake Buchanan Concho Water Snake © N. Scott downstream have inundated many Two other water snakes occur miles of river habitat at both ends of within the range of the Concho Water the current range. Scientists have Snake. Both the Diamondbacked Water estimated the historic range of the Snake (Nerodia rhombifer rhombifer) subspecies based on museum records and the Blotched Water Snake (Nero- and unpublished records supported by dia erythrogaster transversa) have specimens. The probable historic Bend. Recently, Concho Water Snakes dark markings on the back. However, range of this snake is estimated to have been found at all six artificial adult Diamondbacked and Blotched include, at a minimum, the Colorado riffles (fast-flowing, shallow water Water Snakes may be distinguished River from Spence Reservoir down- over a rocky bottom) constructed in from adult Concho Water Snakes by stream to the vicinity of Lake 1989 in the 17-mile stretch of the their larger size. The Diamondbacked Buchanan, Elm, Bluff, and Coyote Colorado River between the Robert Water Snake has a distinct black chain- Creeks (Runnels County), and the Lee Dam and Bronte. like pattern on its back. The Blotched entire Concho River (Tom Green and Although the Concho River has Water Snake has three rows of large Concho Counties) and its headwater been dammed and channelized within squarish blotches on the back, which tributaries, Dove Creek, Spring Creek, the City of San Angelo, a population are especially prominent in juveniles. and the South Concho River (Irion of Concho Water Snakes persists just As Blotched Water Snakes age, they and Tom Green Counties). below the Bell Street Bridge. They become darker in color and may Today, the Concho Water Snake have also been found about 4 river- appear to lack markings. occupies a restricted geographic range miles downstream from Bell Street The cottonmouth is another large in the Concho and Colorado River Dam. From this point they are pre- aquatic snake that may be confused Basins. The current distribution sent in all suitable habitats to the with the Concho Water Snake. The includes relatively continuous occupa- confluence with Ivie Reservoir, a dis- cottonmouth, a venomous snake, is tion of riverine habitat of the Col- tance of about 43 river-miles. usually uniformly black or dark brown orado River below the town of Bronte with little or no trace of a pattern, (Coke County), of Elm, Coyote, and Habitat although both neonates and juveniles Bluff creeks below Winters (Runnels Optimal habitat for the Concho Water are banded; neonates have a yellow or County), and of the Concho River Snake consists of free-flowing streams gold-colored tail tip, juveniles retain it from San Angelo (Tom Green County) but not as distinct. Cottonmouths downstream to its confluence with often vibrate their tails when excited, the Colorado River, and then down- Concho Water Snake 1 over rocky substrates, abundant rock Snakes. Although the type of vegeta- debris and crevices for shelter, and tion does not appear to be important, shallow riffles. Periodic scouring by its use depends on vegetation density floods is important in providing rela- and orientation. For example, preg- tively sediment free rock rubble and nant females seek basking sites pro- open banks. tected by thick vegetation. Larger Riffles, considered critical to trees and shrubs, such as pecan, juvenile survival, are characterized by cedar elm, and willow, with limbs shallow, fast-flowing water connecting that hang over water, provide basking deeper areas of quiet water. Riffles sites for juveniles and adults. Com- begin when the upper pool overflows mon bank and shoreline vegetation at a change in slope and forms used for cover and basking sites rapids. They end when the rapids include switchgrass, devil-weed aster, enter the next downstream pool. Rif- greenbrier, poison ivy, willow, salt fles often contain bars, shoals, or cedar, button bush, hackberry, pecan, islands separated by flowing water. cedar elm, and mesquite. Limestone bedrock shelves in Concho Water Snakes hibernate and along the stream channel seem to during the winter, either singly or in support the largest snake populations. small groups. Adults use a variety of The snakes forage and seek cover sites for hibernation, including cray- among the numerous splits, crevices, fish burrows, rock ledges, debris cracks, and jumbled stream cobble of piles, and concrete low water cross- shelf rock. Other rock, such as lime- ings. These sites are usually within stone boulders, can also provide suit- 20 feet of the water. Newborn snakes able habitat. have been found hibernating in areas Juvenile snakes are generally of loose rock and moist soil. restricted to rocky riffles. Neonates (newborn snakes) are most often Life History found in gravel bars or along the Concho Water Snakes are active pri- shoreline in areas where rocks range marily from March through October. Concho Water Snake river habitat in size from small cobbles to small Adult activity gradually decreases © USFWS Pat Connor boulders. However, some habitats during June and remains low until with thriving populations lack typical mid-September. Activity levels gravel bars. In these areas, juveniles increase again during late September use boulders and shelf rock for cover. and October. The snakes enter the During their second year, snakes hibernation site (hibernacula) during begin to use larger rocks, usually late October, although they can occa- medium to large boulders. sionally be seen on warm winter days Mature snakes use a much wider basking in the open. Newborn Con- range of habitats than juveniles. cho Water Snakes, born in August and Although adults forage in riffles, they September, are commonly found are known to use a variety of cover under rocks in late summer and early sites for resting, including exposed fall. In the heat of the summer, Con- bedrock, thick herbaceous vegetation, cho Water Snakes are active primarily debris piles, and crayfish burrows. Habitat along the shoreline of Spence Reservoir in the early morning and evening © UWFWS Alisa Shull During the latter stages of gestation, until about 9 p.m. gravid females occupy dense patches Research indicates that adult to minnows, large snakes consume of vegetation and brush piles. males move an average of 141 to mosquitofish, channel catfish, flat- In lake habitats, Concho Water 325 ft/day. Pregnant females move head catfish, gizzard shad, and sev- Snakes occupy areas of broken rock less, averaging 62 to 131 ft/day, with eral species of sunfish. The bullhead along the shoreline. Although they distances decreasing as parturition minnow, sheepshead minnow, and seem to prefer the shallower areas, approaches, and increasing again bigscale logperch were found to be they are occasionally found on steeper after the young are born. Linear dis- the dominant prey of snakes in shorelines where rock is present. As tances of river habitat occupied by Ballinger Municipal Lake. in river habitats, first-year snakes use individual snakes range from 689 to Concho Water Snakes catch prey smaller rocks for cover, while mature 1,542 feet. by remaining stationary near fish snakes use medium to large rocks. Long range movements of 3.1 and concentrations or by actively search- When available, dead shrubs and 4.5 miles have been recorded for juve- ing under and around rocks in riffles. trees killed by fluctuating water levels nile snakes dispersing from their birth- Juveniles are most often seen using are used as basking sites by juveniles place. In one instance, a snake moved the “sit-and-wait” strategy. and adults. At Spence Reservoir, 12 river-miles over a four-year period. Mating occurs predominantly in where there are almost no dead trees The diet of the Concho Water April and early May, and sometimes or shrubs, snakes bask on the ground Snake is composed almost entirely of again in October. Litter sizes average among the protection of rocks. fish. In river habitats, minnows are 10 embryos per female, and births Bank and shoreline vegetation is most often consumed. Neonates occur from late July through Septem- important in providing cover and (newborn snakes) feed almost exclu- ber. As females increase in size dur- basking sites for Concho Water sively on minnows, particularly the ing their lifetimes, their litter size red shiner and bullhead minnow. also increases. Their diet becomes more varied as Concho Water Snakes grow 2 Concho Water Snake their body size increases. In addition rapidly and mature early, at about scouring have resulted in siltation of maintenance of high quality surface rocky streambeds, encroaching vege- waters. Enrollment in the CRP of the tation, and loss of riffle habitat primary areas contributing to sedi- required by young snakes. Loss of mentation in the watershed may sig- adequate instream flow due to nat- nificantly reduce the threat of ural conditions (drought) and water sedimentation of riffle habitat. diversion is also a concern. Finally, in an effort to restore Pollution and degradation of former habitat heavily degraded by water quality in the Concho and Col- siltation and vegetation encroach- orado Rivers or their tributaries is ment, six artificial riffles were built another potential threat in certain in 1989 in an unoccupied stretch of portions of the snake’s range. Non- the Colorado River below Spence point source pollution in the vicinity Reservoir. Though this area once of San Angelo, petroleum production, contained excellent habitat and dense Habitat on the Concho River refining, and transportation in the populations of Concho Water Snakes, © USFWS Alisa Shull watershed, treated sewage disposal, none were found in surveys done in pesticide use, and feedlot activities the late 1980’s. In 1991, four of the have been identified as water quality artificial riffles were found to be concerns that could affect habitat. occupied by Concho Water Snakes, These same water quality issues affect and by 1992, all six were occupied. municipal water supplies and recre- Future restoration efforts will likely ational use of lakes and rivers. Keep- involve construction of more riffles ing the water clean benefits people as in river habitat. The use of various well as the Concho Water Snake and man-made structures by Concho other wildlife. Water Snakes indicates high potential Finally, fragmentation and isola- for success with habitat enhancement. tion of populations following various Conservation education that pro- habitat alterations remain a concern. vides information and raises public The full effects of recent habitat mod- awareness is also important. ifications and natural events are Although the number of Concho unknown. water snakes killed intentionally or Artificial riff le habitat inadvertently by people is not known, © USFWS Pat Connor Recovery Efforts public outreach may help reduce Several ongoing and recently com- adverse impacts to this snake. 11 to 12 months of age. Females pro- pleted studies are leading to a better The Concho Water Snake duce their first litters at 2 or 3 years understanding of the habitat require- controversy provides a good example of age. Females grow more rapidly ments, life history, and genetic struc- of an effective compromise between and mature at larger sizes than males, ture of Concho Water Snake human resources needs and endan- with adult females reaching a length populations. During the period 1987 gered species management; objectives on average 30% greater than adult through 1996, the Colorado River which are not necessarily mutually males. Differences in growth rates Municipal Water District (CRMWD) exclusive. Efforts by numerous indi- and mature sizes have been observed monitored Concho Water Snake popu- viduals representing various universi- between populations, suggesting dif- lations at 15 sites three times each ties and local, state, and federal ferences in food availability. year. Physical aspects of the habitat agencies, serve as a model of cooper- Survivorship of Concho Water were recorded and changes noted. ation and compromise. The future of Snakes is directly related to age. Fish populations were surveyed at the the Concho Water Snake is not as Only about 20% of Concho Water monitoring sites each fall. In addi- bleak as once thought. If habitat con- Snakes survive their first year. The tion, potential habitat along the ditions remain stable and adequate adult survival rate is estimated to be shoreline of Ivie Reservoir has been instream flows are maintained, the about 50 percent. Population studies characterized, and researchers are Concho Water Snake will remain a have shown that most adults are less documenting the reservoir’s Concho part of the diversity of Texas for than 4 years old, and only one snake Water Snake distribution. many years to come. in 100 exceeds 5 years of age. Preda- As a condition of building Ivie tion is considered to be a significant Reservoir, the CRMWD is required to Where To See source of mortality. Major natural release water from both Spence and Concho Water Snakes predators include kingsnakes, Coach- Ivie Reservoirs according to a sched- Concho Water Snakes can sometimes whip Snakes, racers, Raccoons, Great ule which scientists hope will main- be found along rocky shorelines of Blue Herons, and various hawks and tain suitable habitat for the Concho Ivie and Spence Reservoirs and owls. Water Snake. These water releases Ballinger Municipal Lake. They may include both continuous daily flows also be seen on the Concho and Threats and Reasons and flushing flows designed to main- Colorado Rivers. If you see one of for Decline tain stream channels. these snakes, remember that they are Habitat loss and degradation has The Conservation Reserve Pro- protected by federal and state laws. been identified as the greatest gen- gram (CRP) of the U.S. Department of Do not disturb them or the surround- eral threat to Concho Water Snake Agriculture provides incentives to set ing area in any way. populations. Reservoir construction aside highly erodible lands and estab- has flooded many miles of former lishing these areas to perennial stream habitat above the dams. native vegetation. The program bene- Below the dams, restriction of stream fits the Concho Water Snake by reduc- flow and prevention of floodwater ing soil erosion and contributing to Concho Water Snake 3 How You Can Help immense impact on the rivers. For More Information You can encourage and support pri- Responsible recreational use should include proper disposal of trash and Contact vate landowners who are managing Texas Parks and Wildlife Department their land to protect the rivers, other potential pollutants, respect for Wildlife Diversity Branch streams, and lakes that serve as habi- private property rights, preventing tat for the Concho Water Snake. Con- harm to plants and wildlife, and gen- 4200 Smith School Road cho water snakes and their prey base erally keeping human impacts to a Austin, Texas 78744 need adequate instream flows. If you minimum. (512) 912-7011 or (800) 792-1112 are a landowner along one of the Finally, you can be involved in or rivers or streams that serve as habi- the conservation of Texas’ nongame U.S. Fish and Wildlife Service tat, we encourage you to learn about wildlife resources by supporting the Ecological Services Field Office Special Nongame and Endangered the habitat requirements of the Con- 10711 Burnet Road, Suite 200 cho Water Snake and other species Species Conservation Fund. Special nongame stamps are available at Austin, Texas 78758 that depend on these waterways. (512) 490-0057 Landowners can help by maintaining Texas Parks and Wildlife Department clear free-flowing streams over rocks, (TPWD) field offices, most state rock debris and crevices for shelter, parks, and the License Branch of shallow riffle areas, and basking TPWD headquarters in Austin. Con- sites, and by being careful with pesti- tributions to this fund help TPWD cides and other potential pollutants. conduct research, manage habitat and Alternatives such as integrated pest develop informational materials and management, organic gardening, and programs for the benefit of nongame the use and management of native and endangered wildlife. Conserva- plants can help reduce reliance on tion organizations in Texas also wel- chemicals and can often save money. come your participation and support. Do what you can as an individ- ual to conserve water, particularly Concho Water Snake moving over rocky streambed during drought periods. In the home, © TPWD Martin Whiting you can save water by installing fix- tures, appliances, and toilets designed to use less water, repairing leaky faucets, and turning off the tap while brushing teeth or doing dishes. Landscaping with native, drought tol- erant plants, watering lawns in the early morning or evening to reduce References evaporation, and installing a rainwa- Dixon, J.R., B.D. Greene, and M.J. Whiting. 1992. 1992 Annual report Concho ter collection system for your home water snake natural history study, Big Spring, Texas. Colorado River Munici- are other effective ways to conserve pal Water District. 128 pp. water. By protecting the natural Dixon, J.R. 1987. Amphibians and reptiles of Texas. Texas A&M University Press, beauty, flow, and water quality of the College Station. 434 pp. Colorado and Concho Rivers, Greene, B.D., J.R. Dixon, M.J. Whiting, and J.M. Mueller. 1999. “Reproductive ecol- landowners can play a role in assur- ogy of the Concho water snake, Nerodia harteri paucimaculata.” Copeia 701- ing that future generations of Texans 709. have the chance to enjoy the rich Greene, B.D. J.R. Dixon, J.M. Mueller, M.J. Whiting, and O.W. Thornton, Jr. 1994. diversity of life these rivers support. “Feeding ecology of the Concho water snake, Nerodia harteri paucimaculata.” Concho water snakes feed almost Journal of Herpetology 28(2):165-172. exclusively on smaller fish. Trot lines Greene, B.D. 1993. Life history and ecology of the Concho water, Nerodia harteri may result in death of Concho water paucimaculata. Unpublished Ph.D. dissertation. Texas A&M University. snakes. If you fish, do not use trot 128 pp. lines in the following lakes and Mathews, A.E. 1989. “Conflict, controversy, and compromise: the Concho water rivers: Spence Reservoir; Ivie Reser- snake (Nerodia harteri paucimaculata) versus the Stacy Dam and Reservoir.” voir; Ballinger Municipal Lake; Con- Env. Management 13(3):297-307. cho River in San Angelo and Rose, F.L. 1989. “Aspects of the biology of the Concho watersnake (Nerodia har- downstream to Ivie Reservoir; Col- teri paucimaculata).” Texas J. Science 41(2):115-130. orado River between Spence and Ivie Scott, Jr., N.J., T.C. Maxwell, O.W. Thornton, Jr., L.A. Fitzgerald, and J.W. Flury. 1989. Reservoirs; Colorado River between “Distribution, habitat, and future of Harter’s water snake, Nerodia harteri, in Ivie Reservoir and Farm to Market Texas.” Journal of Herpetology 23:373-389. Road 45 (near Regency); Colorado Tinkle, D.W. and R. Conant. 1961. “The rediscovery of the water snake, Natrix River in the vicinity of Gorman Falls, harteri, in western Texas, with the description of a new subspecies.” South- Bend and Colorado Bend State Park. western Naturalist 6(1):33-44 If you are a boater or enjoy U.S. Fish and Wildlife Service. 1993. Concho water snake recovery plan. swimming in the Concho or Colorado Albuquerque, New Mexico. 66 pp. Rivers and their tributaries, remem- Werler, J.E. and J.R. Dixon. 2000. Texas snakes: identification, distribution, and ber that your actions, especially when natural history. University Texas Press, Austin, Texas multiplied by thousands of other Whiting, M.J. 1993. “Population ecology of the Concho water snake, Nerodia recreational users, can have an harteri paucimaculata, in artificial habitats.” Unpublished M.S. thesis. Texas A&M University. 137 pp.

4 Concho Water Snake Funds for the production of this leaflet were provided by the U.S. Fish and Wildlife Service, under Section 6 of the Endangered Species Act.