(DRAFT) - Taxonomy
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
TAXONOMY
NAME - SNAKE, WATER, CONCHO
OTHER COMMON NAMES - SNAKE, WATER, CONCHO; SNAKE, WATER and HARTER'S
ELEMENT CODE -
CATEGORY - Reptiles
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - REPTILIA,
ORDER AND SUBORDER - SQUAMATA,
FAMILY AND SUBFAMILY - COLUBRIDAE,
GENUS AND SUBGENUS - NERODIA,
SPECIES AND SSP - HARTERI, PAUCIMACULATA
SCIENTIFIC NAME - NERODIA HARTERI PAUCIMACULATA
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Concho Water Snake
Nerodia harteri paucimaculata (Tinkle and Conant, 1961)
KINGDOM: Animal GROUP: Reptile
PHYLUM: Chordata CLASS: Reptilia
ORDER: Squamata FAMILY: Colubridae
This subspecies, Nerodia harteri paucimaculata, is relatively
small for Nerodia; adults rarely exceed 900 mm (3 ft) total length.
There are 21-23 dorsal scale rows, four rows of dark brown blotches
arranged in alternate fashion on the grayish or reddish-brown dorsal
surface, and distinct to obscure dark spots along either side of the
pink to orange venter (01). Concho water snakes, when compared to
Brazos water snakes (Nerodia harteri harteri), have reduced ventral
spotting (often totally absent), a more reddish venter, differences in
average scale counts of gular, postocular, subcaudal, ventral, and
dorsal rows, and often a reddish dorsal ground color (02).
The initial specimen of the nominant race of this species was
collected in Palo Pinto County, Texas by Phillip Harter in 1936. This
first specimen was at first cataloged as an aberrant Natrix (=Nerodia)
erythrogaster erythrogaster. In a subsequent group of specimens,
however, a nearly identical specimen was noted. Eventually an
Taxonomy - 1 (DRAFT) - Taxonomy
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
additional 21 live specimens were received, and H. Trapido began a
taxonomic study of the form, eventually describing it as a new species
(03). He was reluctant to do so, thinking it might be a race of
Natrix erythrogaster, but noted that Natrix harteri was found only in
shallow, rocky riffles, whereas the sympatric water snakes preferred
the deeper pools with slower moving water and mud or sand substrates.
This mutual exclusion convinced him to give N. harteri full species
rank.
In 1960, Tinkle collected 114 specimens of Natrix harteri from
the upper Colorado River at Robert Lee, Coke County, Texas. Citing
distinct physiological differences and a 225 km (140 mi) land barrier
separating the two river systems containing the races, Tinkle and
Conant (04) described Natrix harteri paucimaculata as a distinct
subspecies.
A 1977 revision of the genus Natrix resulted in four genera. All
North American Natrix, including N. harteri, were grouped in the genus
Nerodia (11).
The type locality for N. h. paucimaculata is Robert Lee, Coke
County, Texas. The type specimen (06) is located at the American
Museum of Natural History (#85542, an adult male). Paratypes are
located at the following institutions: American Museum of Natural
History (Nos. 85543-51), Academy of Natural Sciences Philadelphia
(Nos. 2669-70), Carnegie Museum (Nos. 37533-4), Chicago Natural
History Museum (Nos. 128310-11), University of Florida
(Nos. 14906.2-2), University of Kansas Museum of Natural History
(Nos. 59884-5), Museum of Comparitive Zoology (Nos. 56991-2), Tulane
University (Nos. 17616-7), University of Illinois Museum of Natural
History (Nos. 49336-7), University of Michigan Museum of Zoology
(Nos. 121691-2), United States National Museum (Nos. 142806-7, Texas
Tech University (Nos. 2029 (14 specimens), 2110 (56 specimens),
and 2220 (14 specimens)).
There have been those in the general public (04) who argue that
N. h. paucimaculata is not a valid subspecies from N. h. harteri
because of a lack of distinguishing features to a layperson. These
arguements were voiced principally in opposition to Federal listing
and in favor of the construction of Stacy Reservoir. Enzyme,
hemoglobin, and electrophoresis analysis did not show any discernible
differences between subspecies, but morphological data may be superior
to molecular data in evaluating divergence in N. harteri (19). All of
the experts on this species currently agree that the subspecific
designation is valid.
The Concho water snake is also known as Harter's water snake.
Taxonomy - 2 (DRAFT) - Status
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
STATUS
Coded Status
T: Federal Threatened
Non-consumptive recreational
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Concho water snake (Nerodia harteri paucimaculata) is
designated as Threatened pursuant to the Endangered Species Act of
1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C. 1531-1540),
as amended. Critical Habitat has been proposed in the Texas Counties
of Coleman, Concho, McCulloch, Runnels, and Tom Green.
This subspecies is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
DOD -The U.S. Army Corps of Engineers has responsibility
for the law enforcement/protection of this species
with applicable State and Federal laws on public land
under their control.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Texas
Status - 1 (DRAFT) - Status
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: TX Parks and Wildlife Department
STATE STATUTE: TX Parks & Wildlife Code, Sec. 43, 67, and 68.
UNOFFICIAL LIST: Category 2 (Federally Threatened).
"Endangered, threatened, and watched list of
vertebrates of Texas. TX Organization for
Endangered Species, P.O. Box 12122, Austin, TX.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
None.
ECONOMIC STATUSES:
This species has a cultural value as a component of Texas'
natural heritage of biotic diversity.
82/12/30:47 FR 58454/58460 - Notice of review (vertebrate)
84/05/18:49 FR 21089/21090 - Petition for listing - 90 day finding
85/07/18:50 FR 29238/29239 - Petition for listing - 365 day finding
86/01/22:51 FR 02923/02929 - Proposed rule, Threatened w/ Crit. Hab.
86/09/03:51 FR 31412/31422 - Final rule, Threatened; Crit. Hab. postp.
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
LAND USE -
Cropland and Pasture
Mixed Rangeland
Streams and Canals
Reservoirs
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Riverine, lower perennial RB2
Riverine, lower perennial RB1
Riverine, lower perennial BB2
Riverine, lower perennial BB1
COMMENTS ON HABITAT ASSOCIATIONS -
The habitat of the Concho water snake, Nerodia harteri
paucimaculata, is described as shallow, swift water in shoal or riffle
areas created by rocks on the substrate (02,08,09,10). Individuals
have frequently been found under flat, shelving, sedimentary rocks in
stream beds, a characteristic feature of the upper drainages of the
Colorado River. Reports of adults are less frequent in deeper,
mud-banked pools with slower water (09,11). Juveniles are found only
in riffles; juvenile habitat is a major limiting factor (05). The
habitat at the type location for N. h. paucimaculata was described as
a rocky sandbar with water seldom exceeding one-third meter in depth
(02). The river flowed across a limestone bed, and was not nearly as
shaded by trees and the bank as was the type location for the nominant
subspecies in the Brazos River. Tinkle and Conant found the Concho
water snake swimming in shallow pools or resting under rocks on sand
bars.
Williams (09) described the habitat of N. h. paucimaculata in
more detail. Records of 107 captured adults demonstrated some habitat
breadth: 40 percent were captured on saltcedar (Tamarix spp.) over
shallow riffles; 23 percent from saltcedar over shallow pools; 25
percent in shallow riffles; and 12 percent in shallow pools or on rock
and gravel bars. Juveniles demonstrated a narrower habitat
preference. Of 224 juveniles recorded, 45 percent were on gravel bars
under rocks or debris piles, 35 percent were in shallow riffles, and
the remaining 20 percent were either on saltcedars or in shallow
pools. No Concho water snakes were collected in deep pools or on mud
flats. Saltcedars are used as basking/resting sites (04). Williams
(09) also observed Concho water snakes entering and leaving numerous
holes in high dirt river banks, but their use as hibernacula was not
confirmed.
Scott and Fitzgerald (05) noted that the best stretches of
habitat had 4-6 riffles per 5 km (3.1 mi). The uninhabited lower
Colorado had an average of about 1 riffle per 5 km (3.1 mi). They
hypothesized that such a low density of riffles made it difficult, if
not impossible, for a riffle area to be recolonized if the species
were for some reason extirpated there.
Lands surrounding Concho water snake habitat consist of mixed
rangeland of Texas savanna and agricultural lands, primarily pasture
with some cotton and hay production (04,20).
Habitat Associations - 1 (DRAFT) - Food Habits
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
LIFESTAGE FOOD FOOD PART
General Fish
Food Habits - 1 (DRAFT) - Environment Associations
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G
G Aquatic Features: Pool areas
G Terrestrial Features: Burrows
Environment Associations - 1 (DRAFT) - Life History
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Observations at the town of Robert Lee by Williams (09) indicate
that the Concho water snake, Nerodia harteri paucimaculata, feeds
entirely in shallow riffles and shallow pools. Concho water snakes
have never been observed feeding in deeper pools. In the shallow
rapids the snakes anchor themselves by wrapping the posterior
two-thirds of their body around rocks and probe the water with their
heads in search of smaller fish species. N. h. paucimaculata is
capable of swimming rapidly upstream, staying close to the bottom
where the current is not as strong. Although several individuals were
observed swimming in this manner, it did not appear to be a hunting
strategy (09).
Identifiable remains of food recovered from 32 specimens (through
forced regurgitation) include (09) mostly smaller fish species found
in the river. Notropis lutrensis, red shiner (52 percent); Fundulus
zebrinus, plains killifish (18 percent); and Hybopsis aestivalis,
speckled chub (14 percent), were most frequently regurgitated. One
N. h. paucimaculata contained a single 55 mm Ictalurus punctatus,
channel catfish, and another snake contained one Hybognathus placitus,
plains minnow (09).
No fish species that commonly occur in pools along the river were
found in N. h. paucimaculata stomachs (i.e., Lepomis cyanellus, green
sunfish; L. megalotis, longear sunfish; L. machrochirus, blue gill;
Micropterus salmoides, largemouth bass; Pomoxis annularis, white
crappie; Carpiodes carpio, river carpsucker; Gambusia affinis,
mosquitofish; Dorosoma cepedianum, gizzard shad; Pimephales vigilax,
bullhead minnow; P. promelas, flathead minnow; and Notemigonus
crysoleucas, golden shiner) (09).
N. h. paucimaculata did not appear to compete with sympatric
water snakes for food. Nerodia rhombifera ate mostly larger fish
(50 percent) and anurans (44 percent) in Red River and Bowie Counties,
TX (13) and fish (90 percent) and frogs and crayfish (10 percent) in
Kansas (14). N. erythorogaster fed almost entirely on anurans
(93 percent) in Kansas (14). The fourth aquatic snake in the Colorado
River, Thamnophis proximus ate mostly amphibians (90 percent in
Michigan) (15) and anurans in Texas (16). Limited sampling of these
sympatric species at Robert Lee concurred with these studies (09).
HOME RANGE/TERRITORY:
Williams' detailed study (09) provides the only information on
home ranges of this snake. Since he marked each snake he captured,
recaptures or, in the case of color-marked adults, resightings
provided information on the amount of area used by an individual.
There was no evidence of territorality. Adult males, on average,
moved farther than adult females (males moved 5.7 (+/- 0.32) ft/day
(or 1.7 m/day); females 3.6 (+/- 0.31) ft/day (or 1.1 m/day)). The
majority of individuals moved short distances, as from saltcedar to
shallow riffles, thus staying in a relatively small home range.
The longest upstream (thus voluntary) movement in 24 hours was
341 m (1,120 ft) by an adult male. Thirty-one days later he had moved
192 m (630 ft) back downstream. Severe flooding after heavy
Life History - 1 (DRAFT) - Life History
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
thunderstorms displaced several individuals downstream: one male was
displaced 950 m (3,100 ft) while females were displaced 760 m
(2,500 ft) and 695 m (2,280 ft). In each instance, the snakes were
recaptured after a short period of time within 15 m (50 ft) of the
original capture point, indicating a preference for their old home
range.
Juveniles did not have a distinct dispersal period. Their
overall movement rates were less than the same sexed adults; 3.8 (+/-
0.27) ft/day (or 1.2 m/day) for juvenile males and 2.8 (+/- 0.33)
ft/day (or 0.85 m/day) for juvenile females. Eleven individuals did
not move over 18 m (60 ft) from the original capture point in 200 or
more days. The longer voluntary movements of juvenile males were:
upstream movements of 69 m (2,285 ft) in 271 days and 760 m (2,490 ft)
in 239 days; and downstream movements of 460 m (1,500 ft) in 19 days.
The longest movement in the shortest period was 670 m (2,200 ft) in 32
days. None of the juvenile females exhibited long movements.
PERIODICITY:
This species is chiefly diurnal. Adults feed principally in
early morning and late afternoon; juveniles feed throughout the day
(09). Nocturnal feeding activity in juveniles has been observed
(17,21).
Concho water snakes are inactive during the cold winter months.
They become less active in November and disappear shortly after the
first cold wave. Individuals begin to reappear during warm days of
February but the majority do not become active until mid-March. The
average annual activity period for the species is about 270 days (09).
MIGRATION PATTERNS:
This species is non-migratory. Snakes marked by Williams (09)
provided information on movements of Concho water snakes. The
majority of individuals moved only short distances (i.e., from
saltcedar to shallow riffles), apparently staying in a relatively
small home ranges throughout their lifetime.
Though generally sedentary, longer movements occurred in early
spring and fall, presumably in response to seasonal temperatures.
These movements were generally to and from dense saltcedar thicket in
areas characterized by high dirt river banks with numerous small holes
thought to serve as hibernacula.
COVER/SHELTER REQUIREMENTS:
N. h. paucimaculata uses riffle areas with flat cobbles and
boulders on bedrock substate. Where loose, flat rocks lie upon each
other, the lower rock is frequently partially submerged. The air
space between submerged rock layers provides excellent cover. Two
thirds of the adults found by Flury and Maxwell (06) were using this
cover type. These rock deposits typically were in the swift-flowing
water. Juveniles and subadults rarely used this cover; perhaps the
smaller snakes were unable to swim well within the swift current (06).
Ledge-covered recesses were also used by Concho water snakes.
Juveniles were usually found (84 percent of total recorded) under
rocks on the shore or other cover near the river. All age classes
basked, particularly on tree limbs. Rocks near the stream were also
Life History - 2 (DRAFT) - Life History
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
used, especially during cooler fall weather.
Williams (09) observed Concho water snakes entering and leaving
numerous holes in high dirt river banks, but their use as hibernacula
was not confirmed.
REPRODUCTIVE SITE REQUIREMENTS:
N. h. paucimaculata bear live young; special reproductive site
requirements are not known (01,06,09).
REPRODUCTIVE CHARACTERISTICS:
Mating (promiscuous) is thought to occur shortly after spring
emergence, although it has not been observed in this species (09).
Spring copulation has been recorded for related species (15,18).
Females apparently reach sexual maturity in one year, and it is
speculated that they may not reproduce more than twice in a lifetime
(09). Follicles were present in adult females in early June, and
Williams estimated that embryo development occurred within about 120
days, since juveniles appeared in late August and early September
(09). Larger females (>500 mm) apparently produced more young/litter
than did smaller ones (09), an observation previously reported for
other species of snakes (18). Average Concho water snake litter size
is about 18 (09).
PARENTAL CARE:
The young of N. h. paucimaculata must become self-sufficient at
birth (01).
POPULATION BIOLOGY:
Population structure for N. h. paucimaculata varied seasonally at
Robert Lee (09). The population was composed primarily of three age
groups based on snout-vent length: juveniles, first-year adults, and
second-year adults. No adults over three years were positively
identified and, if present, were an insignificant part of the
population.
Juvenile snakes began to appear in early September and increased
in number until mid-October. Estimates based on mark and recapture
techniques during October indicated a juvenile population of 473
(+/- 39) young in the 3,000 ft (945 m) study area. The sex ratio was
approximately 50:50. The summer snake population of 52 adults was
increased eightfold by the addition of newborn juveniles in late fall.
However, index estimates for the early spring juvenile population was
140 (+/- 17), a decline of 70 percent (incorrectly given as 80 percent
by Williams). This suggested that most did not survive the winter.
By mid-summer the total population had decreased to about 75+
individuals in the area. Predation was speculated to be a factor.
Dispersal was discounted because no marked individuals were found
outside the study area except after heavy flooding.
Of 48 first-year adults on the area in the first summer, only
seven (14 percent) were known to survive until the second year. All
of these survivors were females, two of which disappeared in late
spring. Only eight second year adults (including 6 females) were
present at the initiation of the study, and apparently none survived
to their third year (09). This data suggests either a very
Life History - 3 (DRAFT) - Life History
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
unballanced sex ratio (toward females) in adults (09) or an
inefficiency in the sampling method.
SPECIES INTERRELATIONSHIPS:
Nerodia harteri paucimaculata does not appear to compete for food
with sympatric water snakes (N. rhombifera, N. erythrogaster,
Thamnophis proximus) present in the Concho and Colorado Rivers (09).
N. harteri occupies rocky shallow pools and riffles while the other
aquatic snakes inhabit slower moving, non-rocky pools (02,03,09).
Competition with other species of Nerodia may have played an important
role in habitat selection by the Concho water snake and thus in the
present distribution of N. harteri (02). A further niche separation
appears to be diurnal feeding in N. harteri feed diurnally while
N. rhombifera and N. erythrogaster are most active at night (06,09).
Predation by raccoons (Procyon lotor), oppossums (Didelphis
virginiana), skunks (Mephitis mephitis, Conepatus leuconotus,
Spilogale putorius), kingsnakes (Lampropeltis spp.,) and certain
larger fish like gar, catfish, bass, and sunfish probably occurs (09).
OTHER LIFE HISTORY DESCRIPTORS:
None.
Life History - 4 (DRAFT) - Management Practices
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Regulating Water Temperature
Beneficial Developing/maintaining stream structures
Beneficial Maintaining/Controlling Water Flow
Beneficial Land Acquisition
Beneficial Creating Artificial Habitat/Nesting Structure
Beneficial Controlling/Removing Nonnative Vegetation
Beneficial Controlling/Removing Native Vegetation
Beneficial Transplanting wild animals
Adverse Incidental Capturing/Killing
Existing Incidental Capturing/Killing
Adverse Siltation
Existing Siltation
Adverse Flooding
Existing Flooding
Adverse Irrigating
Existing Irrigating
Adverse Reservoirs
Existing Reservoirs
Adverse Migration barriers
Existing Migration barriers
Adverse Dredging
Existing Dredging
Adverse Developing/maintaining stream bank vegetation
Existing Developing/maintaining stream bank vegetation
Adverse Applying fertilizers
Existing Applying fertilizers
Adverse Applying pesticides
Existing Applying pesticides
Adverse Environmental Contamination/Pollution
Existing Environmental Contamination/Pollution
Adverse Erosion
Existing Erosion
Adverse Grazing
Existing Grazing
Adverse
Existing
Adverse Vegetation Composition Changes
Existing Vegetation Composition Changes
COMMENTS ON MANAGEMENT PRACTICES -
Habitat of the Concho water snake, Nerodia harteri paucimaculata
has been affected by four large mainstream reservoirs on the Concho
and Colorado Rivers, plus several smaller impoundments on tributary
streams. At least two separate aspects of impoundment result in
losses of Concho water snake habitat. Above dams the rocky shoreline
and riffle habitat are inundated. Below dams normal water flow is
curtailed, floodwater scouring is prevented, and the rocky streambed
becomes covered with silt (04). Growth of vegetation in this new soil
Management Practices - 1 (DRAFT) - Management Practices
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
eliminates the rocky-bottomed riffle areas required by juvenile Concho
water snakes (05). The closure of Robert Lee Dam completely
eliminated a large population of this species and 19 miles (31 km) of
habitat. The dam reduced flow 99 percent and habitat became degraded
so that a self-sustaining population does not occur until Bronte,
19 mi (31 km) downstream (05). On the Concho River, the closure of
Twin Buttes Dam reduced immediate downstream flow 74 percent (06). In
addition to these flow reductions immediately downstream from dams,
flows in the Concho-Colorado system have been reduced 60-65 percent by
agricultural and other diversions. Lower flows have reduced suitable
habitat for the snakes and their prey and aggravated other problems,
such as pollution (17). Buildups of algae caused by higher nutrient
loads reduces habitat for snakes and their prey (17). Riverine
habitat has also been degraded due to erosion caused by overgrazing in
nearby uplands and by flushing of pesticides and fertilizers from
nearby fields (17,20).
Stacy Reservoir, planned for the Colorado River, will inundate
32 miles (52 km) of that river and 14 miles (23 km) of the Concho
River in addition to impacts on downstream reaches of the Colorado.
These areas contain good Concho water snake habitat and harbor an
important contingent of the remaining snakes. Furthermore, the
reservoir will fragment the remaining snake population and habitat
into three physically separate units; habitat fragmentation is cited
as the primary cause of recent species extinctions (07).
Concho water snakes are sometimes captured or killed by people
during recreational pursuits. Presently, the effect of this activity
on populations is believed to be minimal; however, instances of
fishermen incidentally killing large numbers of water snakes have been
recorded. This direct mortality is confined mostly to the vicinity of
bridges and road crossings (04).
UNAPPROVED PLAN:
No recovery plan will be written due to the inclusive nature of the
reasonable and prudent alternatives developed from the Section 7
consultation for Stacy Reservoir.
The Concho water snake is threatened by the changes in its
habitat brought about mostly by the diversion of Concho and Colorado
River waters since the arrival of European man. The construction of
Stacy Dam and the filling of Stacy Reservoir in the heart of the
remaining occupied habitat poses the greatest threat to the continued
existence of this species.
The future management of this species is covered under the
"Reasonable and Prudent Alternatives" section of the USFWS December 9,
1986, biological opinion presented to the Corps of Engineers and the
Colorado River Muncipal Water District. This document recommends:
1) Monitoring (spring and twice in the fall) of five juvenile
habitat areas in each of the three reaches isolated by Stacy
Reservoir (upper Colorado River, lower Colorado River, and Concho
River) during construction and filling of Stacy Reservoir for a
total of ten years;
Management Practices - 2 (DRAFT) - Management Practices
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
2) Studies of the Concho water snake including a) all aspects of
their life history, b) genetic viability, c) physical habitat,
d) availability and distribution of food, e) energy budget and
growth of all three Nerodia water snake species, and
f) evaluation of the various proposed management alternatives
(below), with recommendations for improvements;
3) Improved management of the upper Colorado River unit by providing
minimum flow releases from an upstream reservoir, channel
maintenance flows ("prescribed flooding"), vegetation and silt
removal (including native plants and exotics such as saltcedar,
Tamarix cninensis), addition of rock, reintroduction of Concho
water snakes, and protection of rehabilitated habitat;
4) Improved management of the lower Colorado River unit below Stacy
Reservoir by providing minimum flows, channel maintenance flows,
protection of normal river temperatures, habitat improvement to
create or improve riffle habitat, and protection of rehabilitated
habitat;
5) Evaluation of 19 low head dams on the Concho River unit and their
impact on the Concho water snake;
6) Creation of new artificial habitats in Stacy Reservoir that may
be acceptable to Concho water snakes;
7) Continued searches for additional Concho water snake populations
in tributary streams and negotiation with landowners to protect
habitats of such populations already found or those that might be
found in the future;
8) Maintain genetic heterogenity by transferring five female Concho
water snakes to each of the three main populations from its
nearest neighboring population each summer after the filling of
Stacy Reservoir, the resulting barrier to movement between the
three main populations;
9) Employment of a full-time biologist by the Colorado River
Municipal Water District; and
10) A cooperative agreement to be signed by the principal parties to
assure that all phases of the biological opinion will be carried
out before and after construction of Stacy Dam.
Management Practices - 3 (DRAFT) - References
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Wright, A.H. and A.A. Wright. 1957. Handbook of the snakes of the
United States and Canada. Vol. 2. Comstock Publ. Assoc., NY.
Pp. 565-1105.
02 Tinkle, D.W. and R. Conant. 1961. The rediscovery of the water
snake Natrix harteri in western Texas, with the description of a
new subspecies. Southwest. Nat. 6:33-34.
03 Trapido, H. 1941. A new species of Natrix from Texas. Am. Midl.
Nat. 32:673-680.
04 U.S. Fish and Wildlife Service. 1986. Endangered and threatened
wildlife and plants: Determination of Nerodia harteri
paucimaculata (Concho water snake) to be a threatened species.
Sept. 3, 1986. Fed. Reg. 51:31412-31422.
05 Scott, N.J., Jr. and L.A. Fitzgerald. 1985. Status survey of
Nerodia harteri, Brazos and Concho-Colorado Rivers, Texas. Denver
Wildl. Res. Center, U.S. Fish & Wildl. Serv., Mus. of Southwestern
Biol., Albuquerque, NM. 44 pp.
06 Flury, J.W. and T.C. Maxwell. 1981. Status and distribution of
Nerodia harteri paucimaculata). U.S. Fish & Wildl. Serv.,
Albuquerque, NM. 73 pp.
07 Wilcox, B.A. and D.D. Murphy. 1985. Conservation strategy: The
effects of fragmentation on extinction. Am. Nat. 25:879-887.
08 Tinkle, D.W. and G.N. Knopf. 1964. Biologically significant
distribution records for amphibians and reptiles in north-west
Texas. Herpetologica 20:42-47.
09 Williams, N. 1969. The ecology of Natrix harteri paucimaculata.
M.S. thesis. Texas Tech. Univ., Lubbock.
10 Conant, R. 1975. A field guide to the reptiles and amphibians of
eastern and central North America. Houghton Mifflin Co., Boston.
11 Rossman, D.A. and W.G. Eberle. 1977. Partition of the genus
Natrix with preliminary observations on evolutionary trends in
natricine snakes. Herpetologica 33:34-43.
12 Musgrave, G. 1977. The status of Natrix harteri paucimaculata in
the Concho River, Tom Green and Concho Counties, Texas. Angelo St.
Univ., San Angelo, TX. Typescript.
13 Bowers, J.H. 1966. Food habits of the diamond-backed water snake
Natrix rhombifera rhombifera, in Bowie and Red River Counties,
Texas. Herpetologica 22:225-229.
14 Diener, R.A. 1957. An ecological study of the plain-bellied water
snake. Herpetologica 13:203-211.
15 Carpenter, C.C. 1952. Comparative ecology of the common garter
snake (Thamnophis s. sirtalis), the ribbon snake (Thamnophis s.
sauritis), and Butler's garter snake (Thamnophis butleri) in mixed
populations. Ecol. Monogr. 22:235-258.
16 Fouquette, M.J. 1954. Food competition among four sympatric
species of garter snakes, genus Thamnophis. Texas J. Sci.
6:172-188.
17 Rose, F.L. 1985. A preliminary report on a survey of the upper
Colorado River drainage for Nerodia harteri. Rept. to Colorado
Riv. Municipal Water Dist., Big Springs, TX. 11 pp.
References - 1 (DRAFT) - References
Species SNAKE, WATER, CONCHO
Species Id ESIS152007
Date 14 MAR 96
18 Fitch, H.S. 1960. Criteria for determining sex and breeding
maturity in snakes. Herpetologica 13:203-211.
19 Rose, F.L. 1984. Systematics of Nerodia harteri: Final report.
Submitted to U.S. Fish & Wildife Service, Albuquerque, NM. 11 pp.
20 Stefferud, S.A. 1987. Pers. comm. U.S. Fish & Wildl. Serv., P.O.
Box 1306, Albuquerque, NM 87103.
21 U.S. Fish and Wildlife Service. 1986. Biological opinion on Sec.
404 and Sec. 10 permits to the Colorado River Municipal Water
District, for construction of the proposed Stacy Dam and pump
station. Letter to: Col. A.J. Genetti, Jr., Dist. Eng., COE, Ft.
Wort, TX. Dec. 23, 1986. U.S. Fish and Wildl. Serv., Albuquerque,
NM.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 U.S. Fish and Wildlife Service. 1986. Endangered and threatened
wildlife and plants: Determination of Nerodia harteri
paucimaculata (Concho water snake) to be a threatened species.
Sept. 3, 1986. Fed. Reg. 51:31412-31422.
02 Scott, N.J., Jr. and L.A. Fitzgerald. 1985. Status survey of
Nerodia harteri, Brazos and Concho-Colorado Rivers, Texas. Denver
Wildl. Res. Center, U.S. Fish & Wildl. Serv., Mus. of Southwestern
Biol., Albuquerque, NM. 44 pp.
03 Flury, J.W. and T.C. Maxwell. 1981. Status and distribution of
Nerodia harteri paucimaculata. U.S. Fish & Wildl. Serv.,
Albuquerque, NM. 73 pp.
04 Rose, F.L. 1985. A preliminary report on a survey of the upper
Colorado River drainage for Nerodia harteri. Rept. to Colorado
Riv. Municipal Water Dist., Big Springs, TX. 11 pp.
05 Marr, J. 1944. Notes on amphibians and reptiles from the central
United States. Am. Midl. Nat. 32:478-490.
06 Tinkle, D.W. and R. Conant. 1961. The rediscovery of the water
snake Natrix harteri in western Texas, with the description of a
new subspecies. Southwest. Nat. 6:33-34.
07 Tinkle, D.W. and G.N. Knopf. 1964. Biologically significant
distribution records for amphibians and reptiles in north-west
Texas. Herpetologica 20:42-47.
08 Williams, N. 1969. The ecology of Natrix harteri paucimaculata.
M.S. thesis. Texas Tech. Univ., Lubbock.
09 Musgrave, G. 1977. The status of Natrix harteri paucimaculata in
the Concho River, Tom Green and Concho Counties, Texas. Angelo St.
Univ., San Angelo, TX. Typescript.
10 Brnovak, G.T. 1975. An ecological survey of the reptiles of Coke
County, Texas. M.S. thesis. Angelo St. Univ., San Angelo, TX.
11 Lillard, E.E. 1986. Letter of October 13, 1986, to U.S. Fish and
Wildlife Service, Albuquerque, NM.
12 Stefferud, S.A. 1987. Pers. comm. U.S. Fish & Wildl. Serv., P.O.
Box 1306, Albuquerque, NM 87103.
References - 2