(DRAFT) - Taxonomy
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
TAXONOMY
NAME - SALAMANDER, SAN MARCOS
OTHER COMMON NAMES - SALAMANDER and SAN MARCOS
ELEMENT CODE -
CATEGORY - Amphibians
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - AMPHIBIA,
ORDER AND SUBORDER - CAUDATA,
FAMILY AND SUBFAMILY - PLETHODONTIDAE,
GENUS AND SUBGENUS - EURYCEA,
SPECIES AND SSP - NANA,
SCIENTIFIC NAME - EURYCEA NANA
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
San Marcos Salamander
Eurycea nana Bishop, 1941
KINGDOM: Animal GROUP: Amphibian
PHYLUM: Chordata CLASS: Amphibia
ORDER: Caudata FAMILY: Plethodontidae
The following information on the taxonomy of the San Marcos
salamander is taken from the Recovery Plan (01) unless otherwise
indicated. The San Marcos salamander is a member of the
Plethodontidae family of lungless salamanders known as brook
salamanders. This is a neotenic species retaining its gills
throughout its life. The salamander sexually matures in the water.
The specific name "nana" is from the Greek "nanos" or Latin "nanus"
meaning dwarf and referring to the small adult size of these
salamanders (02).
The species was first collected for scientific purposes from San
Marcos Springs on June 22, 1938 by C.E. Mohr and sent to Sherman C.
Bishop (01) who described it as "a small, slender, neotenic species
uniformly light brown above with a dorso-lateral row of pale spots on
either side of the mid-line; yellowish white below; with 16 to 17
costal grooves. Later, Schmidt (14) included E. nana as a subspecies
Taxonomy - 1 (DRAFT) - Taxonomy
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
of E. neotenes without giving his reasons for doing so. These two
forms have numerous differeneces that warrant classifying them as
distinct species (02). E. nana differs from E. neotenes, the only
other species of the genus from the general locality, in its smaller
size (up to 59.6 mm), its uniformly light brown dorsal coloration
relieved only by a few small light spots, and its more slender form
and longer, more slender toes (03). This species is noted for its
moderately large eyes with a dark ring around the lens, its
well-developed and highly pigmented gills, its relatively short
slender limbs with four toes on the fore feet and five on the hind
feet, and its slender tail and well-developed dorsal fin. The San
Marcos salamander is smaller, more slender, differently colored, has
more numerous costal grooves, fewer pterygoid and premaxillary teeth,
and larger eyes relative to its head than other neotenic species.
More detailed morphological descriptions are found in: (03,04,05,06,
07,08,). The holotype can be found at the University of Michigan
Museum Zoology, #89759.
Based on karyotypic analysis, Bogart (09) indicated that
possible populations of E. nana occurred not only in San Marcos
Spring and the Comal River but also in the Sabinal River 8.9 km north
of Vanderpool, Bandera County, TX; Mountain Home in the headwaters of
the river feeding into the fish hatchery at Mountain Home, Kerr
County, TX; and Kerrville 8 to 11 km west of Highway 16 beside Rural
Route 1273, Kerr County, TX. Bogart's work has never been published
and Edwards et al. (01) indicate that there has been a "lack of
opportunity for specialists in the field to review and comment on his
findings leaving them open to question." Also, Sweet (16) stated
that all of the epigean populations of Eurycea on the Edwards Plateau
apart from those in the fault zone springs should be considered as
E. neotenes. Edwards et al. (01) indicate that Bogart's findings are
open to question.
See Bishop (04) for black and white photographs and Conant (15)
for a colored photograph of an adult. No illustrations of the eggs or
larvae have been published (02).
Taxonomy - 2 (DRAFT) - Status
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
STATUS
Coded Status
T: Federal Threatened
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The San Marcos salamander (Eurycea nana) has been designated a
Threatened species 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. The species has this status wherever found including the
State of Texas. Critical Habitat has been designated in Spring Lake
and its outflow, the San Marcos River, downstream approx. 50 m from
Spring Lake Dam, Hays County, Texas (50 CFR 17.95(d)).
Special rules concerning "take" for this species can be found in
50 CFR 17.43(a).
This species 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.
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
DESIGNATED STATUS: Recognized Threatened, Protected Nongame
Status - 1 (DRAFT) - Status
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
Species
ADMINISTRATIVE AGENCY: Texas Parks and Wildlife Department
STATE STATUTE: 31 Texas Admin. Code Sec. 65.173 (127.70.12.003);
and Sec. 57.133 (127.30.09.003), July 1977
Vernon Texas Codes Annot., Parks and Wildlife
Codes, Sec. 43, 67, and 68.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The San Marcos salamander is listed as rare in the 1986 IUCN Red
List of Threatened Animals.
ECONOMIC STATUSES:
This species has value as a component of Texas' natural heritage
of biotic diversity.
77/08/02:42 FR 39119/39120 - Notice of Review.
78/07/14:43 FR 30316/30319 - Proposed Listing.
80/07/14:45 FR 47355/47364 - Final Rule - Endangered w/ Critical Hab.
85/07/22:50 FR 47355/47364 - Five Year Review.
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
LAND USE -
Transportation, communications, and Util
Commercial and Services
Shrub and Brush Rangeland
Streams and Canals
Reservoirs
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Riverine, upper perennial
Lacustrine, littoral UB4
Lacustrine, littoral UB3
Lacustrine, littoral UB2
Lacustrine, littoral UB1
Lacustrine, littoral RB2
Lacustrine, littoral EM3
Lacustrine, littoral AB1
COMMENTS ON HABITAT ASSOCIATIONS -
The San Marcos River arises in a series of spring openings along
the Balcones Fault Zone in the City of San Marcos, Hays County, TX.
The second largest spring system in Texas, the springs at San Marcos
historically have exhibited the greatest flow dependability and
environmental stability of any spring system in the southwestern U.S.
Records indicate that the San Marcos Springs have never ceased
flowing, although the flow has varied and is tied to fluctuations in
their source, the Edwards Aquifer underlying the Balcones Fault Zone.
Partly because of the consistancy of its waters, the San Marcos Spring
ecosystem, including its springrun, the San Marcos River, has a
greater known diversity of aquatic organisms than any other ecosystem
in the southwestern United States (01).
The biological uniqueness of this system has been known for many
years. Many of the species found in the San Marcos River ecosystem
are found nowhere else and are restricted to the first few kilometers
or less of the San Marcos springrun. Other forms are nearly as range
restricted and are limited to the largest spring system in Texas--the
springs issuing into the Comal River in nearby New Braunfels, Comal
County, TX--in addition to the San Marcos River ecosystem (01).
Due to a variety of factors, including increased use of the
aquifer waters for human activities, increased urbanization in the
San Marcos region resulting in increases in flood intensity,
pollution, recreational use and alterations of the river, the San
Marcos ecosystem is in a precarious situation.
The Balcones Fault Zone is the principal geological feature
characterizing the San Marcos area. This fault zone separates the
Edwards Plateau vegetation region from the Blackland Prairies and
South Texas Plains regions. These regions correspond to the
Balconian, Texan and Tamaulipan Biotic Provinces respectively, of
Blair (1950). The headwaters of the San Marcos River issue from
several large fissures and numerous smaller solution openings along
the San Marcos Springs fault. Early Spanish explorers estimated that
a series of 200 springs made up the main spring area. The spring fed
San Marcos River flows primarily southeastward for approximately
Habitat Associations - 1 110 km before joining the Guadalupe River in the vicinity of Gonzales,
Gonzales County, TX. The upper San Marcos River is a rapidly flowing,
unusually clear spring run some 5-15 m wide and up to approximately
4 m deep. For the first few kilometers, to near the Blanco River
confluence, the river flows mostly over a firm gravel bottom with many
shallow riffles alternating with deep pools. The section between the
Blanco River confluence and the Guadalupe River has fewer attributes
of a spring run. Upstream from the junction of the Blanco River with
the San Marcos, three creeks, various storm sewers, and one wastewater
treatment plant discharge into the river. Sink Creek, largest of the
three creeks, discharges large quantities of storm runoff from the
north into Spring Lake. Spring Lake Dam backs water approximately
1.6 km up Sink Creek. The other two creeks, Willow Springs and
Purgatory Creeks, are normally dry except during periods of high
rainfall.
The San Antonio Region of the Balcones Fault Zone extends as a
series of faults and fracture lines from the vicinity of Brackettville
(Kinney County) east to San Antonio (Bexar County) and then northeast
to near Kyle (Hays County). A major aquifer (Edwards Balcones Fault
Zone Aquifer) underlies this fault zone and is the source of water for
San Marcos Springs. Runoff from the southern and eastern portions of
the Edwards Plateau recharge this aquifer through the porous
Cretaceous-aged limestones found in this region. Water from this
recharge flows along the fault zone from west to east and then
northeast. Major springs located along this fault system include the
two largest springs in Texas, Comal Springs in New Braunfels (Comal
County) and San Marcos Springs in San Marcos (Hays County).
The flow of San Marcos Springs has been monitored intermittently
since 1894. Average annual spring flow is 4.4 cubic meters per second
(161.0 cf/s). During drought years much lower flows occurred,
especially during the mid-1950's when Comal Springs did not flow for
part of one year. As of 1979 the lowest recorded monthly flow from
San Marcos Springs was 1.53 cubic meters per second (54 cf/s) during
1956. The lowest measured daily flow rate occurred on 15 and 16
August 1956 when the San Marcos River flowed at only 1.29 cubic meters
per second (45.55 cf/s). Maximum daily spring flows can be greater
than 8.33 cubic meters per second (294.13 cf/s), especially following
periods of high local rainfall and runoff.
The thermally constant water from the San Marcos Springs has long
been noted and generally varies annually by less than 1-2 degrees C
in the headwaters. At the lower end of the springrun habitat only a
slightly greater range of variation in temperature (from 25.5 degrees
C in August to 20.4 degrees C in February) has been recorded between
1967-1971. Waters tend to be alkaline or neutral due to the limestone
aquifer. The pH range of the San Marcos Springs is 6.9-7.8. The
stability of this stream, both in terms of flow dependability and
thermal characteristics, probably provided the appropriate ecological
conditions necessary to allow the unusually high degree of endemism
of the San Marcos biota.
Spring Lake, created on the San Marcos River not far from the
headsprings is the site of a major tourist attraction, Aquarena
Springs, Inc., a private amusement park.
In Spring Lake the San Marcos salamander is found in an area
composed of a sand and gravel substrate interspersed with large
limestone boulders and concrete banks at the Aquarena recreation
facility. Much of the rocky and concrete substrate is colonized by
the aquatic moss Leptodictyium riparium while the filamentous
blue-green algae, Lyngbya sp. coats the sandy substrate (01).
Spirogyra sp., and the carnivorous angiosperm, Utricularia gibba are
also present in small amounts. Rooted aquatic macrophytes include
Sagittaria platyphylla, Myriophyllum brasiliense, Ludwigia repens, and
Habitat Associations - 2 Vallisneria americana are on the shallow (1-3 m) periphery of the
habitat, and Cabomba caroliniana and Egeria densa are found in
association with the muddy-detrital benthos (01).
The salamanders are most commonly found in association
with the dark-reddish colored Lyngbya sp. and in close proximity
to the spring openings (01). Flowing water is apparently
necessary as no members of this species are found in still waters.
The physical and chemical constituents of the water in the area of
preferred habitat are pH 7.2, 21-22 degrees C, dissolved oxygen
4 mg/l+, oxygen saturation of 40 to 50 %, methyl orange alkalinity of
220-232 mg/l and a specific conductance of 510-535 micro-ohms/cm.
(08). Norris et al. (12) has demonstrated that captive salamanders
will not tolerate temperatures of 30 degrees C or greater. In
addition, oxygen consumption was greatest at water temperatures of
25 degrees C as compared with temperatures of 20 or 30 degrees C.
Edwards et al. (01) summarize the requirements of the San Marcos
salamander as follows: clean, clear, flowing water; a substrate of
sand, gravel, and rock; vegetative cover; food supply of living
organisms; and protection from floods.
Habitat Associations - 3 (DRAFT) - Food Habits
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
OMNIVORE
LIFESTAGE FOOD FOOD PART
General Detritus
General Algae
General Molluscs
General Arthropods
Food Habits - 1 (DRAFT) - Environment Associations
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
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 Aquatic Features: Springs [flowing]
G Human Association: Abandoned buildings
G Human Association: Public residential parks
Environment Associations - 1 (DRAFT) - Life History
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Stomach content analyses of 80 preserved specimens revealed that
the San Marcos salamander's natural diet is composed of amphipods and
tendipedid (midge fly) larvae and pupae (01). Niads, small aquatic
snails, and other small insects are less well represented. Both
Lyngbya sp. and grains of sand are occassionally accidentally
ingested (01). The San Marcos salamander is a "lie and wait"
predator. Captive specimens were maintained in the laboratory on
amphipods (01).
HOME RANGE/TERRITORY:
No information is available on home range or territory for this
species.
PERIODICITY:
There is no information on periodicity for this species with the
exception of a peak in reproductive behavior occurring in May and
June.
MIGRATION PATTERNS:
There is no indication of migration for this species.
COVER/SHELTER REQUIREMENTS:
According to Edwards (01) the salamanders are "abundant within
the wiry mesh of the aquatic moss Leptodictyium riparium and the
reddish-brown Lyngbya sp. This latter algae matches the dark dorsal
coloration of the salamander.
REPRODUCTIVE SITE REQUIREMENTS:
Edwards et al. (01) reports that courtship and egg deposition by
E. nana has not been reported, and no eggs have been collected from
the habitat. Courtship and oviposition have, however, been observed
for closely related E. neotenes. Eggs of this latter species were
deposited on plant material, stones, and the bottom of a glass bowl
about 24 hours after courtship. Eggs developed to hatching in 25
days (09). Most, if not all, Eurycea breed in running water of
brooks, caves, or springs. In most cases, adherent eggs are
deposited singly on the bottom and sides of stones, or aquatic
vegetation.
REPRODUCTIVE CHARACTERISTICS:
Unless otherwise indicated, the following material is taken,
essentially unmodified, from Edwards et al. (01). Male E. nana reach
sexual maturity (possess at least one full darkly-pigmented lobe in
each testis) only after attaining a snout-vent length of 19 mm (35 mm
total length). All males with snout-vent lengths greater than
23.5 mm (40-45 mm total length) were mature, possessing
darkly-pigmented testes with one to three lobes (08). In an
investigation by Mackay (13) which did not include data from July and
August, sperm were found in the testes of all mature males collected
from October to May and in the Wolffian ducts of certain males
Life History - 1 (DRAFT) - Life History
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
collected from October to June (except for January and March) in an
investigation by Mackay (13) which did not include the months of
July and August. Mackay (13) found large numbers of spermatozoa in
the Wolffian ducts in November and the ducts were in a distended
condition in June, leading her to postulate a breeding season in June
and possibly another in fall.
Salamanders examined had four classes of ova in the ovaducts:
very small, clear ova, small yellow ova, and large yellow ova.
Females carrying large yellow ova (1.5-2.00 mm in diameter were
considered gravid and presumably ready for oviposition. Large yellow
ova were present in females with snout-vent lengths greater than
20.0 mm (35 mm total length). Females with a snout-vent length
greater than or equal to 26 mm carried 1 to 19 large yellow ova,
possibly indicating oviposition of only a portion of the larger eggs.
Large yellow ova were present in some females in nearly every month
of the year (08).
A total of seven small juveniles of E. nana still possessing
yolk on the venter were collected in February, May, and June 1968.
Juveniles of less than 12 mm total length were collected from
February through October (08). Bogart (09) found very small E. nana
in September, December, March, April, and June but noted they were
most common in the late spring and early summer. He postulated that
the salamander breeds most of the year with a peak in late spring.
PARENTAL CARE:
There is no information on parental care, however parental care
is unlikely.
POPULATION BIOLOGY:
Edwards et al. (01) report that the structure of the E. nana
population is remarkably uniform throughout the year. In all seasons
juvenile (snout-vent lengths usually less than 15 mm) of undetermined
sex represent about 45 percent of the total population. Larger
juveniles (about 15-20 mm snout-vent length) of undetermined sex
represented about 30-40 percent of the population. Mature males
(snout-vent lengths 19 mm and greater) represented about 10-15
percent and gravid females (snout-vent lengths 20 mm and greater)
about 4 percent of the total. The number of salamanders in the upper
portion of Spring Lake may be between 17,000 and 21,000 individuals
(08 in 01).
SPECIES INTERRELATIONSHIPS:
According to Tupa and Davis, the San Marcos salamander is found
in association with the fountain darter (Etheostoma fonticola),
crayfish (Cambrus sp.), two species of freshwater shrimp
(Palaemonetes sp.), many tendipedid larvae, a variety of other insect
larvae, very large number of amphipods (Hyalella azteca), water
mites, small aquatic snails, leeches (Placobdella sp.) and planarians
(Dugesia sp.). Sunfishes and cichlids feed on the salamander as do
catfish (Ictalurus sp.) and largemouth bass (Micropterus salmoides).
Swans (Cygnus olor) and domesticated mallard ducks (Anas
platyrhynchos) feed on the aquatic moss which provides habitat for
the salamander.
Life History - 2 (DRAFT) - Life History
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
OTHER LIFE HISTORY DESCRIPTORS:
The San Marcos salamander is capable of changing dorsal
coloration between light tan and dark brown in accordance with
substrate coloration. The color change occurs via pigment migration
in melanophores appearing as if they are expanding or shrinking. The
external gills of the salamnder expand and appear bright red
(resulting from increased blood flow) in cool, low oxygen waters.
The bushy red gills are prominent on idividuals collected from the
springs but show marked reduction (apparent resorption) in specimens
kept in well oxygenated aquaria (08 in 01).
Life History - 3 (DRAFT) - Management Practices
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Controlling/Restricting Boating Activities
Beneficial Restricting/regulating human disturbance of populations
Beneficial Maintaining/Controlling Water Flow
Beneficial Controlling water levels
Beneficial Restricting/regulating human use of habitats
Beneficial Land Acquisition
Beneficial Water Right Acquisition
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Controlling/Removing Exotic Vertebrates
Adverse Food Supply Reduction
Existing Food Supply Reduction
Adverse Predation
Existing Predation
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Groundwater drawdown
Existing Groundwater drawdown
Adverse Applying fertilizers
Existing Applying fertilizers
Adverse Applying herbicides
Existing Applying herbicides
Adverse Applying pesticides
Existing Applying pesticides
Adverse Environmental Contamination/Pollution
Existing Environmental Contamination/Pollution
Adverse Exotic/Feral/Introducted Species
Existing Exotic/Feral/Introducted Species
Adverse
Existing
Adverse Vegetation Composition Changes
Existing Vegetation Composition Changes
COMMENTS ON MANAGEMENT PRACTICES -
Edwards et al. (01) state that the major reason for the present
status of the San Marcos Salamander lies in increased use of waters
from the aquifer for human activities, increased urbanization in the
San Marcos region resulting in increases in flood intensity,
pollution, recreational use and alterations of the river.
There exists a potential for elimination of the spring flow from
the San Marcos Springs due to water withdrawals from the Edwards
Aquifer, especially from urban and agricultural users of this water.
On a local scale, the City of San Marcos is growing rapidly and
increased urbanization has caused increased flooding and erosion,
pollution, pesticides and herbicides which runoff into the San Marcos
River. Effluent discharges from the secondary sewage treatment plant
of the City of San Marcos is another negative factor (01).
Management Practices - 1 (DRAFT) - Management Practices
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
Spring Lake (altitude 189 m) was created over fifty
years ago by the damming of the San Marcos River not far downstream
from the headsprings. The clarity of its water has made Spring Lake
the site of major tourist attraction, Aquarena Springs, Inc., a
private amusement park featuring glass-bottomed boat rides and a
submarine theater (01).
The population of the City of San Marcos, Hays County, TX rose
from 741 in 1870 to 23,420 in 1980; no other county along the
Balcones Fault Zone had a greater relative growth than Hays County for
the period 1960-1980. Continued rapid population growth of the City
of San Marcos and Hays County is expected (01).
Because the San Marcos Springs' flow is tied inseparably to water
usage over the entire Edwards Balcones Fault Zone Aquifer, human
population growth coupled with increased utilization of groundwater in
the region will decrease flow of water from the San Marcos Springs.
Analyses by the Texas Department of Water Resources in 1977 (10)
projecting water usage from the aquifer through the year 2020 indicate
that increased usage is expected especially in the San Antonio region.
Bureau of Reclamation data suggest that demands on the Edwards
Balcones Fault Zone Aquifer, even considering a "low" rate of growth
for this region, will far exceed the recharge to the aquifer. The
Bureau of Reclamation projects that the probability of continous flow
from the San Marcos Springs by the year 2020 is only 50-75 percent
certain. Others have predicted the continued flow from the San Marcos
Springs will cease around the year 2010 (01).
The City of San Marcos is growing rapidly. Increased
urbaniziation causes increased flooding (due to uncontrolled runoff),
pollution, siltation, and general decrease in species diversity
and species numbers in adversely impacted aquatic environments.
A series of five flood retardation structures initiated by the Soil
Conservation Service on tributary creeks feeding into the San Marcos
River is expected to decrease the severity of flooding in the
watershed and to slightly increase the recharge into the aquifer, thus
producing a slight overall benefit to the ecosystem (01). The
headwaters of the San marcos River at the northmost end of Spring
Lake near the hotel tend to be protected from flooding action.
Protection from scouring by floods undoubtedly contributes to the
continued survival of the San Marcos salamander population since the
salamander is not a strong swimmer and the loss of protective
vegetation and food supply could be critical (01).
Urban pollutants such as locally applied fertilizers, pesticides,
and herbicides also may be negatively impacting on the San Marcos
species.
Another threat to the salamander is predation from several
exotic/introduced species. Most larger associated species are
predators and occur in the vicinity of the salamander habitat,
including several species of sunfishes and cichlids. These species
feed on insect larvae, amphipods, terrestrial isopods, aquatic snails,
freshwater shrimp, fountain darters, and San Marcos salamanders.
Turtles such as stinkpots (Sternotherus odoratus) occasionally are
present in the salamander habitat as are bullheads (Ictalurus sp.)
and largemouth bass (Micropterus salmoides) (01).
The removal of vegetation which provides cover and harbors the
Management Practices - 2 (DRAFT) - Management Practices
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
salamander's food supply (i.e., duck fecal droppings polluting
moss habitat, ducks feeding on moss and algae, removal of algal mats
by Aquarena Springs personnel) is another threat (01).
Introduced swans (Cygnus olor) and domesticated mallard ducks
(Anas platyrhynchos) in the Spring Lake feed on the aquatic moss and
Lyngbya sp. These birds roost nightly on the sidewalk alongside the
salamnaders' principle habitat (08).
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1984. San Marcos Recovery Plan.
U.S. Fish and Wildlife Service, Albuquerque, NM. iv + 109 pp.
The survival of this (threatened) and three endangered San Marcos
River species (San Marcos gambusia, fountain darter, and Texas wild
rice) is tied to the survival of the San Marcos River ecosystem. If
the flow of the San Marcos River, with its natural cycle of variation,
is assured, the chances of the long-term survival of these species
increase. Short term threats (see below) also must be addressed, but
the two types of concerns are totally and inextricably interwined.
The following need to be determined for the San Marcos River system:
1) aquifer characteristics and recharge patterns and zones
that influence flow at San Marcos Springs,
2) impacts of recreational use (i.e. controlling boating, and
human access in specific areas) of the river on listed
species,
3) characteristics of the river's watershed, and
4) pesticide and herbicide use in the watershed.
Management guidelines for the San Marcos River ecosystem need to be
established, including:
1) reduction of pollution load,
2) possible augmention of aquifer recharge,
3) controls on groundwater pumping of aquifer,
4) preparation of water wells to ensure continued flow of
the river,
5) restoration of damaged and enhancement of marginal
habitats (this may include such actions as water right
acquisition, land acquisition, and land use zoning),
6) removal of nonnative organisms,
7) establishment of river recreational use guidelines, and
8) encouragement of proper management by private and public
landowners.
San Marcos salamanders populations should be monitored at least
two times a year. Efforts should be made to identify individual and
population characteristics including:
1) competition with nonindigenous species,
2) food habits,
3) reproductive parameters,
4) survivorship patterns,
5) effects of predation, and
6) the diseases and parasites of San Marcos salamanders.
Management Practices - 3 (DRAFT) - Management Practices
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
Also, the following habitat requirements need to be determined:
1) flow 3) channel conformation
2) temperature 4) and other niche requirements.
San Marcos salamanders should be provided the full protection mandated
by Federal and Texas laws. Finally, public awareness of the
uniqueness of the San Marcos River ecosystem should be increased
through information pamplets, news releases and public involvement.
Conservation efforts for the San Marcos salamander primarily
have involved determining basic aspects of its life history,
abundance, habitats, and other factors affecting its survival (08).
Efforts have been made to ensure the cooperation of the owners of
Aquarena Springs Amusement Park in the management of this species in
following management recommenadations made by the Texas Parks and
Wildlife Department biologists (01).
Management Practices - 4 (DRAFT) - References
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 U.S. Fish and Wildlife Service. 1984. The San Marcos Recovery
Plan for San Marcos River endangered and threatened species. U.S.
Fish and Wildl. Serv., Albuquerque, NM. 109 pp.
02 Brown, B.C. 1967. Eurycea nana. Catalogue of American
amphibians and reptiles. P. 35.
03 Bishop, S.C. 1941. Notes on salamanders with descriptions of
several new forms. Occ. Pap. Mus. Zool., Univ. Mich. 451:6-9.
04 Bishop, S.C. 1943. Handbook of salamanders. Comstock Publ. CO.,
Ithaca, New York. 555 pp.
05 Baker J.K. 1957. Eurycea troglodytes: a new blind salamander
from Texas. Texas J. Science 9(3):328-336.
06 Mitchell, R.W. and J. R. Redell. 1965. Eurycea tridentifera, a
new species of troglobitic salamander from Texas and a
reclassification of Typhlomolge rathburni. Texas J. Science
17(1): 12-27.
07 Schwetman, N.H. 1967. A morphological study of the external
features, viscera, integument, and skeletons of Eurycea nana.
Unpubl. M.A. thesis. Baylor Univ., Waco, Texas. 26 pp.
08 Tupa, D.D. and W.K. Davis. 1976. Population dynamics of the San
Marcos salamander, Eurycea nana Bishop. Texas J. Sci. 32:179-195.
09 Bogart, J.P. 1967. Life history and chromosomes of some of the
neotenic salamanders of the Edward's (sic) Plateau. Unpubl. M.A.
thesis. Univ. of TX - Austin. 79 pp.
10 Texas Department of Water Resources. 1977. Continuing water
resources planning and development for Texas. Phase I. Unpubl.
rept. on file with the TX Dept. of Water Resources, Austin.
11 Longley, G. 1975. Environmental assessment, upper San Marcos
River Watershed. Contract No. AG-48-SCS 02156 for the Soil
Conserv. Serv. Environ. Sciences of San Marcos, Texas. 367 pp.
12 Norris, W.E. Jr., P.A. Grandy, and W.K. Davis. 1963.
Comparative studies on the oxygen consumption of three species of
neotenic salamanders as influenced by temperature, body size, and
oxygen tension. Biol. Bull 125(3):523-533.
13 Mackay, M.R. 1952. The spermatogenesis of the neotenic
salamander Eurycea nana Bishop. Unpubl. M.S. thesis. Univ. of TX
- Austin. 35 pp.
14 Schmidt, K.P. 1953. A check-list of North American amphibians and
reptiles. 6th. ed. Amer. Soc. Ichthyol. and Herpetol. 280 pp.
15 Conant, R. 1958. A field guide to reptiles and amphibians of the
United States and Canada east of the 100th meridan. Houghton
Mifflin Co., Boston. 366 pp.
16 Sweet, S.S. 1978. The evolutionary development of the Texas
Erycea (Amphibia: Plethodontidae). Unpubl. Ph.D. Diss., Univ. of
Calif., Berkeley. 450 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Tupa, D.D. and W.K. Davis. 1976. Population dynamics of the San
References - 1 (DRAFT) - References
Species SALAMANDER, SAN MARCOS
Species Id ESIS202003
Date 14 MAR 96
Marcos salamander, Eurycea nana Bishop. Texas J. Sci. 32:179-195.
02 Bogart, J.P. 1967. Life history and chromosomes of some of the
neotenic salamanders of the Edward's (sic) Plateau. Unpubl. M.A.
thesis. Univ. TX., Austin. 79 pp.
03 U.S. Fish and Wildlife Service. 1984. The San Marcos Recovery
Plan for the San Marcos River Endangered and Threatened Species.
U.S. Fish and Wildl. Serv., Albuquerque, NM. iv + 109 pp.
04 Sweet, S.S. 1978. The evolutionary development of the Texas
Eurycea (Amphibia: Plethodontidae). Unpubl. Ph.D. Diss., Univ. of
Calif., Berkeley. 450 pp.
References - 2