(DRAFT) - Taxonomy
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
TAXONOMY
NAME - TOAD, HOUSTON
OTHER COMMON NAMES - TOAD and HOUSTON
ELEMENT CODE -
CATEGORY - Amphibians
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - AMPHIBIA,
ORDER AND SUBORDER - SALIENTIA,
FAMILY AND SUBFAMILY - BUFONIDAE,
GENUS AND SUBGENUS - BUFO,
SPECIES AND SSP - HOUSTONENSIS,
SCIENTIFIC NAME - BUFO HOUSTONENSIS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Houston Toad
Bufo houstonensis Sanders, 1953
KINGDOM: Animal GROUP: Amphibian
PHYLUM: Chordata CLASS: Amphibia
ORDER: Salientia FAMILY: Bufonidae
Adult Houston toads are small to medium toads with males between
45 and 70 mm snout-vent length and females 52-80 mm. The dorsum is
light brown with a variable number of dark brown to black spots.
These spots usually contain a single, or several fused, nonspinous
warts and the spot may appear as a narrow black margin around the
warts. The venter is cream colored with at least one brown spot in
the pectoral region (usually mottled). The parotoid glands are
elongate but otherwise variable in shape. The interorbital and
postorbital cranial crests are typically thickened. But this
character is much more obvious in the type series than in extant
individuals (01).
Within the jelly tube, the eggs are separated from one another in
compartments. For a more extensive description of the Houston toad
see Sanders (02) and Brown (03). Photographs of adult B. houstonensis
are in Sanders (02) and various other publications cited herein
Taxonomy - 1 (DRAFT) - Taxonomy
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
(05,13,12).
The tadpoles of the Houston toad are quite distinct from all
sympatric anuran species but visually inseparable from those of
B. americanus. The body and upper 3/4 of the tail are thoroughly
pigmented. Total length of 15 specimens examined (stages 33-42 of
Gosner (04)) ranged 13.7-19.4 mm (X=17.3 mm). The labial formula is
is 2(2)/3.
Bufo houstonensis was first described by Sanders (02) in 1953.
There has been some discussion as to its distinct differences from
other bufonids and that natural hybridization may be a cause of a
trend toward extinction. Little evidence indicates that natural
hybridization has such an effect. Only 34 confirmed natural hybrids
(25 B. houstonensis X B. valliceps, 9 B. woodhousei) have been
identified (05,06). No evidence indicates widespread hybridization,
back-crossing, or introgression. Hillis et. al. (06) found that
hybrids make up less than 1 percent of toad breeding choruses
involving B. houstonensis and another Bufo species. Brown (05) only
indicated that natural hybridization potentially could contribute to
the trend toward extinction.
Houston populations of B. houstonensis were originally called
B. terrestris by Harwood (24 in 01). Sanders (24 in 01) used the
Houston area toads as a basis for the description of B. houstonensis,
saying they differed from B. americanus in color pattern, skeletal
morphology, and the presence of "egg compartments." Brown (05 in 01)
showed that the call of the Houston toad differed from that of New
Jersey B. americanus.
A. P. Blair (23 in 01) considered the Houston toad to be a
subspecies of B. americanus but all recent authors have considered it
a full species. W. F. Blair (08 in 01) suggests that it represents a
slightly differentiated Pleistocene relic of B. americanus. Due to
the general acceptance of the latter theory, many herpetologists
feel that the relationships of B. houstonensis to nearby populations
of B. americanus have not been adequately studied and are not well
understood.
Taxonomy - 2 (DRAFT) - Status
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Houston toad (Bufo houstonensis) has been designated an
Endangered 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 areas of
Burleson and Bastrop Counties, Texas (50 CFR 17.95(d)).
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.
DOD -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public land under their control. Also responsible for
management/recovery on Department of Defense lands.
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:
Status - 1 (DRAFT) - Status
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
STATE: Texas
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Texas Parks and Wildlife Department
STATE STATUTE: TX Parks and Wildlife Codes 127.30.09.001-.006
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The Houston toad is listed in the 1986 IUCN Red List of
Threatened Animals as Endangered. It is also listed by the U.S. in
the Convention on Nature Protection and Wildlife Preservations in the
Western Hemisphere Annex (1970).
ECONOMIC STATUSES:
This species has no known economic value.
70/07/25:35 FR 13519/13520 - Listed as Endangered, Pre-Act 6
70/10/13:35 FR 16047/16048 - Re-listed, Pre-Act 7
78/01/31:43 FR 04022/ - Designated Critical Habitat
79/05/21:44 FR 29566/29577 - 5-year review
85/07/22:50 FR 29901/29909 - Notice of review
87/07/07:52 FR 25522/25525 - Notice of 5-year review completion
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
TERRESTRIAL
INLAND AQUATIC
SOCIETY OF AMERICAN FORESTRY TYPES
SAF TYPE STAGE CLOSURE
Loblolly Pine-Shortleaf Pine young tree
Loblolly Pine-Shortleaf Pine mature tree
Loblolly Pine-Shortleaf Pine Old Growth
LAND USE -
Residential
Transportation, communications, and Util
Mixed Urban or Built-up Land
Cropland and Pasture
Evergreen Forest Land
Lakes
Forested Wetland
Sandy Areas other than Beaches
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Palustrine UB
Palustrine SS7
Palustrine OW0
Palustrine EM
COMMENTS ON HABITAT ASSOCIATIONS -
Water is one of the most important parts of Houston toad
habitat as reproduction cannot occur if there is not enough water to
fill breeding pools. The largest aggregations of calling and breeding
Houston toads are found in temporary rain pools. They may, however,
be found in a variety of aquatic habitats. The area surrounding the
primary calling site in Burleson County had been bulldozed and is
grazed by cattle; the pool is surrounded by a minimally 10 m wide
strip of thick yaupon (Ilex vomitoria) growth. Other calling sites
include waters associated with open pasture, cleared shallow ravines,
the vicinity of dwellings around a lake, roadside ditches, lakes,
manmade ponds, cleared areas within the pine forest, pastures, flooded
fields, puddles near cabins, moist spots in residential areas,
prairie potholes, and near runways on Ellington AFB. Water is also
important after breeding as tadpoles will die if pools dry up before
metamorphosis. Adults also require free water for metabolism and
normal functions (01).
Houston toads apparently are restricted to areas characterized by
sandy soils. B. houstonensis is a weak burrower and has difficulty
digging in compacted soil (11). Six Houston toads kept in the
laboratory spent most of the daylight hours buried under sand. A sand
substrate occurs at or near all known localities for B. houstonensis
(05). Upon leaving the breeding pond, toads seek refuge in areas with
sand substrate in such places as under logs, in leaf litter, existing
burrows, undercut banks around ponds,and in the actual sand substrate.
There has been a misconceived assumption that pine trees occur
naturally at all Houston toad localities. A great abundance of
natural loblolly pine (Pinus taeda) usually characterizes the
Habitat Associations - 1 localities in Bastrop County and pines are found at or near some other
localities for B. houstonensis. However, the pine stand at Lake
Woodrow (Burleson County) was planted in 1959 (12). Also, the
habitats at the Skyscraper Shadows/East Haven and Fairbanks localities
(Harris County) were coastal prairie without pines before being
developed for housing. However, a common characteristic of all known
localities for Houston toads is a friable, sandy soil (see above, also
03,13) which, coincidentally, is conducive to pine growth. Thus the
toads are probably reliant upon the substrate but not on the presence
of pine trees.
High temperature may also be a factor. Blair (08) considered
B. houstonensis to be a weakly differentiated species that originated
after isolation from northern adapted B. americanus after the
Pleistocene. Brown (09) suggested that B. houstonensis may still be a
northern adapted species and its inability to adapt to a warmer
climate could be contributing to the trend toward extinction.
Lundelius (10) also suggested that higher temperatures and/or aridity
were the cause(s) of disappearance from Texas of a number of northern
adapted species of mammals in the last 10,000 years.
Habitat Associations - 2 (DRAFT) - Food Habits
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
OMNIVORE
LIFESTAGE FOOD FOOD PART
General Algae
General Arthropods
Food Habits - 1 (DRAFT) - Environment Associations
Species TOAD, HOUSTON
Species Id ESIS202001
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 Terrestrial Features: Depressions
G Terrestrial Features: Burrows
G Terrestrial Features: Downed logs
G Human Association: Farm ponds
G
Environment Associations - 1 (DRAFT) - Life History
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Bragg (11) reported that captive Houston toads fed on various
insects, a small spadefoot toad, and presumably a small Bufo cognatus.
Thomas (14) examined the digestive tracts of 17 adults; all were
empty except one which was stuffed with ants (Crematogaster
cf. minutissima, fide Mehlhop) and one which had beetle remains. Post
metamorphic B. houstonensis presumably feeds on small arthropods and
the tadpoles are known to ingest algae and pollen (14).
PERIODICITY:
Houston toads are primarily nocturnal, resting in burrows during
the day in some secluded place with sand substrate in such places as
under logs, in leaf litter, existing burrows, undercut banks around
ponds, and in the actual sand substrate (01).
MIGRATION PATTERNS:
Houston toads are non-migratory.
COVER/SHELTER REQUIREMENTS:
Houston toads need sandy soils in which to burrow. They
rest in burrows during the day in some secluded place with sand
substrate in such places as under logs, in leaf litter, existing
burrows, undercut banks around ponds, and in the actual sand
substrate (01).
REPRODUCTIVE SITE REQUIREMENTS:
Houston toads appear generally to use rain pools or flooded
fields for breeding, but they may use natural or manmade ponds. They
are also found in a variety of aquatic habitats. The area surrounding
the primary calling site in Burleson County had been bulldozed and is
grazed by cattle; the pool is surrounded by a minimally 10 m wide
strip of thick yaupon (Ilex vomitoria) growth. Other calling sites
include waters associated with open pasture, cleared shallow ravines,
the vicinity of dwellings around a lake, roadside ditches, lakes,
manmade ponds, cleared areas within the pine forest, pastures, flooded
fields, puddles near cabins, moist spots in residential areas, prairie
potholes, and near runways on Ellington AFB (01).
REPRODUCTIVE CHARACTERISTICS:
Houston toads call from in or near the water, with the earliest
calling date being January 22 (14). Reported egg laying dates range
from February 18 to June 26 (06,13). Quinn (15) reported that captive
raised males matured at one year, with active sperm present at eight
months, when snout-vent lengths were 3.1 cm. Females matured sexually
at 1-2 years. Kennedy (13) reported a female produced 728 eggs in the
lab. Egg masses range from 513-5999 eggs from wild caught females
spawned in the laboratory (16).
PARENTAL CARE:
Egg masses laid by the females are left unattended. The tadpoles
are on their own from their hatching through metamorphosis.
Life History - 1 (DRAFT) - Life History
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
POPULATION BIOLOGY:
Limiting factors for Houston toads are friable, sandy substrates,
open water for breeding, and habitat loss (see N-HABITAT and N-REASON
narratives).
Since the late 1940s, populations of Houston toads in Harris
County have decreased markedly. Wottring's field notes (07) indicate
that he collected 66 individuals from a single chorus in 1949 and
still found "quite a lot" in 1953. Brown (05,09) found three Houston
toads during the breeding season of 1965-67. After extensive surveys
in the springs of 1974-78, only 2 toads were observed in SE Houston
in 1976. Despite extensive surveillance, no indication exists of the
Houston toad's presence in Harris County since that time.
Burleson County has a small population of Houston toads near Lake
Woodrow. This assessment is based on verbal comparisons of field
studies by Brown (12 or fewer individuals) in the mid-1960s and
Thomas (around 300 individuals) in the mid-1970s. Most observations
were of one to several calling males. Jim R. Dixon (17) found no
Houston toads during the springs of 1979-82, but in 1983 four calling
males were observed.
The population in Bastrop County has increased. Brown (18)
reported that the population probably was represented by no more than
300 individuals in 1967. By the mid-1970s, Thomas and Porter (19)
estimated 1500 individuals. During the breeding seasons of 1981-1982,
Hillis et al. (06) and Jacobson (14) studied Houston toad populations
with emphasis on several ponds north of Highway 21 in Bastrop County.
They commonly encountered choruses of 30-100 individuals at study
ponds. A mark and recapture program at one pond indicated that 50-75
percent of males on subsequent nights were new and that females were
not observed returning to the ponds. Accordingly, these authors
estimated 300-1000 toads using each pond. As the study area covered
less than 5 percent of the known range in Bastrop County, the overall
population may be large, perhaps 10,000 or more toads (20).
Eggs, adults, and recently metamorphosed toads collected near
Bastrop State Park and captive-reared at Houston Zoological Gardens
were released in Attwater's Prairie Chicken NWR in the spring of 1983.
A total of 24,702 individuals and 22 bloodlines were involved.
Success of the transplant is yet unknown (21).
SPECIES INTERRELATIONSHIPS:
The following anurans frequent the same or adjacent calling sites
as the Houston toad and may use the same resources, at various stages
of their life history: Rana clamitans, R. sphenocephala,
R. catesbeiana, R. areolata, Hyla crucifer, H. cinerea,
H. chrysoscelis, H. squirella, H. versicolor, Acris crepitans,
Scaphiopus holbrooki, Gastrophyryne olivacea, G. carolinensis,
Pseudacris clarki, P. triseriata and P. streckeri. The only Bufo
species known to be sympatric with Houston toad are B. valliceps and
B. woodhousei, though B. speciosus and B. punctatus occur within 20
miles. For a significant portion of the breeding season, Houston
toads are temporally isolated from B. valliceps. Some overlap occurs
in April and May, but breeding site and feeding competition is
probably minimal (03,04). The breeding season of Houston toads and
Life History - 2 (DRAFT) - Life History
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
B. woodhousei is similar, but habitat segregation appears to be the
rule (06).
Hognose snakes (Heterodon nasicus and H. platyrhinos) feed on
Houston toads and a Nerodia erythrogaster (red belly water snake) was
collected that contained 2 Houston toads while swallowing another
(20). Nerodia rhombifera (diamond back water snake), N. fasciata
(banded water snake), and Thamnophis proximus (ribbon snake) are also
potential predators. Other occasional predators could include
Kinosternon subrum (mud turtle), K. flavescens (yellow mud turtle),
Sternotherus odoratus (Stinkpot), and Chelydra serpentina (snapping
turtle). Micropterus salmoides (largemouth bass), Lepomis sp.
(sunfish) and other Piscine predators might feed on toad larvae or
eggs; although closely related B. americanus tadpoles are relatively
immune to fish predators (22).
Warm-blooded associates include various birds and mammals. Those
which are general predators may eat Houston toads.
OTHER LIFE HISTORY DESCRIPTORS:
None.
Life History - 3 (DRAFT) - Management Practices
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Restricting/regulating human disturbance of populations
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Land Acquisition
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Stocking captive-reared wild-strain animals
Beneficial Transplanting wild animals
Beneficial Transplanting Wild Eggs/Wild Seeds
Adverse Climate Alteration
Existing Climate Alteration
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Highway/Railroads
Existing Highway/Railroads
Adverse Soil compaction by heavy equipment in mine areas
Existing Soil compaction by heavy equipment in mine areas
Adverse Strip mining
Existing Strip mining
Adverse
Existing
Adverse Fire
Existing Fire
Adverse Forest Alteration
Existing Forest Alteration
Adverse Harvesting
Existing Harvesting
COMMENTS ON MANAGEMENT PRACTICES -
The most important causes of the decline of B. houstonensis are
probably climatic changes and destruction and/or modification of
habitats (01). Water is one of the most important factors limiting
Houston toads as reproduction cannot occur if there is not enough
water to fill breeding pools. During the early 1960s, spring rains in
the Houston area were below normal, and no breeding choruses were
heard (07). Droughts in the early and mid-1950s may have played an
important role in reducing the numbers of the species. Water is also
important after breeding as tadpoles will die if pools dry up before
metamorphosis. Adults also require free water to survive (01).
High temperature may also be a factor. Blair (08) considered
B. houstonensis to be a weakly differentiated species that originated
after isolation from northern adapted B. americanus after the
Pleistocene. Brown (09) suggested that B. houstonensis may still be a
northern adapted species and its inability to adapt to a warmer
climate could be contributing to its trend toward extinction.
Lundelius (10) also suggested that higher temperatures and/or aridity
were the cause(s) of disappearance from Texas of a number of northern
adapted species of mammals in the last 10,000 years.
Management Practices - 1 (DRAFT) - Management Practices
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
There has been extensive habitat modification in the known
present populations of Houston toads. In Harris County, the growing
city of Houston has been consuming habitat rapidly. Development
(primary recreational including golf courses, artificial lakes, and
camping areas) of Bastrop and Buescher State Parks in the 1960s
changed drainage patterns and adversely affected the toads as did
lumbering (including timber clearing for housing development and
agricultural use) and highway improvement projects (resulting in
altered drainage pattern). Park management improved during the
1970s, as have other land management (reforesting, grazing) practices.
At the Burleson County site the major problem is overgrazing by cattle
which results in habitat alteration (01).
In Bastrop County Highways 71 and 21 cut through pine forests
subjecting B. houstonensis to traffic mortality. Periodic mowing
along highway and on a golf course occasionally kill the species.
Pesticides and herbicides (i.e., Atrazine) used along roads, by
residents, or in surrounding croplands, may adversely impact the
toad (01). Forest management such as prescribed burning to reduce
undergrowth could be detrimental by direct mortality as well as
reducing invertebrate food resources (01). Activities associated
with urban and agricultural development cause soil compaction due
to the use of heavy equipment and plowing, and will adversely
impact the species (01). Since it is a weak burrower and has
difficulty digging in compacted soil (01). A stratum of lignite
crosses a portion of Critical Habitat in Bastrop County. If mining
were to be considered in the future this could have deleterious
habitat impacts (01).
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1984. Houston Toad Recovery Plan.
U.S. Fish and Wildl. Serv., Albuquerque, NM 73 pp.
The first action planned in the recovery of the Houston toad
(Bufo houstonensis) is to maintain and enhance existing toad
populations in their existing habitats. This includes monitoring
existing populations and habitats, identifying population needs and
habitat needs, and assuring protection (i.e., controlling/restricting
herbicide use, pesticide use, pollutants, and development; land
acquisition; and limiting human access) of existing populations in
Bastrop and Burleson Counties. There is a need to improve monitoring
procedures and schedules and recommendations are made. There will
also be an effort to locate additional natural populations of Houston
toads, and to determine the taxonomic status of Bufo houstonensis.
The plan calls for reestablishment (or locating presently unknown
populations) of viable populations in at least 5 counties within the
former range of the Houston toad, and monitoring of populations and
managing of habitats in the new locales. These new populations will
be established by: transplanting wild individuals and their eggs,
and from individuals raised in a captive breeding program. Managing
will involve cooperative agreements with landowners of new locales and
reviews and comments on all projects which might impinge on existing
or reestablished Houston toad populations. Introduced colonies will
Management Practices - 2 (DRAFT) - Management Practices
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
be considered self-sustaining if they persist without any additional
introductions for at least 10 years and if at least 100 calling males
can be located within any single week during years 8, 9, or 10. In
addition, the habitats of both existing and introduced populations
have to be free of threats associated with physical, chemical, or
biological modifications that might make the habitat unsuitable for
the Houston toad. If, in the opinion of the recovery team, after
consultation with herpetological systematists, B. houstonensis is
synonymous with any other toad taxon, it should be reclassified to
threatened status.
Management Practices - 3 (DRAFT) - References
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 U.S. Fish and Wildlife Service. 1984. Houston Toad Recovery Plan.
U.S. Fish & Wildl. Serv., Albuquerque, NM 72 pp.
02 Sanders, O. 1953. A new species of toad, with discussion of
morphology of the Bufonid skull. Herpetologica 9:25-47.
03 Brown, L.E. 1973. Bufo houstonensis. Cat. Amer. Amphib. Rept.
133.1-133.2.
04 Gosner, K.L. 1960. A simplified table for staging Anuran embryos
and larvae with notes on identification. Herpetologica 16:183-190.
05 Brown, L.E. 1971. Natural hybridization and trends toward
extinction in some relict texas toad populations. Southwest Nat.
16:185-199.
06 Hillis, D.M., A.M. Hillis, and R.F. Martin. In Press.
Reproductive ecology and hybridization of the endangered Houston
toad (Bufo houstonensis).
07 Wottring, J. Undated Pers. Comm., Cited in (01).
08 Blair, W.F. 1965. Amphibian speciation. pp. 543-556. In:
H.E. Wright and D.G. Frey (eds.). The Quaternary of the United
States. Princeton Univ. Press, Princeton, NJ.
09 Brown, L.E. 1967. The significance of natural hybridization in
certain aspects of the speciation of some North American toads
(Genus Bufo). Ph.D. Dissertation, Univ. Texas, Austin. X + 126 pp.
10 Lundelius, E.L.,Jr. 1967. Late-Pleistocene and Holocene faunal
history of central Texas. pp. 287-319. In: P.S. Martin and H.E.
Wright, Jr. (eds.), Pleistocene extinctions--The search for a
cause. Yale Univ. Press, New Haven, CT.
11 Bragg, A.N. 1960. Feeding in the Houston toad. Southwest Nat.
5:106.
12 Thomas, R.A. 1977. The endangered Houston toad (Bufo
houstonensis). Final Rept. to: USFWS, Contract No. 14-16-0002-3557,
11 pp.
13 Kennedy, J.P. 1962. Spawning season and experimental
hybridization of the Houston toad, Bufo houstonensis.
Herpetologica 17:239-245.
14 Jacobson, N.L. 1983. Reproductive behavior and male mating
success in the Houston toad (Bufo houstonensis). Draft of M.S.
Thesis, Univ. Texas, Austin. 54 pp. Files of USFWS, Albuquerque,
NM.
15 Quinn, H. 1980. Final report of captive propagation/release of
the Houston toad, Bufo houstonensis. Houston Zoological Gardens,
Typescript, 14 pp. Files of USFWS, Albuquerque, NM.
16 Quinn, H. in Press. Reproduction and growth in Bufo houstonensis.
Southwest Nat.
17 Dixon, J.R. Undated Pers. Comm. in (01).
18 Brown, L.E. 1975. The status of the near-extinct Houston toad
(Bufo houstonensis) with recommendations for its conservation.
Herpetol. Rev. 6:37-40.
19 Thomas, R.A. and F.E. Potter, Jr. 1975. Species status account
-- Bufo houstonensis Sanders, 1953. In: Potter, F.E.,Jr., Special
report, Houston toad study., Texas Parks and Wildlife Dept. 15 pp.
References - 1 (DRAFT) - References
Species TOAD, HOUSTON
Species Id ESIS202001
Date 14 MAR 96
20 Hillis, D.M. and R.F. Martin. Undated Pers. Comm. in (01).
21 Quinn, H. 1983. Preliminary report of the Houston toad release
program from 1 January to 1 June 1983. 3 pp. Files of USFWS,
Albuquerque, NM.
22 Voris, H.K. and J.P. Bacon, Jr. 1966. Differential predation on
tadpoles. Copeia 1966:594-598.
23 Blair, A.P. 1957. Amphibians. Pp. 211-271. In: Vertebrates of
the United States, 1st ed. by W.F. Blair, A.P. Blair, P. Brodkorb,
F.R. Cagle, and G.A. Moore. McGraw-Hill, NY. 819 pp.
24 Harwood, P.D. 1932. The helminth parasite in the Amphibia and
Reptilia of Texas and vicinity. Proc. U.S. Nat. Mus. No. 2940,
81(17):22-25.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 U.S. Fish and Wildlife Service. 1984. Houston Toad Recovery Plan.
U.S. Fish and Wildl. Serv., Albuquerque, NM 72 pp.
02 McClure, W.L. 1976. Pers. Comm. rept. in (01).
03 Dixon, J.R. 1983. Survey of the Houston toad at the Caldwell,
Texas site. Final Rept. to: USFWS, Albuquerque, NM. 3 pp.
04 Sanders, O. 1953. A New species of toad, with a discussion of
morphology of the Bufonid skull. Herpetologica 9:25-47.
05 Blair, W.F. 1956. Call difference as an isolation mechanism in
southwestern toads (Genus Bufo). Tex. J. Sci. 8:87-106.
06 Brown, L.E. 1971. Natural hybridization and trend toward
extinction in some relict Texas toad populations. Southwest Nat.
16:185-199.
07 Guttman, S.I. 1969. Blood protein variation in the Bufo
americanus species of toads. Copeia 1969:243-249.
08 Quinn, H. 1983. Preliminary report of the Houston toad release
program from 1 January to 1 June 1983. 3 pp. Files of USFWS,
Albuquerque, NM.
References - 2