CRS Report for Congress
Endangered Species List Revisions:
A Summary of Delisting and Downlisting
January 5, 1998
Robert J. Noecker
Analyst in Natural Resources Policy
Environment and Natural Resources Policy Division

Congressional Research Service ˜ The Library of Congress

Endangered Species List Revisions:
A Summary of Delisting and Downlisting1
The question of whether the Endangered Species Act (ESA) “works” is an
important part of the debate before Congress concerning both its annual
appropriations and reauthorization of the Act itself. Information on the species that
have been delisted or downlisted from the Lists of Endangered and Threatened
Wildlife and Plants is often cited when judging the ESA’s success or failure. This
report outlines the process and reasons for delisting or downlisting, and summarizes
the 27 species delisted due to extinction, recovery, or data revision, and the 22 species
that have been downlisted from endangered to threatened status due to stabilized or
improving populations.

For additional information, contact M. Lynne Corn, Specialist in Natural Resources,1
Environment and Natural Resources Policy Division.

Introduction ................................................ 1
Choosing Criteria to Evaluate the ESA...........................1
Creation of Endangered Species Lists............................2
Process for Delisting or Downlisting a Species......................3
Extinct Species.............................................4
Tecopa pupfish..........................................4
Longjaw cisco..........................................4
Blue pike..............................................5
Santa Barbara song sparrow................................5
Sampson’s pearly mussel..................................5
Amistad gambusia.......................................5
Dusky seaside sparrow....................................5
Recovered Species...........................................6
Brown pelican..........................................6
Palau fantail flycatcher, Palau ground-dove, and Palau owl.........6
American alligator.......................................7
Rydberg milk-vetch......................................7
Gray whale.............................................7
Arctic peregrine falcon....................................8
Red kangaroo, western gray kangaroo, eastern gray kangaroo......8
Original Data for Classification in Error...........................9
Mexican duck...........................................9
Pine Barrens treefrog.....................................9
Indian flap-shelled turtle...................................9
Bahama swallowtail butterfly..............................10
Purple-spined hedgehog cactus.............................10
Tumamoc globeberry....................................10
Spineless hedgehog cactus................................11
McKittrick pennyroyal...................................11
Cuneate bidens.........................................11
Downlisted Species.........................................11
Lahontan cutthroat trout, Paiute cutthroat trout, Arizona trout.....11
American alligator......................................12
Gray wolf.............................................12
Greenback cutthroat trout................................12
Red lechwe...........................................12
Leopard .............................................. 13
Arctic peregrine falcon...................................13
Utah prairie dog........................................13
Snail darter...........................................13
Tinian monarch........................................14
Aleutian Canada goose...................................14
Nile crocodile..........................................14
Louisiana pearlshell.....................................15
Siler pincushion cactus...................................15
Small whorled pogonia...................................15
Virginia round-leaf birch.................................15
Bald eagle............................................16

Maguire daisy.........................................17
Australian saltwater crocodile.............................17
Appendix: Regulations for Amending Lists of Endangered and Threatened
Wildlife and Plants......................................18

Endangered Species List Revisions:
A Summary of Delisting and Downlisting
Central to the debate before Congress over appropriations for or reauthorization
of the Endangered Species Act (ESA) is the question of whether the Act actually
works. Different standards have been used to judge the ESA a failure and a success.
Opponents of the Act contend that the ESA has failed while costing taxpayers billions
of dollars, citing the low number of “recovered” species removed from the list.
Proponents assert that the ESA has succeeded in preserving endangered and
threatened species and their habitats, citing the significant number of listed species
with stable or increasing populations, or the low number of extinctions of listed
Further controversy arises from uncertainty over the definitions of the terms
“recovered” and “extinct.” Should species that may have been already extinct when
listed under the ESA be used to judge the Act’s effectiveness? If a species has
declined to a point that its very existence is in question, should a later determination
that it is in fact extinct be attributed as a failure of the Act? Should species removed
from the list because of the discovery of additional populations be classified as
“recovered?” Should species downlisted from endangered to threatened due to stable
or increasing populations count as “recovered?” Understanding the process and
reasons for removing particular species from the endangered species list, or for
reclassifying them from endangered to threatened, will help to answer these questions
and to inform the debate.
Choosing Criteria to Evaluate the ESA
To determine whether the ESA has been effective, one must first choose a
standard of measure. The primary goal of the ESA is the recovery of species to levels
where protection under the Act is no longer necessary. If this is the standard of
measure, the Act could be considered a failure. As of July 31, 1997, only 11 species
have been delisted due to recovery. Of the remaining species that have been removed
from the endangered and threatened lists, seven have gone extinct, and nine species
have been delisted due to new or improved data.
Some scientific studies have shown that most species are listed only after they
are very depleted (e.g., median population of 999 animals for listed vertebrates, 10752

invertebrates, and 119.5 plants), and recovery, in the short term, may be unrealistic.
Wilcove, David S., Margaret McMillan, and Keith C. Winston. What Exactly is an2

Therefore, another standard of measure might be the number of species whose
populations have stabilized or increased, even if the species is not actually delisted.
Using this standard, the Act could be considered a moderate success, since a large
number of the 1,676 listed species (41% according to one study) have improved or
stabilized. Twenty-two species originally listed as endangered have been downlisted
to threatened status, with two of these eventually being delisted altogether.
Another standard of measure for the ESA could be the number of species that
have not gone extinct. While extinction can be considered a normal evolutionary
process, widely diverse methods suggest that current rates of extinction exceed
baseline rates by 100 - 10,000 times. With only 7 of the 1,676 listed species having
gone extinct, (although 5 of these were later determined to have been extinct at the
time of listing), this standard could be used to classify the ESA as a success. Species
like the California condor and the red wolf might not exist today without ESA
protection. On the other hand, less charismatic species at risk may have gone extinct
without notice.
In sum, these three different standards would count the ESA as a failure, a
modest success, or a success. Any participant in the ESA debate could therefore find
support for his or her interests by choosing an appropriate standard of measure.
Creation of Endangered Species Lists
Congress first authorized the creation of a federal list of endangered species in
the Endangered Species Preservation Act (ESPA) of 1966. As part of early efforts
to halt or reverse the decline of wildlife species, this Act, in part, directed the
Secretary of the Interior to publish the names of all species found to be “threatened
with extinction” in the Federal Register (FR). The focus of this legislation was the
protection of habitat, primarily through federal acquisition. It did not restrict taking
or trade in interstate commerce of listed wildlife species.3
The Endangered Species Conservation Act (ESCA) of 1969 provided additional
protections for declining species. A major innovation was the authorization to create
a list of wildlife “threatened with worldwide extinction,” and to strictly limit the
importation of these species into the United States. The ESCA also directed the4
Secretary of the Interior and the Secretary of State to seek “a binding international
convention on the conservation of endangered species.”
The Convention on International Trade in Endangered Species of Wild Fauna
and Flora (CITES), the result of that congressional call, was signed by 21 nations in

1973 and took effect in 1975. One of its major contributions to endangered species

Endangered Species? Analysis of the U.S. Endangered Species List: 1985-1991.
Conservation Biology 7(1): 87-93. 1993.
Bean, Michael J. The Evolution of National Wildlife Law. New York, NY: Praeger3
Publishers, 1983. p. 319-321.
Ibid., p. 321.4

protection was the recognition of different levels of endangerment. CITES listed5
species on one of three appendices: Appendix I listing the species most vulnerable to
extinction; Appendix II listing species less vulnerable, or those species whose trade
must be controlled to prevent endangerment; and Appendix III containing species that
could be listed unilaterally by countries wishing to prevent over-exploitation of
populations within their own boundaries. This agreement was significant both in6
substantively regulating international trade, and in providing a framework for
domestic legislation.
Congress passed the Endangered Species Act in 1973, replacing both the ESPA
and the ESCA. In addition to further restrictions on “taking” and interstate7
commerce, the ESA authorized the listing of “endangered” and “threatened” wildlife89
and plants. Those species previously listed under the ESPA and the ESCA were
directly incorporated into the Lists of Endangered and Threatened Wildlife and Plants
under the ESA, found at 50 CFR §17.11(h) and §17.12(h).
Process for Delisting or Downlisting a Species
The processes for delisting or downlisting a species from the Lists of Endangered
and Threatened Wildlife and Plants are the same as the processes for listing (see
Appendix). The Secretary of the Interior may initiate a change in the status of listed
species. Alternatively, after receiving a substantive petition for any change in listing
status, the Secretary shall conduct a review of the species’ status. The determination
to delist, downlist, or uplist a species must be made “solely on the basis of the best
scientific and commercial data available” (ESA, §4(b)(1)(A), “without reference to
possible economic or other impacts.” (50 CFR §424.11(b)) Fish and Wildlife Service
(FWS) regulations also state that, at least once every five years, the Director shall
conduct a review of each listed species to determine whether it should be removed
from the list (delisted), changed from endangered to threatened (downlisted), or
changed from threatened to endangered (uplisted) (50 CFR §424.21).
A species may be removed from the list only if the data substantiate that it is no
longer threatened or endangered for one or more of the following reasons.

Ibid., p. 325.5
While the ESA is the domestic legislation implementing many of the provisions of CITES,6
there is no necessary connection between species’ listing on the Appendices of CITES and
listing under the ESA.
Section 3(18) of the ESA defines the term “take” to mean “harass, harm, pursue, hunt, shoot,7
wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct.”
Section 3(6) of the ESA defines the term “endangered species” to mean “any species which8
is in danger of extinction throughout all or a significant portion of its range other than a
species of the Class Insecta determined by the Secretary to constitute a pest whose protection
under the provisions of this Act would present an overwhelming and overriding risk to man.”
Section 3(19) of the ESA defines the term “threatened species” to mean “any species which9
is likely to become an endangered species within the foreseeable future throughout all or a
significant portion of its range.”

•First, the Secretary may declare a species to be extinct if, after a sufficient
period of time, no individuals of a listed species can be found throughout its
historical range, or all individuals of captive populations have died.
•Second, the Secretary may determine that a species is recovered if the best
available scientific and commercial data indicate that it is no longer threatened
or endangered, and no longer requires the protections of the ESA.
•Third, the original data, or the interpretation of such data, used to list a species
as endangered or threatened may have been in error. This reason could include
discovery of previously unknown populations or habitat, or taxonomic revision
of the listed species.
After a species has been removed from the endangered or threatened list due to
recovery or an error in the original data, the FWS will continue to monitor its status
to insure that proper action has been taken. Emergency re-listing may occur if these
monitoring efforts show that the species is again endangered or likely to become
endangered (50 CFR §424.20).
Extinct Species
Of the 1,676 species on the Lists of Endangered and Threatened Wildlife and
Plants (as of November 30, 1997), seven have been delisted due to extinction. Four
of these species -- the Tecopa pupfish, longjaw cisco, blue pike, and Santa Barbara
song sparrow -- were protected under laws pre-dating the ESA, and therefore were
automatically listed under the ESA when it passed in 1973. They were apparently
already extinct by 1973, however.
Tecopa pupfish. The Tecopa pupfish (Cyprinodon nevadensis) was first
described in 1948 from the outflow streams of the north and south Tecopa Hot
Springs, north of Tecopa, California. In 1970, the declining Tecopa pupfish
population was listed on both the federal and California endangered species lists due
to habitat alteration and introductions of exotic species, primarily bluegill sunfish and
mosquito fish. By 1972, the species no longer occurred where the species was first
found. Surveys done in 1977 failed to locate any other populations. In 1982, the
FWS determined the Tecopa pupfish was extinct and removed it from the endangered
species list (47 FR 2317).
Longjaw cisco. The longjaw cisco (Coregonus alpenae) was one of several
species of deepwater whitefish that was an important part of the smoked fish industry
in the Great Lakes. It was known to occur in Lakes Michigan, Huron, and Erie.
Extensive over-fishing and increased lake pollution led to a population crash in the
first half of the 20 Century. The cisco was further decimated by sea lampreyth
predation and habitat degradation, and has not been seen in Lakes Huron and Erie
since the 1950's. The last collection in Lake Michigan was in 1967, at which time the
species was listed as endangered under the ESPA. In 1983, the FWS declared the
longjaw cisco extinct and took it off the endangered species list (48 FR 39942).

Blue pike. The blue pike (Stizostedion vitreum glaucum) was abundant in the
commercial fishery of the Great Lakes. It was historically found in Lakes Erie and
Ontario, and in the Niagara River. In 1915, population levels began a cycle of
extreme fluctuation caused by over-fishing, leading to the eventual collapse in 1958.
The FWS listed the pike as endangered under the ESCA in 1970, suggesting that
introgressive hybridization with walleye may have caused the final disappearance of
the stock. A survey by the Blue Pike Recovery Team in 1977 found no individuals.
In 1983, the FWS declared the blue pike extinct and removed it from the endangered
species list (48 FR 39942).
Santa Barbara song sparrow. The Santa Barbara song sparrow (Melospiza
melodia graminea) is a subspecies of the song sparrow that was known to exist only
on Santa Barbara Island, Los Angeles County, California. No Santa Barbara song
sparrows have been seen since a fire in 1959 destroyed most of the 640-acre island’s
habitat. In 1983, the FWS determined that M. m. graminea was extinct and removed
it from the endangered species list (48 FR 46336).
Sampson’s pearly mussel. Sampson’s pearly mussel (Epioblasma (=Dysnomia)
sampsoni) is a freshwater bivalve mollusk that was historically found in parts of the
Wabash River in Illinois and Indiana, and parts of the Ohio River near Cincinnati.
Dam construction and siltation eliminated much of the gravel and sandbar habitat
where the species was found. The FWS listed this mussel as endangered under the
ESA in 1976 (41 FR 24064). A status review initiated in 1981 determined that “no
specimens had been collected in over 50 years, despite repeated sampling within its
range.” In 1984, the FWS concluded that Sampson’s pearly mussel was extinct and
removed it from the endangered species list (49 FR 1057).
Amistad gambusia. The Amistad gambusia (Gambusia amistadensis) was a
small fish known only to occur in Goodenough Spring, Val Verde County, Texas, a
tributary of the Rio Grande River. This species was eliminated in the wild when
construction of the Amistad Reservoir in 1968 submerged Goodenough Spring under
approximately 70 feet of water. The FWS listed the Amistad gambusia as endangered
in 1980, at which time it occurred only in captivity (45 FR 28721). The two captive
populations, held by the University of Texas and the Dexter National Fish Hatchery
in New Mexico, died or were eliminated through hybridization and predation. The
FWS ruled the Amistad gambusia extinct in 1987, and removed it from the
endangered species list (52 FR 46083).
Dusky seaside sparrow. The dusky seaside sparrow subspecies (Ammodramus
maritimus nigrescens) was a small songbird that existed only on Merritt Island and
the upper St. Johns River marshes of Brevard County, Florida. Populations of the
sparrow declined as its salt marsh habitat was converted to freshwater mosquito-
control impoundments, or drained. The use of DDT to control mosquitos was also
suspected as a contributing factor in the species’ decline.
Dusky seaside sparrows were first listed as endangered in 1967 under the ESPA
(32 FR 4001). The last remaining wild birds, all males, were taken into captivity in
1979 and 1980 to begin a captive breeding program. The males were mated with
females of a closely related subspecies (Scott’s seaside sparrow, A. m. peninsulae) to
try to preserve their genetic information. The hybrid offspring were not protected

under the ESA and the breeding program proved unsuccessful. The last male sparrow
died on June 16, 1987, and the hybrid offspring died by the summer of 1989. In 1990,
the FWS declared the dusky seaside sparrow extinct and took it off the endangered
species list (55 FR 51112).
Recovered Species
The goal of the ESA is the recovery of a listed species to population levels where
protection under the Act is no longer necessary. A species may be classified as
recovered if its decline has been halted or reversed, and threats minimized, so that its
survival in the wild is likely. According to FWS, there are currently 11 species that
have been delisted due to recovery. (See note on Rydberg milk-vetch.)
Brown pelican. The brown pelican (Pelecanus occidentalis) is a large coastal
bird with a wingspan of nearly seven feet; it feeds almost exclusively on fishes
captured by plunge diving. In the early 1960's, pelican populations suffered dramatic
reductions as a result of organochlorine pesticide pollution. The pesticide endrin was
thought to kill many pelicans through direct toxic effects, while the pesticide DDT led
to eggshell thinning and reproductive failure. The brown pelican was listed under the
ESCA as an endangered species throughout its U.S. and foreign ranges in 1970 (35
FR 16047 and 35 FR 8495). In 1973, the Environmental Protection Agency (EPA)
banned the use of DDT in the United States (37 FR 13369) and began to sharply
curtail the use of endrin. Since that time, pelican populations in the eastern Gulf and
Atlantic coastal regions have reached or exceeded their historical breeding levels.
In 1985, the FWS removed the brown pelican from the endangered species list
in Alabama, Florida, Georgia, South Carolina, North Carolina, and points northward
along the Atlantic coast (50 FR 4938). The brown pelican remains endangered
throughout the remainder of its range, which includes Mississippi, Louisiana, Texas,
California, Mexico, Central and South America, and the West Indies.
Palau fantail flycatcher, Palau ground-dove, and Palau owl. The Palau
Islands are located east of the Philippines in the South Pacific. They were formerly
a U.S.-administered United Nations Trust Territory, and since 1994, have had an
independent constitutional government. World War II fighting caused heavy damage
to many of the islands, and as a result many populations of native species dramatically
declined. The Palau fantail flycatcher (Rhipidura lepida), Palau ground-dove
(Gallicolumba canifrons), and Palau owl (Pyrroglaux podargina) are three native
bird species that were virtually eliminated during the war. These species were listed
as endangered under the ESCA in 1970 (35 FR 8495) based on data from military
surveys done shortly after the U.S. invasion of Angaur and Peleliu in 1944.
Since the end of World War II, the fantail flycatcher, ground-dove, and owl have
returned to near original abundances and are not faced with any foreseeable threats.
None of the species are sought as a game species, and the new constitution of Palau
bans the personal possession of firearms, making it illegal to hunt with any type of
gun. Based on this evidence, the FWS removed the Palau fantail flycatcher, the Palau
ground-dove, and the Palau owl from the endangered species list in 1985 (50 FR


American alligator. The American alligator (Alligator mississippiensis) is a
large aquatic reptile that inhabits wetland areas of the southeast Atlantic and Gulf
states. It is one of only two species (Chinese alligator and American alligator) of the
genus Alligator. Overharvesting due to commercial demand for alligator products led
to significant population declines during the 1950's and 1960's. In 1967, the FWS
listed the alligator as an endangered species under the ESPA. The Lacey Act
Amendments of 1969 prohibited interstate commerce in illegally taken reptiles and
their parts and products. The heavy penalties added under the ESA of 1973, and the
listing in Appendix II of the Convention on International Trade in Endangered Species
of Wild Fauna and Flora (CITES) provided further protection against illegal taking.
Populations have recovered and are now stable but disjunct, and limited to areas of
remaining suitable habitat within their former range.
In 1977, the FWS downlisted the alligator from endangered to threatened in part
of its range, including Florida and certain coastal areas of Georgia, South Carolina,
Louisiana, and Texas (42 FR 2071). In 1987, the FWS downlisted the American
alligator throughout the remainder of its range to “threatened due to similarity of
appearance” (52 FR 21059). This classification reflects a complete recovery of the
alligator, but is intended to facilitate necessary protections for the American crocodile
(Crocodylus acutus) in the United States and foreign countries, and other endangered
crocodilians in foreign countries, whose products are difficult to distinguish from
those of the American alligator. Any proposed harvests under this classification must
comply with the FWS’s special rule on American alligators (50 CFR §17.42(a)) and
existing state statutes and regulations.
Rydberg milk-vetch. The Rydberg milk-vetch (Astragalus perianus) is a small,
flowering plant that occurs in the mountain and plateau region of south central Utah.
The FWS listed the milk-vetch as threatened in 1978 based on data showing that the
plant was known to occur only in two locations: Bullion Canyon, Piute County,
Utah, and Mt. Dutton, Garfield County, Utah (43 FR 17914). Beginning in 1983, the
U.S. Forest Service conducted extensive surveys as part of a management plan
developed for the Rydberg milk-vetch. The surveys resulted in the discovery of 11
additional populations with estimates of over 300,000 plants. Based on this new
information, the FWS delisted the Rydberg milk-vetch in September 1989 (54 FR


The FWS has categorized this delisting as a “recovery” in its published list of
species removed from the endangered and threatened lists. It should be noted,
however, that the information published in the final rule delisting the Rydberg milk-
vetch could also be interpreted as an error in the original data.
Gray whale. Gray whales (Eschrichtius robustus) are large marine mammals
that can reach lengths of 50 feet. They are bottom feeders whose main diet consists
of small crustaceans called amphipods. The eastern North Pacific (California)
population spends the summer feeding in the Bering, Chukchi, and Beaufort Seas.
After migrating along the western shore of North America, gray whales spend the
winter off of the coast of Baja California, where the young are born in shallow

Commercial whaling significantly reduced gray whale populations, with estimates
of 4,000 - 5,000 whales remaining by the mid 1800's. In 1947, the International
Convention on the Regulation of Whaling banned the commercial harvesting of gray
whales, although subsistence harvesting by aboriginal groups was allowed to continue.
Since the ban, the eastern population has recovered to nearly the estimated original
level, and is now neither in danger of extinction, nor “likely to become endangered
within the foreseeable future throughout all or a significant portion of its range.” The
FWS concurred with the National Marine Fisheries Service’s determination, and
delisted the eastern North Pacific (California) population of the gray whale in 1994
(59 FR 31094). The western North Pacific (Korea) population remains listed as
endangered. Gray whales continue to receive protection under the Marine Mammal
Protection Act of 1972 (16 U.S.C. §1361).
Arctic peregrine falcon. The peregrine falcon is a medium-sized brown or
blue-gray raptor that preys primarily on birds. Three subspecies of peregrines occur
in North America — arctic peregrine falcon (Falco peregrinus tundrius); American
peregrine falcon (F. p. anatum); and Peale’s peregrine falcon (F. p. pealei). Arctic
peregrines nest in the tundra regions of Alaska, Canada, and Greenland. They are
highly migratory, wintering mostly in Latin America.
Arctic peregrine falcon populations declined in the 1950's and 1960's as a result
of contamination with organochlorine pesticides such as DDT. These pesticides can
accumulate to lethal levels in the fatty tissues of animals eating contaminated prey.
At lower concentrations the principal metabolite of DDT can disrupt eggshell
formation, causing eggs break easily.
Arctic peregrines were protected in 1970 under the ESCA, and subsequently
covered in 1973 under the ESA. Populations began to recover when Canada
restricted the use of DDT in 1970, followed by an EPA ban on DDT in the United
States in 1973 (37 FR 13369). The United States restricted the use of other
organochlorine pesticides, including aldrin and dieldrin, in 1974. The FWS
downlisted the arctic peregrine falcon from endangered to threatened in March 1984
(49 FR 10520), and removed it from the list of threatened species in October 1994
(59 FR 50796). Arctic peregrines are still protected under the similarity of
appearance provision of the ESA listing all Falco peregrinus found in the wild in the
contiguous 48 states as endangered. Arctic peregrines also continue to be protected
under the Migratory Bird Treaty Act (16 U.S.C.§703-712).
Red kangaroo, western gray kangaroo, eastern gray kangaroo. Kangaroos
are large marsupial mammals indigenous to Australia. Marsupial populations in
Australia began to decline with European settlement and the expansion of sheep
ranching. A dramatic drop in kangaroo populations resulted from the development
of a commercial market in kangaroo hides and meat. Citing evidence of excessive
commercial utilization, the FWS listed the red kangaroo (Macropus rufus), eastern
gray kangaroo (Macropus giganteus), and western gray kangaroo (Macropus
fuliginosus) as threatened species in December 1974, and banned the commercial
importation of kangaroos, their parts, and products (39 FR 44990). The FWS also
asserted that Australia’s regulatory control of hunting and trade were inadequate.

In April 1981, the FWS lifted the importation ban on the three threatened
kangaroos after accepting the management programs of four Australian states. The
FWS determining that managed “taking” would not be detrimental to the survival of
the species, and removed the red kangaroo, eastern gray kangaroo, and western gray
kangaroo from the list of threatened wildlife in 1995 (60 FR 12888). A subspecies
of eastern gray kangaroo (M. g. tasmaniensis) which occurs solely in Tasmania,
retains its endangered classification under the ESA.
Original Data for Classification in Error
Information collected after a species has been listed as endangered or threatened
may show that the data used for listing, or the interpretation of such data, were
incomplete, erroneous, or affected by later amendment of the ESA. The FWS
determined that it listed eight species based on data that were incomplete or in error.
(See note on Rydberg milk-vetch.) These delistings were the result of: (1) better
data, including foreign scientific and commercial information; (2) scientific or
taxonomic revision; and (3) discovery of previously unknown populations or habitats.
(See [http://www.fws.gov/~r9endspp/delisted.pdf] for more information.) The FWS
listed one species based on data that, as a result of subsequent amendment to the
ESA, were determined to no longer be valid criteria for listing.
Mexican duck. The Mexican duck (once classified as Anas diazi) was
historically found in Arizona, New Mexico, Texas, and throughout northern Mexico.
This species was listed as endangered in 1967 under the ESPA based on evidence of
habitat loss and declining populations due to hybridization with the common mallard
duck (A. platyrhynchos). The Mexican duck was later determined to be a subspecies
of A. platyrhynchos, and according to the FWS, “the interbreeding of two subspecies
of the same species is an expected natural phenomenon. Protection under the
definition of ‘species’ in the Act for one phenotype [an organism’s general
appearance] in a geographic segment or population of the same species is not
permissible.” (43 FR 32258) In short, the Mexican duck no longer qualified as
sufficiently distinct under the ESA’s definition of a species to warrant protection.
Moreover, the loss of natural habitat was determined to no longer be a threat, because
the species was found to be able to live in newly created agricultural areas. In 1978,
the FWS removed the Mexican duck from the endangered species list (43 FR 32258).
Pine Barrens treefrog. The Pine Barrens treefrog (Hyla andersonii) is a small
amphibian that occurs in New Jersey, the Carolinas, and Florida. In 1977, the Florida
population only was listed as endangered under the ESA based on “the present or
threatened destruction, modification, or curtailment of its habitat or range.” Surveys
at that time showed that there were only seven small breeding sites in Okaloosa
County, with less than 500 estimated individuals. Surveys started in 1978 by the
Florida Game and Fresh Water Fish Commission found more than 150 additional sites
in Okaloosa, Walton, Santa Rosa, and Holmes Counties in Florida, and six sites in
Escambia and Covington Counties, Alabama. Based on this new evidence, the FWS
delisted the Pine Barrens treefrog in 1983 (48 FR 52740).
Indian flap-shelled turtle. The Indian flap-shelled turtle (Lissemys punctata
punctata) is a softshell turtle occurring in southern and central India and Sri Lanka.
A closely related turtle, L. p. andersoni, occurs in northern India, Pakistan, Nepal,

Bangladesh, and Burma. The flap-shelled turtle was placed on Appendix I of CITES
in 1975 at the request of Bangladesh. However, L. p. punctata was the taxa listed,
not L. p. andersoni. Under a broad rule placing 159 taxa from Appendix I of CITES
on the ESA’s List of Endangered and Threatened Wildlife, the FWS listed L. p.
punctata as endangered in 1976 (41 FR 24062). Although L. p. punctata was the
subspecies listed by the FWS, its stated range included regions from which L. p.
andersoni, not L. p. punctata, is known to occur. It is unclear which subspecies --
L. p. punctata or L. p. andersoni, or both -- was meant to be included in the CITES
and ESA listings.
Subsequent reviews of the literature and available data could find no evidence
to support this endangered status. To the contrary, scientists now classify L. p.
punctata and L. p. andersoni as only one subspecies. This subspecies is the most
common aquatic turtle in India. Consequently, the FWS removed the Indian flap-
shelled turtle from the endangered species list in 1983 (48 FR 52740). This action did
not affect the turtle’s status on Appendix I of CITES.
Bahama swallowtail butterfly. The Bahama swallowtail butterfly (Heraclides
(Papilio) andraemon bonhotei) is a tropical insect whose occurrence in Florida
represents the northern limit of its distribution. This dark brown and yellow butterfly
is restricted to tropical upland hardwood habitat, now found in the United States
primarily in the Florida Keys. It was listed as threatened under the ESA in 1976 (41
FR 17736), at which time it was found only in Dade and Monroe Counties, Florida.
The Bahama swallowtail was later found to be only a sporadic resident of the United
States, and not distinct from the Bahamian population of the same subspecies.
Moreover, the 1978 Amendments to the ESA limited protection at the population
level to vertebrates (ESA, §3(15)). As a result of ESA amendment, the FWS took
the Bahama swallowtail butterfly off the endangered species list in 1984 (49 FR

34501), since it was neither a vertebrate nor a distinct population.

Purple-spined hedgehog cactus. The purple-spined hedgehog cactus
(Echinocereus engelmannii var. purpureus) was first described as a distinct
taxonomic group in 1969 from specimens collected near St. George, Utah. It was
determined to be very rare and was listed as endangered under the ESA in 1979 (44
FR 58866). Subsequent investigations found that the purple-spined hedgehog cactus
is simply a dark-colored, short-spined phase that occurs interspersed throughout
populations of E. e. chrysocentrus; the two types of plants cross-pollinate readily in
nature. Since E. e. chrysocentrus is common and widely distributed in the Mojave
Desert of Arizona, California, Nevada, and Utah, in 1989, the FWS delisted the
purple-spined hedgehog cactus (54 FR 48749).
Tumamoc globeberry. The Tumamoc globeberry (Tumamoca macdougalii)
is a perennial vine in the gourd family with small greenish-yellow flowers and bright
red fruits. It occurs from south central Arizona south through southern Sonora,
Mexico. The FWS listed the globeberry as endangered under the ESA in 1986 based
on the known presence of only 30 isolated populations in Pima County, Arizona, and
five populations in Sonora, Mexico (51 FR 15906). In 1988 and 1989, the Bureau
of Reclamation conducted surveys required by § 7 of the ESA to determine the impact
of a Central Arizona Project canal and pipeline on the globeberry. These surveys
determined that the species occurred across a more extensive range and was less

habitat-specific than previously thought. Finding few threats of extinction in its newly
identified habitat, the FWS removed the Tumamoc globeberry from the endangered
species list in 1993 (58 FR 33562).
Spineless hedgehog cactus. Botanist Karl Schuman first described the spineless
hedgehog cactus (Echinocereus triglochidiatus var. inermis) in 1896 from specimens
collected in southeast Utah and southwest Colorado. The FWS listed this subspecies
as endangered in 1979 under the ESA based on its rare occurrence (44 FR 64744).
The recovery plan for the spineless hedgehog cactus noted a question of its true
taxonomic status, and later studies determined that it is simply a spineless form of the
red-flowered hedgehog cactus (E. t. var. melanacanthus) that is widely distributed
from northern Colorado and Utah to Durango and San Luis Potosi, Mexico. Finding
that the spineless hedgehog cactus is “not a discrete and valid taxonomic entity and
does not meet the definition of a species (which includes subspecies),” the FWS
removed it from the endangered species list in 1993 (58 FR 49242).
McKittrick pennyroyal. The McKittrick pennyroyal (Hedeoma apiculatum)
is a perennial herb, four to six inches tall, with dense leaves and showy pink flowers.
The species is endemic to the Guadalupe Mountains in northwest Texas and southeast
New Mexico, where it occurs above 5,400 feet in limestone outcrops. The FWS
described this pennyroyal as having “limited distribution, low numbers, and low
reproductive potential” when it listed it as threatened under the ESA in 1982 (47 FR

30440). Subsequent surveys found this herb to be more widespread and abundant,

and less vulnerable to human disturbance than previously thought. In 1993, the FWS
took the McKittrick pennyroyal off the threatened species list (58 FR 49245).
Cuneate bidens. The cuneate bidens (Bidens cuneata) is an herb of the thistle
family with yellow flowers. It was first described in 1920 from specimens collected
on the Hawaiian island of Oahu. The plant was listed as endangered in 1984 based
on surveys indicating its rare occurrence (49 FR 6099). A recent revision of the
Hawaiian members of the Bidens genus determined that B. cuneata is an outlying
population of B. molokaiensis that is common along the windward cliffs of nearby
Molokai island. These new data indicated that cuneate bidens is “not a discrete
taxonomic entity,” resulting in the FWS delisting B. cuneata in 1996 (61 FR 4372).
Downlisted Species
Species that have stabilized or increased in number may be reclassified from
endangered to threatened status. ESA proponents assert that downlisting can be an
important part of the recovery process, and a measure of success for the ESA.
However, these species are often not counted by opponents as successes for the ESA
because they have not met the Act’s goal of complete removal from the list. Twenty-
two species have been downlisted from endangered to threatened status.
Lahontan cutthroat trout, Paiute cutthroat trout, Arizona trout. The
Lahontan cutthroat trout (Oncorhynchus (=Salmo) clarki henshawi), Paiute cutthroat
trout (O. c. seleniris), and Arizona trout (Oncorhynchus apache) are western trout
species with limited distributions. O. c. henshawi occurs in most streams of the
Truckee, Carson, and Walker River drainages in California and Nevada. O. c.
seleniris occurs in Silver King Creek and its tributaries in Alpine County, California.

O. apache occurs in the headwaters of the Salt and Little Colorado Rivers in east
central Arizona.
These species were listed as endangered under the ESCA of 1969 due to
“destruction, drastic modification, or severe curtailment of their habitat,” and
hybridization with introduced trout species, especially the brook and rainbow trout.
State and federal recovery programs successfully cultured and reintroduced
populations in areas from which they were depleted, and reduced the threat of
hybridization by eliminating exotic species. In 1975, the FWS downlisted the
Lahontan cutthroat trout, Paiute cutthroat trout, and Arizona trout from endangered
to threatened (40 FR 29863). A special rule under this downlisting action allows the
regulated taking of these species for sport fishing purposes.
American alligator. See section under “Recovered Species.”
Gray wolf. The gray wolf (Canis lupus) was historically found over most of
North America, from central Mexico to the Arctic Ocean. Systematic eradication
programs, habitat destruction, and over-hunting of prey populations eliminated wolves
from most of the contiguous United States by the 1940's. In 1967, the timber wolf
subspecies Canis lupus lycaon, was listed as endangered under the ESPA of 1966 (32
FR 4001). In 1973, the FWS listed the northern Rocky Mountain subspecies, C. l.
irremotus, and the Texas subspecies, C. l. monstrabilis, as endangered under the
ESA (38 FR 14678). In 1978, the Secretary clarified the legal and taxonomic
confusion that arose from these listings by downlisting the Minnesota population of
wolves from endangered to threatened, while all other North American gray wolf
populations south of Canada remained listed as endangered, without reference to
subspecies (43 FR 9607).10
Greenback cutthroat trout. The greenback cutthroat trout (Oncorhynchus
(=Salmo) clarki stomias) is a fish endemic to the headwaters of the South Platte and
Arkansas Rivers in Colorado. Habitat destruction caused by mining, logging, grazing
and irrigation projects, in addition to hybridization with introduced trout, drastically
reduced populations of the greenback cutthroat. By 1930, this species was believed
to be extinct. Later rediscovery allowed state and federal conservation programs to
culture and reintroduce populations in its historical range. These programs also
eliminated many of the exotic species responsible for hybridization problems. In
1978, the FWS downlisted the greenback cutthroat trout from endangered to
threatened (43 FR 16343), recognizing that threats from habitat destruction and
hybridization remain. A special rule under this downlisting action allows for the
regulated taking of this species for sport fishing purposes.
Red lechwe. The red lechwe (Kobus leche) is a species of African antelope
whose historical range included parts of Namibia, Botswana, Angola, Zaire, and
Zambia. Unregulated commercial and subsistence hunting, combined with habitat
destruction, led to population declines through the first half of the 20 Century. Theth
FWS listed the red lechwe as endangered under the ESCA in 1970 (35 FR 8495).
Control of hunting and listing on Appendix I of CITES resulted in stable or increasing

For more information, see CRS Report 97-747ENR, Reintroduction of Wolves.10

populations over much of their range. In 1979, the Conference of the parties to
CITES changed the listing of the red lechwe from Appendix I to Appendix II, and in
1980, the FWS downlisted the red lechwe from endangered to threatened (45 FR
65132). With the Appendix II listing, § 9(c)(2) of the ESA allows “the importation
of legally taken sport-hunted trophies.”
Leopard. The leopard (Panthera pardus) is widely distributed across Africa,
China, Japan, Korea, India, Sri Lanka, and Southeast Asia. An uncontrolled
commercial fur trade (e.g., the United States imported more than 17,000 leopard
hides from 1968 to 1969) sharply depleted leopard populations. In 1970, the FWS
listed the leopard as endangered under the ESCA (35 FR 8495), prohibiting the
import of live animals, their parts and products. P. pardus was also added to
Appendix I of CITES, providing for further control of commercial trade in hides.
Subsequent surveys determined that leopard populations in some areas were
recovering, and in 1982, the FWS downlisted the southern Africa leopard populations
from endangered to threatened (47 FR 4204). A special rule allows the import of
“legally taken sport-hunted leopard trophies.” Other populations of leopard remain
listed as endangered under the ESA.
Arctic peregrine falcon. See section under “Recovered Species.”
Utah prairie dog. The Utah prairie dog (Cynomys parvidens) is a burrowing
rodent of the squirrel family that occurs only in southern Utah. Early ranchers
believed that the prairie dog competed directly with livestock for food. The ranchers
actively sought to eliminate them through habitat alteration and poisoning. In 1973,
the FWS listed the Utah prairie dog as endangered under the ESA (38 FR 14678),
pursuant to the ESCA of 1969. The protections provided by the ESA allowed
populations to increase, and in 1984, the FWS downlisted the Utah prairie dog from
endangered to threatened (49 FR 22330). To mitigate conflict between ranchers and
expanding prairie dog populations, a special rule was included in the downlisting that
allows the “taking” of up to 5,000 prairie dogs per year.
Snail darter. The snail darter (Percina tanasi) is a small fish, typically less than

3.5 inches, that occurs in sandbar habitat in six tributaries of the Tennessee River.

The FWS listed the snail darter as endangered under the ESA in 1975 (40 FR 47506),
at which time it was known from only one population at the mouth of the Little
Tennessee River. In 1979, federal law exempted the Little Tennessee River Tellico
Reservoir Project from the ESA, allowing a dam to be completed that inundated the
known population. Before and after dam completion, the FWS introduced the snail
darter into other streams in the area with only limited success. Subsequent surveys,
however, found populations in six Tennessee River tributaries in Tennessee and
Alabama. These discoveries allowed the FWS to downlist the snail darter from
endangered to threatened in 1984 (49 FR 27501). This historic conflict between an
endangered species and development played a major role in the evolution of the
ESA. 11

For more information about the history of this species, which was the centerpiece of11
arguably the most famous legal battle in the history of the ESA, see CRS Report 90-242ENR,

Tinian monarch. The Tinian monarch (Monarcha takatsukasae) is a small
brownish song bird that is endemic to the island of Tinian, north of Guam in the
Mariana Archipelago. Deforestation, first for sugarcane production, and later as a
result of World War II combat activities, caused a severe depletion of the monarch
population. The FWS listed the Tinian monarch as endangered in 1970 under the
ESCA (35 FR 8495) based on pre- and post-war data. The island has since become
revegitated with a shrubby legume (Leucaena leucocephala) in which the monarch
has thrived. In 1987, the FWS downlisted the Tinian monarch from endangered to
threatened (52 FR 10890). The Service noted three threats preventing the complete
delisting of the species: 1) potential defoliation of Leucaena by introduced plant lice;

2) potential introduction of the predatory brown tree snake (Boiga irregularis); and12

3) the species’ existence is limited to one small island.

Aleutian Canada goose. The Aleutian Canada goose (Branta canadensis
leucopareia), one of the smallest of 11 subspecies of Canada geese, nests on remote
islands off the coast of the Alaska Peninsula and in the Aleutian Archipelago. Most
Aleutian geese migrate along the Pacific coast flyway of North America and winter
in Oregon and California. Some geese migrate along the western coast of the Pacific
and winter in Asia and Japan. Populations of Aleutian geese declined due to arctic
fox (Alopex lagopus) introductions on their breeding islands, and recreational and
subsistence hunting in the Pacific flyway. The FWS added B. c. leucopareia to the
list of U.S. endangered species under the ESPA in 1967 (32 FR 4001), and to the list
of foreign endangered species under the ESCA in 1970 (35 FR 8495). Fox control
programs on breeding islands and hunting closures in important wintering areas are
primarily responsible for increasing goose populations. In 1990, the FWS downlisted
all populations of the Aleutian Canada goose from endangered to threatened (55 FR

51106), noting that the species still faces threats from disease, predation, and,

especially on the wintering grounds, storms and habitat loss.
Nile crocodile. The Nile crocodile (Crocodylus niloticus) is a large aquatic
reptile that was historically found throughout Africa and as far north as Syria. Habitat
destruction, unregulated commercial trade in hides, and hunting to eliminate threats
to humans, livestock, and fisheries led to significant population declines. The
crocodile was first listed as endangered under the ESCA in 1970 (35 FR 8495), and
on Appendix I of CITES in 1975. As countries began to implement management
practices, especially ranching for the controlled harvest of hides, crocodile populations
stabilized or increased. Zimbabwe’s successful management led to a downlisting of
their ranched populations in 1987 (52 FR 23148), and a downlisting of their wild
populations in 1988 (53 FR 38451). In 1993, the FWS downlisted all populations of
the Nile crocodile from endangered to threatened (58 FR 49870). The species has
also been moved from Appendix I to Appendix II of CITES in Botswana, Malawi,
Mozambique, and Zambia, allowing for regulated commercial trade in crocodile hides
from these countries.

Endangered Species Act: The Listing and Exemption Process, Appendix B.
For more information, see CRS Report 97-507 ENR, Non-Indigenous Species: Government12
Response to the Brown Tree Snake and Issues for Congress.

Louisiana pearlshell. The Louisiana pearlshell (Margaritifera hembeli) is a
freshwater mussel approximately 4" long that was known to exist only in the Bayou
Boeuf drainage, Rapides Parish, Louisiana. Due to its limited distribution and threats
from destruction of river habitat, the FWS listed this species as endangered under the
ESA in 1988 (53 FR 3567). Since the listing, M. hembeli has been found in the Red
River drainage, Grant Parish, Louisiana. Subsequent surveys done under the recovery
plan expanded the known range to eight streams of the Red River drainage and 11
streams of the Bayou Boeuf drainage. While the discovery of additional populations
removes the immediate threat of extinction, threats remain from population
fragmentation by impoundments, collecting, and sedimentation from gravel mining.
For these reasons, the FWS downlisted the Louisiana pearlshell from endangered to
threatened in 1993 (58 FR 49935).
Siler pincushion cactus. The Siler pincushion cactus (Pediocactus sileri) is a
4-5" spherical or cylindrical cactus with 1" spines and yellow flowers. It is found
primarily on gypsum soils at altitudes between 2,800 and 5,400 feet in southwest Utah
and northwest Arizona. The FWS listed this species as endangered under the ESA
in 1979 (44 FR 61786) based on evidence that its small populations with limited
habitat were threatened by gypsum mining, off-road vehicle use, road construction,
collection, livestock, and development of the Warner Valley Power Plant. Under the
Siler Pincushion Cactus Recovery Plan, the FWS closed certain areas to off-road
vehicles, fenced off areas of high cactus density, and surveyed potential habitat. As
a result of these and other measures, the FWS determined that the Siler pincushion
cactus was no longer in danger of extinction, and in 1993, downlisted it from
endangered to threatened (58 FR 68476).
Small whorled pogonia. The small whorled pogonia (Isotria medeoloides) is
a perennial orchid that inhabits young and maturing stands of mixed-deciduous or
mixed-deciduous/coniferous forests. The species was widely distributed from
southern Maine and New Hampshire, through the Atlantic seaboard states, to
southern Tennessee and northern Georgia. The FWS listed I. medeoloides as
endangered under the ESA in 1982 (47 FR 39827) when they estimated less than 500
individuals remained in 17 populations. Since listing, the FWS has identified three
primary population centers: 1) the Appalachian foothills of New England; 2) the Blue
Ridge mountains where Tennessee, North and South Carolina, and Georgia share
borders; and 3) coastal plain and piedmont counties of Virginia. Management actions
at these and other sites have provided adequate protection and allowed populations
to stabilize or increase to meet recovery plan objectives. Thus, the FWS downlisted
the small whorled pogonia from endangered to threatened in 1994 (59 FR 50852).
Virginia round-leaf birch. The Virginia round-leaf birch (Betula uber) is a
species from southwestern Virginia with smooth, dark-brown or black bark that can
reach heights of 45 feet. Botanists assumed this species to be extinct when no
specimens could be found from 1950 to 1975. In 1975, 41 trees were found along
Cressy Creek, Smyth County, Virginia. Due to its limited population, the FWS listed
B. uber as endangered under the ESA in 1978 (43 FR 17910). Although this natural
population declined from vandalism and transplantation in the late 1970's, a FWS
recovery plan established additional populations through propagation management
with the help of the U.S. National Arboretum, the Virginia Agricultural Experimental
Station, and others. Populations have met recovery plan goals, and in 1994, the FWS

downlisted the Virginia round-leaf birch from endangered to threatened (59 FR


Bald eagle. The bald eagle (Haliaeetus leucocephalus) is typically associated
with estuaries, large lakes, major rivers, and seacoast habitats. Its historical range
included most of North America from central Alaska and Canada to northern Mexico.
Beginning in the mid to late 1800's, a decline in eagle populations was attributed to
a drop in waterfowl and shorebird prey populations, direct killing, and habitat
destruction. The Bald Eagle Protection Act of 1940 (16 U.S.C. 668) prohibited
direct killing in most of the eagle’s range except Alaska, where the state paid a bounty
for killing eagles to protect the salmon fishery. In 1952, the exemption allowing
Alaska’s bounty was revoked.
Following World War II, the widespread use of the organochlorine pesticide
DDT caused significant reproductive failure, leading to another sharp decline in eagle
populations. DDE, the primary breakdown product of DDT, caused eggshells to beth
thin and to break easily. The FWS listed bald eagle populations south of the 40
parallel as endangered under the ESPA in 1967 (32 FR 4001). In 1978, the FWS
listed all remaining birds in the lower 48 states as endangered under the ESA, with the
exception of populations in Michigan, Minnesota, Wisconsin, Oregon, and
Washington, where eagles were listed as threatened (43 FR 6233). The EPA banned
the use of DDT in the United States in 1973 (37 FR 13369). Bald eagle recovery
plans were developed in each of five established recovery regions. With annual
spending exceeding $1 million during the period 1985-1995, eagle populations have
increased across most of the United States. FWS data for 1995 estimate 4,712
breeding pairs in the lower 48 states, up from a low of 417 pairs in 1963. In 1995,
the FWS downlisted the bald eagle from endangered to threatened in all of the lower

48 states (60 FR 36000).

MacFarlane’s four-o’clock. MacFarlane’s four-o’clock (Mirabilis
macfarlanei) is a perennial plant with hemispherical clumps 24-47" in diameter, and
large, funnel-shaped magenta flowers. The species was described in 1936 from a
population found along Snake River, Oregon. From 1947 to the mid 1970's, M.
macfarlanei was not found and was thought to be extinct. In 1977, two populations
were located containing approximately 27 individual plants. The FWS listed the four-
o’clock as endangered under the ESA in 1979 based on this limited distribution (44
FR 61912). Extensive surveys conducted as part of the species’ 1985 recovery plan
located over 7,000 plants in three disjunct areas: the Snake River unit, Idaho County,
Idaho, and Wallowa County, Oregon; the Salmon River unit, Idaho County, Idaho;
and the Imnaha River unit, Wallowa County, Oregon. With reclassification objectives
of the recovery plan met, the FWS downlisted MacFarlane’s four-o’clock from
endangered to threatened in 1996 (61 FR 10693), but noted that continued threats
from habitat loss warrant continued protection as a threatened species.
Maguire daisy. The Maguire daisy (Erigeron maguirei) is a perennial herb with
both white and orange flowers that is endemic to sandstone canyons and mesas of San
Rafael Swell, Emery County, Utah, and Capitol Reef, Wayne County, Utah. In 1985,
the FWS listed E. m. var. maguirei as an endangered species under the ESA due to
its limited distribution (50 FR 36090). Later studies determined that populations
formerly recognized as E. m. var. maguirei and E. m. var. harrisonii “do not merit

recognition as separate varieties.” By considering these two former varieties as a
single unit of E. maguirei, the FWS found there to be more individuals than
previously believed. In 1996, the FWS downlisted the Maguire daisy from
endangered to threatened (61 FR 31054), noting that the small, reproductively
isolated populations continue to face threats from mineral development, recreation
activities, livestock trampling, and loss of genetic variability.
Australian saltwater crocodile. The saltwater crocodile (Crocodylus porosus)
is a large aquatic reptile distributed across southwest India, Southeast Asia, the
Pacific Islands, and the northern coast of Australia. Due to habitat loss, unregulated
hunting, and poaching for a commercial trade in hides, all populations of the saltwater
crocodile, except for Papua New Guinea’s (where the species was somewhat more
healthy), were moved from Appendix II to Appendix I of CITES in 1979. In the same
year, the FWS listed all populations outside Papua New Guinea as endangered under
the ESA (44 FR 75074). In 1985, Australia’s saltwater crocodiles were returned
from Appendix I to Appendix II of CITES due to their successful management of wild
and ranched populations. The Appendix II listing of CITES allows for the export of
ranch-produced hides. In 1996, the FWS downlisted the Australian population of
saltwater crocodile from endangered to threatened, with a special rule that allows the
import of ranched crocodiles and their products (61 FR 32356). The FWS has
proposed a classification of Papua New Guinea’s population of crocodile as
threatened due to similarity of appearance (59 FR 18652).

Appendix: Regulations for Amending Lists of Endangered and
Threatened Wildlife and Plants

50 CFR § 424.11 Factors for listing, delisting, or reclassifying species.

(a) Any species or taxonomic group of species (e.g., genus, subgenus) as defined
in § 424.02(k) is eligible for listing under the Act. A taxon of higher rank than species
may be listed only if all included species are individually found to be endangered or
threatened. In determining whether a particular taxon or population is a species for
the purposes of the Act, the Secretary shall rely on standard taxonomic distinctions
and the biological expertise of the Department and the scientific community
concerning the relevant taxonomic group.
(b) The Secretary shall make any determination required by paragraphs (c) and
(d) of this section solely on the basis of the best available scientific and commercial
information regarding a species’ status, without reference to possible economic or
other impacts of such determination.
(c) A species shall be listed or reclassified if the Secretary determines, on the
basis of the best scientific and commercial data available after conducting a review of
the species’ status, that the species is endangered or threatened because of any one
or a combination of the following factors:
(1) The present or threatened destruction, modification, or curtailment of its
habitat or range;
(2) Overutilization for commercial, recreational, scientific, or educational
(3) Disease or predation;
(4) The inadequacy of existing regulatory mechanisms; or
(5) Other natural or manmade factors affecting its continued existence.
(d) The factors considered in delisting a species are those in paragraph (c) of this
section as they relate to the definitions of endangered or threatened species. Such
removal must be supported by the best scientific and commercial data available to the
Secretary after conducting a review of the status of the species. A species may be
delisted only if such data substantiate that it is neither endangered nor threatened for
one or more of the following reasons:
(1) Extinction. Unless all individuals of the listed species had been previously
identified and located, and were later found to be extirpated from their previous
range, a sufficient period of time must be allowed before delisting to indicate clearly
that the species is extinct.
(2) Recovery. The principal goal of the U.S. Fish and Wildlife Service and the
National Marine Fisheries Service is to return listed species to a point at which
protection under the Act is no longer required. A species may be delisted on the basis
of recovery only if the best scientific and commercial data available indicate that it is
no longer endangered or threatened.
(3) Original data for classification in error. Subsequent investigations may
show that the best scientific and commercial data available when the species was
listed, or the interpretation of such data, were in error.

(e) The fact that a species of fish, wildlife, or plant is protected by the
Convention on International Trade in Endangered Species of Wild Fauna and Flora
(see part 23 of this title 50) or a similar international agreement on such species, or
has been identified as requiring protection from unrestricted commerce by any foreign
nation, or to be in danger of extinction or likely to become so within the foreseeable
future by any State agency or by any agency of a foreign nation that is responsible for
the conservation of fish, wildlife, or plants, may constitute evidence that the species
is endangered or threatened. The weight given such evidence will vary depending on
the international agreement in question, the criteria pursuant to which the species is
eligible for protection under such authorities, and the degree of protection afforded
the species. The Secretary shall give consideration to any species protected under
such an international agreement, or by any State or foreign nation, to determine
whether the species is endangered or threatened.
(f) The Secretary shall take into account, in making determinations under
paragraph (c) or (d) of this section, those efforts, if any, being made by any State or
foreign nation, or any political subdivision of a State or foreign nation, to protect such
species, whether by predator control, protection of habitat and food supply, or other
conservation practices, within any area under its jurisdiction, or on the high seas.