| Kanab
Ambersnail |
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Kanab Ambersnail (Oxyloma
haydeni kanabensis)
By Jeff Sorensen |
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 Current
Status:
The Kanab ambersnail (KAS) was listed as an
endangered species in 1992 by the U.S. Fish
and Wildlife Service (USFWS)1.
KAS is also a species of conservation priority
for the Arizona Game and Fish Department (AGFD)2.
This landsnail is restricted to wetlands,
springs, and seeps3. Based on morphological
identification, only two wild populations
of KAS are known to currently exist on the
Colorado Plateau in the Grand Canyon region.
In southern Utah, one population is found
at Three Lakes, a privately-owned wet meadow
near Kanab, Utah3. The other population
is found in Arizona at a large, riverside
spring called Vaseys Paradise (VP) within
Grand Canyon National Park. A third population
of KAS may have existed in Kanab Canyon, Utah,
but the exact location of the type locality
is not well documented3.
The Arizona population was discovered in 1991,
and is geographically isolated from the Utah
population (including different watersheds).
Recent surveys in southern Utah discovered
additional populations of ambersnails, but
morphological and genetic analyses indicate
they are a non-listed relatives, Oxyloma haydeni
and Oxyloma retusa4. One population
of Oxyloma haydeni occurs on the South Rim
of the Grand Canyon at Indian Gardens5,
while a second population is found at a riverside
marsh at -9 mile in the Lees Ferry reach8.
KAS populations in the American Southwest
are believed to be relictual populations from
the Late Pleistocene ice age (approximately
11,000 years ago)5, when springs,
seeps, and wetland habitat were more abundant6,7.
Historically, the Grand Canyon region may
have harbored many populations of ambersnails
in closer proximity to each other across the
landscape (and possibly lost under Lake Powell).
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Habitat:
KAS live in association with watercress (Nasturtium), monkeyflower (Mimulus),
cattails (Typha), sedges (Carex), and rushes (Juncus)5.
KAS populations in the Grand Canyon region occur in areas with water
sources originating from limestone or sandstone geologic strata5.
KAS coexist with other species of mollusks: Catinella (succineid landsnails),
Deroceras (limacid marsh slugs), Hawaiia (zonitid landsnails), Fossaria
(limnaeid springsnails), and Physa (physid freshwater snails)5,8. |
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Biology:
Wild KAS are believed to live approximately 12-15 months9. Over-winter
mortality of KAS can range between 25 and 80%5,10,11. Young
snails enter dormancy in October-November and typically become active again
in March-April. Mature KAS mate and reproduce during the summer months,
and deposit clear, gelatinous egg masses on wet plant litter, live plants,
or bedrock5.
KAS are hermaphroditic (having both male and female reproductive tracts)12,
and controlled experiments indicate they are capable of self-fertilization13.
Taxonomic identification is primarily based on morphological distinctions
of the reproductive tract12, although recent genetic analyses
are now being used to determine relatedness within and among populations.
Fully mature KAS measure up to 23-mm (nearly one inch) in shell size13.
They are brown in appearance, and are visually characterized by an elongated
first whorl. KAS are pulmonate (air-breathing) mollusks12, but
are able to survive underwater for up to 32 hours in cold, highly oxygenated
water14. Historic floods in the Colorado River basin may have
dispersed KAS downstream to new sites or other populations.
The flatworm trematode, Leucochloridium cyanocittae,
is a host-specific parasite of mature ambersnails15.
Passerine birds likely distribute the parasite
across the region5. Between 1-10%
of the VP population may be infected with
this naturally occurring parasite15.
Leucochloridium has not been observed in any
other mollusks in the Grand Canyon region15.
Some KAS investigators believe that parasitized
KAS have reduced fitness and increased susceptibility
to predation. In 1997, two parasitized KAS
were collected at VP, and were found to still
be capable of producing eggs11.
KAS mortality due to the Leucochloridium parasite
is not well documented, but assumed to be
low. |
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Threats:
Current threats to KAS include loss and/or
adverse modification of wetland habitat, which
is scarce in this semi-arid region3.
The habitat for the Utah population is at
risk due to commercial development by the
private landowner3. In Arizona,
KAS habitat at VP is threatened by high water
discharges from Glen Canyon Dam. During the
March 1996 experimental beach/habitat-building
flow (BHBF) in Grand Canyon, up to 16% of
KAS habitat at VP was lost or degraded10.
Recovery of this habitat to pre-flood conditions
required over two years11. Hundreds
of KAS were believed to have been swept downstream
and drowned in the flood-swollen Colorado
River during the 1996 BHBF10.
Historically, Grand Canyon experienced annual floods of 90,000+ cubic-feet
per second (cfs)5--in contrast, the 1996 BHBF was only 45,000
cfs. Since Glen Canyon Dam began impounding water in 1963, KAS habitat
at VP has increased by approximately 40%5. Several flows >45,000
cfs have occurred in the last 30 years in Grand Canyon, so the VP habitat
is continually experiencing cycles of disturbance and recovery11.
On a lesser scale, trampling by recreationists and flash floods from the
talus slope above VP also contribute to habitat loss and direct KAS mortality.
The presence of poison ivy at VP keeps most river runners and hikers out
of KAS habitat, while plateau-origin flash floods are rare disturbances
at VP5.
Passerine birds and deer mice are believed to be occasional predators on
KAS3,10. Hard evidence of KAS consumption and predation rates
by birds and mice are not available, but analysis of mice feces indicates
that snails are not regularly eaten by rodents16. |
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Research:
Ecological studies of VP KAS were conducted
by interagency teams between 1995 and 19975,10,11.
Contracted monitoring surveys of VP KAS continued
in 1998-9916. AGFD has continued
monitoring of the VP population to date. Since
1995, habitat at VP has been topographically
mapped each season. Replicated subsampling
(multiple 20-cm diameter plots) of distinct
vegetation patches was used to sample the
KAS population. Plot sample data was paired
with habitat area measurements to estimate
KAS densities using a statistical technique
called "bootstrapping"5.
Genetic analyses using Amplified Fragment
Length Polymorphism and mitochondrial DNA
techniques were conducted on numerous ambersnail
populations across the United States and Canada.
The results from these analyses indicate that
VP KAS are genetically distinct and should
be listed as a separate taxon4.
Experimental research in the rearing of captive
KAS at Northern Arizona University (under
static greenhouse conditions) and at Glen
Canyon Dam (in an outdoor setting) provided
a better understanding of the life history
and habitat requirements of this landsnail.
These studies were completed in 2001 and compiled
in a masters thesis by investigator, Clay
Nelson. As an objective of the KAS recovery
plan, a small refugium population of VP KAS
was transferred to an outdoor enclosure at
The Phoenix Zoo in May 199914.
Within two months, successful KAS reproduction
at the zoo refugium occurred, as evidenced
by numerous young snails14. Unfortunately,
this refugium population did not survive past
September 2000 - likely due to an insufficient
initial stock size, prolonged high air temperatures,
low humidity, and reduced vegetative cover
within the enclosure24. |
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Legal
Issues:
Current management restrictions on the operation
of Glen Canyon Dam limits the take of VP KAS
habitat from high flows at 17% of the total
occupied habitat at VP17,18. Additional
USFWS Biological Opinions in 1996 and 1997
stipulated that a second population of KAS
be discovered or established in Arizona before
another experimental BHBF occurs19,20.
However, recently this requirement was dropped18.
Since 1995, over 350 springs and seeps in
the Grand Canyon region have been investigated
by various KAS researchers, but no additional
KAS populations have been found in Arizona5,8,21.
Possibly 10 protected KAS populations in the
region are needed before this landsnail can
be considered for down-listing to threatened
status3. Unfortunately, captive
populations do not contribute to the number
needed for down-listing3. |
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Recovery Efforts:
To further KAS recovery objectives and Biological
Opinion concerns, AGFD and the National Park
Service attempted to establish a new wild
population of KAS in Grand Canyon National
Park from VP stock15. Following
numerous habitat surveys, site evaluations,
and environmental compliance reviews, three
natural springs along the Colorado River corridor
were stocked with young KAS (150 ambersnails
per site) in September 199814.
All KAS release areas were above the historic
flood elevation (~100,000 cfs stage) and would
not be affected by dam operations. A second
translocation of 150 KAS per site was conducted
in late July 1999, to boost population densities
and improve genetic variability14.
Since that initial stocking in 1998, one translocation
site (Upper Elves Chasm) appears to have established
as a new population - continued monitoring
has detected numerous KAS persisting and reproducing
at the initial release area, including migration
into suitable adjacent habitat14, 23.
The successful establishment of a second wild
KAS population in Arizona will aid in the
conservation of this native landsnail and
move one step closer to down-listing this
rare species15, 24. |
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| Project Cooperators: |
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Arizona
Game and Fish Department, Nongame and
Endangered Wildlife Program |
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Utah Division of Wildlife
Resources |
| - |
U.S.
Fish and Wildlife Service, Arizona Ecological
Services Office and Salt Lake City Office |
| - |
U.S.
Bureau of Reclamation, Upper Colorado
Region |
| - |
Central
Utah Project Completion Act Office |
| - |
Grand
Canyon Monitoring and Research Center
|
| - |
National
Park Service, Grand Canyon National
Park and Glen Canyon National Recreation
Area |
| - |
Western
Area Power Administration |
| - |
The
Phoenix Zoo |
| - |
Northern
Arizona University, Biological Sciences
Department |
| - |
Bureau of Land
Management, Shivwits Resource Area |
| - |
Bureau
of Indian Affairs |
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References:
|
1
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U.S.
Fish and Wildlife Service
(USFWS). 1992. Endangered
and threatened wildlife
and plants, final rule
to list the Kanab ambersnail
as endangered. Federal
Register 57 (75): 13657-13661.
|
2
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AGFD.
(2006). Arizona 's Comprehensive
Wildlife Conservation
Strategy: 2005-2015. Arizona
Game and Fish Department,
Phoenix , Arizona . |
3
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USFWS.
1995. Kanab ambersnail
(Oxyloma haydeni kanabensis)
recovery plan. U.S. Fish
and Wildlife Service,
Denver , Colorado . 21
pp. |
4
|
Miller,
M.P., L.E. Stevens, J.D.
Busch, J.A. Sorensen,
and P. Keim,. 2000. Amplified
fragment length polymorphism
and mitochondrial sequence
data detect genetic differentiation
and relationships in endangered
southwestern U.S.A. Canadian
Journal of Zoology 78:
1845-1854. |
5
|
Stevens,
L.E., F.R. Protiva, D.M.
Kubly, V.J. Meretsky,
and J.R. Petterson. 1997a.
The ecology of Kanab ambersnail
(Succineidae: Oxyloma
haydeni kanabensis Pilsbry,
1948) at Vaseys Paradise,
Grand Canyon , Arizona
: Final Report. U.S. Bureau
of Reclamation Glen Canyon
Environmental Studies
Program Report, Flagstaff
. |
6
|
Spamer,
E.E. 1993. Late Pleistocene
(?) land snails (Mollusca:
Gastropoda) in "red
earth" deposits of
the Grand Canyon, Arizona
. The Mosasaur 5: 47-58.
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7
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Szabo,
B.J. 1990. Age of travertine
deposits in eastern Grand
Canyon National Park ,
Arizona . Quaternary Research
34: 24-32. |
8
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Sorensen,
J.A. and D.M. Kubly. 1997.
Investigations of the
endangered Kanab ambersnail:
monitoring, genetic studies,
and habitat evaluation
in Grand Canyon and northern
Arizona . Nongame and
Endangered Wildlife Program
Technical Report 122.
Arizona Game and Fish
Department, Phoenix ,
Arizona . |
9
|
Clarke
A.H. 1991. Status survey
of selected land and freshwater
gastropods in Utah . Final
Report. Contract no. 14-16-0006-89-021
(revised). Prepared for
the U.S. Fish and Wildlife
Service by Ecosearch,
Inc., Portland , Texas
. |
10
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Stevens,
L.E., V.J. Meretsky, D.M.
Kubly, J.C. Nagy, C. Nelson,
J.R. Petterson, F.R. Protiva,
and J.A. Sorensen. 1997b.
The impacts of an experimental
flood from Glen Canyon
Dam on the endangered
Kanab ambersnail at Vaseys
Paradise, Grand Canyon,
Arizona: Final Report.
Grand Canyon Monitoring
and Research Center ,
Flagstaff . |
11
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Interagency
Kanab Ambersnail Monitoring
Team (IKAMT). 1998. The
endangered Kanab ambersnail
at Vaseys Paradise, Grand
Canyon , Arizona : 1997
Final Report. Prepared
for the Grand Canyon Monitoring
and Research Center ,
Flagstaff . |
12
|
Pilsbry,
H.A. 1948. Land Mollusca
of North America . The
Academy of Natural Sciences
of Philadelphia Monographs
II: 521-1113. |
13
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C.
Nelson, pers. comm. |
14
|
J.
Sorensen, pers. comm.
|
15
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Arizona
Game and Fish Department
AGFD. 1998a. Environmental
Assessment: Establishment
of new populations of
Kanab ambersnail in Grand
Canyon ( Coconino County
, Arizona ). Prepared
by AGFD for the National
Park Service. |
16
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Meretsky,
V. and D. Wegner. 1999.
Kanab ambersnail at Vaseys
Paradise, Grand Canyon
National Park , 1998 Monitoring
and Research. Prepared
by Steven W. Carothers
Associates, Inc. for Grand
Canyon Monitoring and
Research Center , Flagstaff
. |
17
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USFWS.
1994. Biological Opinion
on the operation of Glen
Canyon Dam as the modified
low fluctuating flow alternative
of the final environmental
impact statement operation
of Glen Canyon Dam. U.S.
Fish and Wildlife Service,
Denver , Colorado . |
18
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USWFS.
2000. Amendment to the
1996 and 1997 Biological
Opinions on the Operation
of Glen Canyon Dam. U.S.
Fish and Wildlife Service,
Denver , Colorado . |
19
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USFWS.
1996. Biological Opinion
on the effects of the
Spring 1996 Beach/Habitat-Building
Flow, Glen Canyon Dam.
U.S. Fish and Wildlife
Service, Denver , Colorado
. |
20
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USFWS.
1997. Biological Opinion
on the November 1997 Fall
Test Flow from Glen Canyon
Dam. U.S. Fish and Wildlife
Service, Denver , Colorado
. |
21
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Sorensen,
J.A. and D.M. Kubly. 1998.
Monitoring and habitat
surveys of the endangered
Kanab Ambersnail in Grand
Canyon and Northern Arizona
. Nongame and Endangered
Wildlife Program Technical
Report 125. Arizona Game
and Fish Department, Phoenix
, Arizona . |
| 22 |
Nelson,
C.B. 2001. Life history
of the Kanab ambersnail
on native and non-native
host plants in Grand Canyon
, Arizona . Master's Thesis.
Northern Arizona University
, Biology Department, Flagstaff
. |
| 23 |
Sorensen,
J.A., C.B. Nelson, and D.K.
Bolen. 2003. Kanab ambersnail
2003 progress report: analysis
of habitat data, status
of translocated populations,
and additional habitat surveys.
Nongame and Endangered Wildlife
Program Technical Report
220. Arizona Game and Fish
Department, Phoenix , Arizona
. |
| 24 |
Sorensen,
J.A. and C.B. Nelson. 2002.
Interim Conservation Plan
for Oxyloma (haydeni) kanabensis
complex and related ambersnails
in Arizona and Utah . Nongame
and Endangered Wildlife
Program Technical Report
192. Arizona Game and Fish
Department, Phoenix , Arizona
. |
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