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Kanab Ambersnail
 
Kanab Ambersnail (Oxyloma haydeni kanabensis)
By Jeff Sorensen
 
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).
 
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.
 
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.
 
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.
 
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.
 
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.
 
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.
 
Project Cooperators:
- Arizona Game and Fish Department, Nongame and Endangered Wildlife Program
- 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
 

 

References:

1

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

AGFD. (2006). Arizona 's Comprehensive Wildlife Conservation Strategy: 2005-2015. Arizona Game and Fish Department, Phoenix , Arizona .

3

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.

7

Szabo, B.J. 1990. Age of travertine deposits in eastern Grand Canyon National Park , Arizona . Quaternary Research 34: 24-32.

8

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

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

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

C. Nelson, pers. comm.

14

J. Sorensen, pers. comm.

15

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

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

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

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

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

USFWS. 1997. Biological Opinion on the November 1997 Fall Test Flow from Glen Canyon Dam. U.S. Fish and Wildlife Service, Denver , Colorado .

21

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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