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Iowa Pleistocene Snail (Discus macclintocki)

Five-Year Review: Summary and Evaluation

Below are the General Information and Results portions of the Five-Year Review. Go here for the complete 19-page Review (PDF).



1.1 Reviewers

Lead Regional Office:

Carlita Payne, Recovery Coordinator, Midwest Region (612-713-5339)


Lead Field Office:

Kristen Lundh, Rock Island Ecological Services Field Office, Rock Island, IL (309-757-5800)


Cooperating Field Office: Driftless Area National Wildlife Refuge, McGregor, IA (563-873-3423)


1.2. Methodology used to complete the review

The Service solicited information from the public through a Federal Register notice (71 FR 16177) requesting new information on Iowa Pleistocene snail (Discus macclintocki) that may have a bearing on its classification as endangered. This review was completed by Cathy Henry at the Driftless Area National Wildlife Refuge (NWR) in McGregor, Iowa and Kristen Lundh, Rock Island, Illinois Field Office, Ecological Services. The Driftless Area NWR was established to meet recovery goals of the Iowa Pleistocene snail. Therefore, the majority of information related to this species was available at the Refuge or developed by Refuge staff through literature review, annual monitoring and site visits. The new information used to compile this review (Clark et al 2008) has undergone peer review during the publishing process.


1.3 Background


1.3.1 FR Notice citation announcing initiation of this review:

Federal Register vol. 71, No. 61, Thursday March 30, 2006, pp 16176-16177


1.3.2 Listing history

Original Listing


FR notice: Final Determination that Seven Eastern U.S. Land Snails are Endangered or Threatened Species July 3, 1978; 43 FR 28932


Entity listed: Species


Classification: Endangered


1.3.3 Associated rulemakings: NA


1.3.4 Review History

The Iowa Pleistocene snail was included in a cursory five-year review of all species listed in 1978 (December 8, 1983; 48 FR 55100) and a cursory review of all species listed before January 1, 1991 (56 FR 56882; November 6, 1991). These 5-year reviews resulted in no change to the listing classification of endangered.


1.3.5 Species’ Recovery Priority Number at start of review Recovery Priority number 14: Degree of threat considered low at the species level with high potential for recovery.


1.3.6 Recovery Plan

Name of plan: National Recovery Plan for Iowa Pleistocene snail (Discus macclintocki)


Date issued: March 22, 1984


Dates of previous revisions: NA



2.4 Synthesis

The Iowa Pleistocene snail has a very specific habitat tolerance and currently only occurs on 37 sites. Since the issuance of the 1984 recovery plan and the 1991 5-year review, there is additional information on genetics and population demographics. Buffer area needs have been more precisely identified to protect and preserve the algific slopes and their associated sinkholes from disturbance, runoff and other adverse adjacent land uses. Eighteen additional colonies have been located since completion of the recovery plan in 1984. Eighteen more colonies have also been protected through conservation easements or fee title acquisition, since the recovery plan, but the surrounding habitat remains vulnerable on many of these sites (USFWS 2006). Global warming and invasive species are emerging as new threats to the habitat of the Iowa Pleistocene snail. There is little new information on the life history of the snail.


The recovery criteria for downlisting are protection of 16 colonies and documentation of population status of stable or increasing via a monitoring program. The recovery criteria for delisting is protection of at least 24 sufficiently dispersed viable breeding colonies. Twenty-four colonies have been protected to date (USFWS 2006). However, 13 of the protected colonies need additional buffer protection to their habitat to ensure they are permanently protected (USFWS 2006). In addition, sites at the south end of the range in Iowa and in Illinois remain unprotected (USFWS 2006). These sites should be considered part of the ‘sufficiently dispersed’ protection criteria. More information is needed to better define a viable breeding colony from a genetics and population sustainability standpoint. The recovery plan states that 500 snails would be an effective breeding population -- this should be confirmed in future life history studies.


Algific slopes that do not contain Iowa Pleistocene snails should be evaluated for reintroduction suitability. A monitoring method has been developed and evaluated as suitable for monitoring recovery goals (Clark et al 2003). Monitoring will continue by the Driftless Area National Wildlife Refuge.


The recovery criteria numbers were based on the known populations at the time of recovery plan development and the potential for finding more. Protection of the majority of the sites was essentially advocated. Since there are now 37 known sites, the recovery criteria should be reviewed to consider the new sites. Criteria should also be more specific regarding what constitutes protection because of the need for buffer around the snail’s habitat. Protection might be defined as “encompassing the entire algific slope and associated snail colonies and the sinkholes presumed to be associated with the site and buffer of at least x number of feet above the slope and at least x number of feet below the slope”.


Global warming is perhaps the largest looming threat to the Iowa Pleistocene snail. More information on ice formation and melting in algific slopes is needed to understand how global warming or other effects of climate change will potentially affect this species. Modeling under different climate scenarios may help with predictions. Perhaps the climate scenarios can be achieved by obtaining estimates of the underground ice masses, air flow, and modeling under various climate scenarios. Presumably, with gradually warmer seasons, insufficient ice may reform in the winter to last through the summer, or the ice mass may disappear too fast in the summer. Eventually some threshold may be reached where cold air flow will cease. Temperatures on the algific slopes would then increase and snail colonies could conceivably be lost in one season. Climate change is happening gradually and any effects on the ice will likely take many years, but once that potential threshold is reached, the snails could be quickly impacted. Establishment of a laboratory colony for preservation, for additional life history study, and for study of how this glacial relict survives its cold environment may be justified.


The reclassification criteria outlined in the recovery plan has been partially met as 11 of the 16 colonies are protected, and according to the FY 2008 recovery data call, the overall status is “stable”. The endangered status of the Iowa Pleistocene snail should remain because the original threats outlined in the final listing rule, recovery plan, and the additional threat of global warming, are present. The snail still meets the definition of endangered throughout all of its range and therefore, no change in the classification is recommended.



3.1 Recommended Classification:


__x_ No change is needed


3.2 New Recovery Priority Number _NA____ .



The recovery plan should be revised to include all currently known sites, monitoring and genetics information, global warming threat, and subsequent revised and more specific recovery criteria. More specific determination of the potential impacts of global warming should be done. Temperature monitoring should continue. If sufficient understanding of potential negative impacts is reached, a captive snail colony should be considered to propagate the species. Protection of sites through land acquisition and conservation easements should continue as well as landowner contact and education. The Driftless Area NWR expanded its acquisition boundary and acreage so that acquisition for this and other species can continue (USFWS 2006). The Iowa DNR has a USFWS Landowner Incentive Program grant in which additional conservation easements may be funded. Additional funding is needed to continue acquisition.


All potential sites where conditions are suitable for the Iowa Pleistocene snail should be thoroughly surveyed to determine their presence or absence so that all sites are known. The surveys should probably be done prior to revision of the recovery plan so that recovery criteria can reflect the total known sites. Information needs include viable breeding colony size, temperature tolerances, food requirements, and methods for potential reintroductions.


Above are the General Information and Results portions of the Five-Year Review. Go here for the complete 19-page Review (PDF).


Back to Five-Year Review page


Last updated: April 14, 2015