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Mountain-Prairie Region
Contaminants of Concern in South Dakota

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Anticoagulant Prairie Dog Rodenticides

Of particular concern in South Dakota and other western states is the use of anticoagulant rodenticides to poison black-tailed prairie dogs.  Wildlife that ingest anticoagulant bait or feed on animals that consume Rozol (secondary exposure) are at risk of being negatively affected (click here for anticoagulant fact sheet).  This is especially true for predators and scavengers that may feed on poisoned prairie dogs and select internal tissues, like the liver, that contain the highest body burden of anticoagulant residues.  Raptors that feed on prairie dogs may be especially vulnerable to secondary exposure because dead or dying prairie dogs that can be difficult to spot from ground level are more easily spotted from above (click here for video of dying prairie dog). Raptors may “key-in” on anticoagulant debilitated prairie dogs resulting in repeated exposures. 

The delayed and subtle toxicity of prairie dog anticoagulants to raptors combined with their tendency to travel great distances and seek concealment when injured results in much uncertainty on how exposure may hinder their ability to survive and reproduce.  Use of anticoagulant rodenticides for prairie dog control may present an increased secondary risk to non-target species reminiscent of times before strychnine use was banned (click here for PBS 1970 broadcast of Prairie Killers). 


Wildlife Lead Ingestion

Lead poisoning can be a significant cause of mortality to wildlife.  Regulations for the use of nontoxic shot were instituted nationwide in 1991 to protect waterbirds.  However, waterfowl can still be exposed through the ingestion of old lead shot from wetlands.  Waterbirds such as loons, swans, cormorants, herons and pelicans may also ingest lead fishing sinkers.  Doves and other upland game birds may also be exposed to spent lead in hunted areas where they feed or obtain grit.  Raptors and other predators and scavengers are also at risk to lead exposure by incidental ingestion of lead bullet fragments when they consume animals shot with lead bullets.   Please consider the use of nontoxic alternatives for hunting and fishing and visit the sites linked below for more information:



Photo: Gregory Stempien

Debilitated ferrruginous hawk.
Click on image for more information.


Selenium Toxicity

There is a long history of selenium toxicity in South Dakota, not only to fish and wildlife, but also to livestock and humans (Harris 1991).  In the 1930’s, selenium was determined to be the cause of alkali disease, which was first  described and reported in 1860 when it affected cavalry horses in South Dakota (Madison 1860 as cited by Seiler et al. 2003).  Naturally occurring selenium can be found at high concentrations in South Dakota glacial deposits and Cretaceous soils.  The most consistently seleniferous soils in SD tend to be in the Pierre Shale and the Niobrara Formation (Stach et al. 1990).  Selenium can leach from soil by rainfall, subsurface drainage, or irrigation and can accumulate in the water, bottom sediments, plants, and animals.  Elevated levels can cause harmful effects, particularly to fish and aquatic bird species (Seiler et al. 2003).

In 1985 the U.S. Department of the Interior (DOI), through the National Irrigation Water Quality Program (NIWQP), began a series of field investigations at 26 areas in the Western U.S. to determine whether irrigation drainage has had harmful effects on fish, wildlife, and humans (Seiler et al. 2003).  NIWQP reconnaissance areas in South Dakota included the Angostura Reclamation Unit in Custer and Fall River Counties and the Belle Fourche Reclamation Project in Butte County.  Selenium was routinely measured at concentrations that could be problematic at sites upstream and downstream from both study areas (Sando et al. 2001).  The Belle Fourche sites also had 4 of 10 avian eggs with selenium concentrations that exceeded a 6 microgram per gram threshold for embryotoxicity (Seiler et al. 2003).  Selenium concentrations were also measured by the NIWQP for lands irrigated with non-DOI water at Lake Andes, Pocasse, Shadehill, Rapid Valley, Redwater, and the James River.   

NIWQP investigations no longer exist; however, on-going efforts to address selenium concerns in SD include sampling agricultural tile drain effluents that discharge into Service managed wetlands (see “Environmental Contaminant Investigations” section above) and coordination with South Dakota Department of Natural Resources and the U.S. Environmental Protection Agency to develop selenium water quality criteria that adequately protect wildlife (Lemly and Skorupa 2007). 



Harris T. 1991.  Death in the Marsh.  Island Press, Washington DC. 265 p.

Lemly AD, Skorupa JP.  2007.  Technical issues affecting the implementation of US Environmental Protection Agency’s proposed fish tissue-base aquatic criterion for selenium.  Integrated Environmental Assessment and Management 3(4):552-558.

Madison TC. 1860.  Sanitary report-Fort Randall, in Coolidge RH, Statistical report on the sickness and mortality in the Army of the United States, January 1855 to January 1860: 36th [U.S.] Congress Senate Exchange Document, v. 52, p. 37–41.

Seiler RL, Skorupa JP, Naftz DL, Nolan BT.  2003.  Irrigation-induced contamination of water, sediment, and biota in the western United States-synthesis of data from the National Irrigation Water Quality Program.   US Geological Survey. US Geological Survey professional paper 1655. 123p.

Sando SK, Williamson JE, Dickerson KK, Wesolowski EA.  2001.   Irrigation Drainage Studies of the Angostura Reclamation Unit and the Belle Fourche Reclamation Project, Western South Dakota: Results of 1994 Sampling and Comparisons with 1988 Data..  Water-Resources Investigations Report 01-4103. 65 p. 

Stach RL, Olson OE, Palmer IS, Helgerson RN, Chadima SA.   1990.  Selenium in South Dakota waters.  Report of investigations 112.  Science Center University of South Dakota, Vermillion, SD.  69 p. 



National EC Webpage:

Region 6 EC Webpage:


For further information on South Dakota contaminants issues,
contact Matt Schwarz at 605-224-8693 ext. 232.



Last updated: September 9, 2013

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