Can Water Catchments Mitigate for Wildlife (Bighorn Sheep) Mortality, Due to Occurrence of Blue Green Algae (_Cyanobacterial_ Toxins) in Owyhee Reservoir?
Reservoir drawdowns and general climate conditions have increased the potential for _cyanobacterial_ (blue-green algae) blooms. To mitigate for mortalities associated with poor water quality, Reclamation and other cooperators install water catchments or guzzlers, which collect precipitation to provide drinking water for a variety of wildlife from large game (Bighorn Sheep) to small birds. Water collected is stored in underground tanks where it is kept cool and doesn't evaporate and can be accessible year-round.
* Can artificial water catchments be used to expand centers of wildlife (Bighorn Sheep) activity away from potentially toxic water sources and into areas with higher quality forage where water was previously unavailable, thereby reducing mortality from blue-green algae poisoning?
* What is the relationship between installation time and use of water catchments by wildlife (Bighorn Sheep) and the distance to existing (herd) units, forage availability and access to escape terrain?
Need and Benefit
Reservoir drawdowns and recent and projected climate conditions have increased the potential for _cyanobacterial_ blooms. Although Reclamation, in conjunction with the Tribes, U.S. Geological Survey (USGS) and agencies in other regions, has conducted research on water and climate conditions that encourage outbreaks of _Microcystis_ and _Anabaena cyanobacterias_, strategies to mitigate resulting mortality of sensitive wildlife species are largely untested.
In 2001-2002 a bloom of _Microcystis aeruginosa_ or cyanobacteria in Owyhee Reservoir led to toxic water conditions that were implicated in the death of at least 14 bighorn sheep and other wildlife. In response, Reclamation, in conjunction with Oregon Department of Fish and Wildlife (ODFW), Bureau of Land Management (BLM), and the Foundation for North American Wild Sheep (FNAWS) initiated the construction of 12 water catchments to provide alternate water sources for bighorn sheep and other wildlife. The simplest artificial water catchments use a sheet of tin or rubber (tarp) to divert precipitation into underground tanks to provide long-term storage with minimal evaporation; the tanks then gravity feed a small water source that can be accessed by wildlife.
However, the effectiveness of the catchment devices in changing habitat use and wildlife use of the reservoir as a water source is unknown. Although water catchments for wildlife have been a long-standing management tool, experimental approaches that evaluate changes in habitat use or distribution of the target wildlife species following the addition of water catchments are rare.
Leslie Gulch, located in the Owyhees, in the southeastern portion of Oregon, provides an ideal opportunity to evaluate the success of water developments for mitigating water poisoning risk and improving nutrition for bighorn sheep. 34 bighorn sheep were radio collared in 2001 and 676 locations were collected during 2001-2003 (when no guzzlers were present and a _cyanobacterial_ poisoning event occurred). In late 2007, 35 radio collars were installed (31 females, 4 males, collars last 3-4 years). Five water developments have been put in place since 2005, with an additional five to seven slated to be installed by 2011.
Therefore, we are uniquely poised to monitor how the ongoing water developments are utilized by wildlife species, and to determine by radio telemetry how or if the distribution of the bighorn sheep will change.
Bighorn sheep habitat use changes seasonally. To determine whether water catchments will shift bighorn away from the reservoir during periods of high risk for _cyanobacterial_ blooms, or at least expand the forage resources accessible to bighorn during periods of water limitation, we will monitor the movement of and habitat use by radio collared bighorn sheep. We will monitor use of existing water sources via motion-detecting digital cameras. Observations near guzzler locations will also be used to collect data on forage, escape routes, temperatures and other data. Freely-available satellite photos of photosynthetic activity (Normalized Difference Vegetation Index [NDVI]) and forage quality (estimated from bighorn fecal samples) will allow monitoring how spatial and temporal shifts in forage quality and availability interacts with water availability to predict habitat use by bighorn sheep.
The Owyhee country is vast and rugged, and access is often difficult. Personnel must have the knowledge and equipment to conduct such research in such an environment, which is why both internal and external capabilities are limited. This research/evaluation could be applied to many other reservoirs or water bodies experiencing water quality issues associated with climate change and/or toxic algal blooms, and other sensitive wildlife species mortalities and could be tied into other Reclamation research on _cyanobacterial_ blooms.
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This information was last updated on April 25, 2015
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