NDOW Explanation of Recommended 2014 Bighorn Ewe Hunts and Associated Bighorn Herd Management Strategies

The Nevada Board of Wildlife Commissioners voted in their January/February 2014 meeting to allow bighorn sheep ewe hunting at the recommendation of the Nevada Department of Wildlife (NDOW). The ewe hunt was a decision of last resort based on several factors of bighorn sheep management.

Successes of Bighorn Sheep Restoration

NDOW in partnership with non-governmental organizations (NGO’s) that support bighorn conservation and public land managers have been highly successful in restoring bighorn sheep. When the first bighorn release occurred in 1968, it was estimated that only 3,000 bighorn existed in Nevada. That number has grown to 11,000 in 2014, more than doubling sheep populations.

This aggressive bighorn restoration program has primarily used animals from herds nearing their habitat carrying capacity as the source stock for creating new herds.

bighorn-sheep-populations

Consequences of Success

Researchers and bighorn managers have recognized high bighorn densities and population numbers are not sustainable. Bighorn are nomadic, seeking optimal habitat conditions and herd densities. However, today, herds are often restricted to a single mountain range or section of a mountain range due to man-made infrastructures and habitat fragmentation.

These factors have reduced the ability of growing herds to disperse. Increased concentration of animals leads to a greater risk of disease and severe habitat resource limitations such as lack of adequate water during the summer.

With more animals than ever are dependent on the same sources for food and water, and drought conditions continually worsening, these larger herds are in jeopardy.

Additionally, there is recent confirmation of herds exposed to, carrying, and shedding Mycoplasma ovipneumoniae. This M. ovipneumoniae is a bacteria, which has been recognized west wide and in Nevada, as playing a significant role in the bighorn sheep pneumonia complex that typically causes high summer lamb mortality and often contributes to long-term poor lamb recruitment.

Drought conditions, disease, overgrazing by domestic and feral animals and high population growth rates have all contributed to several bighorn herds exceeding their sustainable management levels.

The regular removal of sheep from capture and translocation efforts, had to date alleviated the need for any other population management tool such as ewe hunts. However, this is no longer the case.

Limitations of Translocation

The growth of Nevada’s bighorn population over the last decade has been nothing short of remarkable. This extreme rate of increase has made it challenging to manage herd populations solely through capture and translocation. Each year available release sites are fewer due to successful bighorn release efforts.

In addition, bighorn translocation guidelines are now more restrictive as greater awareness and data support the likelihood of disease transmission and the resulting negative impacts to bighorn herds. Efforts are needed, working together with NGO’s, public land managers, private landowners, and public land domestic sheep operators, to create more low risk release sites to accommodate future bighorn population growth through capture and transplants.

NDOW continues to accommodate other western states in providing animals for their bighorn restoration programs. For California bighorn sheep, there are no states or tribal nations that have expressed interest in receiving animals from Nevada. For desert bighorn, Nevada continues to provide source stock for Utah Division of Wildlife Resources (UDWR) bighorn sheep restoration program. Other states like Arizona and California have continually been offered Nevada’s bighorn sheep for transplant stock but have yet to make a formal request.

NDOW develops a big game release plan every two years that is approved by the Board of Wildlife Commissioners. The current plan covers release opportunities through June 2015. For both California and desert bighorn, there are herd augmentations identified. But with the confirmation of herds exposed to, carrying, and shedding Mycoplasma ovipneumoniae, augmentations will not be conducted into these herds for the foreseeable future.

Ewe Hunting as a Last Resort

For 2014, with limited release site opportunities within Nevada and in other states, and a total of over 500 animals above sustainable management levels for several herds, NDOW is recommending ewe hunts in 4 of the 60 bighorn hunt units.

NDOW biologists completed extensive scientific inquiry and modeling methods to determine the best solutions to combat overpopulation, habitat restrictions, disease incidence and other factors placing bighorn in danger.

Biologists focused on the overall health and sustainability of bighorn sheep herds to ensure long-term success of these animals in Nevada. Thus, it was determined that removing individual animals via hunting, including ewes, was the last tool left to accomplish this goal.

Ewe Hunting Info for Individual Units

The recommended ewe quota for Unit 068, the Sheep Creek Range, is intended to use a combination of harvest and removal for transplant stock to reduce the herd to a sustainable level. The goal is to remove 30 bighorn by this winter due to deplorable range conditions that have placed this herd in peril of experiencing high mortality in the short term.

For desert bighorn sheep, the Unit 212 (Lone Mountain) ewe hunt is based on the highest ever recorded population (430). M. ovipneumoniae was detected in the Lone Mountain herd in 2014 with sampled animals showing signs of pneumonia, eliminating it as an option for transplant stock. The population is 150 or more above its desired sustainable level. The 2014 recommended quota reflects the approach of taking multiple years to reach its sustainable level.

Unit 213, Monte Cristo Range herd has also exceeded its sustainable management level by 80 animals. This herd is too close to some of the identified release sites to use as source stock. Additionally, known movement with Lone Mountain may have already spread pneumonic pathogens to the Monte Cristos. The recommended ewe quota will help reduce the herd closer to its sustainable level. NDOW will still consider the herd for 2014 captures if a release site can be identified and sampling doesn’t detect M. ovipneumoniae.

The Unit 268, Muddy Mountain herd which is managed together with the Black Mountains is estimated at over 900 bighorn (record high). This is 200 above its sustainable management level. Recent coordination with UDWR staff has identified 50-75 as the target goal for capture and removal from the Muddys for relocation to Utah. Recent concerns of in-state releases involving habitat degradation, lack of separation with domestic sheep, and inability to benefit herds based on past releases, have caused some release sites to no longer be considered. Also, until alternate capture timing can be accommodated, Muddy Mountains will not be considered for more northerly releases. Over 200 bighorn have been removed from the Muddys over the last 7 years and the population is still increasing. The recommended ewe quota in concert with removals for the state of Utah may result in 1/3 of the necessary population reduction to reach its sustainable level. Continued drought conditions are so severe in the Muddys, that temporary water stations are planned for summer 2014 prior to fall removals.