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Current Program Update

Current Program Update: January 15th, 2013
Kofa NWR Desert Bighorn Sheep Herd Update
For immediate updates, check the “press releases” section.
[Please see archived updates for additional background]


Project Objective:
The purpose of this joint Arizona Game and Fish Department and U.S. Fish and Wildlife Service effort is to restore the Kofa desert bighorn sheep herd to numbers that will once again support the herd’s critical and historic role as a source of animals for translocation to resurrect herds throughout the southwestern United States. Many herds were extirpated during the late 19th and early 20th centuries.  Causes are attributed to the unregulated market-hunting to support frontier development and diseases transferred from domestic livestock. However, through regulated hunting, concerned sportsmen, and the department’s translocation program, Arizona’s bighorn sheep herd is estimated at nearly 6,000 animals. Additionally, because of the program, two species of bighorn sheep now call Arizona home - the desert bighorn and Rocky Mountain bighorn.

Herd Survey Update:
The last annual Kofa NWR bighorn sheep herd survey was conducted in October 2012. That survey estimated the population on the refuge at 428 animals. (news release)

Biologists’ analysis of surveys during the past 6 years indicate no significant decline or improvement to the herd’s population. Wildlife agencies and conservationists remain concerned about the decline in bighorn sheep populations on the refuge, especially in comparison to the estimated 812 animals from the 2000 survey.

Historical averages for the herd based on survey data before the significant decline between 2000 and 2006 and using the same survey methods, put the herd at an average estimate of 800 animals (1981-2000 survey data).

The official joint news release of the survey results issued on Jan. 7th, 2013 is available here.
The next annual survey is tentatively scheduled for October of 2013. Results will be posted in the press release section of this site.

Water Management
The range water conditions as of the winter of 2013 are adequate. The rainfall during the sumemr of 2012 filled most waterholes. Frequent inspections of all priority waters will continue throughout the summer months. If it becomes necessary to maintain water availability at all priority locations, supplemental water will be hauled to these sites.

Hidden Valley Tank - The Kofa National Wildlife Refuge, Arizona Game and Fish Department, and the Yuma Valley Rod and Gun Club recently cleaned out and resealed this critical water source for bighorn sheep. It had been leaking water.

Predation Management and Monitoring:

Efforts continue to capture and radio colar mountain lions on and near the refuge.  Collared lions that show a propensity for killing bighorn sheep have been and will continue to be lethally removed.

Although predation may not be the primary cause of the initial decline in bighorn sheep numbers, the recently established lions have the potential to further depress or inhibit recovery of a sheep herd that is already depressed, particularly on Kofa NWR.  Research indicates that mountain lion predation can have significant population-level effects. Learn more about this here.

The criteria for “offending” mountain lion is one that has demonstrated a focus on bighorn sheep by killing at least two in a six-month period.  The “offending lion” criteria selected for both the investigative report and the Kofa Mountains Complex Adaptive Predation Management Plan is among the most conservative of the existing management plans for other at risk bighorn sheep populations. 

Radio-collared bighorn sheep:

Approximately 42 bighorn sheep with satellite and/or vhf collars are being monitored. This includeds 23 new animals that just had VHF collars attached in November 2012.  Only 1 collared sheep has died since the last update in April 2012 and it was not caused by predation, however, we were only monitoring about 15 sheep during most of this time.


Radio-collared mountain lions:
(For clarification, radio collar designations are as follows: K = Kofa collared, R = regionally collared; M = male, F = female, 01 = sequential number is unique based on location and gender, ie: KM01 = is Kofa male number 1, KF01 = would be Kofa female number 1)

Since the start of this project 16 lions have been captured and collared.  Of these, 7 adult males and 3 female lions have been lethally removed.  One male lost his tracking collar, one female lion was legally harvested, and two females and one female kitten (offspring of RF01) died of natural causes.

  • RF01 (Regional Female #01) –This female was captured in a cage trap in GMU 41 on April 4, 2010. At that time she was estimated to be 8-9 years old, weighing 70-75 pounds. She continued to be monitored, spendt most of her time along the Gila River and occasionally in the desert parts of GMU 41, but spent little time in the Kofa National Wildlife Refuge. In September 2010, her den was located in dense vegetation on the Gila River and a 2-week old kitten was captured, collared and released. This female kitten, RF02, stayed with its mother until its death of unknown cause on December 12, 2010.  RF01 was recaptured in January 2012 to replace her failing collar.  She eventually drowned in a commercial fish pond in July 2012

  • KM06 (Kofa Male #06) – This male lion was captured in the New Water Mountains on the northeast boundary of Kofa NWR on January 28th, 2012.  He was estimated to be 3 years old and weighed 101 pounds.  He ranged mostly east and north of the Refuge.  KM06 was lethally removed in late April 2012.  He had killed 4 bighorn sheep, 2 of which were in the Predation Management Area.
  • KM07 (Kofa Male #07) - This male lion was captured in the Castle Dome Mountains in the southern part of the Kofa NWR in April 2012.  He was estimated to be 2-3 years old and weighed 102 pounds.  In a short time he killed 2 bighorn sheep on the Refuge and was lethally removed in May 2012. 
  • KM08 (Kofa Male #08) - This male was captured in the Kofa Mountains in December 2012.  He has ranged both off and on the refuge but has so far not killed any bighorn sheep.  He continues to be monitored closely.
  • KF04 (Kofa Female #04) - This 7 to 9 year old female was captured in the Kofa Mountains in February 2012.  She was lethally removed in May 2012 after killing 4 bighorn sheep, all on the Refuge.

The Department continues to seek opportunities to monitor and manage the effects mountain lions have on the Kofa bighorn sheep population while in its declined state, through tracking their range, movements, predation, and other aspects of the predator-prey dynamic.  Trail cameras are being utilized throughout the refuge to monitor lion activity and specifically evaluate trail patterns. 

The Kofa NWR Mountain Lion Management Plan and Environmental Assessment (EA) for “Limiting Mountain Lion Predation on Desert Bighorn Sheep on the Kofa National Wildlife Refuge” has been approved by the U.S. Fish and Wildlife Service and published in the Federal Register. To learn more click here.

Translocations remain suspended at this time. The last translocation from the Kofa was in 2005. To learn more about translocations click here.

Disease Monitoring
Results from blood samples taken from bighorn sheep captured and collared from 2007 through 2011 are being analyzed. Interpretation of the results is difficult. Although titers to viral diseases such as PI3 and BRSV are often positive, the animals rarely, if ever, show clinical signs of disease. Additionally, thirty of forty samples from the animals screened in 2010 tested positive for Mycoplasma, which is often an indicator of respiratory disease. While this is cause for some concern and could indicate that a pneumonia related event occurred in the Kofa herd, none of the animals have shown symptoms of pneumonia.

Recreational Impact
Frequent human disturbance of ewes during lambing season may cause them to abandon areas for less optimal habitat, which could in turn affect lamb survival. Researchers at the University of Arizona and United States Geological Survey (USGS) have expressed interest in conducting comprehensive studies documenting the effects of public use on bighorn sheep. Funding for such studies is being pursued.

The 2012 desert bighorn sheep ram hunting season (only rams are hunted) ran December 1-31. The season included six permit-tags (5 from Game Management Units on the Refuge and 1 from a GMU that includes a small portion of land in the northern part of the Refuge) that could have been filled on Kofa lands, the lowest number of tags issued for the refuge since 1981. Of these permit-tags, five rams were harvested from the refuge.

The limited hunt permit-tags are available through a lottery application process. The distribution of the hunt permit-tags were as follows: one (1) tag in Unit 45A (same as 2011), one (1) in Unit 45B (same as 2011), and three (3) in Unit 45C (same as 2011).

A portion of Unit 44B South includes some of the Kofa NWR range in its boundaries and could include a sheep harvest from the Kofa. Only one (1) tag was allocated to Unit 44BS, bringing the maximum possible harvest from the Kofa NWR herd to six (6) rams. This allocated harvest would account for only 1.5 percent of the 2010 estimated herd population.
Mandatory harvest reporting and physical check-in is required for all bighorn sheep hunters.

Additionally, there is one (1) Special Big Game Tag (Commissioner’s tag) allocated for bighorn sheep that could be used in the southwest region of the state that does include the Kofa NWR units. This special tag is valid all year long. However, historically, this tag has only occasionally been used for hunting on the Kofa NWR.

About hunting and conservation: Game and Fish maintains ram to ewe ratios that biologically assures healthy reproduction capabilities for the Kofa bighorn sheep herd. These limited male-only hunt harvests have no impact on the population’s ability to reproduce. In fact, a single male ram is capable of breeding multiple ewes.

Equally important to note, the sale of hunting licenses and big game tags funds the annual surveys and other management needs for this struggling herd as well as the more than 50 years of bighorn sheep management in the state. The Arizona Game and Fish Department does not receive any funding from the state’s general tax fund.

Research and Monitoring
Twenty-three (23) bighorn sheep were captured in November 2012 for collar replacement and health assessments. Eighteen collars were placed on a new animals and five replaced old or non-functioning collars on previously collared animals.

There are currently 42 working collars on bighorn sheep on the Refuge. Fourteen are satellite/GPS collars that transmit location data daily, and 28 are VHF-only collars.  Arizona Game and Fish Department personnel monitor these radio-collared sheep closely.

Field work on the New Mexico State University research project on condition-health correlates of the radio-collared sheep ended this past year and we are awaiting the final report.

December 21st, 2010 - The United States Court of Appeals for the Ninth Circuit has ruled that the USFWS failed to prove that the Yaqui and McPherson tanks were needed for bighorn sheep and has sent the case back to the U.S. District Court in Arizona for further review and action. For more information, visit the U.S. Court of Appeals for the Ninth Circuit website at, The case is Wilderness Watch v. USFWS, No. 08-17406.

Case history: On September 5th, 2008, U.S. District Court Judge Mary H. Murguia, ruled that the U.S. Fish and Wildlife Service (FWS) use of motorized equipment for the redevelopment of those tanks did not violate the Wilderness Act and the agency complied with the National Environmental Policy Act (NEPA). Wilderness Watch filed an appeal with the Ninth Circuit Court of Appeals in San Francisco regarding redevelopment of two existing water catchments. The appeal was heard by the court in December 2009.

Site news:



Archived Program Updates
NOTE: The following files are PDF's and require the free Adobe Acrobat Reader.For text-only, use Adobe Access.

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