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Predation Management
 


Three un-cached kills – Two bighorn sheep and one mule deer
– killed at Dripping Springs over a 3-4 day period by a
collared lion (KM01), May-June 2007
.

The primary goal of the Kofa Mountains Complex predation management plan is to aid in the recovery of the Kofa Mountains Complex bighorn sheep population. The goal is to reverse the decline and ensure a population level that can once again support an active bighorn sheep transplant program.

This management plan has been developed to address mountain lion predation on a depressed desert bighorn sheep population located in the Kofa Mountains Complex of southwest Arizona.  This complex includes the Kofa, Castle Dome, New Water, South Plomosa, Tank and Little Horn mountains.  The majority of the area under consideration falls within the boundaries of the Kofa National Wildlife Refuge (Kofa NWR).  This plan follows the spirit and guidance of the Arizona Game and Fish Commission Predation Management Policy and the Arizona Game and Fish Department Predator Management Team Report.

Specifically, the Arizona Game and Fish Commission Predation Management Policy states:

“Actions by the Arizona Game and Fish Department (department) should be based on the best available scientific information. Mountain lions and coyotes will be managed to ensure their future ecological, intrinsic, scientific, educational, and recreational values, to minimize conflict with humans, and to minimize adverse impacts on other wildlife populations.

The department will develop site-specific management plans when either of these two species is considered to be inhibiting the ability of the Department to attain management goals and objectives for other wildlife species.”

Furthermore, the Department’s Predator Management Team Report states that; “Predators and their prey cannot be managed separately” and that “as a Department we must strive to develop the biological and social data necessary to manage predators with a program that is biologically sound and publicly acceptable.”

Documentation of mountain lions in the area began around 2000, a factor which may help explain continued depressed, even declining, sheep numbers even in the face of otherwise improved rainfall conditions.  Mountain lions have historically been only rare transient visitors to the Kofa refuge.  There are no verified records of mountain lions on the refuge between 1944 and 2001.  During a research project conducted in the Kofa Mountains from 1993 through 1996, 50 bighorn sheep were radio collared and 17 mortalities were investigated.  None of the 17 could be attributed to lion predation.  From 1995-1997, surveys were conducted for lions in 18 mountain ranges and along the Colorado and Gila Rivers in southwestern Arizona, including the Kofa NWR.  They confirmed the presence of only three individual lions (all believed to be males in the Mohawk and Growler Mountains which are outside the Kofa Mountains Complex), and suggested that a distinct, self-sustaining mountain lion population did not currently exist in southwestern Arizona.  They found no evidence of lions on the Kofa NWR.

Beginning in 2004, Kofa NWR staff placed eight active infrared and two passive digital remote cameras at water holes.  The refuge documented at least 5 lions on the refuge in 2006.  The actual population density is unknown, but photographs of spotted juveniles or females with kittens have been obtained in successive years, suggesting a local breeding population.  Little is known about the movement or diet of mountain lions on Kofa NWR.  Cache sites have been found containing mule deer, bighorn sheep, and badger.  The distinctive tracks of a large male have been observed both on and off the refuge.

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. Variables influencing mountain lion predation might include relative availability of alternate prey and escape terrain, vulnerability of individual prey, weather, and behavior of individual predators.  Declines in the Peninsular and Sierra Nevada populations of bighorn sheep, which are currently listed as endangered by the USFWS, have been attributed, at least in part, to mountain lion depredation.  Other populations, such as the San Gabriel Mountains herd in California, have declined since 1989 from over 500 animals to less than 90, almost exclusively attributed to mountain lion depredation.  Because a single mountain lion may kill on average one big game animal per week, even a small number of lions can inhibit the recovery of the Kofa NWR sheep herd.  Five lions have the potential to not only take most recruitment but significant portions of the adult breeding population as well.


Cached bighorn sheep killed by collared lion (KM01)
at Dripping Springs, June 2007.

We conclude that any amount of predation on bighorn sheep by lions in the Kofa Mountains Complex is significant and represents additive mortality in these GMUs that have already been impacted by drought.  Removal of individual lions known to be killing sheep or a reduction in the number of mountain lions in areas where sheep are being killed by lions is deemed necessary to reduce any further sheep population decline and will aid the recovery of the Kofa Mountains Complex bighorn sheep population.


 

 
Related AZGFD Info
   
 

Map of the Kofa Mountains Complex Predation Area


[pdf, 256kb]


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