Chemical Immobilization for Mountain Lions
The mountain lion (Puma concolor) is the largest wild felid in the North American continent. It is also frequently known as the cougar or puma. Mountain lions are obligate carnivores that can be found in varied habitats in the U.S. and Canada, although they tend to prefer and occur in greater numbers in the foothills and mountains of western states and territories. Throughout history, mountain lions enjoyed the broadest geographic range of any North American mammal. Unfortunately, by the 1960s, widespread hunting greatly reduced the geographic distribution and population of these animals; this was largely driven by human fear and the protection of livestock. “Until 1965, the status of mountain lions in Colorado was that of a varmint, with a $50 bounty. In 1965 their legal status changed to that of a big game animal, reflecting growing public appreciation and concern for mountain lions.”1 After decades of management reforms, mountain lion populations in western states in the U.S. are now viable across much of the animal’s historic range.
Mountain lions can adapt to a wide range of habitats, preferring areas that provide sufficient hiding cover and large prey, such as deer and elk. Males occupy large territories, often covering over 115 square miles, which they vigorously defend from other males. Females occupy relatively smaller territories (about 38 square miles) that can overlap with the territories of other females. Young adults are generally transient, moving throughout the above areas searching for unclaimed territory.2
The eastern cougar, a subspecies of mountain lion, was declared officially extinct by the U.S. Fish & Wildlife Service in 2011, although individuals from western populations have been confirmed to wander as far as the East Coast. Florida panthers, the other U.S. subspecies of mountain lion, are listed as critically endangered on the endangered species list. There are less than 160 Florida panthers left in the wild.2
Morphology, Range & Habitats
Male mountain lions are larger than females, weighing an average of 130-150 pounds and eight feet in length. On average, females weigh 80-100 pounds and may be up to seven feet long. The average life span of mountain lions is approximately twelve years. Females begin to reproduce at about two years of age, usually having two to three kittens per litter. The average population density in suitable habitats is about two to three independent adult (>2 years of age) mountain lions per 38 square miles, with females tending to outnumber males.2
Natural sources of mortality for mountain lions include predation from bears and wolves, defending territory and food from other mountain lions, disease, and injury, generally from attacking large prey.2 In most populations, human-caused mortality (including hunting) is a significant source of mortality; in urban areas, human-caused mortality more frequently results from vehicle collisions and management-related removals due to human conflict.
Human interactions with mountain lions are a cause for public concern, particularly in western states such as California and Colorado, where human expansion into mountain areas favored by mountain lions is ongoing. While aggressive encounters (mountain lion attacks on humans) remain rare, as mountain lion habitat has been increasingly encroached upon by humans, the number of mountain lion interactions has increased. These range from chance sightings to predation upon pets to attacks.2 The preponderance of literature suggests that mountain lions are afraid of people and tend to avoid direct contact, with most interactions being a surprise for both the human and the mountain lion.
The behavior of mountain lions toward small children can elicit a prey response, although human injuries from mountain lion attacks are extremely rare. That said, mountain lion attacks have increased in recent decades as human populations have expanded into traditional mountain lion habitats. “From 1890 to 1990 there were nine documented fatal attacks and fifty-four non-fatal attacks on humans in the United States and Canada, but between 1991 and 2003 there were seven fatal and thirty-eight non-fatal attacks. Unsurprisingly, the upsurge in attacks corresponds to a large increase in human-mountain lion incidents, likely due to habitat reduction, increased recreational activity, and possible increases in mountain lion populations.”2
Reasons for Capture and Immobilization
Mountain lions are captured for any number of reasons, with most captures conducted by wildlife management agencies being for the purpose of research. More often than not, an animal will be weighed, measured, sexed, and marked with ear tags or transponders. This is often the case even in instances where relocation is necessary. Depending on the research needs, radio collars may be attached for tracking purposes. To conduct all of these operations on a fully-responsive mountain lion would be challenging at best. In such cases, chemical immobilization is the path of least resistance.
Large cats such as mountain lions can be chased by hunting dogs and treed, then darted with drugs. There are two major classes of drugs used for the immobilization of all wildlife: cyclohexanes and opioids. The latter are chemical modifications of morphine, and a class of drugs that should never be used on felids.1 Cats often have severe reactions to opioids, such as hyperexcitability and convulsions. Cyclohexanes, on the other hand, are both safe and efficacious when used with wild felids. Ketamine and tiletamine are two cyclohexane drugs that are often used on cats. Both of these drugs are modifications of the drug phencyclidine (PCP). As such, these drugs are controlled substances requiring special licensure from the U.S. Drug Enforcement Agency (DEA).
Immobilization Drugs and Protocols
For the immobilization of mountain lions, cyclohexane drugs should be combined with tranquilizers such as xylazine or medetomidine in order to avoid the rough induction and incoordination often associated with cyclohexane use in felids. Both xylazine and medetomidine of these tranquilizers can be reversed (or antagonized), which helps to shorten the amount of time the animal is immobilized.1 Handbook of Wildlife Chemical Immobilization (Arnemo & Kreeger, 2018) recommends ketamine at 2 mg/kg plus medetomidine 0.075 mg/kg to immobilize mountain lions. This may be supplemented with ketamine at 2 mg/kg as needed, and reversed with atipamezole at 0.3 mg/kg.3
For mountain lions, Chemical Immobilization of Wild and Exotic Animals (Nielsen, 1999) recommends:
- Ketamine in doses of 5 to 20 mg/kg, with or without 0.5 to 4 mg/kg of xylazine,
- Telazol® in doses of 1.5 to 40 mg/kg, or
- Medetomidine in doses of 0.04 to 0.10 mg.kg with 2 to 3.5 mg/kg of ketamine.4
Atipamezole (0.35 mg/kg) may be used effectively as a reversal agent for the above listed drugs.
Equipment to deliver drugs to mountain lions include hand-held syringes for cats caught in box traps, pole syringes for cats in foothold traps, and blow pipes, dart pistols or rifles for cats in trees. Mountain lions can be safely darted with dart rifles or pistols.4 Once immobilized, the animal’s eyes should be covered and treated with an ophthalmic ointment or saline. This is because most animals’ eyes remain open with the administration of cyclohexane drugs, resulting in dryness.1,4 “Respiration and rectal temperatures should be continuously monitored; pulse and cardiac function are rarely impacted by these drugs. Pulse oximeters, which measure the oxygen saturation of hemoglobin, are useful devices to monitor respiration, but are not absolutely necessary.”1
1Kreeger, T. Chemical Capture of Free-Ranging Felids. Wild Cat News, Jan. 2018.
2nwf.org.
3Arnemo, J., Kreeger, T. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed.
4Nielsen L. Chemical immobilization of wild and exotic animals. Iowa: Iowa State University Press, 1999; 227-281.
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