Chemical Immobilization for Bobcats

Bobcats (Lynx rufus) are approximately twice as the size of the average housecat. They have long legs, large paws, and tufted ears similar to those of their larger relative, the Canada lynx. Bobcats are brown or brownish-red with a white belly and a short, black-tipped tail. Bobcats are elusive and nocturnal, so they are rarely seen by humans. Their range encompasses most of North America; bobcats adapt well to diverse habitats such as forests, swamps, deserts, and even suburban areas. The average life span of the bobcat is seven years.

Bobcats are entirely carnivorous. They are fierce hunters that can kill prey much bigger than themselves, but typically eat rabbits, birds, mice, moles, squirrels, and other smaller game. Bobcats hunt by stealth, delivering a death blow with a leaping pounce that can cover 10 feet.¹ Very rarely, they have been known to take down small deer, usually in the winter months when smaller game are scarce. Overall, the bobcat is important for keeping populations of rodents and rabbits under control.

Bobcat Habitats and Behavior

While they have been known to encroach on rural and suburban human populations, bobcats generally favor remote, rocky outcrops and heavily wooded areas. Bobcats are solitary animals, with rugged terrain, deep forests and caves serving as ideal dens and hunting grounds for this elusive cat. The home ranges established by bobcats tend to be large, and they guard them fiercely. While male territories will sometimes overlap, females won't share their space with other female bobcats.² An individual bobcat's territory can span up to 30 square miles for males and five square miles for females. These territories are clearly marked by the bobcat's urine and/or feces.

Unlike domesticated cats, bobcats enjoy the water and are very good swimmers. They have excellent vision, hearing, a well-developed sense of smell and an eerie cry that can be heard for miles.¹ Skilled climbers, bobcats easily maneuver around rocky terrain and are known to climb tall trees while pursuing their prey.

Breeding takes place in Spring, although bobcats will occasionally mate a second time later in the season. A litter of one to six kittens is born after a gestation period of about 50 days. Females choose a secluded den to raise their kittens, which remain with their mother for 9 to 12 months.² During this time, the young learn to hunt before setting out on their own.

Historically, populations of bobcats have been difficult to monitor because of their reclusiveness; traditional field survey methods tend to produce very low detection rates. However, new methods of detecting bobcats have been developed in recent years, including camera traps (automatic cameras), hair-snares, scent stations, and dogs trained to detect bobcat scats.¹

Physical and Chemical Restraint

In wildlife management scenarios, it is often necessary to chemically restrain animals to perform even the most basic procedures. This is certainly true when one is working with carnivores, even smaller species such as the bobcat. Considerations for the choice of restraint methods include the safety of humans and animals, environmental factors, as well as knowledge and preference.

Although physical restraint of native carnivores may be appropriate in some management and medical situations, it does affect animals in various physiologic and psychological aspects (i.e., stress). In relation to bobcats, physical restraint typically precedes an anesthetic procedure, in that bobcats are usually trapped prior to such procedures, rather than being darted.² Unlike many native species, bobcats will actually enter cage traps willingly; thus, this can be an effective capture method. According to some of the literature however, foothold traps remain the most effective method for trapping bobcats. More often than not, this protocol includes a visual attractor (such as a prey animal hide hung from wire), bait and a walk-through path created by rocks, sticks or other terrain that forces the cat to step into the foothold trap.³

As indicated earlier, most native carnivores—particularly large, wild, or fractious individuals, or those requiring extensive procedures or surgical manipulation—will require chemical restraint.^2,4 In these cases, pre-immobilization planning is essential for successful chemical immobilization. The use of drugs for restraint and immobilization is an essential part of the wildlife veterinarian's role in managing native carnivores; these drugs permit manipulative procedures that otherwise would be impossible to perform.

In selecting the appropriate immobilizing agent(s), there are several aspects to consider. An ideal restraint drug or formulation should have a high therapeutic index, be compatible with other drugs, have a short induction period, an available reversal agent, be stable in solution, be effective in small volumes, and can be administered intramuscularly. Anesthetic protocols that allow quick induction, short processing time, and rapid reversal are necessary for wildlife veterinarians performing minimally invasive procedures (including the attachment of radio collars and morphometric measurements).⁴

Ketamine hydrochloride, a dissociative anesthetic, has several advantages that justify its widespread use in wildlife immobilization and in veterinary medicine in general. The most significant are that it is effective on a large spectrum of species, it can be given intramuscularly, and it has a large margin of safety.³ However, when used alone, ketamine may present problems such as body rigidity due to muscular contraction, excess salivation, convulsions, vomiting and hyperthermia. These side effects may be counteracted by combining ketamine with muscle relaxants such as xylazine HCl, an α-adrenergic tranquilizer.

For the chemical immobilization of bobcats, the Handbook of Wildlife Chemical Immobilization (Arnemo & Kreeger, 2018) recommends tiletamine hydrochloride and zolazepam hydrochloride (Telazol) at a dosage of 10 mg/kg. This may be supplemented with ketamine at 5 mg/kg.⁵ Chemical Immobilization of Wild and Exotic Animals. (Nielsen, 1999) recommends the same formulation at dosages of 13.3 mg/kg.⁶ Inasmuch as the bobcat is a relatively small carnivore that can be safely monitored and released from a cage or other enclosure during its recovery, reversal agents are not deemed to be critical, as with larger wild cats.