A tranquillizer gun (also spelled tranquilizer gun or tranquilliser gun), capture gun or dart gun, is a non-lethal air gun often used for incapacitating animal targets via drugs usually referred as tranquilizers. These guns shoot darts with a hypodermic needle tip, filled with a dose of tranquilizer solution that is either sedative, comatosing or paralytic, which once injected will temporarily impair the target's physical function to a level that allows it to be approached and handled in an unresisting and thus safe manner. Tranquillizer guns have a long history of use to stun wildlife when they are in a place where they pose a threat to others and themselves without having to kill the animal, or used to capture wildlife risking serious injuries to both the hunter and the target. They are also used for recreation, which animal rights groups protest against. Tranquillizer darts can also be fired by crossbow or breath-powered blowgun.
For thousands of years various peoples have used poisoned arrows (for example tipped with curare), to incapacitate animals before killing them, but the modern tranquillizer gun was invented only in the 1950s by New Zealander Colin Murdoch. While working with colleagues who were studying introduced wild goat and deer populations in New Zealand, Murdoch had the idea that the animals would be much easier to catch, examine, and release if a dose of tranquillizer could be administered by projection from afar. Murdoch went on to develop a range of rifles, darts, and pistols that have had an enormous impact on the treatment and study of animals around the world.
The first modern remote drug delivery system was actually invented by scientists at the University of Georgia in the 1950s, and was the direct predecessor to the Cap-Chur equipment used worldwide for decades.
In Kenya in the early 1960s, a team headed by Dr. Tony Pooley and Dr. Toni Harthoorn discovered that various species, despite being of roughly equal size (for example, the rhinoceros and the buffalo), needed very different doses and spectra of drugs to safely immobilize them.
The dart, usually .50 caliber (12.7 mm), is essentially a ballistic syringe loaded with an immobilizing drug and hypodermic needle and is propelled from the gun by means of compressed gas. In flight, the dart is stabilized by a tailpiece, a tuft of fibrous material, making it behave somewhat like a badminton shuttlecock. The same syringe design may be used interchangeably in certain blowguns. The needle may be plain or collared; a collared needle has a barb-like circumferential ring that improves retention of the needle and syringe for recovery and to assure that the full dose is administered.
There are several methods of powering fluid injection once the dart strikes its target. These include expansion of compressed gas, creation of gas by chemical fluid reaction, release of a compressed spring, and creation of gas by explosive charge . For example, a design with compressed air or butane in the rear of the dart creates constant compression on the injection fluid. The fluid is restrained within the syringe by placing a gasket-like collar or cap over the hole in the needle. Upon striking the target, the cap is punctured by the needle or the collar is pushed back, and the needle tip continues into the target. At the same time, the fluid is no longer restrained by the gasket, so the compressed gas chamber forces the injection fluid chamber to empty into the target (see diagrams from Veterinary Technician). It has also been suggested that the momentum of a steel ball at the rear of the dart could push the syringe plunger in some designs. In each of these methods, intramuscularly injects carries a dose of barbiturate or other sedative drugs into the animal. The tranquilizer drug causes the target to become sleepy and suddenly unconscious within 45 minutes. Because of the power of the drugs, the handlers then have to move quickly to secure the animal for transport, monitor its vital signs, protect its eyes and ears, and then inject antidotes when needed. Many large animals are acutely sensitive to stress and can easily die without careful treatment; in order to counter stress in targeted animals, the gun is quiet, and there is usually a valve on the gun to control the dart velocity by varying the amount of gas pressure used to propel it.
Several immobilizing drugs have been devised for use in tranquillizer darts. These include:
- Combelen (Bayer)
- Domosedan (Farmos)
- Dormicum (midazolam) (Roche)
- Detomidine (Farmos)
- Fentanyl and Carfentanyl (Janssen Pharmaceutica)
- Etorphine hydrochloride (M–99, Novartis)
- Haloperidol (Kyron Laboratory)
- Haldol (Johnson & Johnson) contains haloperidol and inactive ingredients.
- Immobilon, a mixture of etorphine and a phenothiazine tranquillizer such as acepromazine or methotrimeprazine.
- Valium (diazepam) (Roche)
- Xylazine (Rompun, Bayer)
- Sodium Thiopental (Abbott)
Military and police use
Tranquillizer darts are not generally included in military or police less-than-lethal arsenals because no drug is yet known that would be quickly and reliably effective on humans without the risks of side effects or an overdose. This means that effective use requires an estimate of the weight of the target to be able to determine how many darts (if any) can be used. Shooting too few would result in partial effects only, while too many can kill the target. According to James Butts, former Chief of Police of Santa Monica, "Tranquilizing agents don't affect everyone uniformly. Therefore you cannot predict whether or not you have a sufficient dose to tranquilize the individual. Second, any tranquillizer will take time to enter the bloodstream and sedate the individual. If someone is advancing on you with a deadly weapon or a threatening object, there's no way a tranquillizer would take effect in the two to three seconds it would take someone to seriously injure you."
- What is chemical capture? Archived 2006-04-26 at the Wayback Machine
- Anaesthetics also used in dart guns Archived 2009-10-06 at the Wayback Machine
- NZ Edge Heroes biography of Colin Murdoch
- Bush, Mitchell (1992). "Remote Drug Delivery Systems". Journal of Zoo and Wildlife Medicine. 23 (2): 159–180. JSTOR 20095205.
- Chancey, Erin. "Remote Injection Systems". VetFolio. Retrieved 31 Dec 2018.
- Tranquillizer agents Archived April 26, 2006, at the Wayback Machine
- Van Buren, Abigail (8 June 1997). "Tranquilizer Guns Could Do More Harm Than Good". Chicago Tribune. Retrieved 17 July 2017.