Safe Capture Chemical Immobilization
These days, a cursory web search will show that there are literally hundreds of safe capture chemical immobilization courses being offered in the U.S. alone. Typically sponsored by universities, zoos and wildlife management bureaus, these courses offer comprehensive instruction and continuing education in safe capture and chemical immobilization techniques to those in the field.
These courses are usually led by experienced wildlife managers and often, leading veterinarians in this field. The sheer number of courses being offered as well as their frequency give an idea of how prevalent the need is for such instruction, and how important it has become to the management of wildlife in developed nations and more exotic wildlife in other nations. In some cases, modules in safe capture chemical immobilization for domestic animals are included in such courses for animal control personnel, as there is some crossover in the procedures relative the safe capture of domestic animals that can pose potential dangers to the public.
The Need for Safe Capture Chemical Immobilization
Many situations are encountered in the field where the capture and restraint of free-ranging wildlife is required. Improved understanding of the margins of safe capture, chemical immobilization, and handling of free-ranging animals for research and management has been a function of the documentation and examination of efforts involving various species, study designs, and environmental conditions.1 The capture of free-ranging animals is an important foundation of wildlife research. Minimizing harm, especially mortality, is a principal ethical concern therein. Injuries or mortality are an inherent risk in capture and chemical immobilization, and often requires adjustments to accepted techniques.
In order to limit the potential for harm to animals, many jurisdictions have developed formalized training and ethical guidelines for capture and chemical immobilization of wildlife. However, training cannot replace real-time field experience and handling of animals, since it is through experience in the field that veterinarians and wildlife managers have been able to minimize injuries and mortalities to animals by making proactive adjustments to standardized capture protocols.
Ungulates are the most common large mammals captured by wildlife biologists, and special care in the capture of these animals is often needed due to the high potential for injury due to excitability and lengthy handling times.1 Ungulates are members of a diverse class of large mammals with hooves. These include horses, rhinoceroses, cattle, pigs, giraffes, camels, sheep, deer, hippopotamuses and dozens of others. Carnivores commonly captured for study and relocation in North America include bobcats, mountain lions, wolves and bear.
Physical Restraint of Wildlife
The physical restraint of wildlife is appropriate for simple procedures such as physical examination, injections, venipuncture, etc. Physical restraint should only be performed by operators who are familiar with the normal behavior patterns of the species that is to be restrained, and the duration of procedures should be kept to a minimum. Appropriate restraining devices may be required to avoid injury to animal and handlers. Physical restraint techniques should be evaluated ahead of time to determine if the attendant stress on the animal is justified.
Catchpoles (or snare poles) are among the most versatile tools used to capture and restrain animals. These are very often used in the capture of domestic animals by animal control personnel. A catchpole is a long stick with a cabled loop at one end. For most species, the loop is placed over the animal’s head and then tightened to hold the animal. Unfortunately animals like Bobcats and even feral domestic cats can accidentally suffocate if the loop is placed around their necks.3 Some catchpoles swivel, allowing the animal to twist without being suffocated. Commercial catchpoles often lock once the cable has been secured, and also have a quick-release. Catchpoles also require that the handler is in relatively close proximity to the animal, which is often impractical.
Live traps (leg or cage traps) are effective devices for capturing many species. In addition to stress, these carry both advantages and disadvantages. These tend to limit the risk to human captors, and if chemical immobilization is required, it tends to be a fairly simple matter when an animal is already trapped. Unfortunately, live trapping is labor-intensive, and the wrong animal can be trapped. If a live trap is used improperly, an animal may die in it from lack of food or water, exposure to heat during the summer or weather extremes. Some animals can injure themselves because of the stress of being restrained, or while trying to escape. Traps are often impractical in the case of trapping larger animals.
Nets are also often used in the physical restraint of wildlife. Two common designs are the throw net and hoop net. Throw nets are tossed over the target animal or fired as a projectile via a custom-made or commercial apparatus (e.g., net-gunning). Hoop nets are attached to the end of a long handle, and are basically used to scoop up the animal. Disadvantages include a captured animal climbing out of a shallow net.
In some cases, a combination of physical and chemical restraint of wildlife is required. This may involve the initial trapping, netting of an animal, after which chemical restraint is administered in order to quiet the animal and reduce the risk to handlers before procedures are performed.
Chemical Restraint of Wildlife
Chemical capture is the use of anesthetic drugs to immobilize an animal. Humans have been using chemical capture for hunting for thousands of years. Indigenous people on several continents have utilized blowpipes made from native plants to fire darts at the animals they hunt. Dipping these wooden darts in naturally-occurring paralytic drugs gave hunters the ability to more effectively hunt their prey.
While chemical restraint is designed to keep animals safe from injury and also to keep them calm during procedures, early drugs had significant drawbacks. In the past, the safety margin to the animals was very narrow and miscalculating the dose could very easily cause an animal’s death. In the 1960s, biologists had a significant breakthrough when a mixture of morphine, hyoscine, and various tranquilizers was pioneered for use in the chemical restraint of wildlife.3 This new mixture was much safer for the animals. The most recent major advance in chemical capture and chemical restraint for transporting wildlife has been the adoption of long-acting tranquilizers normally used for humans. These drugs have significantly reduced the numbers of animals that perish during long-distance transportation while in captivity, and following introduction into new habitats. Veterinarians and wildlife managers anticipate that progress will continue in both drug development and in delivery equipment.
In terms of administration, it is important to choose a drug delivery system that will deliver the appropriate volume of drug with the minimum amount of physical trauma to the animal. Hand-held injection requires an animal to be physically restrained before administration, while remote drug administration systems do not. There are four basic types of remote drug delivery systems, including pole syringes, blow pipes and dart pistols. The latter are more accurate and have a range of approximately 20 meters, but their greater power represents an increase in the risk of danger to the animal.
The fourth method is darting with rifles, a procedure which has becoming prevalent in the case of large ungulates and carnivores.2 Often, this involves the use of motor vehicles or helicopters to approach the animal; this allows for access to areas that would otherwise be impractical or pose inordinate danger to humans. Benefits of this approach are relatively low capture stress relative to other methods, ability to select specific individuals, and its utility in dense cover. Drawbacks to this method can include drug-induced decreases in respiratory and thermoregulatory abilities.3
1DelGiudice, Glenn D., et al. Understanding Margins of Safe Capture, Chemical Immobilization, and Handling of Free-Ranging White-Tailed Deer. Wildlife Society Bulletin (1973-2006), vol. 33, no. 2, 2005, pp. 677–687
2Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
3Nielsen, L. Chemical Immobilization of Wild and Exotic Animals. (1999) Ames, Iowa, Iowa State University Press.
About NexGen Pharmaceuticals
NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.
Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.
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