What is Used to Capture Animals?
Every year, millions of wild animals are captured as part of damage and disease control programs, population regulation activities, wildlife management efforts, and research studies.1 Many areas of animal capture—particularly those associated with protected or endangered wildlife species—are closely regulated by both state and federal governmental agencies in the U.S., and national, provincial and state regulations related to animal capture can vary widely. Regardless of the reasons for capture, ethical (animal welfare) concerns remain highly important. Thus, the efficiency of animal capture protocols, devices and systems are critical aspects of wild animal capture.
Successful capture programs result from the efforts of wildlife biologists, wildlife managers and veterinarians who plan, create, study and test methods prior to their implementation. Licenses and permits, as well as specialized training can be required by government agencies for personnel engaging in animal capture. Institutional Animal Care and Use Committees (IACUCs) are mandated for universities and research institutions using animals for research by the Animal Welfare Act (administered by the U.S. Department of Agriculture), which determine whether scientists have ensured that pain and distress are being minimized by the techniques used.2
Animal Capture: Equipment and Devices
There are numerous methods for capturing wild animals, and a myriad of devices that are used, depending on such things as the reason for capture, the target species and its physiological parameters, geographic area and other determinants.
Trapping involves the use of mechanical devices that capture animals without the trapper being present. Trapping is one of the most common and effective methods that landowners and some wildlife managers use for managing wildlife damage. There are both live traps (which trap the animal alive, the intent being to keep it alive until it can be retrieved) and lethal traps (which are designed to kill an animal when triggered). Cage traps (which have walls made of wire mesh) and box traps (which have solid walls made of wood, plastic or metal) are types of live traps.1 These typically have either gravity doors (the door falls due to gravitational force when the trap is sprung) or spring-loaded doors (the door closes with the aid of a spring when triggered). Box and care traps come in many configurations; some are designed with numerous compartments to capture multiple animals. Trappers usually exploit an animal’s sense of smell by baiting traps with food items, doing so in such a way that the odors of the bait have an opportunity to disperse into the air.2 Manufacturers produce cage traps for homeowners (retail grade) as well as professionals, such as wildlife management and animal control personnel.
Live traps for birds are also available in many designs and configurations, with many being similar to cage traps.1 Most are designed to capture particular species of birds. Some will capture one bird at a time, while others can capture many birds. Mist nets had been used by Japanese hunters for nearly 300 years to capture birds, and were introduced in the U.S. in 1947.3 Mist nets are often used by hunters and poachers, but they are also used by biologists to capture wild birds and bats for banding or other research projects. Mist nets are typically made of nylon or polyester mesh suspended between two poles (resembling a volleyball net apparatus), and the mesh size of the netting varies according to the size of the target species. When properly deployed, mist nets are nearly invisible.
Foothold traps are mechanical devices consisting of a pair of metal jaws designed to capture animals by gripping an animal's foot once triggered. Leg snares (or leg-hold traps) are designed to restrain an animal with a looped wire. These are used primarily on foxes, coyotes, raccoons, wolves, lynx, and bobcats. These traps are placed in areas where animals are known to frequent. Cable restraints are devices that are similar in appearance to snares and are designed to capture animals in a manner that holds them relatively unharmed and alive until the trapper returns.4
Due to concerns over the humane treatment of animals, foothold traps, leg snares and cable restraints have given rise to some controversy. As a result, they are illegal in some U.S. states, and tightly regulated in others.
Killing animals via the use of lethal traps is typically not employed for most of the above listed purposes (such as general wildlife management or research). In most cases, these methods are reserved for the most extreme circumstances, such as disease outbreaks or cases of extreme infestation of nuisance animals, such as rats. Body gripping traps (also called conibear traps) are a type of lethal trap. These are traps that are triggered when an animal attempts to go through the trap. These come in a variety of sizes, and are widely used by landowners (e.g., farmers, ranchers) and animal control personnel in cases involving nuisance animals.2
Wildlife Capture: Chemical Immobilization
The chemical immobilization of wild animals is a form of veterinary anesthesia that is often used as a primary method in the capture of wild animals.5 Historically, chemical immobilization can be traced back to certain tribes from South America who used curare-coated arrows in their quest for food. Though this method was effective and curare derivatives were used for many years, an effort began in the late 1950s by wildlife managers in South Africa to develop new and more efficacious methods to immobilize animals for research.6 Since then, a great deal of progress has been made in developing new drugs and techniques for delivery. Due to constant changes in restraint techniques, equipment and even immobilization drugs, chemical wildlife capture has improved over the past few decades.
Restraining an individual animal often requires the use of anesthetic drugs to allow a safe and efficient immobilization prior to handling. Anesthesia plays an important role in wildlife veterinary medicine, since the majority of the procedures carried out involve chemical restraint techniques. Preventive medicine, surgery, imaging and anesthesia itself are the key interventions carried out on wildlife. Each time an individual animal is immobilized, any number of procedures may performed on the animal to take advantage of the immobilization, depending on need and circumstance. Wild animals may be immobilized for relocation purposes, bio-measured, ear-tagged, implanted with a microchip, vaccinated, radio collared or even de-wormed. In certain instances, blood and hair collection may also be performed for DNA testing.5
For chemical capture, veterinarians, wildlife managers and animal control personnel administer anesthetic drugs to wildlife species, using different types of delivery systems. There are different approaches to administering drugs in chemical restraint procedures: oral, hand-held injection, pole syringe and remote delivery.7 If an animal is large, dangerous or unapproachable, remote delivery systems using blow darts, gunpowder explosive darts or compressed gas projectors are the most suitable choices. Animals are generally targeted either by personnel on foot, in ground-based vehicles, or from a helicopter.
Interested in learning more about safe capture? The San Diego Zoo now offers courses in safe capture techniques and best practices. Learn reliable, safe, and effective techniques for the species you work with and the scenarios you encounter!
3Low, S. H. (1957). Banding with mist nets. Journal of Field Ornithology. 28 (3): 115–128.
4usda.gov.
5West, G., et. al. Zoo Animal and Wildlife Immobilization and Anesthesia, Second Edition, John Wiley & Sons, Inc., July 2014.
6Williams, D. E. and Riedesel, D. H. (1987) Chemical Immobilization of Wild Ruminants, Iowa State University Veterinarian: Vol. 49 : Iss. 1, Article 6.
7Arnemo, J., Kreeger, T. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.
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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