Capturing the wild : overview of wildlife capture methods, immobilizing agents and challenges involved to captures in general

Wildlife capture is an event in which a wild animal is caught by a human. Reasons for wildlife captures vary: marking, collaring with a tracking device, disease surveillance, translocations related to conservation or commercial purposes, treating injuries and taking samples for research are some examples. Objective information about movement patterns and numbers of animals is needed for population management. Increased interest in disease monitoring and understanding the complex relationship between wildlife, people, domestic animals and environment has lead to a need for interdisciplinary approach to health issues, also known as ‘One Health’. Gaining information from wildlife by capturing them has an important role in health research of all species. Wildlife capture is often a complex event that should be carefully planned. Multiple non-chemical methods for capturing are available, such as traps, net-guns, drop-nets, drive nets or driving a group of animals into a corral. Chemical immobilization is usually done by remote delivery using a dart that injects immobilizing drugs to the animal. A large variety of drugs and drug combinations are used for wildlife captures. The animal species and previous research, equipment used and procedures that are supposed to be done during the capture are some of the main factors determining the type and length of anaesthesia needed, and therefore the specific drug combination preferred. When talking about wildlife captures, two essential terms are usually involved: immobilisation and anaesthesia. Immobilized animal is uncapable to move or its movement is more or less restricted by physical restraint or immobilizing drugs. General anaesthesia is a drug-induced state characterized by anti-nociception, suppressed reflexes and loss of consciousness of the animal. Certain drugs can be used to create anxiolytic (calming), sedative (mental calming) or narcotic (opioid analgesics induced sedation) effects, and these may also create a smoother induction, maintenance or recovery from general anaesthesia. There are multiple capture-related challenges and risks for both animals and humans involved. In the field unexpected events, such as sudden weather changes, injuries, failures of equipment, drug complications or accidental exposures, abrupt physiological reactions or getting infected by a pathogen from another species, can occur. Prevention is often easier that dealing with an accident or medical condition that has already happened. This literature review aims to explain briefly why and how wildlife is captured, and gives a concise overview about some issues that need to be considered before a wildlife capture. In the end a short insight on Finnish large carnivore captures is presented with reflections to methods used in several other countries