Wildlife Animal Sedation

The use and study of wild animals frequently involves physical handling and in some instances the performance of surgical or other stressful procedures. With few exceptions, the requirements for domestic species are typically those of pain relief and relaxation to provide patient comfort to and convenience for the surgeon.¹ Thus, sedation agents can be selected without much concern for excessive restraint of the animal before procedures take place.

The preparation of the wild animal for chemical restraint, sedation or anesthesia most often must be made without the benefit of a physical examination to determine physiological condition or specific needs. In many cases, the animal must receive the initial medication via propelled dart or other systems used from a point distant from the animal.²

Since it is difficult to measure preanesthetic responses in wild animals, attempts are often made to evaluate specific responses to certain medications in domestic animals and relate these to the gross responses seen in both domestic and exotic (wild) animals.¹

Non-Lethal Capture Methods

Traps are often used to capture individual animals or mass populations of wild animals; these are usually placed in areas where the target animals frequently visit, such as water holes. The traps are laid in a funnel shape where the animals are driven from large area leading it into the trap. Sometimes, food or live bait is kept near traps to attract predatory animals for capture. Even the opposite sex animal can also be used to attract the counterpart. In the case of animals in zoos, traps can be used in their feeding cell or night shelter.³

Nets can include varieties such as mist nets, drive nets, projection or cannon nets or bait nets. These can be used to capture aggressive or injured animals. Snares can also be used to capture problematic animals, but snares must be monitored so that as soon as the animal is trapped, it is immediately removed to prevent strangulation.²

Physical (manual) restraint methods have several limitations, however. Physical restraint often requires long-term planning, and it can be very expensive to perform physical capture in the wild (such as the hiring of helicopters and other vehicles for driving or chasing animals). Also, individual subjects from groups of animals cannot be tracked and anaesthetized individually using such methods. Thus, in these instances, chemical capture and handling is often a preferable method for immobilizing wildlife and zoo animals.

Chemical restraint is advantageous over physical capture because it allows examining and treating sick or injured animals or animals caught in snares or traps in the wild.² Remote Drug Delivery (RDD) has become an important tool for wildlife veterinarians and managers, allowing the safe delivery of medication and vaccines, while keeping capture stress to a minimum.¹

Drug Delivery Systems

The employment of remote drug delivery (RDD) methods represents a unique event, and there is no “one strategy serves all” solution.² Furthermore, remote drug delivery is a good strategy for individual capture. Depending on the project purpose, the species to be treated, the individual animal, the habitat, and its ambient influences, all must be accessed and implemented to develop an adequate strategy.

The reasoning behind the premise of less capture stress induced when using tranquilizer darts rests on the fact that the target animal a) will not know where the dart is coming from; b) cannot see nor smell a predator, and therefore; c) does not detect any immediate threat. A remote drug delivery system that utilizes compressed air or CO₂ gas is a very powerful technology that demands knowledge and requires extensive training to avoid injury to the animal. One must practice with different darts, distances and scenarios until familiar enough to be capable and competent to handle the projector.³

Remote drug delivery systems for long-distance wildlife management are one of the most reliable means of animal capture, causing a minimum of capture-related stress and the lowest risk of injury when used accordingly and competently.

These days, there are many immobilizing drugs available, and just as variable are the effects that they have, depending on the wildlife species and their sensibility to the agent used. Inasmuch as there is no one-drug solution for wildlife immobilization, each agent has its advantages and risks. Therefore, in modern chemical immobilization protocols, agents are often combined (associated) to maximize their individual strengths while minimizing their risks.

A big challenge in the field is determining the right dosage for the species. This is where the veterinarian’s experience will come into play. A good starting point is an average weight, reported from prior studies.² Which drug to use for chemical immobilization should be based on stringed protocols however, founded in thoroughly conducted research.

An anesthetic or sedation protocol should be carefully developed for a given species, considering environmental circumstances, the purpose of capture or procedures and the depth of anesthesia required.