Wounds in Deer During Capture and Chemical Immobilization

Whether using traps or drugs, capture events carry inherent risks to wildlife regardless of species. These risks are often more pronounced when dealing with larger species such as deer and other hoofstock in the field. During capture/chemical immobilization, these risks include such complications as capture myopathy, aspiration, dehydration, hypothermia, hyperthermia, respiratory depression and/or arrest and cardiac arrest.

Due to the reduced level of stress on wild animals resulting from chemical immobilization (as opposed to traps) and the refinement of drugs over the years, this has become the preferred method of immobilizing wildlife for research, study and wildlife management. Some of the listed complications can still come about as the direct result of chemical immobilization however, either due to inadvertent overdose, comorbidities or latent sensitivities in individual animals.

A complication that can be considered less critical than others, but which must be seriously considered, is that of wounds incurred during capture events. These can occur as a result of a deer attempting to flee prior to immobilization, as it loses physical coordination during take-down after darting or, rarely, from the darts themselves.¹

Physical injuries are one of the most common threats to wild deer. In some cases, animals can incur severe injuries that kill them directly. In other cases, their injuries can affect them in ways that are indirectly fatal. Aside from human-related causes, these can come about as a result of myriad events, such as evading predators, fighting for mates or territory and accidents. Even when an animal doesn’t die as a direct or indirect result of an injury, it can be left in a permanently compromised state or with chronic pain.²

When an animal suffers a wound during capture/chemical immobilization, ethical imperatives dictate that those undertaking the required research or wildlife management protocols make every effort to ensure that the animal is promptly treated so that it can make as complete a recovery as is possible.

Deer Basics

There are approximately 40 species of deer spanning the globe. While most of these are found in Asia, deer remain one of the most popular big game species in North America. Deer occur on all of the continents except Australia and Antarctica, although many species have been introduced outside of their original habitats as game animals. In all save one species of deer, only the males carry antlers; in the reindeer or caribou (Rangifer tarandus), both sexes have antlers.⁴ Antlers are usually branched and serve as sexual ornamentation as well as weapons during the mating season.

Deer are known as cervids (family Cervidae), and belong to the order Artiodactyla, which (like various antelope species) are hoofed mammals with an even number of toes on each foot. They are also members of the suborder Ruminanti; so, like cattle, they are ruminants, or cud-chewing plant-eaters. Thus, deer have a four-chambered stomach; the rumen (the first chamber) stores undigested food that is later regurgitated back into the mouth, where it is chewed and swallowed a second time.^3,4

There are seven species of deer that are native to North America, with numerous sub-species. They range from northern Canada through Central America, and from the east coast of the North American continent through the west coast.

Deer are considered specialized herbivores, typically feeding on young grasses, herbs, lichens, foliage, buds, aquatic plants, woody shoots and fruit. They rely little on coarse, fibrous grasses, since they have not evolved a digestive system comparable to those found in bovids.³ The deer’s preference for high-quality food is believed to have its origin in the high demands of antler growth for minerals, protein, and energy.³ Other distinguishing characteristics of deer include scent glands and lack of a gallbladder.⁵

Treating Wounds in Deer

Most deer injuries connected with capture events are experienced when a deer attempts to flee human pursuers,¹ and the most common injuries suffered are lacerations. While remote drug delivery via the dart itself is unlikely to result in a serious injury, darting can on occasion result in minor lacerations. Finally, in some cases an animal may need to be immobilized specifically for the treatment of a serious wound it has suffered due to other causes.

Cleaning the wound is the first step. If it is a small, shallow laceration, this can be done by flushing with a commercial povidone-iodine or other scrub solution. More serious wounds can be flushed with povidone-iodine diluted with saline, and should generally not be sutured to allow for drainage.¹ The literature recommends high volume, high-pressure irrigation unless the tissue is very delicate. The suggested lavage volume is 50 to 100 mL of fluid per centimeter of wound area.

Low-pressure irrigation is gentle to tissues and does not force bacteria deeper into the wound, but it does not debride as well as high-pressure irrigation, which can be performed with a pressurized fluid bag or a large syringe with an 18-gauge catheter.² For suturing more superficial wounds that have been cleaned, a veterinarian should perform the procedure.

Deer receiving lacerations prior to or during an immobilization event should receive systemic antibiotics to reduce the likelihood of infection. Procaine penicillin G combined with benzathine penicillin G is a common formulation is these instances. Long-acting oxytetracycine is also frequently used to treat hoofstock that have suffered lacerations.²

Considering the risks associated with chemical immobilization, there is no way to guarantee that injuries will not occur, particularly under field conditions. The drug formulations currently available for immobilizing deer and other wildlife have been refined to a degree that eliminates much of the risk that existed years ago, however. With the right drug formulations, proper planning and safety precautions in place, capture teams can have the expectation of effective and incident-free chemical immobilization of deer in most cases.