Capture events carry inherent risks to wildlife regardless of species or the method of capture used. These risks are often more pronounced when dealing with larger species such as deer and other hoofstock in the field. Due to the reduced level of stress on wild animals resulting from chemical immobilization (as opposed to traps or nets) and the refinement of drugs over the years, this has become the preferred method of immobilizing wildlife for research, study and wildlife management.
Certain 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.
One complication that is often considered less critical than others, but which must be seriously addressed when it occurs, is that of wounds incurred during capture events. These can happen as the result of an animal 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 a deer 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.
There are approximately 40 species of deer around the world. 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.3
One exception to this rule is the Chinese water deer (Hydropotes inermis). This is a small Asian deer that is native to river valleys in Korea and the Yangtze River valley in China. It is the only species of deer in which both males and females lack antlers. Instead, bucks have long, curved upper canine teeth that protrude from the mouth and which may exceed two inches in length, resembling fangs. The Chinese water deer is also the only deer with inguinal lymph nodes.3
In their lack of antlers, Chinese water deer are often said to resemble extinct primitive deer, but evidence reveals that they probably evolved from ancestors with antlers that were subsequently lost. As such, their morphology indicates that they are New World deer (see above).4,5 Male Chinese water deer stand about 20 inches tall at the shoulder and weigh up to 30 pounds, while females weigh up to 25 pounds. The lifespan of the Chinese water deer is 10 to12 years.
Chinese water deer have a uniformly colored medium-brown coat; their tails are short, and they lack a rump patch. The coat is coarse and thick, and they have fur-covered ears, which are adaptations to the cold, snowy winters of their native region.6 The hind legs of the Chinese water deer are powerful and longer than the front legs. As a result, the haunches are higher than the shoulders, which gives them a rabbit-like appearance when running.
Chinese water deer are herbivores; they are selective feeders that take small morsels from nutritious plants, especially herbs, but may take grasses and other flora if food is limited. They are most active during the mornings and evenings, usually looking for food in pairs or alone.While the Chinese water deer’s native range is China and Korea, they can now be found in the United States, Argentina, the United Kingdom and France. They were first kept in zoos in the United Kingdom in 1873, but began escaping in 1929. Their numbers increased through introductions into deer parks and subsequent escapes; the British population now accounts for approximately 10% of the world’s total water deer population.7
Most injuries in Chinese water deer associated with capture events are experienced when an animal 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 a deer 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 in treatment. If the injury 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 may be used, as this 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.
Chinese water deer or any large animal 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
Given 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 Chinese water 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 Chinese water deer in most cases.