Chinese Water Deer Chemical Immobilization and Sedation

Deer are one of the most well-recognized and popular wildlife species in North America. One of the more unusual deer species is the Chinese Water deer (Hydropotes inermis). This is a small deer that is native to the river valleys of eastern China and Korea. Simply called “water deer” by many, these animals were initially introduced to zoos in England in the late 1800s. Some were deliberately released into surrounding woodlands in the early 1900s, and there have subsequently been numerous releases, translocations, and escapes in the UK.¹ Since then, water deer have also been introduced to numerous other countries, including the United States.

Chinese water deer are the only deer in which bucks (males) have no antlers; instead, they carry tusk-like canines. Slightly smaller than a roe deer, the Chinese water deer’s large, fluffy ears, black eyes and small black nose are said to give them a teddy bear-like appearance.² They favor wet, marshy habitat and are strong swimmers.

Chinese water deer are a light brown color and lack the white rump seen in other species of deer. Males typically 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.² 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.³

Chinese water deer seem to prefer wetlands adjoining woodlands, although they have been known to range onto nearby farmland. They typically feed on weeds, grasses, herbs and some browse, usually around dawn and dusk. Water deer do not form herds, but are seen either solitarily or in family groups of a doe with her fawns. Groups sometimes come together at choice feeding areas.^2,3

Chinese Water Deer and Chemical Immobilization

Wildlife management programs, research and conservation efforts sometimes require the capture and manipulation of Chinese water deer. The development of less invasive procedures over the years has allowed researchers, veterinarians and management personnel to obtain certain data without the need to handle animals. Some information, however, can only be obtained by capturing animals.⁴

Technological advances like global positioning system (GPS) collars, heat sensitive transmitters and advanced physiological monitoring equipment now allow detailed research on wildlife species such as water deer, but still require the initial capture and manipulation of individual animals.⁵ Live captures are also required in conservation biology for animal translocations, reintroductions or population restocking.

Captures of water deer can involve the risk of mortality, reduction in survival probability or injury of individual animals. Mortality is the most important factor when evaluating the safety level of a capture methodology.^4,5 In the case of mortality occurring during capture, this rate is easy to measure, while delayed mortality is much more difficult to determine.

The effects of chemical immobilization can differ greatly depending upon the capture methodology employed. The relevant published research agrees that captures by remote delivery of immobilizing drugs via darting lower a deer’s stress levels, thus decreasing the subsequent capture effects compared to other techniques.⁶ This is one of the main reasons why chemical immobilization has become the preferred capture method for large mammals like deer.

Drugs Used for Chemical Immobilization

There are three classes of central nervous system (CNS) immobilization drugs that are used on Chinese water deer:

• Opioids
• Cyclohexamines
• Neuroleptics

Opioids

• The most potent drugs available for immobilization
• Specific antagonists readily available
• Reduced volume of drugs are typically required
• The only class of drugs practical for remote immobilization of large animals
• Potentially toxic to humans

Cyclohexamines

• Also known as dissociative agents
• Produce altered consciousness
• Dissociate mental state from environmental stimulation.
• Retain many vital reflexes
• The animal cannot walk but can move tongue, blink, swallow
• The animal may feel some pain
• Should be used in conjunction with other drugs, such as neuroleptics

Neuroleptics

• Also referred to as tranquilizers
• Produce calmness and relaxation
• Do not cause loss of consciousness or alleviate pain perception
• Can cause death before they cause loss of consciousness
• Used in conjunction with other drugs (e.g., cyclohexamines)
• Common neuroleptics include zolazepam, diazepam, xylazine
• Common reversal agents include yohimbine, tolazoline

Chemical Immobilization Techniques for Chinese Water Deer

In a zoo or deer farm, less stress on animals is likely to occur than in the field, as these animals tend to be far more acclimatized to humans and procedures. In some cases, intramuscular hand injection can be used when working with captive animals that are cooperative, or those that have been cornered in squeeze cages or enclosures. When hand injecting, rapid delivery while minimizing risk to the handler or animal is essential. Pole syringes are may be used in these cases, since these afford greater distance than approaching an animal for a hand injection. Drug delivery by pole syringe requires manual injection follow through to administer the drug, as the handle is usually a direct extension of the plunger. As in the case of hand injection, larger bore needles should be used to ensure complete drug delivery.

Remote chemical immobilization is usually carried out by approaching water deer and shooting a dart from a helicopter, snowmobile, an off-road vehicle, or from the ground. While this can significantly reduce stress compared to physical capture methods, it still impacts an animal’s stress levels. A frightened animal will have an increased heart rate, as well as higher levels of cortisol and other stress-related biochemicals.^6,7 An approach from the ground tends to produce even lower stress levels in deer, because they will be less frightened than if a noisy vehicle is used. On the other hand, this is more difficult to accomplish, because it requires a closer approach with animals that are extremely alert, fast and agile.

If a water deer’s skin has been breached by anything larger than a hypodermic needle (including biopsy instruments), analgesia will be required. Invasive surgeries should be conducted using general anesthetics with the animal at a surgical plane; intraoperative analgesia that continues after anesthetic recovery should be provided in some form to every surgical patient.¹ For analgesic drugs, doses and frequencies of administration are more difficult to gauge, even with close clinical observation for discomfort.⁸ These observations can be even more difficult to make in the field than in a clinic, farm or zoo setting, compounding the difficulty in these assessments.

Most of the opioid analgesics (Buprenorphine, Fentanyl, Butorphenol, Oxymorphone, etc.) are not effective after 12 hours. Longer‐lasting, non‐steroidal anti‐inflammatory analgesics (NSAIDs) such as Meloxicam, Carprofen, Flunixin, Ketoprofen,etc. have longer durations of action than opioids, and can be administered in conjunction with opioids to increase potency of effect and duration of action.⁷

Reversal Agents for Chinese Water Deer

Whether sedation or general anesthesia has been used, reversal agents are often required to neutralize sedation or anesthetic agents, allowing animals to completely recover from being anesthetized. This is even more important in the field than in a clinic or zoo setting, because a chemically-compromised animal will be in danger of injury, predation and other hazards.

The duration of anesthesia will be influenced by the drugs used, species or subspecies, age, sex, body weight, procedure performed and the amount of stimulus during the procedure. Due to all the factors that influence duration of anesthesia, the literature maintains that anesthetic drugs should always be titrated to effect. If gas anesthesia (e.g., isoflurane) is being used, titration of anesthetic depth can be controlled almost immediately by adjusting the amount of anesthetic gas being administered to the animal. In addition, anesthetic duration can be extended for as long as the anesthetic gas is administered.⁶

Injectable anesthetics and sedatives (which may be used for less invasive or higher-risk procedures) however, do not have this flexibility. Once a dose has been administered, it cannot be “un-administered” to facilitate the end of anesthesia coinciding with the end of the procedure.⁸ Here, reversal drugs are used to bring about the desired effect.

Atipamezole is a synthetic α2-adrenergic antagonist. Developed to reverse the actions of compounds such as medetomidine and dexmedetomidine.

Naltrexone hydrochloride is an opioid receptor antagonist that is used in veterinary medicine to block receptors as a reversal agent for opiate agonists such as butorphanol. 

In recent years, great care has been taken with chemical immobilization protocols and drug development to keep these within safety margins through the use of novel anesthetics, including combinations of true anesthetics, neuromuscular blockers and tranquilizers.⁶ Thus, modern chemical immobilization techniques have dramatically reduced the side-effects of drugs and mortalities. Additionally, the use of antagonists to anesthetics is now widely employed, as this avoids the undesirable and potentially harmful effects of drugs and facilitates speedy recovery from chemical immobilization events.^4,5

In recent years, veterinary custom compounding pharmacies have widely expanded the variety, availability and efficacy of immobilizing drugs through the development of custom formulations for wildlife such as water deer.

One such formulation is the MKB2™ Kit, an original formulation containing:

• Medetomidine 20 mg/ml
• Ketamine 100 mg/ml /
• Butorphanol 50 mg/ml

The MKB2™ Kit also includes the reversal agents:

• Atipamezole 40mg/ml
• Naltrexone 50 mg/ml

The MKB2™ Kit was developed for the chemical immobilization of numerous large exotic hoofstock species. It is an excellent choice for anesthetizing elk, deer, fallow deer, white-tailed deer, roe deer and exotic wildlife species.

Overall, the drug formulations currently available for immobilizing deer and other large wildlife species have been refined to a degree that eliminates much of the risk that existed just a few years ago. With the right drug formulations, proper planning and safety precautions in place, experienced personnel can have the expectation of effective and incident-free chemical immobilization of Chinese water deer.