Barasingha Deer Chemical Immobilization and Sedation

The capture and manipulation of wild deer is sometimes required for the purposes of research, conservation and wildlife management. Over the years, the development of less invasive procedures has allowed researchers, deer farmers, veterinarians and management personnel to obtain certain data without the need to handle animals. Some information, however, can only be obtained by capturing animals.¹ Additionally, individuals from among captive animal populations (e.g., on preserves, deer farms) must also be restrained and manipulated for physical assessment, medical treatment and areas of animal husbandry.

Advances in technology (e.g., global positioning system collars, heat sensitive transmitters, advanced physiological monitoring equipment) now allow detailed research on wildlife species such as deer, but still require the initial capture and manipulation of individual animals.² Live captures are also required in conservation biology for animal translocations, reintroductions or population restocking.

The Barasingha or “Swamp Deer”: Background

Deer are cloven-hoofed ungulates that typically have a compact build, long, slender legs and antlers in the males of the species. The deer family (Cervidae) is very large, and includes most of the species familiar in North America.³ Cervids are the second most diverse family after bovids, which include antelope, bison, buffalo, cattle, goats and sheep.⁴ Members of the deer family are found all over the world, except for Australia and Antarctica. Globally, there are over 40 species of deer.

The barasingha deer (Rucervus duvaucelii) is native to India and Nepal, and it is one of the most widely-recognized deer of the Indian subcontinent. It is extinct in both Bangladesh and Pakistan however, where it once roamed freely. Also called the swamp deer, it is found mostly in damp areas, such as reed beds and marshes. The name “barasingha” is derived from the Hindi words for “twelve ends”, referencing this deer’s antlers, which can have from 12 to 20 tines.

In the late 1960s, the numbers of barasingha deer in India decreased drastically due to hunting, habitat loss and disease. It was brought back from the verge of extinction over several decades through breeding programs and conservation practices. Habitat improvement and captive breeding led to a substantial increase in the population.⁴ Today, there are fragmented populations in central and northern India, as well as southwestern Nepal.² In the U.S., introduced populations may be hunted on carefully-controlled ranches and reserves.

The barasingha is a large deer, with some animals attaining an overall length of up to 71 inches (180 cm) and weighing up to 620 lbs (280 kg). Their coats are a medium-brown color, which darkens during the winter months. Some individuals have yellowish spots scattered over their coats, and fawns typically have light spots. The hair around the deer’s neck may be longer, forming a shaggy mane.^3,4

In the wild, barasingha deer have a number of natural predators, and they have an apprehensive, nervous manner as a result. Always on high alert, they emit a loud, barking call to signal danger; this warning is similar to the alarm call of the roe deer. Barasingha deer feed by day, but can also be found resting during the hottest times of the day. In the winter, large herds form, which dissipate during the summer into smaller herds composed chiefly of females and their fawns. During the summer, males live separately from females in small bachelor groups.³

Barasingha deer females are monoestrous, and usually give birth to a single fawn after eight months of gestation. Fawns are weaned at around six months, and the female is ready to breed again about a year after giving birth. Stags reach puberty at two years of age, and females reach puberty at 18 to 24 months.^3,4

Barasingha Deer and Chemical Immobilization

The capture of barasingha deer can involve the risk of mortality, as well as a reduction in survival probability or the injury of individual animals. Mortality is the most important factor when evaluating the relative safety of a capture methodology.^3,4 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 on barasingha deer 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 an animal’s stress levels compared to other techniques, thus decreasing the subsequent capture effects.⁶ This is one of the chief reasons why chemical immobilization has become the preferred capture method for large mammals.

Drugs Used for Chemical Immobilization

There are three classes of central nervous system (CNS) immobilization drugs that are used to sedate/anesthetize barasingha deer. Combinations of drugs from these classes are often used due to the synergistic effects produced and increased effectiveness. These drug classes include:

• 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 Barasingha Deer

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 drug delivery is usually carried out by approaching barasingha deer and shooting a dart from a helicopter, snowmobile, an off-road vehicle, or from the ground. While this significantly reduces stress compared to physical capture methods, it still impacts an animal’s stress levels. A frightened barasingha deer is likely to 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, because animals will be less frightened than if a noisy vehicle is used.

Analgesia will be required if a deer’s skin has been breached by anything larger than a hypodermic needle, and this includes biopsy instruments. Invasive surgeries should be conducted using general anesthetics with the animal at a surgical plane. Intraoperative analgesia that continues after recovery should also be provided.¹ For analgesic drugs, doses and frequencies of administration are more difficult to gauge, even with close clinical observation (for discomfort).⁷

Most of the opioid analgesics (buprenorphine, fentanyl, butorphenol, oxymorphone, etc.) will not be 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 Barasingha Deer

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, zoo or farm setting, because a chemically-compromised barasingha deer will be in danger of injury, predation and other hazards.

The duration of sedation or anesthesia will be influenced by the drugs used, the species or subspecies, age, sex, body weight, procedure performed and the amount of stimulus during the procedure. With consideration of all the factors that influence duration of sedation/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 In these cases, 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. 

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.^1,2

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 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 other exotic wildlife species.

Overall, the drug formulations currently available for immobilizing barasingha 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 barasingha deer.

¹Brivio F, Grignolio S, Sica N, Cerise S, Bassano B (2015) Assessing the Impact of Capture on Wild Animals: The Case Study of Chemical Immobilisation on Alpine Ibex. PLoS ONE 10(6): e0130957.
²Powell RA, Proulx G (2003) Trapping and marking terrestrial mammals for research: integrating ethics, performance criteria, techniques, and common sense. ILAR J 44: 259–276.
³worlddeer.org.
⁴animalia.bio. 
⁵animaldiversity.org. 
⁶Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed.
⁷Nielsen, L. Chemical Immobilization of Wild and Exotic Animals. (1999) Ames, Iowa, Iowa State University Press.
⁸Lance, W. Exotic Hoof Stock Anesthesia and Analgesia: Best Practices. In: Proceedings, NAVC Conference 2008, pp. 1914-15.