Dehydration in Barasingha Deer During Capture and Chemical Immobilization

There are few wildlife species that are as well-recognized and iconic as deer, particularly in North America. Deer are hoofed mammals which belong to the order Artiodactyla; these animals are also referenced as cervids, as they also belong to the family Cervidae. There are over 60 species of deer that are recognized worldwide, and deer occur on all continents except Antarctica. These animals occupy a range of diverse habitats, from rainforests to temperate zones.

The barasingha deer (Rucervus duvaucelii), also known as the swamp deer, is a species that is native to the Indian subcontinent. In the late 1960s, the total population of barasingha deer was estimated at less than 3,800 individuals across India and Nepal. The losses leading up to the 1960s were due to overhunting, disease and the conversion of large grassland areas into cropland.²

Thus, the barasingha deer was considered an endangered species for many years. It was brought back from the verge of extinction over several decades through successful breeding programs and conservation practices.³ Today, there are large but fragmented populations in northern and central India, and the barasingha deer has been introduced into several countries.^1,2 In the U.S., this deer may be hunted on carefully-controlled ranches and reserves.

In its native India, there are three subspecies of barasingha deer:

1. Wetland barasingha (Rucervus duvaucelii duvacelii)
2. Hard-ground barasingha (Rucervus duvaucelii branderi)
3. Eastern barasingha (Rucervus duvaucelii ranjitsinhii)³

One of the noteworthy physical characteristics of the barasingha deer compared to other deer species in India is that its antlers have more than three tines. It is from this feature that the deer derives its name, which loosely translates into "twelve-horned" in Hindi. Mature stags often have 10 to 14 tines, and some have been known to sport up to 20.³

The barasingha is a relatively large deer with a shoulder height of approximately 45 inches and an overall length of nearly 6 feet. Stags weigh from 350 to 630 lbs., and females weigh from 290 to 320 lbs. Some larger stags have been reported as weighing up to 570 lbs.¹ The barasingha’s coat is woolly and yellowish brown with white spots along its spine. Its throat, abdomen, inside of the thighs and beneath the tail is white, and its coat becomes a brighter orange-brown color in summer. The females are a bit paler in color than males, and the young have faint spots.³

Barasingha deer are grazing animals, eating a diet of grasses and aquatic plants. During the day, they feed with peaks during the mornings and late afternoons. In India, herds comprise from 8 to 20 individuals; large herds may have up to 60 individuals. During the rut, barasingha deer will form large herds of adults. Their breeding season lasts from September to April, and fawns are born after a gestation period of 240 to 250 days in August to November.^2,3

Chemical Immobilization and Stress

The chemical immobilization of barasingha deer is sometimes required for medical examination, blood sample collection and animal identification, and the importance of performing such procedures for research and conservation projects is widely acknowledged.⁴ As these activities continue to become more common, the need to assess their negative effects increases in order to ensure ethical standards and the validity of research results. Research in this area has revealed that the physiological and behavioral effects of capture are as important as the direct risks of injury or death of an animal.²

There are a number of common stressors involved in the chemical immobilization of barasingha deer that can lead to complications during or after an immobilization (sedation or anesthetic) event. The overall health of the individual animal is also a factor affecting the potential for complications during and after immobilization.

These stressors fall into four categories:

• Physiological: Heavy exercise, hemorrhage, hyperthermia, shock, pain, infection
• Physical: Trauma/surgery, intense heat/cold
• Chemical: Hypoxemia, acid-base imbalance, anesthetic drugs
• Emotional: Anxiety, fear⁴

Chemical immobilization agents are represented by the third category, although elements of the other three are often factors in immobilization events. The physical stress of capture and/or attempts to escape during capture on the part of an animal certainly constitute physiological stress; surgical and even environmental conditions can bring about physical stress, and anxiety and fear are nearly always a component to some degree in a capture scenario.

The effects of acute stress during capture can include spikes in adrenaline, cortisol levels, heart rate, blood pressure, respiration, metabolic rate, blood glucose, lactic acid and body temperature, while bringing about a decrease in pH and a redistribution of blood within the organs. The effects of capture and anesthesia can activate the fight-or-flight response, HPA-axis activation, hyperthermia, respiratory depression (hypoxemia), lactid acid build-up, acidosis; in severe cases, this can lead to neurological/myocardial dysfunction, multi-organ failure, capture myopathy and death.⁵

Dehydration Risks in Barasingha Deer

Dehydration (a reduction of the body’s water content) is potentially quite dangerous in that it can lead directly to cardiac arrest. All animals require water to ensure their bodies are working properly. It is so important that essentially all bodily functions require it to remain operative. If an animal loses more water and electrolytes than it is taking in, it will begin to dehydrate and its health will quickly deteriorate.

Electrolytes are minerals that naturally occur in all animals, and they are essential for proper health. Electrolytes are comprised of sodium, chloride, and potassium, and facilitate the movement of nutrients into cells, aid in muscle function, and help regulate nerve activities.^4,5 An animal’s natural activities—breathing, urinating, and defecating, as well as simple evaporation—all cause it to lose fluids. When an animal eats and drinks, the lost water and electrolytes are replaced. If the animal’s fluid intake becomes less than what they are losing, dehydration will occur. This causes a reduction in bodily fluids that reduces blood flow and the delivery of oxygen to organs and tissues.

Understanding Dehydration in Barasingha Deer

To understand dehydration, an understanding of the distribution of fluid and water in the body is essential. Total body water (TBW) comprises approximately 60% of an animal’s body weight. Approximately 67% of TBW is found inside the body’s cells; this is referred to as intracellular fluid (ICF). The remaining 33% of TBW is the extracellular fluid (ECF), which comprises:

• Interstitial fluid, which bathes cells and tissues (~24% of TBW)
• Plasma, the liquid portion of blood, which constitutes most of intravascular volume (~8%–10% of TBW)
• Transcellular fluid, which comprises synovial joint fluid, cerebrospinal fluid, bile, and the fluid in the linings of the peritoneal cavity, pericardium, and pleural space (~2% of TBW)⁴

A simple approximate formula for the distribution of fluids in the body is the 60:40:20 rule:

• 60% of an animal’s body weight is water,
• 40% of body weight is ICF,
• 20% of body weight is ECF.^4,5

Dehydration can be caused by hyperthermia, chronic vomiting or diarrhea, excessive urination or wound drainage. Due to the stressful nature of capture and chemical immobilization events, they have been known to bring about dehydration. In both human and veterinary practices, IV fluids are usually often administered prophylactically, depending on the nature of the procedure. Veterinarians often provide fluid therapy to patients for many reasons, including correction of dehydration, expansion and support of intravascular volume, correction of electrolyte disturbances, and encouragement of appropriate redistribution of fluids that may be in the wrong compartment (e.g., peritoneal effusion).⁴

Each species of deer has its own anesthesia recommendation with intra-species variations of dosages because of diverse individual responses to anesthetic agents.^4,5 These variations are factors for the risk of dehydration in these species, and related factors (e.g., stress, venue, individual animal and field conditions) must also be taken into account. Prior to the development of novel drug formulations, some hoofstock species were known to be notoriously difficult to immobilize successfully.

Treating Dehydration in Barasingha Deer

Monitoring core body temperature is essential during the chemical immobilization of barasingha deer.⁵ During anesthetic/immobilization events, hydration status can be assessed using various tests. One of the easiest tests to perform is a skin tent test to check the turgor (moisture level) of the skin. To do this, the skin over the thorax or lumbar region is pulled away from the back. In a well-hydrated animal, the skin immediately returns to its normal resting position. If the tent formed remains standing, it is a likely indication of dehydration. If there is evidence of dehydration in a deer during a procedure, all administration of immobilizing drugs must be immediately suspended. Fluid therapy should begin in the form of lactated Ringer’s solution or 0.9% saline, IV, SQ or IP.⁴

Perioperative IV fluid therapy is very common in veterinary medicine and allows practitioners to restore intravascular volume, correct dehydration, and administer IV medications quickly.⁶ While perioperative fluid therapy under many field conditions may be impractical, fluids should always be available in the case of dehydration when chemically immobilizing deer.

¹worlddeer.org.
²animalia.bio.
³animaldiversity.org.
⁴Laricchiuta P, De Monte V, Campolo M, Grano F, Iarussi F, Crovace A, Staffieri F. Evaluation of a butorphanol, detomidine, and midazolam combination for immobilization of captive Nile lechwe antelopes (Kobus magaceros). J Wildl Dis. 2012 Jul;48(3):739-46.
⁵4rivio 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.
⁶Kreeger T., Arnemo, J., Raath, J. Handbook of Wildlife Chemical Immobilization, International Edition, Wildlife Pharmaceuticals, Inc., Fort Collins, CO. (2002).