Hypothermia and Hyperthermia in Dromedary Camels During Chemical Immobilization

There are two main species of camel; the Bactrian camel (Camelus bactrianus), and the dromedary camel (Camelus dromedarius). All camels are camelids, the family that includes camels, alpacas and llamas. They are members of the biological family Camelidae, and the only family in the suborder Tylopoda.¹ While camels are ruminants like cattle, they differ from other ruminants in some significant ways: 

• They have a three-chambered digestive tract rather than a four-chambered one.
• Their upper lip is split in two, with each part being under separate muscle control. This adaptation allows camels to forage for tough plants that are inaccessible to other species.
• They have an isolated incisor in the upper jaw.
• Their red blood cells are oval shaped, which helps to facilitate their flow when the animal is dehydrated.
• Their red blood cells are also more stable in order to withstand high osmotic variation without rupturing when these animals drink large amounts of water (sometimes up to 30 gallons at one sitting).^2,3

The ancestors of modern camels are believed to have evolved in North America, later spreading to Asia and subsequently becoming extinct in North America.¹ Camels were first domesticated beginning approximately 3,500 years ago. While nearly all camels existing today are domesticated, there are still populations of wild Bactrian camels (C. ferus) in their native range in central China and Mongolia.

Dromedary camels have been so widely domesticated that wild dromedary camels are generally understood to be extinct. Their original native range includes northern Africa, the Middle East and western Asia. Dromedary camels have a long neck, a deep chest and a single hump, as opposed to Bactrian camels, which have two humps. The hump is composed of fat and fibrous tissue, which allows the camel to store energy when food is scarce.¹

The dromedary camel has a number of unique adaptations that suit them to living in the desert. A double row of long eyelashes protects their eyes from blowing sand and dust. During sandstorms, they have the ability to close their nostrils to prevent sand from entering the nose and throat.² They are also able to conserve water in a variety of ways. Camels are able to fluctuate their body temperature throughout the day, which allows them to conserve water by not sweating as the ambient temperature increases.³

Since camels can carry more weight than horses or donkeys, need less water and are able to thrive on tough desert plants, they have been long valued as pack animals. Camels were used extensively to carry cargo on the Silk Road, the network of routes used by traders between Europe and Asia for many centuries. Dromedary camels were used primarily on western Silk Road routes, while Bactrian camels were used in the colder areas of Central Asia, Mongolia and China.²

In the 1840s, dromedary camels were introduced into Australia to assist in the exploration of the inland continent. Today, there are over one million feral camels in the rangeland ecosystems of Australia. Unfortunately, these animals are causing significant damage to the natural environment. Modern control methods include using radio-collared camels to enhance population control programs, which involves immobilizing individual camels. This procedure carries the risk of giving rise to a variety of complications in the immobilized animals.

Hypothermia and Hyperthermia in Dromedary Camels

Even considering the high level of domestication of dromedary camels and their agreeable nature when it comes to handling, their capture can be a stressful event which has the potential to cause capture-induced hypothermia or hyperthermia. Either of these complications can result in morbidity or mortality. The severity of the capture-induced hyperthermia has been associated with the likelihood of organ damage, alterations in electrolyte balance (possibly leading to dehydration and/or cardiac events), increased oxidative stress and death.⁴ It has also been called one of the primary indications for the development of capture myopathy, a potentially fatal complication of capture.

The mechanisms underlying the increase in body temperature during capture-induced hypothermia and hyperthermia are not fully understood, but the sympathetic stress response appears to be a factor. Even with animals engaging in low levels of activity during capture with mild ambient temperatures can develop severe hyperthermia.⁵

Thermoregulation in Dromedary Camels

The normal temperature of a dromedary camel at rest varies from about 34°C to more than 40°C.⁷ Due to the harsh environments that camels occupy, they have evolved with a unique ability for thermoregulation. This is referred to as adaptive hypothermia, or an ability to cool their bodies to avoid hyperthermia. It has been observed that male dromedary camels in rut have cooler body temperatures in the beginning of the day, which may be a factor in reproductive success.⁸ It is not known if Bactrian camels display the same adaptation.

In summer, the dromedary camel’s daytime body temperature variations when deprived of drinking water may exceed 6°C, but in animals with access to water, the variations are similar to those found during other seasons.⁷ These wide variations in temperature are tolerated by the camel, whereas in other animals, if body temperatures exceed more than 2 to 3 degrees higher than lower than the norm during an immobilization event, there is cause for concern.

Preventing Hypothermia and Hyperthermia in Dromedary Camels

Monitoring body temperature should always be standard procedure during all anesthetic events involving dromedary camels. While hypothermia is more common in small animals because of the large surface area-to-volume ratio, instances of both hypothermia and hyperthermia have both been reported during the capture of camels. Some of the drugs used in chemical immobilization are known to suppress normal thermoregulatory mechanisms, thereby potentially causing hypothermia or hyperthermia. Hyperthermia however, is also common immediately after the immobilization of both captive and free-ranging hoofstock due to excitement and struggling after being darted.^9-10

Intubation has been widely recommended for any anesthetized camel that needs to be transported or anesthetized for greater than twenty minutes,⁴ and monitoring core body temperature is essential in camel anesthesia.⁹ Until the more recent use of formulated drugs (e.g., combinations of α2-agonists such as medetomidine, detomidine, xylazine and their reversal agents), opioids were the mainstay of camel anesthesia in wildlife and captive care.¹⁰

Treating Hyperthermia in Dromedary Camels

Physically cooling captured camels is one method that is widely recommended for improving their chances for survival during chemical immobilization. Thus, handlers in the field should be prepared for this contingency and have the proper equipment on hand. Physical cooling has been known to be highly effective even when capture-induced hyperthermia in a camel is severe.

Recommendations for cooling captured camels include placing the animals in the shade and dousing them with water using portable mist sprayers, followed by rapid intravenous (IV) fluid therapy.⁹ In animals with body temperatures greater than 41°C, the use of cold water enemas and intravenous infusion of cold Ringer’s lactate has been recommended.¹⁰

Ice packs have also been reported to restore the body temperature of hyperthermic animals to pre-capture levels.⁹ Since carrying water is far less cumbersome and difficult than transporting and maintaining ice-packs in the field however, the literature recommends that water-dousing is the most practical and effective first intervention for cooling an camel with capture-induced hyperthermia.

Treating Hypothermia in Dromedary Camels

Hypothermia during anesthetic events is a common adverse effect of anesthesia in many species. Smaller animals tend to be more susceptible to hypothermia during anesthetic events, but large hoofstock and even carnivores can be affected.¹⁰The availability of thermal support (e.g., external heating devices) during and after anesthesia can dramatically improve outcomes in the event of hypothermia during or after a procedure. Handlers should be mindful that the time of recovery from anesthesia will be longer in case of injectable anesthesia rather than inhalant anesthesia.

In addition to abnormally low body temperature, signs of hypothermia in dromedary camels can include:

• Shivering
• Stiff muscles
• Pale or gray gums
• Fixed and dilated pupils
• Low heart and breathing rate

Shivering may be the only outward symptom of mild hypothermia. As hypothermia increases in severity, some of the other listed symptoms can become evident. The camel’s vital signs are likely to become increasingly erratic as its body goes into heat conservation mode.⁹ At this juncture, its body is trying to keep its vital organs from shutting down by restricting the blood flow from other parts of the body.

Water bottles filled with warm water and placed around the camel’s body can be used to reverse hypothermia. External heating devices may also be used, although some of the literature states that heating pads should be used with care, as it is easy to burn an animal’s skin.¹⁰ Returning the camel to a warm environment (if possible) and/or using heat lamps (if available) can also be helpful.