Deer are among the most well-known of the wild animals in North America, where there are around a half dozen species that are common, as well as other subspecies and non-native species. Deer are cervids (Family Cervidae), which differ from other ruminants in that males grow antlers that are comprised of bone. These are shed and regrown annually, and increase each year in size and intricacy. Except in the case of caribou (Rangifer tarandus), female deer do not grow antlers.
An exception to this rule is the Chinese water deer (Hydropotes inermis), in which neither the males nor females grow antlers. The Chinese water deer is a small deer that is native to the Yangtze flood plain in eastern China and Korea. Simply called “water deer” by many, they were introduced to England in the late 1800s;1 since then, they have also been introduced to numerous other countries, including the United States.
Chinese water deer are a medium-brown color and lack the white rump seen in other species of deer. Instead of antlers, the bucks (males) have tusk-like canines which protrude downward from the upper mandible. Slightly smaller than a roe deer, Chinese water deer are said to resemble teddy bears due to their large, fluffy ears, black eyes and small black nose.2Their name is largely derived from the fact that they favor wet, marshy habitat and are strong swimmers.
Male water deer stand about 20 inches tall at the shoulder and weigh up to 30 pounds, while females weigh up to 25 pounds. 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 gait when running.1
Chinese water deer prefer wetlands adjoining woodlands, although they will occasionally range onto nearby farmland. They typically feed on weeds, grasses and herbs, 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
Chinese water deer rarely congregate in herds, usually being found alone or in pairs. Their unobtrusive behavior and concealment in dense vegetation affords excellent protection from predation. To ensure their solitude, water deer bucks do not tolerate other animals of their sex in close proximity and defend their territories vigorously.
The rut for Chinese water deer is in December, when males fight viciously for females with their “tusks.” The marked aggressiveness of bucks towards one another increases even more during the mating season. If an opponent is defeated, he is pursued and driven out of the territory.1
Chinese water deer does typically give birth to 2 to 4 offspring after a gestation of 160- 210 days, although up to 8 fawns have been reported. Fawns are born from May to June. Although they are usually weaned after 3 months, fawns often remain with their mother into winter before dispersing in the spring.2
Capturing wild deer is a highly stressful event which has the potential to cause capture-induced hypothermia or hyperthermia, either of which can result in morbidity or mortality. The severity of the capture-induced hyperthermia has been associated with the likelihood of organ damage, rhabdomyolysis, alterations in electrolyte balance (possibly leading to dehydration events), increased oxidative stress and death.3 It has also been called one of the primary indications for the development of capture myopathy, a deadly complication.
The mechanisms underlying the fluctuations in body temperature during capture-induced hypothermia and hyperthermia are not fully understood, but one significant factor appears to be the sympathetic stress response. Even with animals engaging in low levels of activity during capture with mild ambient temperatures can develop severe hyperthermia.3,4
The average body temperature for most deer is 101.4°F (38.5°C), with 105°F (40.6°C) being the threshold for hyperthermia.7 When these exceed more than 2 to 3 degrees higher or lower than the norm during an immobilization event, there is cause for concern and intervention may be required.6 In the case of capture-induced hypothermia, outward signs may also be evident (see below).
When immobilizing water deer, the constant monitoring of body temperature is essential. Thermometers should be able to read over a wide temperature range; baselines and thresholds should be established before the capture so proper treatment can take place if body temperatures rise or fall to unacceptable levels.
Hypothermia is more common in small animals because of the large surface area-to-volume ratio, but instances of both hypothermia and hyperthermia have both been reported during the capture of all deer species. Some drugs used in chemical immobilization are believed to suppress normal thermoregulatory mechanisms, thereby causing hypothermia or hyperthermia. Hyperthermia however, is also common immediately after immobilization of both captive and free-ranging deer due to excitement and struggling while darting.3,4
Monitoring core body temperature is essential in all deer anesthesia,3,5 and intubation has been widely recommended for any anesthetized deer that needs to be transported or anesthetized for greater than one hour. 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 deer anesthesia in wildlife and captive care.3
One method that is recommended for improving the chances of survival for deer with extreme capture-induced hyperthermia is physically cooling captured animals. Recommendations for cooling captured water deer include placing the animals in the shade and dousing them with water using portable mist sprayers, followed by rapid intravenous (IV) fluid therapy.4 In animals with body temperatures greater than 41°C, the use of cold water enemas and intravenous infusion of cold Ringer’s lactate has also been recommended.3,4
Another recommended method for physically cooling animals is the use of ice packs, as these have been reported to help restore the body temperature of hyperthermic animals to pre-capture levels.3 The authors point out that since carrying water is far less cumbersome and difficult than transporting and maintaining ice-packs in the field, they recommend that water-dousing is probably a more practical and effective first intervention for cooling deer with capture-induced hyperthermia.
Hypothermia during sedation/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.5 Therefore, having thermal support available in the form of external heating devices during and after anesthesia is prudent. In general, the time of recovery from anesthesia is typically longer in case of injectable anesthesia rather than inhalant anesthesia.
In addition to abnormally low body temperature, signs of hypothermia can include:
In cases of mild hypothermia, shivering may be the only outward symptom. As hypothermia increases in severity, the other usually symptoms become evident. The deer’s vital signs are likely to become increasingly erratic as its body goes into heat conservation mode.3,4 At this point, the animal’s focus is on keeping its vital organs working by restricting the blood flow from all other parts of the body.
Hypothermia can be reversed through the use of water bottles filled with warm water and placed around the deer’s body. 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.4 Returning the animal to a warm environment and/or using heat lamps can also be helpful.
1mammal.org.uk.
2britannica.com.
3Haskins, S.C. (1995). Thermoregulation, hypothermia, hyperthermia. In: SJ. Ettinger. & EC. Feldman (Eds), Veterinary internal medicine (4th edition) (pp. 26–30). Philadelphia. U.S.A. W.B Saunders Company.
4Arnemo, J., Fahlman, A. (2008). Biomedical protocols for the free-ranging brown bears, gray wolves, wolverines and lynx. Hedmark University College, Norway and Swedish University of Agriculture Sciences, Sweden.
5Arnemo, Jon & Kreeger, Terry. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007.
6Richardson, D. Journal of Mammalogy, Volume 56, Issue 3, 29 August 1975, Pages 698–699.
7Wolfe L.L., et. al. Immobilization Of Mule Deer With Thiafentanil (A-3080) Or Thiafentanil Plus Xylazine. J Wildl Dis. 2004;40(2):282-287.