A Colorado State University graduate of 1979, Roger Klingenberg is a widely recognized researcher, author, lecturer and instructor of reptile medicine and surgery. He is well known among herpetologists for publications including Understanding Reptile Parasites and The Ball Python Manual. He is a managing partner in a three-person small and exotic animal hospital and is active in the Association of Reptilian and Amphibian Veterinarians.

No in-depth studies have determined exactly why hibernation is necessary to the long-term physiological well being of mature North American box turtles (Terrapene sp.). But those that are not allowed to hibernate usually experience a progressive physical and mental decline. Ovulation and spermatogenesis, and therefore successful reproduction, will not occur without proper seasonal cooling. It follows that hormones other than reproductive may also be affected by hibernation. One hypothesis is that hibernation prevents damage to the thyroid gland. This author hypothesizes that the lack of proper hibernation may lead to irreparable damage to the immune system. Seasonal changes have been seen in the status of the immune system. Populations of white blood cells change from summer to fall, with decreases in lymphocyte counts and overall splenic pulp immune population. Without replenishing these defense systems through hibernation, the turtles become immunocompromised.

When mature box turtles are ready to hibernate, they stop eating, become lethargic and attempt to burrow or hide. This point in time varies with the locale and local population of turtles. In general, this begins in mid-September to mid-October but could commence later in the fall and winter. It is essential that box turtles are healthy prior to hibernation. A pre-hibernation examination, including an accurate body weight, should be the first step toward the winter nap. The turtle is weighed on a gram scale so its weight can be monitored every 2-3 weeks during the course of hibernation.

One of the most common ailments noted in box turtles is hypovitaminosis A. If vitamin A deficiency is suspected from the dietary history (e.g., diet of insects only with no green vegetables), a vitamin A injection is administered at 200 IU IM prior to hibernation. A turtle with clinical signs of hypovitaminosis A must be treated for at least 4-6 weeks before hibernation can begin.

Hyperplastic metaplasia of the lacrimal system leading to ocular changes is one of the most visible clinical signs of hypovitaminosis A. This condition results in decreased secretions as evidenced by the accumulations of mucous in this turtle that would normally be excreted through the nasolacrimal canal.

Eyes become so dry that accumulations of normal eye secretions are no longer seen.

This turtle has dry, half-mast eyes and swollen and puffy eyelids, which are also characteristic of hypovitaminosis A.

Immature box turtles may continue normal activity and feeding behavior throughout the winter until they are several years of age. It is not imperative that healthy immature turtles are hibernated as long as they continue to thrive. However, if behavioral changes characteristic of pre-hibernation are exhibited, even very late into the winter, the turtle should be hibernated, even if only for a brief time.

Adults that have recently recovered from moderate to critical illness may avoid hibernation that season.

Turtles from the southeast US are accustomed to a shorter cool season and may continue to exhibit normal behavior into the fall and winter. In these cases, it is prudent to either delay or skip hibernation altogether based on the continued normal behavior of the turtle. If in doubt, hibernation is suggested if health issues do not exist.

Food withdrawal: In anticipation of hibernation, turtles should be maintained under normal husbandry conditions with food withheld for 10-14 days. It is essential for the gastrointestinal tract to be emptied before cooling to prevent infections secondary to the retention of undigested food.

Soaking: Turtles are soaked at least every 48 hours prior to hibernation, which provides hydration and encourages emptying of the GI tract. A soaking consists of a 20-30 minute period of letting the turtle lounge in a container (not the family’s kitchen sink) with about ¾ inch of tepid water. After clearing the GI tract, the turtles are kept at room temperature (65°F) for 2-3 days, 60°F (possibly a base-ment) for another 2 days, then placed in their hibernaculums and moved to a cool room maintained at 45-50°F.

One example of an appropriate hibernaculum is a plastic sweater box (e.g., Rubbermaid ) approximately 12”x 12” x 12” with six small holes drilled in the lid. The box is filled two-thirds full with a mixture of shredded newspaper and peat moss that has been moistened with water (but does not drip when compressed in the hand). The turtle will readily burrow into this mixture, which will help prevent dehydration. Although the light cycle is one of the subtle clues reptiles use to recognize seasonal changes, turtles hibernated in the dark do just as well as those exposed to a light cycle.

The two most important factors in hibernating box turtles are maintaining hydration and monitoring them. Every 2-3 weeks, the turtles are removed from the hibernaculum and warmed to room temperature for 2 hours during which time they are examined, weighed and soaked. If any health concern is encountered such as nasal discharge or failure to open the eyes, the turtle is warmed up and the health issue is addressed. It is typical for the turtle to lose only 1-2% body weight. A weight loss of 10% or more may necessitate the removal from hibernation, although hydration will often quickly correct acute weight losses. Again, the turtles are allowed to soak for 20-30 minutes at a time in tepid water. The substrate is checked for moisture content and remoistened if needed. The turtles being returned to hibernation are taken directly from soaking at room temperature to the cool room with no deleterious effects.

Turtles originating from the Northeast, Midwest and western US ideally should be hibernated for 3-4 months, although a 6- to 8-week hibernation period is usually adequate. Turtles that originate from the South and southeast require shorter periods of cooling, often as short as 4- 6 weeks. If the turtle has been checked every 2-3 weeks and is thriving with stable body weight, there is no rush to stop hibernation. Once it is determined that hibernation will cease, the turtle is moved to 60°F for 2 days, then to 65°F, and then to room temperature. The turtle is soaked every other day and feeding is resumed 2 days after acclimating to the warm room under normal husbandry conditions.

This turtle’s eyes are effectively glued shut, and the eyelids are stretched. The opaque appearance is due to accumulations of caseated pus trapped under the eyelids secondary to a concurrent bacterial conjunctivitis.

Bacterial infection in this turtle suffering from hypovitaminosis A may be seen as typical ocular lesions and aural abscesses.

As vitamin A is essential to the integrity of the respiratory lining, turtles with inadequate levels of vitamin A will often exhibit dyspnea, nasal discharge and open-mouthed breathing. Radiographs can help determine the extent of respiratory ailments.

Over 15 years ago, when I continued to see debilitated turtles presented in the spring, I realized many of my clients couldn’t, or wouldn’t, hibernate their turtles. So I decided to do it for them. This client service has since grown into a clinic tradition that has spawned loyal and grateful clients in a win:win situation. When the turtle begins to show pre-hibernation behavior in the fall, clients are encouraged to continue to attempt feeding, soaking and normal care, and to bring the turtle in whenever it has gone 2 weeks without eating. If a client’s turtle continues to eat, drink, and stay active beyond this time, there is no rush to begin and we’ll take turtles in all winter long.

For the first 2 years I hibernated turtles as a free client service. For the current hibernation season we charge $20 per month for routine hibernation care. If we have seen the turtle for a well visit during the previous year the pre-hibernation exam is waived. New clients or turtles are charged a pre-hibernation exam fee of $35.50 plus added fees for a vitamin injection, medications or hospital charges. Obviously, this is not a major profit center of our hospital. However, the goodwill and client-to-client conversation created will retain and attract new clients to your practice. For me, the simple joy of seeing stomping turtles coming out of hibernation makes it worthwhile.

By Roger J. Klingenberg, DVM. Copyright 2000. Reprint, transfer or use of this article or photographs on other webpages or publications is forbidden without the written consent of ExoticDVM.
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