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Polar Bear Blood Draw Training At Oregon Zoo

By Jenny L. DeGroot, Amy Cutting, Amy A. Hash, Nicole J. Nicassio-Hiskey, Robert L. Draughon, Sara M. Morgan, Celess D. Zinda, Philip H. Fensterer, & Kelli Harvison — Oregon Zoo

Originally published in Soundings Volume 39, Number 4 — Fourth Quarter 2014

While polar bears (Ursus maritimus) have lived under human care for decades, the species can still be a challenge when training advanced husbandry techniques. At the Oregon Zoo Polar bears are managed in a protected contact scenario, which allows keepers limited access to them for routine sampling and screening. While they do not hibernate, in the fall and winter months, the bears are less active and less food-motivated for training sessions. The bears have still participated in training sessions during these months due to positive relationships with their keepers, consistent training, and the use of their most preferred food items, including capelin and even sherbet. Despite these challenges, Oregon Zoo has become the first known facility to successfully train 1.1 polar bears for voluntary blood draws. This behavior has allowed veterinary staff to more closely monitor the health of the geriatric siblings, Conrad and Tasul, both 29-years-old. Blood samples are taken from both bears quarterly for health screening, and the behavior is routinely practiced. The ability to collect polar bear blood voluntarily has not only enhanced the welfare of the two bears at Oregon Zoo, but also led to collaboration with the United States Geological Survey (USGS) on several wild polar bear research projects.

Figure 1. Tasul’s foot being radiographed.

Conrad and Tasul are both in relatively good health, despite their advanced age. Both bears show signs of arthritis. Conrad has a history of conjunctiva inflammation, while Tasul has a number of environmental allergies that manifest on her feet, including grass, pollen, and hay. During a routine physical in January 2006, radiographs showed that Tasul had developed bone spurs in her right rear foot. Vet staff monitored the bone spurs in subsequent physical exams over the next several years. Keepers decided to train Tasul for voluntary foot radiographs to monitor the bone spurs without the use of anesthesia. This behavior required her to place her rear foot through an access port in the squeeze crate (Figure 1). While training this behavior, keepers realized that access to her foot might allow access to the dorsal metatarsal vein.

There are two different crates used daily with the polar bears. The first is a smaller squeeze crate, and the second is a larger transport crate. Both are attached to the access doors to the holding den, and protrude into the keeper workspace. Free access to these crates allows Conrad and Tasul to observe the keeper work area. Almost every day Conrad and Tasul eat their morning diets in the crates. They are allowed to enter or exit at will and are commonly asked to participate in training sessions for behind-the-scenes tours while in the crates. Because Conrad and Tasul have had positive experiences and associations with these crates, they are extremely comfortable eating and participating in training sessions inside the crates.

Figure 2. The squeeze crate, with panel open for foot access.

Because of Tasul’s bone spurs, keepers chose to begin training her foot presentation first. This training began in December 2010. To begin the foot presentation training, Tasul was first trained a roll-onto-side behavior in the crate. This would allow keepers access to her feet for radiographs. Bridging and reinforcing small body movements made this behavior fairly easy to train, within a few months. Once Tasul was reliably performing the roll-onto-side behavior, the 30.5 cm square (1 ft x1 ft) access panel near the foot end of the crate was lowered (Figure 2).

Figure 3. Two keepers were required to manage the polar bear during training.

Two keepers were present throughout the entire training for the radiographs. One keeper handled Tasul’s foot and controlled the access panel (Figure 3). The second keeper fed Tasul and maintained stimulus control while she was resting on her side. Communication between keepers was essential for safety. If Tasul were to sit up and turn toward the foot panel, the feeder could quickly communicate to the other keeper so they could shut the panel.

Capelin, Tasul’s favorite food item, was fed to her on a continuous schedule of reinforcement. Tasul was required to lay flat, on the left side of her body the entire session. The long-term goal was for Tasul to accept manipulation on her more sensitive right foot, where veterinary staff had found that she had bone spurs. The bears were not previously trained to be touched, so any form of touch was a new experience for Tasul. Keepers chose to work with Tasul’s less-sensitive left foot first in order to make the touching experience as positive as possible. Any time her foot was touched, she was bridged and fed a fish. This counter-conditioning worked well. Initially, Tasul was extremely reluctant to allow her foot to be touched and would vocalize if her foot was touched for too long. Keepers did not increase the duration of the touching session until Tasul showed no signs of frustration, such as vocalizing or pulling her foot away. As long as Tasul participated in the session, she was reinforced with fish. Over time, Tasul became comfortable having her left foot manipulated. The behavior then progressed by reinforcing Tasul for voluntarily moving her foot through the access door.

Next, a radiograph plate and mock radiograph machine were introduced. Once Tasul proved she was comfortable with the medical equipment, along with the manipulation of her foot, the veterinary staff was able to successfully take radiographs of her left foot in May 2011. Tactile training on Tasul’s sensitive right foot took a couple of additional months, and radiographs of her right foot were completed in August 2011. The right foot, although more sensitive, took three months to train as opposed to the five months it took to train her left foot; this may be because Tasul was already familiar with her other foot being touched. Once she was fully comfortable with the radiograph behavior, staff started training a voluntary blood draw in August 2011.

Figure 4. Hair clippers expose the vein site on Tasul’s foot.

Figure 5. Heat packs were applied to increase blood flow.

Figure 6. Alcohol and chlorhexidine wipes were introduced to clean the site.

Figure 7. Surgical tubing was used as a tourniquet.

Hair clippers were introduced to Tasul next. First, the clippers were turned on low and set nearby for noise desensitization. Next, the keeper placed their hand between the vibrating clippers and Tasul’s foot. Over time, the setting was increased, and eventually the keeper’s hand was phased out so the clippers could vibrate against Tasul’s foot. A small area of hair was shaved and then a larger area to expose the vein site (Figure 4). A veterinary technician identified the dorsal metatarsal vein, and the location of the vein was marked on Tasul’s skin with a black sharpie pen so keepers could begin desensitization training for needle poking. Finally, heat packs were applied to the top of the foot to assist with blood flow (Figure 5), and rubbing alcohol and chlorhexidine were introduced to clean the site (Figure 6).

The next step was the desensitization of a tourniquet around Tasul’s ankle. To facilitate a quick release in case Tasul pulled her foot away, surgical tubing was simply held tight by the keeper rather than tied (Figure 7). Keepers did not want to risk possible ingestion of the tubing if Tasul pulled her foot out of the access door. Because the tourniquet pulled at her hair and added pressure, it took Tasul about a month to become comfortable with this step.

Figure 7. Surgical tubing was used as a tourniquet.

Finally, keepers began poking Tasul’s foot near the vein for desensitization. Keepers transitioned from poking her skin with their fingernail to a blunt needle, and then began inserting increasingly larger needles (25-, 23-, and 21-gauge). Tasul maintained her position with little to no reaction for each progressive step. Veterinary staff decided to use a 21-gauge butterfly catheter when collecting blood to allow some flexibility in case Tasul moved her foot; if Tasul wiggles her foot slightly, and the veterinary technician can move along with her without dislodging the needle (Figure 8). The staff succeeded in drawing blood from Tasul on 4 December 2011.

Figure 9. Conrad being trained for voluntary blood draws in the custom-built crate.

Figure 10. The safety bar in place during a blood draw.

The blood draw training took four months to complete, building on the radiograph behavior. The total training time from the beginning of touching Tasul’s foot to the successful blood draw was about one year. Tasul was trained first because she was already trained to present her foot for radiographs, and her crate had an access panel already in place. Once Tasul’s blood draw training was complete, staff decided to begin training Conrad. However, Conrad’s crate did not have any access panels, and he was too large to fit in Tasul’s crate. Oregon Zoo received donated funds to build a custom crate for Conrad, fitted with multiple access panels. Beginning in March 2012, keepers used the same training steps to train Conrad for voluntary blood draws, and his training was complete by September 2012. Conrad did show some signs of discomfort when his foot was touched, and would sometimes pull his foot away from the keeper. However, he did not vocalize to show discomfort as Tasul did. Conrad’s training progressed a bit faster than Tasul’s, as it was complete in six months, as opposed to one year for Tasul. Tasul’s feet may be more sensitive than Conrad’s due to the bone spurs as well as her allergies that manifest on her feet. Today both bears give reliable quarterly blood samples (Figure 9). Staff has added an additional safety bar to both crates, based on suggestions offered by colleagues. These bars are used during blood draw sessions. Each bar slides across the width of the crate and over the bears’ shoulder area (while lying down). The bar serves as a stopping mechanism in case the bear sits up during a procedure (Figure 10). This safety feature allows the keeper at the bear’s foot additional time to close the panel access door if needed.

Training blood draws has allowed multiple advances in polar bear husbandry and research at Oregon Zoo. Veterinary staff was able to successfully perform voluntary intravenous anesthesia induction on Tasul twice in order to care for an abscess on the left side of her torso, her allergy medication injection site. Previously, the polar bears were darted or pole injected to administer anesthetic drugs, procedures that can be stressful for all involved. In general, stress can affect how an animal experiences an anesthetic event, including increased or decreased heart rate or breathing rate, low or high blood pressure, poor blood oxygenation, an increased need for inhalant anesthetic, and a slower recovery time, among other things. These parameters were compared for the different styles of anesthesia induction. Vet staff also looked at Tasul's blood glucose levels as those levels can show an increase due to stress (Latimer, 2011). They compared the levels acquired during anesthesia induced with a dart to those that were induced intravenously using the trained behavior. The value was higher with darting than with IV anesthesia. For these reasons it appears that the IV induction did decrease the stress for the animals involved in these anesthesia events.Keepers and veterinary staff were pleased that Tasul cooperated for voluntary anesthesia induction. Voluntary anesthesia did pose a challenge, as Tasul could be fed very little food during the induction process; however, Tasul cooperated fully. For Tasul’s first voluntary anesthesia, veterinary staff injected the anesthetic directly into the vein, but it took over ten minutes before she was recumbent. On Tasul’s second procedure, she was recumbent in less than one minute and her recovery was also very fast. It is unclear why it took less time during the second procedure.

After hearing about the success of the voluntary blood draws with both Tasul and Conrad, Dr. Karyn Rode from USGS asked Oregon Zoo to participate in a nutritional ecology project that required obtaining frequent blood and hair samples from both bears. She hoped that the data would help establish the rate at which carbon and nitrogen isotopes turn over in polar bear tissues and refine the use of stable isotopes to estimate diets of free-ranging polar bears. Because Arctic sea ice extent is closely linked to polar bear food intake, which in turn affects body condition, reproduction, and survival, understanding how polar bear diets have changed over the decades could shed light on some of the challenges wild bears are facing due to the climate change crisis. Researchers have over 40 years of banked blood and hair samples from two different free-ranging polar bear populations in Alaska. Testing these banked samples will allow researchers to accurately estimate the diets and long-term diet trends of these bears. For ten weeks, Conrad and Tasul were fed a terrestrial diet (polar bear chow, freshwater fish, beef suet, fruits, and vegetables), followed by ten weeks of a high-fat marine diet (capelin, salmon, herring, and salmon oil). Blood and hair samples were collected throughout the feeding trials. When the bears were on the high-fat marine diet, several benefits were seen by keeper and vet staff. Hair coats appeared healthier, as there was noticeably less patchiness and hair loss. Both bears lost weight, but appeared lean and healthy, with no increase in appetite. Keeper staff also noticed an increase in activity level. Because of these positive changes, keeper, vet, and nutrition staff at Oregon Zoo agreed to change Conrad and Tasul’s diet long-term.

Figure 11.Tasul wearing the accelerometer collar on exhibit.

This collaboration led to another research project with biologist Anthony Pagano from the USGS Alaska Science Center. This project required Tasul to be trained to wear an accelerometer collar while being videotaped (Figure 11). This paired data will help researchers calibrate and identify detailed movements like eating, drinking, walking, running, and resting with wild bears. Accelerometer data is species specific, and no data had been previously collected for polar bears. This information will then be compared to wild polar bears to help quantify energetic costs, which could help determine the effects of declining sea ice on polar bear energetics. This work is currently being analyzed and is not yet published.

The successful training of voluntary polar bear blood draws has enhanced the care of Tasul and Conrad at Oregon Zoo. Not only is veterinary staff able to more closely monitor the bears’ health with quarterly blood samples, but they are also able to use an intravenous anesthetic induction procedure. The blood draw behavior led to multiple collaborations on polar bear research, which in turn have resulted in an improved diet for Tasul and Conrad and helped scientists better understand wild polar bear populations. Oregon Zoo is excited that Conrad and Tasul’s blood samples may facilitate more research projects in the future, including hormone, nutrition, and behavioral research. Oregon Zoo managers are exploring the possibility of converting a portion of the exhibit to a metabolic swimming chamber for future research applications, and are incorporating what has been learned into the design of the new polar bear exhibit, slated to open in 2018.


Latimer, Kenneth S. (2011.) Duncan & Prasse's Veterinary Laboratory Medicine:  Clinical Pathology, 5thEdition.Chichester:  Wiley-Blackwell.