Looking at the inside of a polar bear
A polar bear at the Brookfield Zoo may have just made history during his physical exam.
OF COURSE there was duct tape.
Amid the precise administration of anaesthetics, the heart-rate monitoring and the many other cautious scientific preparations involved in getting a polar bear into a CT scan machine at Brookfield Zoo in Illinois, the United States, recently, it came down to good old duct tape (laid over cloth strapping) to hold the animal in place so that detailed images could be made of its innards.
The animal strapped to the hightech, high-weight capacity, medical device table like a loose (and furry!) pipe in a handyman’s basement was Hudson, Brookfield’s 12-year-old male. He had been put under earlier in the morning for a variety of procedures.
More than just the ursine equivalent of an annual physical, these included the potentially groundbreaking ones of undergoing the CT scan and having semen extracted for a couple of tries at artificial insemination. (Hello, lady polar bears of Brookfield and of Madison, Wisconsin’s Dane County Zoo!)
And, yes, making sure an apex predator is effectively sedated is an especially important job when you consider that, at one point, more than 40 Brookfield staff got involved in the pushing, pulling, truck driving, strapping and gurney wheeling involved in getting the bear from its enclosure to the computerised tomography machine. An early wake-up would not be a happy moment, for bear or, especially, humans.
The CT scan will be the first, or at least one of the first, Brookfield veterinary radiologist Marina Ivancic believes, of a living polar bear. It will be helpful in building a baseline of knowledge for the species whose existence in captivity becomes increasingly important as its icy natural habitats diminish.
More immediately, it will let the zoo’s veterinary staff examine Hudson in areas standard medical exams or even ultrasounds cannot reach, probing deep into the body to see anything from a tumour to arthritis.
“This is the first opportunity we’ve had to get an animal this size through a CT scan,” said Dr Michael Adkesson, the zoo’s vice president of clinical medicine. Only six zoos have a version of the device at all, and Brookfield has the biggest, but it only recently acquired a new, sliding, spinning table – made for horses, with a 953kg capacity – that lets it feed its biggest animals through the CT imaging “donut”.
“We’ve got the largest scanner, and with this table, we’re also now not limited by the weight of the patient,” Adkesson said. Hudson checks in at about 465kg.
In addition to the routine checkup plus scan, “we’re taking advantage of having him under anaesthesia to do semen collection on him, hopefully for successful artificial insemination, which has not been done in a polar bear before,” said the veterinarian.
Captive polar bears have been mating but have not been as successful in reproducing as species management experts hoped. Developing reliable artificial insemination techniques, as has been done in other large mammals, would be a big plus for bears and their keepers.
“We would then be able to just move semen between facilities and we wouldn’t have to actually move the bear,” he said.
So the semen was taken from the animal in a procedure that did not involve a magazine and a private room. (A chemical stimulates the reproductive system and pushes sperm towards the tip of the urethra, where specialists draw it out.)
Good news: In the two samples taken, microscopic examination showed “about 90% motility, which is about as good as you can do” on the fertility scale, explained Erin Curry, a reproductive physiologist from Cincinnati Zoo, Ohio, assisting with the process. “We were very pleased with the collection today.”
Fresh semen is the best semen so Curry planned to drive immediately to Madison, Wisconsin, the next day to perform procedure No.1, then return to Brookfield the next day to try to impregnate Hudson’s sometime natural partner there.
“So if you see the Cincinnati Zoo truck driving on the highway, you know we’ve got the polar bear sperm,” she said.
Meanwhile, the Brookfield staff manoeuvred Hudson onto the fancy new table, turning him onto his back, which would have been cute in an animal that had not evolved into a killing machine. At Adkesson’s direction, they moved him a little this way and a little that so that he would line up precisely with the donut.
“It’s a little harder than we thought,” the doctor said.
“It was a lot easier during the dry run when there was no bear on the table.”
It would take several hours before the images would be fully taken, processed and able to be analysed on the big screen in the radiology office of Ivancic.
But even a preliminary “scout” image showed promise. “This grey part is the fat,” she explained, pointing to a smaller screen outside the CT room. “The white here is the pubic bone.”
Adkesson headed back into the room with a crew of staffers to manoeuvre the bear into slightly better scan position. But it was all pretty good.
“Any CT images of polar bears is going to be a huge win for the zoo community,” said Ivancic.
“I don’t know if there are any others out there.” – Chicago Tribune/Tribune News Service