Dr. Freeland Dunker, San Francisco Zoo's head veterinarian, examines one of the bladder stones he removed from Cactus, the desert tortoise.
The reptile returned to public display this week after undergoing an unusual operation in which the zoo's head vet, Dr. Freeland Dunker
, had to cut into his
"We faced a unique challenge," Dunker
"In a mammal, bird or anything else without a shell, this would be fairly routine surgery."
One stone was the size of a baseball and the other three were as big as golf balls.
They added up to 553 grams, a little over a pound -- which is a lot for an animal like Cactus, who normally weighs 8 pounds and enjoys eating his
discovered the stones in 1994 and has monitored them over the years.
During last week's 90-minute operation on Cactus, Dunker
cut a 3-by-4- inch rectangle in the tortoise's plastron, or underbelly shell, partially scoring the flap closest to the head.
"I hinged it and left it up like the hood of a car," Dunker
"Then we had our starting point."
After removing the stones, he
applied a fiberglass patch and sealed it with five-minute epoxy.
It will take two years to heal.
"It was like fixing a ding in a surfboard," said Dunker
, who performed a similar operation in 1992 on a tortoise from San Francisco's Randall Museum
"Tortoises, being a desert animal, use their bladders as a canteen for water exchange," Dunker
"They recirculate it through their bladder.
This urine can get stagnant, especially after drought or hibernation."
said that wild tortoises will urinate as a defense when they're picked up and often die as a result, after losing all their water.
If it cracks during the two-year healing period, Dunker
will reinforce it.
And it will be with Cactus for the rest of his
life, just like the one that fellow zoo resident Helga received years ago after her
shell was sliced open to deal with another byproduct of tortoise anatomy: Her
eggs were blocked and rotting inside her
shiny underneath," Dunker