By Bridie Smith and Science Editor
It was a tough call as to who had the more unenviable job. The answer depended which end of a large and potentially dangerous predator you would rather be working on: the head (read canine teeth) or the tail (read anal gland).
Thankfully it was a moot point, as Melbourne Zoo's 14-year-old Sumatran tiger Binjai arrived in surgery anesthetised and on a stretcher. Binjai's 92-kilogram bulk was a dead weight for keepers and vet staff, who were charged with preparing her for not one but two operations.
The c-word had been mentioned after a tumour on one of her anal glands was detected in October. The only way to find out if it was cancerous was to get in there and have a look. That job fell to Stewart Ryan, from Melbourne University's vet school.
"You need to know what is it, where is it and how bad is it," Dr Ryan said. "They are the three questions you have to be able to answer."
14-year-old Sumatran tiger Binjai positioned on the X-ray table at Melbourne Zoo.Credit: Joe Armao
Before getting gowned up, Dr Ryan and Melbourne Zoo senior vet Helen McCracken wanted to establish if there were signs of tumours elsewhere. If the tumour was cancerous, there was a risk it could have spread to Binjai's lymph nodes or lungs.
X-rays, which required staff to use sandbags to keep Binjai in various positions on a table, gave the big cat the all-clear.
The X-rays also let dentist and long-time volunteer Stephen Coles off the hook. He was anticipating to perform a root canal on Binjai's upper left canine, which had been chipped, potentially exposing the nerve and risking infection.
However, after comparing the right canine to the chipped left canine, Dr Coles said there was enough of a dentine barrier evident in the X-rays to protect the root of the tooth from infection.
Melbourne Zoo's female tiger Binjai on the operating table after having her teeth checked and an anal gland removed. Credit: Joe Armao
"It all looks OK, so there is no reason to intervene at this stage," he said. "But you're only as good as your teeth, so it's something to be monitored."
Dr Ryan and Dr McCracken will have to wait until the end of the week to learn if the removed tumour sent to pathologists is cancerous and if it is, what type. However, Dr Ryan said the smooth appearance of the large thumbnail-sized tumour suggested it was benign.
Sumatran tiger Binjai during her operation at Melbourne Zoo.Credit: Joe Armao
Nevertheless, zookeepers and vets will be on alert, watching Binjai's behaviour and noting any change in routine.
"We will remain vigilant," Dr McCracken said.
Sandbags hold Melbourne Zoo's female tiger Binjai in place as vet staff prepare to ultrasound her bladder.Credit: Joe Armao
In large and small species of cats, anal glands are found either side of the animal's anus, roughly at 8 o'clock and 4 o'clock. They secrete a smell, which attaches to their faeces.
Binjai arrived at Melbourne Zoo from Rotterdam Zoo in June 2004 as part of an international breeding program for Sumatran tigers, coordinated out of London.
Vet staff monitor 14-year-old Binjai as Stewart Ryan removes a tumour and one of her anal glands. Credit: Joe Armao
Listed by the IUCN as critically endangered, there are just a few hundred Sumatran tigers remaining in the wild. Habitat destruction due to their native forests being cleared for palm oil plantations and poaching are the main threats. Keeping their captive population as genetically diverse as possible is key to the health of the species.