Joburg's feline wildlife is thriving. According to SPCA branches, cat shelters and vets, the city and its surrounding suburbs are seeing feral cats multiplying in places like shopping centres and office complexes.

"If there were a decrease in the population, we would be seeing a decrease in the calls," said Samantha Berger, founder of Kitty Haven, a rescue and rehabilitation organisation.

Instead, Kitty Haven has gone from receiving one to two calls a day two years ago to five to 10 calls a day this year. The Joburg SPCA receives roughly five complaints about cats a day and Friends of the Cat gets 20 calls, which it says is many more than it got five years ago.

For Adele Joffe, founder of Friends of the Cat, things are out of control. "This whole problem is so vast, I can't keep up with the massive amount of phone calls," she said. "It could blow up into something big. In fact, I'm sure it will."

Berger agrees. "I've physically seen more colonies at every office complex. I can't afford to sterilise all of them."

Feral cats can either be born wild or be domestic cats that have reverted to being wild.

According to Warren Baleta, director of the Feral Foundation, in seven to 10 years one female and one male cat can indirectly be responsible for the birth of 400,000 cats.

Cat "colonies" can be found throughout the Joburg area in places such as malls, office complexes and factories, and around restaurants, hospitals and golf courses.

Tara Hospital in Sandhurst currently has a population of roughly 80 feral cats on its premises. Wendy Blott, head of nursing at the hospital, noticed a problem five years ago.

"These cats just found their way to the hospital and of course, after a while, they started to multiply and then it got out of control," she said.

Blott called Friends of the Cat, who sterilised the cats, returned them to the hospital premises and now feeds them. The cats now keep the rodent population down.

The biggest draw for cats is usually the food. "Feral cats especially like complexes, where there is food," said Dr Remo Lobetti, Wits branch chairman of the South African Veterinary Association.

Colonies can range from 20 to hundreds of cats. They survive on scraps fed to them by people daily.

"Many carry viral diseases, feline leukaemia and feline Aids," said Dr Platzhund of 702 Talk Radio.

Although these diseases can't be transmitted to humans, these cats pose other problems. They break into buildings, trigger alarms and leave messes.

The organisations stress that the only way to tackle the overpopulation is to sterilise cats.

"I've seen people shoot and poison and remove their feral populations but that won't get rid of the problem," says Baleta. "You get rid of one feral and another will take its place. You need to sterilise the cat and return it where it was."

Sunday Times