Feral cat populations have increased significantly across Canada.

The kitties gather around train yards, back-alley trash bins, under porches and other urban haunts, looking to score a meal.

In Toronto, it's estimated there are as many as 100,000 of the scrappy animals on the loose, and the numbers are similar in Montreal. Populations have bred to 44,000 in Edmonton, 25,000 in Windsor, Ont., and the cats are abound in Ottawa, as well.

Their rising numbers are cause for concern, experts say, since they can carry disease transferable to humans and household pets, such as rabies, cat scratch disease, tapeworm and hookworm infection and are a threat to local wildlife.

Last summer, a Winnipeg woman's hand was severely disfigured by bacterial infection after being bit by a feral cat she had attempted to take in.

"There's a serious problem in most municipalities," says Mike Cohen, a city councillor in Montreal's Cote SaintLuc borough, "but many cities have shut their eyes to it."

New citizen groups, however, are cropping up nationwide to tackle the problem.

Last March, Cohen and a small army of volunteers formed the Cote SaintLuc Cats Committee to trap, neuter and return (TNR) the thousands of feral cats that roam their community.

These TNR programs aim to curb the growth of feral colonies, which average roughly 10 cats each, by sterilizing, vaccinating and returning the animals to where they were found.

"Our program has trapped and neutered 50 cats in its first year," says Cohen. "That prevented hundreds of unwanted kittens being born."

Yet they continue to multiply. "We're making a small difference right now, but if you don't do anything, their numbers will be even larger," he says.

It's a hard-fought battle, says Dr. Esther Attard, a staff veterinarian with Toronto Animal Services. "If you can sterilize 80 per cent of a colony, that colony won't grow," she says. "It's a big job to do that, but it's better than just euthanizing them. Otherwise they breed and you get more cats to take their place."

A breeding pair of felines can, on average, produce 5.6 kittens a year.

Volunteers remove any cats that can be socialized and put them up for adoption. But cats more than one year old that have never known a human home are considered wild.

"By removing kittens and any friendly strays that have joined the colony, we immediately reduce not only present colony numbers, but future numbers, too," says Virginia Dobson, co-founder of the Little Cats Lost TNR effort in Edmonton.

This month, the city is giving Dobson and her partner Lisa Paskar $30,000 to expand the operation they started three years ago and to monitor their success at four pilot sites. "The funds will also allow us to develop messaging and support to help community residents understand what we do," she says.

Already overburdened with high numbers of unwanted and abandoned animals, the Edmonton Humane Society and city-operated Animal Care & Control Center are unable to take on the work needed to make a TNR program successful, Dobson says.

Traditional animal welfare organizations are on the ropes in other cities, too. Donations to the Toronto Humane Society plunged 50 per cent last year, and Montreal faces its own challenges as it works to reform animal welfare services.

Yet, community groups seeking to fill the vacuum by stepping in with TNR programs are wasting their time, says Chris Hassall, a conservation ecologist at Ottawa's Carleton University.

"One of the main things you notice when you look at the research literature around trap-neuter-return is how poorly we understand these feral cat colonies," he says. "I'm skeptical of the role TNR could play. There are lots of emotional arguments and little intensive research to back it up."

That's not to say feral cats don't pose a significant concern to public health and local wildlife, Hassall says. "We know that, given the opportunity, they will eat reptiles, amphibians and that 20 per cent of their diet are birds."

"In an urban environment, we're already looking at an ecologically desolate place and that additional pressure can have a big impact." There's also the fact that 80 per cent of rabies shots are given in the U.S. because of contact with infected cats, he adds.

"Sometimes, people will approach these animals thinking they can help and end up getting bitten," notes Attard. "They can also start using people's porches as a litter box."

Two large-scale studies of TNR programs in California and Florida, Hassall says, showed no decline in the population of feral cats because gains were offset by people introducing new animals into the area.

To create an effective TNR program, he says, would require thorough monitoring and complimentary efforts, such as adoption and vigorous public education campaigns.

Dobson agrees and says these are exactly the efforts the expanded Little Cats Lost program is taking on. "There has to be a mix of initiatives to get overpopulation under control," she says. "We also need to push for lowincome spay and neuter services and a licensing for these animals."

Dobson and Cohen look to Calgary's innovative Animal and Bylaw Services, led by director Bill Bruce, as a model to aspire to. The program's annual operating budget of $5.3 million is all raised through its initiatives, rather than taxpayer money.

"We've seen the effectiveness of these programs ourselves," says Dobson, "now we just need to show others that it works."