Spring is quite possibly the least favorite season of employees and volunteers who labor in animal shelters. For them, spring is "kitten season" and it can be overwhelming.

"Yes, kitten season is in full swing," said Daniel Musher, development director at Animal Rescue League of Western Pennsylvania.

Right now 174 cats and kittens are available for adoption at the Larimer shelter. An additional 196 are being cared for in foster homes and 49 are waiting for owners to reclaim them.

Cats start producing litters of kittens as early as March or April and the kitten birthing season can continue through October. Many females will have two litters in that period.

"June is traditionally the busiest month in terms of the number of cats and kittens that arrive in shelters," said Gretchen Fieser, director of marketing and business relationships at the Western Pennsylvania Humane Society.

The Humane Society currently has 151 cats available for adoption at its North Side and Elizabeth Township shelters, and those are just the tip of the iceberg.

From May 5 through last Monday, the Humane Society took in 746 felines, many of them kittens.

Some of the animals that arrive in shelters during kitten season will be killed because the supply of cats and kittens outstrips the supply of people who want to adopt them.

Last year, the Animal Rescue League found homes for 2,649 felines. In 2005, Western Pennsylvania Humane Society found homes for 2,794.

But the Animal Rescue League killed 2,293 cats in 2006. The Humane Society killed 6,401 cats in 2005, the most recent figures on the shelter's Web site. That's a grand total of 8,694 cats killed in Allegheny County.

The rescue league and Humane Society are Allegheny County's "open door" shelters. They never turn away an animal, but they have to kill some to make room for the endless tide of incoming dogs and cats.

Other local rescue programs and shelters, including Animal Friends in Ohio Township, have "no kill" policies and generally are full, with waiting lists.

Animal control companies, and some shelters, kill cats and dogs that are not reclaimed by owners. Also killed are stray or feral cats, owner-less animals fending for themselves.

With so many animals being killed, officials in tiny West Elizabeth were stunned last week to find themselves the target of protesters carrying signs accusing them of gassing and killing cats.

"We haven't killed any cats at all," said borough Council President Louise Biddle, "and we're willing to listen to all sides. We are not hard to get along with."

But the council is considering authorizing its animal control contractor, Ferree Kennels, to trap and kill stray cats. The borough would pay Ken Ferree $10 for each cat killed.

Council took up the issue after residents complained about an ever-growing number of outdoor cats that spray urine and tear up lawn furniture.

About a dozen protesters, representing at least four animal groups, appeared at a council meeting on Tuesday to protest the killing of any cats. They especially object to Mr. Ferree's use of carbon monoxide gas to kill animals. While that method is legal in Pennsylvania, most shelters use lethal injections of drugs.

Discussion will resume tomorrow at 7 p.m. when council reconvenes its meeting.

Mr. Ferree, who works for about two dozen municipalities, said he and his family have been receiving "harassing and threatening phone calls."

"It's very unfair to target one person. I am just doing my job," he said in a telephone interview. "I am not the bad guy here. I'm just providing a service to my valued customers.

"There is no quick or short term solution" to cat overpopulation problems, Mr. Ferree said. "I take in maybe 12 cats a month. No more than 150 a year. That includes cats hit by cars and cats brought in by their owners. I have a scanner for microchips and cats with microchips are returned to owners."

He also said he cooperates with local shelters who occasionally come to his kennel in McKeesport to take adoptable cats and dogs.