They came in crates, humane traps and plastic storage bins with holes poked in the top. Twelve hours later, all of them would be leaving without something.

More than 100 cats -- and their caretakers -- assembled inside a pole barn at the Porter County Fairgrounds at 9 a.m. Tuesday: the Neuter Scooter, a low-cost, mobile spay/neuter clinic, was in town.

As "meows" echoed throughout the building, veterinarian Tess Peavy, co-founder of the Neuter Scooter, reviewed instructions.

For Peavy, and her partner, Oscar Armendariz, the Neuter Scooter is a family affair. Assisting them were sons Joe, 18; Gabriel, 8; Elijah, 4; and daughter Aria, 6.

In just 45 minutes, they checked in 72 female and 39 male cats, who were preregistered online at the Neuter Scooter's Web site, www.neuterscooter.com.

Surgeries are $40 prepaid or $50 the day of the clinic. Residents leave their cats at 9 a.m. and return for pick up in the evening. Vaccinations are included.

Peavy said 85 to 90 percent of the cats she neuters are not "owned."

"They are just those who walk up to people's homes," said Peavy. "They are not pets, but people are feeding them or have rescued them. They don't want them to reproduce."

Sandy Ogle, Porter County Animal Shelter director, contacted Peavy for the clinic's second visit to Porter County.

"The need is so great," said Ogle, who, through donations, had two shelter cats neutered Tuesday by Peavy. "This helps people a lot. I'd like to see them here every other month."

This summer, the Neuter Scooter, based in Bloomington, Ind., will visit nine cities, including South Bend, Plymouth, and Michigan City. The goal is 1,000 cats per month; they have neutered 10,000 to 12,000 cats each year since they began in 2002.

Peavy said city officials contact her when they realize that euthanasia is an expensive and ineffective response to stray overpopulation. She and her staff recently performed 180 surgeries in two days for the Hawaii Cat Foundation in Honolulu, and they will soon return a second time to Veneta, Ore., at the town's request.

Yet, Northwest Indiana is their busiest location.

Those who stood in line Tuesday are grateful for the clinic's services. Joe Osika, of Valparaiso, has been feeding Blossom, a skinny brown tabby, for two years near his home. Blossom has had 13 kittens over the years, only two of which have survived.

"We get tired of seeing them all die," said Osika. "We try to break the chain. If you don't, they just keep going. Someone has to care about them."