BETH OSTROSKY STERN has cared for more than 2,000 cats at home. Not all at the same time.

The 50-year-old is a pet foster parent. She and her husband, satellite radio host Howard Stern, take animals waiting for permanent adoption into their homes. It all started a decade ago when the couple’s beloved bulldog Bianca died. “When she passed, we grabbed a litter of kittens and decided to foster them just to get my mind off of Bianca and onto nurturing other little ones.”

Pet fostering has become important because animal shelters are crowded, and some pets require more attention than shelter staff can provide. Retirees, empty nesters and older adults make ideal candidates for the volunteer role. “I put animals before everything,” Beth Stern says. “If I had children, I wouldn’t be able to do that. When the kids are out of the house, or if you don’t have children, you can focus your time and your energy on these little lives that need you.”

Pet fostering requires less commitment than full pet ownership. “I can foster on my own schedule,” says Martine Korach, 57, a retired teacher in Long Beach, California, who volunteers for the Society for the Prevention of Cruelty to Animals Los Angeles (spcaLA). Her foster duties don’t conflict with medical appointments or travel.

What kind of pet can you expect in foster care? Typically large-breed dogs that will benefit from more space; kittens or puppies that need extra attention; pets that are undergoing medical treatment and require special care; or sometimes dogs or cats that are shy or fearful in a shelter environment, says Eileen Hanavan, director of volunteer and foster engagement at the ASPCA Adoption Center.

All those kittens in Stern’s first fostering stint eventually found “forever homes,” and Stern realized she had found a calling. “My husband and I looked at each other and I said, ‘I’m not gonna stop.’ And he goes, ‘Why would we stop? This was such a great experience.’ It’s emotionally draining but ... I’ve found my life purpose. I feel so lucky that I’m able to help.”

Stern has become a board member and national spokesperson for the North Shore Animal League America. When we talked to her, she had 14 foster cats in her home and anticipated taking on a mother cat with seven kittens. And she owns six cats and a rabbit. But fostering can be as fulfilling to people who can only care for one or two animals at a time.

Michael Price, 61, a retired sales director for AT&T, got into pet fostering after he started volunteering at spcaLA about six years ago. He says that often the most difficult aspect of the job is learning not to become attached when the animals find an adoptive home or go to a shelter when room is available.

Price remembers early on, when he and his partner, Richard, bonded emotionally with an adult cat. “I thought, I’m not cut out to do this. I was too attached to the animal, and this is breaking my heart to let him go.” Then he had a realization. “I finally just thought, That’s not my role here. I am a pit stop on their way to find their ultimate home. My job here is to make the time I have with them as beneficial as possible.”

Stern has a different strategy. “I can have an animal for two days or 10 months, and I get attached to every one,” she says. “I cry every single time, but after I hand them off to their new situation, I go pick up another one who needs me. That helps me through it.”