Charlie Yaeger is no young pup.

At 100, though, the Duluth great-grandfather is determined not to slow down. At least, not too much.

Frequently on weekends, you can find Yaeger decked out in his red cap and volunteering for the Georgia Society for the Prevention of Cruelty to Animals.

“I’ve just always loved animals,” said Yaeger, who started volunteering with his daughter, Chris Cooper, three years ago. “I don’t have a medical degree, so I can’t handle humans. This is my way of sharing life (with animals), of showing them love, keeping them safe and well fed.”

Yaeger, who moved to Georgia to be closer to his two youngest children after his wife, Madeline, died in 1996, is probably the oldest active volunteer at the Georgia nonprofit, and perhaps in much of the metro area’s volunteer world.

“I’m always trying to recruit people 50 and older to volunteer,” said Laura Wade, the volunteer coordinator for the Georgia SPCA. Older volunteers, she’s found, are usually dependable and have the free time to help.

“He’s such a people person,” Wade said of Yaeger. “He’s great at meeting people and explaining the (adoption) process. I never knew how old he was, he has such a youthful spirit. He’s like a child, with dogs especially. He’s a natural and we could always use more Charlies.”

“This is something that we can do together and we are both huge animal advocates,” Cooper said.

Experts say there are emotional and physical benefits for older American who volunteer. It helps prevent isolation and fosters feelings of still being a productive member of society. It also keeps them active, which has positive benefits on their health. Studies have found that older adults who volunteer are able to delay or even reverse declining brain function.

Yaeger likes his independence. He lives in a two-bedroom house on his own, travels, still drives and has a Facebook page with 99 friends. Parked outside is a white Nissan Versa, which he bought as a 98th birthday present to himself. He sets his oven timer so it goes off every 40 minutes, at which point he will get up and move around.

Cooper comes to visit her dad several times a week. At least two of her dogs usually come along. He calls them his grandbabies. During a recent visit to his home, Yaeger insisted on including the dogs — Samantha, a black lab-corgi mix, and Mia, a feisty Chihuahua — in a photograph.

Yaeger grew up in Norwood, located outside Cincinnati. His father, Harry, was an inventor-engineer for a business machine company. His mother, Albertina, was a music lover, playing piano to accompany his dad’s violin on Sundays at their home. Yaeger remembers sitting inside a large Victrola cabinet as his father listened to music on one of the very early home music machines.

Yaeger attended Lehigh University, but quit after two years, deciding he had learned all he could. His daughter said he was more interested in "doing things" than keeping his head in the books.

He worked in a variety of industrial jobs as a metallurgist and in quality control. After a few jobs in plants that made weapons or support aircraft, he was ready for a change.

“I decided I didn’t want to make weapons anymore,” Yaeger said.

He then moved to North Carolina, where he managed a paper mill and later assembled a cooperative of mountain craftsmen. Then he led business development and expansion at the Winston Salem Industries for the Blind.

“I wanted something that gave life, instead of taking it away. Those were the best years of my life,” he said.

Yaeger, who loves big band music and stays glued to MSNBC, attributes his longevity to prayers and not asking for things, “but being grateful. My motto is everyday is Thanksgiving. If you want to find the good in the world, you can.”

And he has — as a volunteer.