02/26/2010 at 08:00 AM EST
Webster works like a service dog, but he isn't one. And he sometimes acts like a bratty little kid, but he isn't that either. Webster is a 21-year-old capuchin monkey that lives with Marine Cpl. Tim Jeffers, who lost his legs, right eye, part of his right forefinger and part of his skull in Iraq in 2006.
Jeffers, 25, lives with Webster in an apartment in San Diego. Through intensive rehabilitation, Jeffers can move about with the help of a wheelchair or custom made prosthetic legs. But tasks like turning on a light switch and using a remote can cause him great pain, which is where Webster comes in.
"To me, the most indispensable thing about Webster is his companionship," Jeffers tells PEOPLE. "If someone would point a gun at Webster, I would actually jump in front of the bullet for him. I never thought I would say that in my life about anybody."
The 5-lb. monkey was trained by Helping Hands: Monkey Helpers for the Disabled
, a Boston-based organization that trains monkeys to assist those with disabilities.
Helping Hands placed Webster with Jeffers in 2008. It typically takes time for new recipients to acclimate to their furry companions, but for Webster and his new master, it took less than a week. 15 months later, Jeffers may only be his master in theory.
"I still pay the bills, but he tells me what to do," Jeffers says. "He gets fussy, like a little kid. He always wants my food, even though he isn't going to get my food."
That's because Webster has a restricted diet, one that's limited to protein and complex carbohydrates. Even though he loves oatmeal and chicken, Webster is "a fiend for Cheetos," Jeffers says.
It's trying to keep the Cheetos and pizza away from his monkey, along with all the other facets of being responsible for Webster's care, that keep Jeffers going.
"Webster has this way of really making Tim happy," says Jeffers's mother, Brenda Pitts. "Webster is his reason to get up every morning, and that is good. I am glad that he has Webster."For more on Marine Cpl. Tim Jeffers and Webster, pick up the latest issue of PEOPLE, on newsstands now.