But Uli, a married father of five who holds down three jobs, couldn't do it alone.
"The problem in my area was the number of stray cats increasing dramatically," he says. "A newborn baby could not reach adulthood because of the lack of attention given to them - to give medicine when they're sick."
Then he found his angels.
In 2014, Kristen Connelly, who lives in Oxnard, California, stumbled upon Uli's Facebook profile.
"He has such an amazing interest in cats," she tells The Dodo. "And I thought, I really need to know this person."
So she sent him a friend request. And then Connelly asked him if there was anything she do to to help him.