11/20/2012 at 05:05 PM EST
knows a good cause when he sees one.
The End of Watch
actor was honored Monday night at FIJI Water's New Eyes for the Needy 80th Anniversary dinner, held at Colicchio & Sons in New York, for his work with the organization.
"Jake, who brought his mom as his date, talked at length to the small room – and he didn't even have to give a speech! – he shared some personal stories from childhood," an onlooker tells PEOPLE.
Gyllenhaal explained to guests that he got involved with the organization as a child because his grandpa, a doctor, made him donate his eyeglasses every time his prescription changed.
He added that while "all his friends were trying to save the seals, he maintained 'If you can't see the seals, how can you help them?' " the source adds.
Sporting a beard, Gyllenhaal and his mom sat next to How to Make It in America
actress Lake Bell and her fiancé Scott Campbell.
Although not in attendance, Jay-Z, Adam Levine
and Gwyneth Paltrow
all donated items and experiences to the event's auction.
– Jennifer Garcia