Years before it was called “street art”, Dan Witz was painting images of colorful humming birds on walls in New York City. In more recent years, the renowned artist has been working with PETA to raise awareness about the plight of abused and exploited animals.

Last week, Witz began scattering heartbreaking paintings of caged baby monkeys around the Washington, D.C. area to protest the gruesome experiments by the National Institute of Health on infant primates.

The NIH admits using monkeys to study the effects of stress on infant primate development, but claims to take steps to ensure the ethical treatment of the monkeys. Well. Dan Witz and PETA disagree, and hope to encourage the American public to protest the abuse.

Each painting in the D.C. project comes with hashtags so that viewers can search social media for more information on NIH treatment of animals. You can find out more about the issue here.