Why a Former Undercover Investigator Is Sending Marshmallows to Monkeys in Labs

New memoir Marshmallows Are Their Favorite documents an undercover investigation at a primate lab and launches with a public campaign for the monkeys still inside

LOS ANGELES, Oct. 6, 2026 /PRNewswire/ -- Former undercover animal cruelty investigator Lindsay Oliver today released Marshmallows Are Their Favorite: Undercover at a Primate Lab (Ender Press), the true story of her four months inside one of seven U.S. National Primate Research Centers.

Forget bananas. The monkeys Oliver met loved marshmallows. That discovery inspired the book's title and a public campaign. At sendmarshmallows.com, supporters can purchase bags of marshmallows and write personal notes for the monkeys held at all seven primate centers.

"A favorite is personal," Oliver said. "It tells you there is an individual there."

Oliver worked inside the facility as a lab technician, recording what happened with covert cameras. The monkeys were used in experiments involving diet drugs, alcohol, and nicotine. But as they emerged as individuals and coworkers became friends, the investigation grew far more personal and complicated than she expected.

"I spent four months lying to people I came to like," Oliver said. "The hardest part wasn't the risk of getting caught. It was separating the people I was deceiving from the system I came to expose."

The campaign aims to collect 1,000 bags for coordinated deliveries in December. Each delivery will include supporters' messages and a letter asking the labs to begin transitioning toward sanctuary and human-based science.

Marshmallows Are Their Favorite is available in hardcover and eBook wherever books are sold.

About Lindsay Oliver: Oliver is an award-winning former undercover investigator who has conducted or overseen more than 100 investigations and is featured in the documentary Eating Animals, produced by Natalie Portman. She is Executive Director of Animals International US and founder and CEO of Justify, a nonprofit supporting lab workers and advancing human-based science.

Media Materials: lindsayoliver.com/press
Media Contact: Lindsay Oliver |  [email protected] | 323-538-0079

SOURCE Ender Press