Rooney Mara and Kate Mara

Kate and Rooney Mara recently flew to Liberia, Africa, with The Humane Society of the United States to visit more than 60 abandoned chimpanzees left to die by the New York Blood Center one year ago.

The chimpanzees were used as part of invasive research for decades by the NYBC, which decided to pull the funding required to care for them earlier this month. After the visit, the two sisters wrote an open letter to persuade the NYBC to renew its financial obligation to the abandoned chimpanzees.