The Children’s Eternal Rainforest (Bosque Eterno de los Niños) encompasses 55,600 acres (22,500 hectares) of protected forest, making it the largest private reserve in Costa Rica. The park was born from a classroom fundraising project that began in 1987 in Sweden and the United States, known as the Children’s Rainforest Movement. To date, students from 44 countries around the world have contributed to the purchase of rainforest near Monteverde for the purpose of protection. The Children’s Eternal Rainforest is among the last of Costa Rica’s reserves to house jaguars, who live alongside 120 other species of mammals, 440 species of birds and 700 species of butterflies — three percent of the world’s butterfly population. Bajo del Tigre, one of the park’s most popular trails, takes visitors on a 2-mile (3.5-kilometer) walk through the park’s secondary forest. Nightly twilight walks give a glimpse into the nocturnal fauna of the park.