Austrian researchers studying the mammals of Piedras Blancas NP in 2003 and 2004 compiled a list of 96 species sighted or documented by camera traps. The fourteen species of carnivores include raccoons, coati, kinkajou, olingo, skunks, grison, tayra and five species of cats (jaguar, ocelot, margay, jaguarundi and puma). It is, however, highly unlikely that tourists will encounter a wildcat as they are elusive and nocturnal. Two-toed sloths are rare in the Esquinas forest but can be found in the coastal areas around Golfito. Around 20 years ago, the giant anteater was seen for the last time by local hunters, but it is extinct today. The northern tamandua has been sighted near Esquinas Lodge and the silky anteater was recorded in the mangroves near Golfito.

White-face capuchin and squirrel monkeys are often seen in the lodge garden, whereas howler monkeys are usually heard and seen on the Golfo Dulce coast and spider monkeys have been regularly sighted since 2006. Five species of american opossums have been recorded, including the mexican mouse opossum, the gray four-eyed opossum and the common opossum. Rodents include the agouti paca, collared peccaries and several species of mice, squirrels and rats. With 53 different species, bats are the richest mammal group in Piedras Blancas NP. Most of the species are fruit eaters like Artibeus watsoni and Carollia perspicillata. The vampire bat is a real blood feeding animal and was found foraging in open habitats near La Gamba.

Since 2003, the number of park rangers has increased from 6 to 16. They patrol the trails and the coast, and there is a consensus among the local inhabitants that populations of peccaries, agoutis and other animals that had been hunted are rising.