Pygmy marmosets are arboreal creatures, scampering, dashing, and leaping from tree to tree in the sheltered areas of South America‘s rainforest canopy. Their sharp claws help them attach to tree trunks and vines. They gnaws holes in tree and vine bark to eat tree gum and the insects (especially butterflies) that the gum attracts.

Each pygmy marmoset weighs less than an apple. They’re the tiniest monkeys on the planet and one of Earth’s smallest primates.

See how they play, jump, climb, and sound their ‘forest alarm’ in this clip from the PBS Nature‘s Undercover in the Jungle.

For this Ecuador-based episode, naturalists set up over 50 remotely operated cameras and mini-cams that filmed non-stop, day and night, for an entire month—”from the dark rainforest floor right up to a tangled canopy 300 feet in the air.”

Some additional background on their calls from Wikipedia:

The pygmy marmoset is well known for its communication abilities including an intricate system of calls. The trill is used during feeding, foraging, and when traveling and the group is close together. The J-call is a series of fast notes repeated by the caller and is used at medium distances. Both calls are used as contact calls. The long call is used when the group is spread out over distances greater than ten meters or in response to a neighboring group.

Watch this next: Phayre’s Leaf Monkeys with a bright orange baby. Plus, watch more videos about monkeys on TKSST.