They might be the world's smallest monkeys, but these little creatures are ready to rumble when dinner is on the line. A rival group's tree looks inviting; time for a clash of the (tiny) primates.

A different type of killer stalks the treetops of the Amazon.

It is ravenous, relentless and without pity...the pygmy marmoset.

It may look like four ounces of "cute and fluffy," but the world's smallest monkey is no plaything.

It can leap 15 feet in a single bound and move along the slightest of branches to snatch its prey.

Insects, though, are merely an afternoon protein boost.

This family of marmosets gets its main meal from a bump-covered tree.

The bumps are scar tissue, built up over months of daily attacks by these vicious sap-suckers.

The marmosets feed mostly on gum.

Using specially adapted teeth and claws, they rip open the freshly covered wounds and keep the sap flowing...until the tree is too scarred to provide any longer.

Then they'll move on to fresh territory that's inhabited by other marmosets.

Marmoset families are like the Hatfields and McCoys and don't take lightly to interlopers.

The incoming Hatfields invade the McCoys turf, itching for a fix.

The McCoys retreat to a nearby tree.

They watch helplessly as the newcomers raid their stash.

Chirping and scent-marking, the parents gather up their frightened young and launch a counter-attack.

The Hatfields are forced to flee.

The sweet nectar of success.

They may look cute, but don't get between a marmoset and its gum.