Think Thumbelina, but as a monkey...

Pygmy marmosets are the smallest true monkey in the world, standing at just 5 inches tall (not including the length of their tail) and weighing 4.5 ounces. They inhabit the Amazon Rainforest in South America, climbing to the tops of the trees, as their small size allows them to cling to branches that are too thin to hold the weight most animals. Despite the name however, the monkeys are not true marmosets and its genus, Cebuella, is unique; true marmosets belong to the genera Callithrix or Mico.

The tiny pygmy marmoset monkey, Cebuella pygmaea.

The marmosets prefer to inhabit trees on the banks of rivers, where the upper foliage is usually more easily assessable and the open view makes it easier to spot birds of prey, one of their main predators. The monkeys occupy a similar niche to squirrels in Europe, although their diet predominantly consists of tree gums and saps and is occasionally complimented with insects. The monkeys are highly mobile, being able to jump distances of up to 5 metres at a time! This is possible due to their small size, as they exert much more force in their muscles compared to the size of their body than larger animals, like humans, do - the same reason that ants can carry objects much bigger than themselves. This amazing jumping ability allows them to easily traverse great distances, well for them at least, in search of food and is a fantastic defence against predators.

Although pygmy marmosets aren't particularly intelligent for a primate and have an unusually underdeveloped brain, they have a surprisingly developed communication system. Their 'language' consists of clicks and squeaks, many of which are too high pitched for humans to hear and scientists have identified certain calls that have specific meanings, such as that a predator is in the vicinity.

The monkeys are also highly territorial, with males competing with each other to be the dominant, breeding male. Rather than fighting with each other, which many animals do at great physical cost, the monkeys flatten the fur on their head and pull faces at each other, whilst simultaneously grabbing and displaying their genitals. Whereas this may look hilarious to us, for the competing males it is an epic duel and signifies their place in the group's social hierarchy, including whether or not they are allowed to mate.

Fortunately, the monkeys haven't been too badly effected by the mass deforestation of their habitats as of yet; maybe because their small size means that they don't need much space to survive in. Although, this could change very soon - species have a habit of appearing to fine for an extended period of time and then, suddenly plummet in number to become an endangered species in a matter of years. Hopefully though, this will never happen and the comical primate will survive for generations to come.

Notice the pygmy marmosets hands that have claws instead of nails and, since they are New World monkeys, do not have opposable thumbs.