An Eastern Pygmy Marmoset, the world’s smallest species of monkey, has given birth to twins at Chester Zoo.

The tiny babies, weighing in at just 15 grams, will measure just five inches in length when fully grown.

Arriving to mum Audrey and dad Gumi, the mini-monkeys were born on July 25 but have only now grown to a size whereby they’re big enough to spot.

Photo Credits: Chester Zoo

Dr. Nick Davis, Deputy Curator of Mammals at the zoo, said, “Pygmy Marmosets actually have relatively large babies for their tiny size. An adult will only weigh up to around 150 grams and so each baby equates to around 10% of its body weight.”

Davis continued, “After giving the babies their regular feeds, mum Audrey, like all other female Eastern Pygmy Marmosets, steps aside while dad takes on the parental chores. The youngsters can therefore often be seen being carried by dad, Gumi, for long periods of time as mum takes a well-deserved break.”

Eastern Pygmy Marmosets (Cebuella pygmaea) are native to the rainforests of western Brazil, southeastern Colombia, eastern Ecuador and eastern Peru. They are generally found in evergreen and river edge forests and are known to be a gum-feeding specialist, or a “gummivore”.

The Pygmy Marmoset is the world’s smallest “true monkey”. They have a head-body length ranging from 117 to 152 millimeters (4.6 to 6.0 in), a tail of 172 to 229 millimeters (6.8 to 9.0 in), and the average adult body weighs in at just over 100 grams (3.5 oz.).

They are currently classified as “Least Concern” on the IUCN Red List of Threatened Species. They are threatened by both habitat loss and from being captured for the pet trade.

More great photos below the fold!