Critically endangered twin cotton-top tamarin monkeys born at Animal Kingdom

The critically endangered cotton-top tamarin monkey population at Walt Disney World just doubled in size.

Weighing about as much as a chicken egg and measuring about four inches long, twin cotton-top tamarins were born at Animal Kingdom's Discovery Island. They are the first of their species to be born at Disney World since 2001, according to the park.

"These pint-sized newborns cling tightly to their parents as both mom and dad acrobatically leap from branch to branch in their habitat on Discovery Island," Dr. Mark Penning, vice president of Disney Parks' Animals, Science and Environment division wrote in a Disney Parks Blog.

Penning said it's too soon to know the sex of the monkeys, so they have yet to be named. Currently sharing parenting duties, their parents will carry them on their backs for up to 14 weeks.

Twins are typical for cotton-top tamarins, Penning said, and even when fully grown, adults will weigh less than a pound and are about the size of a squirrel.

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Native to Columbia, cotton-top tamarins are considered to be "critically endangered" by the International Union for Conservation of Nature Red List of Threatened Species. There are an estimated 7,500 remaining in the wild, and the biggest threats to this species include deforestation, the illegal pet trade and loss of habitat.