KANSAS CITY, Mo. (AP) – The Kansas City Zoo is welcoming the arrival of twin golden lion tamarins, an endangered monkey species.

The babies were born last week. They are on view in the zoo’s Tropics exhibit.

The zoo’s general curator, Liz Harmon, says the babies are only about one-and-a-half times the size of a human thumb.

Visitors have to look closely to spot the twins as they cling tightly to their mother.

Deforestation in the bright orange primates’ native Brazil has reduced their numbers. Some captive tamarins are being returned to the wild, but Harmon said the zoo’s babies probably will remain in the breeding program.

It’s still too early for zookeepers to determine their gender.