Thirteen rare dwarf monkeys have been stolen from Wissel zoo in Epe, the zoo authorities confirmed on Thursday.

The haul included a pair of golden lion tamarins, six silvery marmosets, three pygmy marmosets, a cotton-top tamarin and an emperor tamarin. Some of the monkeys are included on the Cites list of the world’s most endangered species.

The theft was spotted by a keeper on Thursday morning when he noticed the cages had been forced open and 13 of the collection of 45 monkeys were gone.

Zoo spokesman Bernard Holdijk told reporters he is extremely concerned about the welfare of the monkeys. In particular, they are prone to stress and require very careful looking after, he said. The freezing weather conditions are also a danger.

The zoo authorities have contacted other zoos with specialist monkey collections warning them to increase security measures.