The threatened species had been smuggled from Java and Sumatra, a vast, jungle-covered island home to many rare animals.
Officials seized the suspect in the city of Kediri, East Java province Thursday after receiving numerous reports and monitoring various social media accounts where animal smugglers often sell their prey.
“We have caught one suspect, the seller aged 23. We’ve been monitoring this for a long time,” Beny Bastiawan, a senior official at the environment and forestry ministry told AFP.
The suspect planned to sell the animals for 200,000 rupiah ($15) each in the local market but officials estimated they would have been worth 2 million rupiah if sold in China, Bastiawan added.
The 10 endangered animals are now under the surveillance of vets at the environment and forestry ministry.
Under Indonesian law, a person caught selling protected animals faces a maximum of five years in jail and a 100 million rupiah ($7,500) fine.
The slow loris, a small primate known for its big eyes and grey fur, is closely related to the lemur and found across Southeast Asia.
The International Union for Conservation of Nature categorises the lorises in Sumatra as vulnerable while the wreathed hornbill is listed as a threatened species.