Later on Tuesday, several Iranian media outlets, including the semiofficial ILNA news agency, said two other conservationists were also released, Sepideh Kashani and Taher Ghadirain.
The four are among more than 2,000 prisoners granted amnesty on the occasion of Eid al-Fitr, which celebrates the end of the Muslim holy month of Ramadan.
The United Nations Environment Program on Monday welcomed the release of Bayani and Jowkar, who are members of the nonprofit Persian Wildlife Heritage Foundation. Iranian authorities released Sam Rajabi, another member of the group, in 2023.
The conservationists were arrested in 2018, along with Kavous Seyed-Emami, the 64-year-old founder of the Persian Wildlife Heritage Foundation. Seyed-Emami, an Iranian-Canadian dual citizen, died while awaiting trial under disputed circumstances.
Bayani was sentenced to a 10-year prison term in 2019, while the others received six-to-eight-year terms on espionage charges. The case against members of the nonprofit Persian Wildlife Heritage Foundation came as protests and unrest shook parts of Iran amid a government-imposed internet shutdown.