Staff members place bags filled with food for giraffes at the Johannesburg Zoo in Johannesburg, South Africa, on May 1, 2020. The zoo has been closed since March 26 due to the COVID-19 pandemic. (Photo by Shiraaz Mohamed/Xinhua)

A staff member prepares food for animals at the Johannesburg Zoo in Johannesburg, South Africa, on May 1, 2020. The zoo has been closed since March 26 due to the COVID-19 pandemic. (Photo by Shiraaz Mohamed/Xinhua)

A staff member feeds an elephant at the Johannesburg Zoo in Johannesburg, South Africa, on May 1, 2020. The zoo has been closed since March 26 due to the COVID-19 pandemic. (Photo by Shiraaz Mohamed/Xinhua)

A staff member looks after rhinoceros at the Johannesburg Zoo in Johannesburg, South Africa, on May 1, 2020. The zoo has been closed since March 26 due to the COVID-19 pandemic. (Photo by Shiraaz Mohamed/Xinhua)