Ten orangutans have been released back into the wild in the Indonesian portion of Borneo island, with helicopters used to ferry the critically endangered great apes deep into the forest from rehabilitation centres.
In total, five males, a mother with two babies, and two other females were released with assistance from Indonesian conservation agencies.
The Bornean orangutans included Nenuah, a 19-year-old female who was repatriated from Thailand, according to the Borneo Orangutan Survival Foundation (BOSF).
"Using a helicopter is the best way to transport orangutans during the pandemic," said Denny Kurniawan, BOSF program manager, noting it would have taken three days of driving to reach one drop-off area, adding to the risk of COVID-19 transmission.
Orangutans and other apes are known to be susceptible to human respiratory illnesses, so veterinarians donned protective suits and masks during final medical checkups.
"Efforts to help curb the spread of the COVID-19 virus have hampered many conservation-related activities," said Handi Nasoka, acting head of Central Kalimantan's conservation agency.
Rehabilitation has been a slow process for other orangutans that arrived at one centre with Nenuah in 2006, the foundation said in a statement, adding that most of the apes have found it difficult to develop the skills needed to fend for themselves in the wild, due to lengthy periods spent in captivity.
There are only estimated to be around 100,000 Bornean orangutans left in the wild, according to the World Wildlife Fund, more than half the population being depleted over the past 60 years.
They have suffered from illegal poaching, as well as destruction of habitat due to large-scale logging and replacement of forests with cash crops such as palm oil.
Australian Associated Press