SINGAPORE - Twin red ruffed lemur babies were born at the Singapore Zoo on Feb 22, at a time when Covid-19 began its spread across the globe.

The lemur babies, which have not been named yet, are almost five months old and have begun to welcome visitors following the zoo's reopening on July 6.

"(The twins) can often be spotted enjoying meals with their parents at (the zoo)," Wildlife Reserves Singapore (WRS) said in a video it posted on Facebook on Thursday (July 16).

The last time the zoo welcomed the birth of the critically endangered red ruffed lemur was 11 years ago when the twins' father, Bosco, was born.

His mate, eight-year-old Minnie, arrived in Singapore Zoo from Japan in 2016.

The couple was specially matched for conservation breeding because of their compatibility, said WRS in a statement.

"Reproduction for these rust-coloured primates is notoriously difficult as they only breed once a year," the reserve said.

"On top of this, females are only fertile for one out of the few days they are sexually receptive, making this twin birth particularly special."

With the new additions, there are now five red ruffed lemurs, 12 ring tailed lemurs and three black and white ruffed lemurs at the Singapore Zoo.

Red ruffed lemurs are native to the north-eastern part of Madagascar and the biggest threat they face is habitat loss due to illegal logging and hunting.

There are between 29,000 and 52,000 red ruffed lemurs left in the wild.

They are a sister species to the black and white ruffed lemurs native to eastern Madagascar.

Even though the two species do not co-exist in the same geographical range, they are able to understand each other's calls and communicate.