Twin red ruffed lemur babies were born at the Singapore Zoo on Feb 22.

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)," the Wildlife Reserves Singapore (WRS) said in a video it posted on Facebook yesterday.

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 were specially matched for conservation breeding because of their compatibility, said the WRS.

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

"On top of this, females are fertile for only 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 zoo.

Red ruffed lemurs are native to north-eastern Madagascar. 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.