A pair of Tanzanian geckos, a boisterous Bornean orangutan and a languid pygmy hippo.

These were among the 540 animals born to the Wildlife Reserves Singapore (WRS) last year - 173 at the Singapore Zoo, 43 at River Safari, 90 at the Night Safari and 234 at Jurong Bird Park.

The animals are of 145 species, 39 of which are listed as threatened.

Among the critically endangered species is Khansa, the 46th successful orangutan birth at the zoo, which is now eight months old.

Its birth came as a silver lining to the 2016 announcement by the International Union for Conservation of Nature (IUCN) that Bornean orangutans were to be moved up from endangered to critically endangered.

To maintain genetic diversity, orangutans born under the care of WRS have been sent to zoos in countries such as Malaysia, Japan, and Australia as part of an exchange programme.

Another critically endangered species is the electric blue gecko, which saw two hatchlings in December, bringing its total count to nine.

The Tanzanian native is among the most threatened gecko species in the world due to its popularity in the illegal pet trade. Baby geckos are brownish green in colour, but males turn electric blue when they grow older. Their chances of surviving in the wild are quite "precarious", said Dr Cheng Wen Haur, WRS' deputy chief executive officer and chief life sciences officer.

Now less than a month old, the pair's gender has yet to be identified as they have not reached sexual maturity.

Endangered species which celebrated their first birth in almost a decade include the king penguin and jaguar.

King penguin chick Maru - meaning "round" in Japanese - was given a name befitting its tubby build. First revealed to the public last month, it was raised by the bird park's breeding and research centre to maximise its chances of survival. Barely a month old, the jaguar cub has yet to be named by its zookeepers. It will need at least two more months before it can make its first public appearance.

"Everything that (the WRS does), including breeding them in our care and protecting them in their native habitats, is very important. There's no way we can slacken off," said Dr Cheng.