It has been a tireless campaign to save Australia's most critically endangered reptile from extinction, but a lack of habitat and global warming means the Western Swamp Tortoise still faces a long road to recovery.

Brought back from the brink of extinction after just 30 of the animals were left in the world, numbers of the tortoise have been slowly rising since a breeding program began at Perth Zoo in 1989.

With what is expected to be 46 tortoise hatchlings this year, the zoo has now bred nearly 1,000 of the creatures in captivity.

Perth Zoo keeper Bradie Durell said the total population of the tortoise, found only in WA, now stands at between 400 and 500, with 200 of those currently at the zoo.

"We can breed and release on average 30 a year," he said.

"The issue now is that we don't actually have places to release them to."

Mr Durell said the Western Swamp Tortoise was found at Ellen Brook and Twin Swamps Nature Reserves, plus two release sites at the Mogumber and the Moore River Reserves.

"At this stage we have released as many as we want to into those sites, and now we have to kind of step back and observe ... whether the populations are viable and they are going to take care of themselves," he said.

"If we could find more habitats, essentially we could get their numbers up and get them off the critically endangered list."

Much of the species habitat has been destroyed by developments.

"Not only are they dealing with loss of habitat and global warming, but they also have to deal with the introduced predators like most other Australian animals," Mr Durell said.

A delicate breeding process

The breeding season at Perth Zoo starts in July and most of the eggs are laid in November.

Tortoise eggs are stored in an incubator at the Perth Zoo before hatching. ( ABC News: Eliza Laschon )

They are dug up and placed into incubators for around 130 to 180 days before hatching.

The keepers then have the delicate job of sometimes helping them hatch out of their egg before placing them into man-made ponds where they are raised.

Mr Durell said every tortoise was different, with some taking five minutes to make their way to the water while some took over an hour.

The zoo keeps a key showing red nail polish markings on baby tortoises so it can identify them. ( ABC News: Eliza Laschon )

"The first breath is usually the most uncoordinated, and essentially after they've done that they seem to be perfect," Mr Durell said.

"It's just the learning process. They need to figure out how to be a turtle."

When the tortoise reaches 100 grams, usually at around three years of age, it is released into the wild by the Department of Parks and Wildlife (DPW).

However the program does not stop there, as the DPW then tracks the tortoises.

Researchers are also continuing to work on finding new habitats which could potentially home the tortoise in the future.