Behind the scenes at Perth Zoo, in a room full of glass aquariums with mesh tops, lives one of Australia's rarest marsupials.

Rustling quietly, the dibblers dart from one end to the other, then sprint on their plastic wheels. There are 25 in here, and they are ready for their breakfast.

Dibblers are tiny carnivores, who once hunted with speed and agility across the leaf litter of Western Australia and South Australia.

Scientists know this because they have found records — in the form of ancient bits of regurgitated owl dinners — in the sub-fossil deposit.

That owl vomit tells a depressing story, showing a dramatic contraction in the dibblers' range after European human and fox settlement.

The dibblers are now known to persist in just five locations, many of them established after breeding program reintroduction.

Perth Zoo's native species breeding program has been working with dibblers since 1997.

They started with populations from a group of islands off the WA coast, and are now working exclusively to breed mainland populations.

The two populations are still classified as the same species, but they differ greatly in size, and scientists have deemed that it is best to keep the populations genetically separate, mirroring the natural island effect.

"They've been separated on those Jurien Bay Islands for hundreds, thousands of years," Ms Cathy Lambert, the supervisor of the native species breeding program at Perth Zoo, said.

"They've adapted to life on an island, and generally that means that you get smaller. So that's what happened to the dibbler."

When it comes to reproduction, size matters

Dibbler size plays a big part in reproductive success.

"With dibbler mating, it only works if the male is bigger than the female," Ms Lambert says.

"She will reject any dibbler that she can fight off, the strategy being that she wants, presumably, the biggest strongest male to sire her young.

"If he can't overpower her, it won't work."

In the context of a breeding program, complete with a stud book and a nationally crucial conservation outcome, this is an important piece of information.

"We stage it so that if we have a male that's a very similar weight to a female that he's genetically suited to, then we juggle around his diet a little bit before the breeding season, give him a few more meal worms and crickets and get him up," Ms Lambert says.

"If he's five to 10 grams heavier than the female come mating time, that's usually enough to sort them out."

A young dibbler, newly weaned and ready for release in the wild. ( Supplied: Perth Zoo )

A balanced diet: Insects, worms 'in peak condition'

The quality of the food that is fed to the animals is supremely important, so the zoo farms its own mealworms, wood roaches and crickets specifically for its breeding programs.

These are housed in another room near the dibblers. When you walk in, it is a sensory overload, with a rich musk of wood roach so thick you can almost taste it, and a surround-sound cricket chorus.

The invertebrates are raised with the best available food and accommodation. They are in peak condition when they are released into dibbler enclosures.

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"[Wood roaches] are a bit more of a challenge for the dibbler than the cricket, because they're a bit smarter," Ms Lisa Mantellato, a technical officer with the zoo's native species breeding program, said.

"What they tend to do is go and hide very quickly and stop moving and then it's harder for the dibbler to detect them.

"These animals also have the best care possible because we're feeding them to our precious endangered animals."