A six-year-old giraffe named Kitoto is on the final leg of an epic 4,200-kilometre journey across the Nullarbor to Perth Zoo.

Kitoto, which means "child" in Swahili, left Sydney's Taronga Zoo on Monday and crossed the WA-SA border on Wednesday afternoon.

The 4.5-metre tall giraffe has been an odd sight for passing motorists on the Eyre Highway as the animal regularly pops its head out the back of a specially built crate.

Kitoto's convoy, which includes a team of veterinarians following the truck, is due to arrive at Perth Zoo in the early hours of Thursday morning.

Perth Zoo life sciences director Maria Finnigan told the ABC the journey had taken six months of planning.

"We've had regular updates and she's travelling very well … drinking and eating as they stop along the way," Ms Finnigan said.

"I'm sure it's very interesting for people driving along the Nullarbor to see her.

"They're a magnificent species you'll see across the African savanna … you can be quite a distance away and suddenly a giraffe will pop out, so that chequered pattern they've got is actually quite camouflaging even though they're quite big animals."

Ms Finnigan said there had been a 40 per cent decline in the number of giraffes in the wild in the past 15 years, largely due to loss of habitat and poaching.

Breeding plan

Kitoto's journey across four states is part of plans for the giraffe to breed with Perth Zoo's 14-year-old male giraffe Armani.

A proven breeding bull, Armani has already sired three calves.

Last year, eight-year-old giraffe Asali made the 2,200km-journey back to Monarto Zoo in Adelaide after a lack of chemistry with Armani.

Last year a giraffe named Asali was transported from Perth Zoo to Monarto Zoo in SA. ( Supplied: Perth Zoo )

Ms Finnigan said the keepers would take it slow in introducing Kitoto to Armani.

"She needs to literally find her feet," she said.

"First off we will let her rest from the journey and then introduce her to our older female first, who can show her the ropes, and then down the track we will introduce the male so they run as one herd."