Adelaide Zoo prepares to welcome first-of-their-kind tiger cubs

Adelaide Zoo tiger Delilah is preparing to become a mum, a year after arriving at the wildlife park.

The six-year-old Sumatran tiger has fallen pregnant to the zoo's male tiger, Kembali. The cubs will be the first-ever Sumatran tigers born at Adelaide Zoo.

The two were only introduced in the middle of the year, after she was brought across from Australia Zoo last December.

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It's a big breakthrough for the zoo, which has been attempting to breed Sumatran tigers for more than 15 years.

With just weeks to go, keepers say the first-time mother has put on seven kilos, and is more affectionate and sleepy.

"To have a pregnancy in less than 12 months of her arrival is just fantastic," Elain Bensted from Zoos SA said.

"It was amazing they were such a good pair. Kembali is an amazing male tiger, very impressed, and the cubs are going to be stunning."

Fewer than 400 of the creatures remain in the wild due to poachers and loss of habitat due to palm oil plantations.

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Delilah could give birth as early as Christmas Day.

Keepers won't know how many cubs are on their way until they arrive. The average is three or four.

They expect to allow visitors to help choose the names once they arrive safely.

It's fitting, as this is the year of the tiger in the Chinese Zodiac.

Sumatran tigers are the smallest of the tiger species, and aside from during courtship, are largely solitary animals.