Melbourne elephant birth edges closer

As her 22-month pregnancy enters its final stage, Melbourne Zoo's expectant elephant Num-Oi is being watched more closely each day.

Vets are giving Num-Oi an ultrasound each week and testing her hormone levels twice a week, ahead of the expected birth in mid-to-late May.

Once there are signs of an imminent birth, Num-Oi will be monitored on CCTV 24 hours a day.

That will require staff to work around the clock from a caravan that was delivered to the zoo on Tuesday.

"It's going to be tough on the team but it's very necessary to keep a good eye on Num-Oi and make sure everything goes really well with the birth," elephant keeper Dominic Moss said.

Mr Moss is confident Num-Oi, whose first calf Sannok died before his first birthday, will be a great mum.

"For Num-Oi to have another calf in her life will be so important," he said.

"She's a brilliant mum and she's devoted to any calf.

"They say elephants are sometimes just born mothers and she's definitely a born mum."

Any chances the youngest of the herd, two-year-old Man-Jai, won't like the new addition was dismissed by Mr Moss.

"Man-Jai's big sister is a bit offish with him at times and having a little baby for him to play with, he is going to absolutely love it," he said.

The calf, whose gender will remain unknown until the birth, is expected to top the scales at over 100 kilograms.