How Avatar's Zoe Saldana conquered the universe

Zoe Saldana is delightfully hyper. She arrives for our photo shoot at the Hotel Shangri-La in Los Angeles like a long slender tornado, darting lightly between clothes changes while talking at a pace of about 100 ideas a minute. A New Yorker through and through, she hates to sit still: 'Getting a manicure or a pedicure is like torture for me!'

Clearly, a woman with supernatural levels of energy, which is perhaps why she has been cast as, variously, an officer on the Starship Enterprise (in JJ Abrams' surprisingly watchable 2009 Star Trek prequel), a pirate of the Caribbean (she got to slap Johnny Depp), and, most recently, in James Cameron's $500 million labour of love, Avatar, as a sinuous blue huntress from the planet Pandora.

Ten years in the making, this is Cameron's first major film as director since Titanic, and the starring role is a huge break for Saldana - except for the pesky fact that we won't actually see her on screen. The film's innovative 'motion capture technology for animation' means that all her movements, from balletic leaps to dilating pupils, are translated into a cartoon version of herself, an on-screen avatar that is her and yet is not her - for a start, she's entirely blue.

When she sees her character on billboards, does she recognise herself? 'Sure. I just see me, except blue. And with a different forehead and nose.' And a tail. 'Right. That's a limb I can only imagine having. As humans, we lost our innocence and we lost our tails... Actually, I tried not to think of it too much, I focused on how my torso was moving, then what the tail does is something that Jim [James Cameron] and the team add on after. And how my ears twitch, too. My character is very agile, a hunter and a warrior. We looked a lot at the feline kingdom for inspiration. And she's very playful, so we looked at dolphins...'

Handily for one trying to imitate a feline dolphin, Saldana has ballet training, having graduated from the Dominican Republic's premier dance academy, the Ecos Espacio de Danza. This stood her in good stead for working with the notoriously shouty James Cameron. 'My experience of working with Jim was nothing but absolutely amazing, but I also come from a ballet background and you can't get more ruthless and kaiser-like than a ballet teacher. They're just relentless. It teaches you to become like a soldier. Jim pushed me because I allowed him to push me and I pushed him, too. Being on set was enticing and addictive, and Sam [Worthington, her co-star] and I just didn't want to wrap at the end of the day.' Her voice is warm, persuasive and very fast. Her full stops sound like commas and her commas are barely there. Everything comes tumbling out like a forward somersault.

'I think part of life is learning from your mistakes and if that's your view of life then Jim has really learned from his experiences.' He's mellowed, in a word. But she's on to the next thought: 'Yes, it helps if you're working with someone nice, but at the same time, if I start having a problem with someone not being nice, I'm the one with the problem, right?'

Zoe's character is Neytiri, the princess of the Na'vi, a civilisation plucked entirely from Cameron's imagination, complete with their own language and customs. 'My character is very childlike,' she says, 'and luckily for me I have a niece who was three and a half at the time when I started doing all my research for Avatar, so she was my little guinea pig.' When it came to finding the innocence within herself, Zoe had to dig deep. 'I'm 31 and I come from Queens, New York, and I'm very street savvy. I've seen a lot of shit.'

The middle of three sisters, she lost her father in a car crash when she was nine. 'My parents were a good team at raising us, they were very good friends, and my mom never expected to have to raise us without my father. She had us when she was very young and she never expected to work. It was a shock for all of us, for my mom having to become the father and the mother, and we did lose a lot of innocence and have to mature quickly.'

Fearing Queens was no place to raise three daughters singlehanded, her mother packed them off to school in her homeland, the Dominican Republic. Was it fun? 'It was never fun, boarding school. Oh my God, no. We did not care for that. We did not want to be away from our mom. We saw all the sacrifices that she and my grandmother and my great-grandmother were making just so we could have a good education, but at the end of the day we were suffering because we needed a mom's touch, we needed to smell her and just be around her.' Zoe's mother stayed in the States, working to keep the family afloat. 'She did everything from cleaning bathrooms, to working as a nanny, to translating legal documents. I'm so grateful to her. You see kids being so inconsiderate with their parents, but every five dollars Mom takes from her purse, that's money she made from the sweat of her brow.' There's no time to cue violins, as Zoe is on to the next instalment.

'When I was 17, we said, "Mom, you did great, you kept us safe and away from drugs, but we belong in America. Let us come home." And so we did, and when we got back some of the friends we'd left behind were already having second and third babies. No joke.' Nowadays, says Zoe proudly, her mother does 'Nothing! Although she told us last week that she's thinking about going back to school and becoming a paediatric nurse.' Zoe's mother is a sci-fi geek, which came in useful when Zoe needed background for playing Uhura in Star Trek, and loves going to premieres. 'But she's clear that what I do is no more special than what my sisters do.' (Her older sister is a paramedic, and the youngest works as a music producer at Milk Studios; both are based in New York.) 'I've never felt that one of us was favoured or unfavoured, and in Latino culture that's actually not common. In Latino culture it's old country ways where you choose: one child's going to be a maid, and one child's going to be successful, and one's going to work in the village. My mother didn't want any part in that.'