EDINBURGH Zoo's pandas are to be put together today after a morning examination found the female Tian Tian ready to mate.

The zoo said early today that the signs are positive with the bear believed to have gone into ovulation last night.

So far the signs have been encouraging for the pair after keepers swapped the pandas in their enclosures to mark their scent to increase interest.

Zookeepers will put the two bears together three times today for about 15 minutes, and have to be prepared to separate them should they become aggressive during the process, as can happen in the wild.

If they don't show immediate interest keepers can encourage the bears by gently moving them together with a bamboo pole, or by lifting Tian Tian's tail with the same method. When exactly that will happen is unclear, but a zoo spokeswoman said: "She has been rubbing her scent all over his enclosure, rubbing against his hay and he has been doing the same in her enclosure.

"She's telling him she's a female panda of breeding age and is almost ready to mate. They are showing all the signs they are quite willing.

"They have both had cubs before, although not together.

"They are pandas of the world, they are both experienced and know what to do."

Yang Guang has also been eating twice his normal daily intake, getting through as much as 40kg a day, for the past two weeks. The spokeswoman added: "This is innate behaviour to build up his strength. Sometimes you can't see him for the piles of bamboo."

Tian Tian has been eating slightly less as her biological balance changes.

Another option to aid the process is artificial insemination, but the zoo said it would not carry out the process this year.

The female is fertile for just 36 hours during the entire year, and this can happen any time between March and May.

Judging a pregnancy can also be difficult. If Tian Tian and Yang Guang mate this week, it might not be until mid-July before positive or negative results can be confirmed.