Panda-ring to the camera: Unusually amorous Yang Yang and Long Hui try for their FOURTH baby

Pandas are not typically known for their lovemaking prowess in zoos, but one pair seem to have no problems at all getting some action. 

Two amorous Giant Pandas have caused a 'sensation' by being the only pandas in Europe to mate in captivity, and have already produced three babies since they arrived at the zoo in 2003.

Yang Yang and Long Hui were seen romping on several occasions recently at Schonbrunn Zoo in Vienna.

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Rare footage shows the pair mating energetically - before the female loses patience and cuffs the male about the head.

The Giant Pandas are normally loners but more recently they have been restless, not eating too much, leaving their mark everywhere and making a lot of noise.

Zookeepers noticed their behaviour change around a week ago and let the two bears get together.

Staff at Schonbrunn Zoo now have an anxious wait of around two months to see if the mating was successful and Yang Yang is pregnant.

It is the only zoo in Europe where the pandas breed naturally.

Giant Pandas are particularly poor at reproducing while in captivity, making the Schonbrunn Zoo pandas' efforts all the more praiseworthy.

The issue of pandas' lack of reproduction can be attributed to a number of factors. 

Despite possessing the digestive system of a carnivore, the species has evolved to depend almost entirely on bamboo, which provides little energy for the bears. 

The average length of a mating session between two pandas is between 30 seconds and five minutes.

They also have a short mating season and timing is everything, with female pandas generally only interested for two or three days a year during the spring.

Giant pandas reach sexual maturity between the ages of four and eight, and may be reproductive until age 20.