JERUSALEM (AFP) - The latest export from the land of milk and honey is a grass-chomping mammal that hangs out in rivers and lakes and is apparently hard to sedate.

Israel's top safari says it has become the world's top exporter of hippopotamuses, having successfully sent more than a dozen of the artiodactyls to zoos worldwide in the past few months.

"There is no profit in this export field, but without a doubt we are a unique zoo because zoos in general have only a small number of hippos," said Sagit Horowitz, the spokeswoman for the Ramat Gan Safari outside of Tel Aviv.

But with more than 40 hippopotamuses in the zoo and a high birth rate -- with the average pregnancy lasting eight months -- the zoo had to find a way to scale down their population.

"We reached the point where we had nothing to do with so many of them," Horowitz told AFP. The zoo is today the world's only exporter of hippopotamuses, she said.

Fourteen hippos have so far been shipped by air or sea to Kazakhstan, Russia, Turkey, Ukraine and Vietnam at huge costs.

"And there is a long list of zoos asking for hippopotamuses," she said.

The secret of the trade is catching the beasts, which can reach up to 3.5 tonnes, while sleeping.

"If you shoot a tranquilliser at them when they are awake, they run into the pond and there is no chance of catching them there."

Once the animal is knocked out, it is lifted with a bulldozer and put into a crate.

The safari's latest exports are two hippos that are due to leave Israel on Tuesday for their new home in Ukrainian zoos, she said.