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An Australian researcher is hoping to help save the threatened hippopotamus by studying samples of drool from animals taught to salivate on command.
The hippo, despite its cute image, is one of the most dangerous of Africa's animals, and getting close enough to collect sample for analysis has always proved challenging.
But Steve Johnston, a Queensland zoologist, said yesterday that he had had some success with a group of Nile hippos at a zoo in Mexico.
One of the zoo's vets has trained the animals to walk into an enclosure and - a bit like Pavlov's dogs - drop their jaws on cue, releasing a flood of slobber in the expectation of being fed.
Mr Johnston said: "These things produce a massive amount of saliva. It actually comes out like a drinking fountain, and we collect it in a paper cup."
Mr Johnston, a lecturer in reproductive biology, told Australian Associated Press that while hippos bred well in captivity, next to nothing was known about their reproductive cycles.
He is hoping to devise a non-invasive test that could determine whether a hippo was pregnant, sexually mature or infertile.
The World Conservation Union says the common hippopotamus is in serious danger of extinction, as a result of poaching and destruction of habitat.
Mr Johnston is also planning to collect semen from large animals at the zoo, including white rhinos and giant ant-eaters.
The samples are destined for a study on sperm DNA damage, being conducted in collaboration with the University of Madrid.
It enables them accurately to predict fertility. Mr Johnston said that ant-eaters were anaesthetised before their semen was collected.
Rhinos, on the other hand, were awake. "The keepers start by rubbing the rhinos on the leg to get them excited," he explained. "It's really a masturbation technique."
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