Tony Perry: "Very important to have male clones"

Until now this type of cloning had only been used to produce female animals - mice, sheep and cows.

Fibro was born at the University of Hawaii and Professor Tony Perry, who works alongside the mouse's creators, told the BBC: "It is very, very important that we have male clones."

Goats have been cloned but only females

"The importance of cloning is partly commercial and there will often be cases where it is desirable to clone from extremely valuable males," he said. Prize bulls or endangered animals could be targets for male cloning.

The cloning technology used to create Fibro is called nuclear transfer. DNA from a cell is removed and inserted into an egg that has had its nucleus removed.

Christine McGourty reports: "The arrival of the first males is a crucial step forward"

The new hybrid develops into an embryo which is implanted in a surrogate mother to develop. The world's most famous clone, Dolly the sheep, was created in this way.

All previous clones produced from adult cells were female and the cells were taken from parts of the female reproductive system, such as mammary glands and ovaries.

But Fibro was produced using a cell from the tip of an adult male's tail, showing that easily gathered cells can be used for cloning.

Dairy cows were a primary focus for cloning

"This also shows that cloning is not an exclusively female phenomenon," said Professor Perry.

This first male clone has been produced three years after the birth of Dolly, but the time lag is for practical reasons rather than scientific ones.

Laboratories carrying out cloning simply had female cells readily available to them, rather than male ones, because the focus of much the research was copying elite dairy cows.

Ian Wilmut: "Male clone not a surprise"

"It's a useful confirmation," says Professor Ian Wilmut at the Roslin Institute in Edinburgh, Dolly's home. "But it is what we expected. There is nothing fundamentally different in the structure of cells of males or females."

Professor Wilmut says his team has never tried to produce male clones. The teams in Honolulu and Edinburgh lead the world in cloning technology.

Fibro is normal in all respects, including body weight, growth and fertility. However, he is the only one of 274 transferred embryos to survive longer than an hour after birth, showing that there is still much that scientists do not understand about the cloning process.

Fibro, named after the "fibroblast" cell from which he was probably derived, was created by Teruhiko Wakayama and Ryuzo Yanagimachi. They published their work in the journal Nature Genetics.