A 20-foot python from a zoo in America has given birth without the help of a mate.

Thelma, an 11-year-old reticulated python - the longest species of snake in the world - laid 61 eggs in the summer of 2012. This is despite having had no contact with a male in her four years at Louisville Zoo in Kentucky, USA.

After six months of extensive tests on the shed skins of the mother and her daughters, a study published in July this year in the Biological Journal of the Linnean Society confirmed that Thelma was the sole parent, in the first recorded example of virgin birth in the species.

Bill McMahan, Curator of Ectotherms at Louisville Zoo, told National Geographic: “We didn’t know what we were seeing. We had attributed it to stored sperm. I guess sometimes truth is stranger than fiction."

The research revealed that offspring were in fact the result of terminal fusion automixis, a process whereby cells known as polar bodies fuse with the egg to trigger cell division, effectively acting as sperm.

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McMahan added: “It is not uncommon for a snake to lay infertile eggs, so the staff was surprised when the eggs appeared to be full and healthy instead of shrunken and discoloured shells.

“It is a very exciting thing to be able to witness something like that first hand, especially something that has never been documented before in this species.”

Virgin births have been observed in other species of reptiles, including other pythons, as well as birds and sharks.