The world's longest snake has given birth to six pythons without the aid of a male in what is believed to be a first for the species.

An 11-year-old female reticulated python, named Thelma, gave birth to six female offspring at the Louisville Zoo in Kentucky despite not being homed with any males.

Following tests, DNA evidence have now proved the 20ft (6m) long snake is the sole parent and that Thelma had a "virgin birth".

"We didn't know what we were seeing. We had attributed it to stored sperm," said Bill McMahan, the Louisville Zoo's curator of ectotherms, (cold-blooded animals).

"I guess sometimes truth is stranger than fiction."

Surprisingly, virgin births are not as rare as you may think. Many invertebrates, such as insects, can produce offspring asexually while other animals, such as komodo dragons, hammerhead sharks and other species of snakes, are also known to have given birth without mating.

However, this is the first time it has been recorded in a python.

Warren Booth, a biologist at the University of Tulsa in Oklahoma, told National Geographic: "Pythons are an old, ancient species. We've seen this in more advanced species like garter snakes."

The process of reproduction without a male – parthenogenesis – occurs when the body produces cells known as polar bodies which behave like sperm instead of dying. These cells then fuse with an egg to create the offspring.

Parthenogenesis occurs for different reasons, often due to the lack of males present. This could be seen as the main reason Thelma, who has been held in capacity with two other females, choose to reproduce in this way. However, McMahan suggest the virgin birth could have also been a result of her "ideal" living conditions at the zoo.

"It takes a lot out of [pythons] to reproduce, and she had everything she needed. I had fed her a really big meal, 40 pounds [18 kilograms] of chicken. She was living in an exhibit larger than the typical size. There were heat pads. Everything was optimal," he said.