Even more unusual is that the genetic make-up of the babies is unlike any previously recorded among vertebrates, the group which includes almost all animals with a backbone.
All female, the little ones were also all born with a distinctive rare caramel colouration – a rare recessive genetic trait carried by the mother but not by any of the potential fathers.
The captive-born female boa constrictor gave birth at the same time as being housed with four male snakes but DNA tests showed none was the daddy, confirming the first instance of a known virgin birth among boa snakes.
‘The results may require scientists to take another look at reptile production,’ said Warren Booth, a geneticist at North State University. Asexual reproduction in snakes could be more common than thought, he added.
While invertebrates such as insects can produce offspring asexually, usually by cloning themselves, it remains a novelty among vertebrate animals.
In 2006, scientists discovered that two komodo dragon lizards had produced eggs that developed without being fertilised by sperm, while the following year saw another team find that captive female hammerhead sharks can also reproduce without having sex.