Reports concerning the animal world indicate that an eastern diamond rattlesnake recently gave birth to 19 healthy offspring five years after mating.
In other case a female copperhead snake that never mated gave a virgin birth.
Researchers that documented the unusual birth said it proved that snakes and certain other animals can either give true virgin - dadless - births, or may store sperm for long periods.
Actual mate-less virgin birthing, known as parthenogenesis, "has now been observed to occur naturally within all lineages of jawed vertebrates, with the exception of mammals," Warren Booth, co-author of the study, told Discovery News.
"We have recently seen genetic confirmation in species such as boa constrictors, rainbow boas, various shark species, Komodo dragons, and domestic turkeys, to name a few," he stated.
Booth, an integrative molecular ecologist at North Carolina State University, analysed DNA from the female copperhead that had been on exhibit - without a mate - for years at the North Carolina Aquarium at Fort Fisher.
Molecular DNA fingerprinting excluded the contribution of a male in her giving birth, which produced a litter of four normal-looking offspring.
The eastern diamond-backed rattlesnake's birthing moment was even more dramatic, as she suddenly produced 19 very healthy offspring consisting of 10 females and nine males.
DNA analysis confirmed that the 19 babies have a dad.
"This snake was caught when it was around one year old, and therefore would be considered sexually immature," said Booth, who co-authored the paper with Gordon Schuett of Georgia State University.
"It was housed in isolation from males up to the time that it gave birth. Therefore, this snake was mated in the wild as a sexually immature juvenile," he explained.
He and Schuett said internal sperm storage tubules or an ability to twist a portion of the uterus might explain how the rattlesnake stored sperm for five years.
To manage the second trick, Booth said "a region of the uterus becomes convoluted and contracted, which may act as a plug sequestering the sperm until ovulation."
The study was published in the Biological Journal of the Linnean Society.