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Snake Surprise – “Virgin” Female Boa Constrictor Gives Birth

coiled boaA female Boa (Boa constrictor) shocked herpetologists by giving birth to live young that she produced by cloning rather than mating.  What’s more, the process used to create the young is new to the animal world – it has not been seen in any other vertebrate.

Asexual Births in other Species

Asexual reproduction or parthenogenesis – producing young without mating – is well known among insects and certain fishes (including Hammerhead Sharks), some of which can even switch sexes several times.  It has also been recorded in a small number of reptiles, such as the Brahminy Blind Snake, American Whiptail Lizards and the Komodo Dragon. 

Among certain Whiptail Lizards, the entire species seems to consist of females only, while in Komodo Dragons (and now Boas), females usually mate but have the “option” not to.  Biologists debate the reasons for such an unusual strategy, but in the case of the Blind Snake, it has paid off – single females transported worldwide in soil (their alternate name is Flowerpot Snake) have established many populations far outside of their natural range, including several in Florida.  Had they relied upon sexual reproduction, a pair or a fertilized female would be needed to start a new population – an unlikely event where stowaways are concerned.

A Completely New Type of Parthenogenesis

The discovery of a parthenogenic Boa was published this week (November, 2010) in the journal Royal Society Biology Letters.  Researchers note that the female snake in question had previously mated and produced young, but then went on to produce 2 litters via cloning.  They suspected something was amiss because all 22 youngsters were female, and caramel-colored, a recessive trait not carried by any of the potential fathers.

baby boaThe researchers were shocked to find that the young snakes had been produced by a cloning process known only from lab experiments, but never before seen in nature.  The youngsters were “half-clones” of their mother, having inherited 2 copies of ½ her genes (please see article below for a detailed explanation).

Observe and Share

The Boa Constrictor is one of the most thoroughly-studied snakes in the world, and millions have been bred in captivity. Yet we have only just now learned that it can reproduce by a means previously unknown to biologists. 

Further Reading

Virgin Snake Mom: further details and photos of the uniquely-colored youngsters.

Asexual reproduction in sharks and Komodo Dragons.

Coiled Boa image referenced from wikipedia and originally posted by Belizian
Baby Boa image referenced from wikipedia and originally posted by Destructive Eyes


  1. avatar

    I must say Iam somewhat skeptical/surprised!(same goes for the hammerhead thing-genetic data is promising but I’d be a believer if a virgin female raised a baby in captivity gives birth) Is their anyone out there who has kept a lone female Boa constrictor as a pet and then had it produce young without mating? Unless perhaps a previous mating is required to start the cloning process.

    All the Best-and thanks for this post!

    • avatar

      Hello Joseph, Frank Indiviglio here.

      Thanks for your thoughts…yes, quite puzzling. Komodo Dragons born in captivity have given birth in absence of males; same for Flowerpot snakes, but not boas as far as I know. Certain NA whiptailed lizards do mate to start the process, in one case with males not of their species; same for some fishes. This article goes into the genetics of the boa situation in a bit more detail.

      Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  2. avatar

    Parthenogenesis may not be as unusual as we might thing it is.Monitors have been reported to go through as well (commodo dragons)

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog. Seems only birds and mammals rely solely upon sexual reproduction…as far as we know!

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  3. avatar

    The Lepidodactylus lugubris gecko is also parthenogenetic. As for birds, they are capable of parthenogenesis. It appears rarely in chickens and turkeys, but usually the embryos die.
    It could logically exist in other, less studied species. Mammals have the peculiarity of having areas of the genome which should be contributed either by the mother or the father for normal function. At least for the well studied placental mammals, I don’t know for marsupials or monotremes, which incidentally have a completely different chromosome system. Thus parthenogenesis is possible only with lab manipulation.

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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