Girl Power: Female Boa Constictors Reproduce Alone

New evidence shows that boa constrictors can reproduce without sex. But one boa constrictor had babies asexually and the old-fashioned way. Her sexually produced snake (left) is shown beside one of the asexually produced females (right). [NCSU]

Scientists in the US have made a discovery which revolutionises the way we thought reptiles reproduced, by showing that female boa constrictor snakes can produce offspring without mating.

It was found that a so called "super mom" could produce large litters of all-female babies which show no evidence of male influence. The offspring has no genetic fingerprint that males were involved in the reproductive process and they all retained the distinctive recessive colour mutation.

This is the first time that asexual reproduction (producing offspring without mating) has been seen in boa constrictors.

Dr. Warren Booth, lead author of a paper just published in Biology Letters describes why boa constrictors may use both sexual and asexual forms of reproduction: "Reproducing both ways could be an evolutionary ‘get-out-of-jail-free card’ for snakes. If suitable males are absent, why waste those expensive eggs when you have the potential to put out some half-clones of yourself? Then, when a suitable mate is available, revert back to sexual reproduction.”

Whereas mammals are well-known for having X and Y sex chromosomes (males have one X and one Y; females have two X chromosomes), snakes have Z and W chromosomes.

Male snakes have two Z chromosomes and females have a Z and W. The female babies produced asexually in this study all had two copies of the W chromosome. This has never been seen before and was previously believed to be impossible.

Booth pointed out that the "super mom" snake had the opportunity to reproduce the "old-fashioned way", as there were a number of male snakes available. He also doubts that environmental changes triggered this rare change in behaviour in the snake.

Further studies will look at the development of the new offspring to determine how they reproduce when they reach sexual maturity.

Footprints prove reptiles were first to conquer dry land

The tracks were left by reptiles living 500 kilometres
from the nearest seashore

Reptile footprints which are 318 million years old have given scientists a new insight into the evolution of life on land.


The footprints were discovered in rock slabs broken away from sea cliffs at the Bay of Fundy in New Brinswick, Canada prove that reptiles were the first vertrebates (animals with a backbone) to leave the swampy coasts and make their homes on dry land.

The footprints were discovered by Howard Falcon-Lang of University of London during a trek along the coast in 2008.

"It's a very significant event in the history of life," Falcon-Lang said in an interview.

"About 400 million years ago, animals with backbones started to come on land, but these were frog-like creatures. And amphibians such as frogs have to return to the water in order to breed. They lay soft eggs that very easily dry out."

But Falcon-Lang said when the reptiles came along, they laid eggs with hard shells that they could lay on land, and could therefore start moving away from the shore.

The scientist said that he had actually been looking for something when he tripped over, scrapped his knee and came face-to-face with the small footprints (about 4 cm long) which were likely made by a reptile approximately 20 cm long and resembling a gecko.

"It really is that extraordinary," Falcon-Lang said. "You're capturing an event that probably just took a few minutes."