‘Virgin birth’ is recorded in a crocodile for the first time after a female gives birth in Costa Rica – despite living ALONE for 16 years

• An 18-year-old female American Crocodile has given birth to fertilised eggs 
• This is despite living alone at a zoo in Costa Rica for the past 16 years 

Nature has once again proven that life finds a way, as a female crocodile has given birth to fertilised eggs – despite having lived alone for the past 16 years.

This is the first time scientists have shown that a crocodile can produce offspring without mating, and they now say that dinosaurs might have been able to do the same thing.

Zookeepers discovered that an 18-year-old female American Crocodile, an apex predator growing up to 20ft, was guarding a clutch of 14 eggs in her enclosure, despite not having seen a male in over a decade.

It is not entirely uncommon for lone crocodiles to lay unfertilised eggs which are usually discarded; however, researchers were surprised to discover that seven of the eggs were actually fertilised.

While the eggs did not hatch after three months of incubation, one was found to contain a fully formed female foetus which was nearly genetically identical to its mother.

Zookeepers discovered that an 18-year-old female American Crocodile, an apex predator growing up to 20ft, was guarding a clutch of 14 eggs in her enclosure, despite not having seen a male in over a decade (stock image)

How does a ‘virgin birth’ work? 

‘Virgin birth’ is a natural process called facultative parthenogenesis, meaning a female is able to produce young without any involvement from a male.

It’s extremely rare in nature, although it is found in some other species, most notably mayflies, turkeys, pythons, and boa constrictors.

This particular case involved a mechanism called ‘terminal fusion automixis’, meaning the female fertilizes her own eggs using a genetic by-product called the second polar body.

This means that both parents are the mother and they have two pairs of the mother’s DNA.

Animals in the wild generally do not reproduce in this way, however, some research now suggests that endangered animals might do so more frequently as finding a mate becomes harder.

According to Warren Booth, associate professor at Virginia Tech who led the study, this discovery could offer ‘tantalizing insights into the possible reproductive capabilities of extinct archosaurian relatives of crocodilians’ including the dinosaurs.

Crocodiles branched away from other dinosaurs around 240 million years ago, yet these ancient lizards also share a common ancestor with birds dating back at least 267 million years.

With proof that crocodiles and birds can both produce young without mating, Booth says that this capability is ‘a trait likely possessed by a distant common ancestor of these lineages’, meaning that dinosaurs too might have exhibited ‘virgin births’.

However, ‘virgin birth’ is not the product of divine intervention or sneaky visits from the zoo’s male crocs, but a natural process called facultative parthenogenesis.

Facultative parthenogenesis is the rare ability to produce offspring without the need for sexual reproduction.

While this can be mistaken for a phenomenon called ‘long-term female sperm storage’ in which an animal may produce offspring long after mating, researchers used genetic analysis to prove there was no male involvement whatsoever.

The female embryo was 99.9 per cent genetically identical to its mother, showing that it had no father. 

However, this does not mean that it was a clone.

While the eggs did not hatch after three months of incubation, one was found to contain a fully formed female foetus which was nearly genetically identical to its mother (stock image)

This is the first time scientists have shown that a crocodile can produce offspring without mating, and they now say that dinosaurs might have been able to do the same thing

The scientists believe that the female crocodile fertilized her own eggs, meaning that the offspring contained two copies of its mothers DNA.

According to Booth, what makes this discovery ‘particularly interesting’ is that crocodile reproduction is quite different to any other animal previously known to be capable of facultative parthenogenesis.

Crocodiles lack all sexual chromosomes – the X and Y components of our DNA – meaning that the sex of crocodile offspring is not determined by their parents but by the weather.

In a process known as temperature-dependent sex determination, whether a crocodile becomes male or female depends on what temperature the egg is incubated at.

Above 99ºF (33º) or below 86ºF (30ºC), 100 per cent of crocodile eggs will become female, while around 89º (31.5ºC) the offspring are mostly male.

This research was published in the Royal Society’s Biology Letters. 

A TIMELINE OF CROCODILE EVOLUTION

250,000,000 BC – Xilousuchus

Three feet long. 5-10lbs. Lived in the swamps of eastern Asia. Ate small animals. Ridge of fan-like ‘sails’ on their back. Split off into pre-historic crocodiles and early dinosaurs. 

228,000,000 BC – Phytosaur

Alive during the early Jurassic period. Most related to crocodilians. Herbivores. Looked much like modern day crocodiles – except their nostrils were located on the top of their head rather than the tops of their snout.

200,000,000 BC – Erpetosuchus

Bipedal. Didn’t resemble modern crocodiles in behaviour or body shape except the shape of their head. 

110,000,000 BC – Sarcosuchus 

Middle Cretaceous period. 40ft long. 10-15 tons. Ate dinosaurs and fish. Lived in the rivers of Africa. Odd protrusion on it’s snout. Looked and behaved like it’s modern decedents, but it was twice as long and about 10 times as heavy. 

100,000 BC – Stomatosuchus 

36 ft. long. ten tons. Ate plankton and krill with its high pelican-like jaw. 

80,000,000 BC – Beinosuchus

Greek for terrible crocodile. Lived in the rivers of North America. About 33 ft long and 10 tons. They had a 6ft. long skull. Fed on fish, shell fish, and land creatures. Evidence in fossils suggests that they attacked large North American tyrannosaurs.

70,000,000 BC – Champsosaurus  

Five ft long, 25-50 pounds, ate fish, and lived in the rivers of North America and western Europe. Long narrow profile and a tooth studded snout. Survived the Cretaceous-Paleogene extinction event that killed off three-quarters of the plant and animal species on Earth – including the dinosaurs.

65,000,000 BC – Cretaceous-Paleogene Extinction Event

Non-avian dinosaurs were wiped out and more than half the world’s species were obliterated. This mass extinction paved the way for the rise of mammals and the appearance of humans. 

55,000,000 BC – Crocodylidae (Modern day crocodile)

The modern day crocodile – including the saltwater, Nile, and American variants – spread throughout the world. Though it looks prehistoric, it is a highly evolved and complex organism that is a successful predator.

23,000,00 BC – Quinkana

Nine feet long, 500 pounds. Consumed red meat in woodlands. Long curved teeth and long legs, unlike modern croc’s short legs. These crocodiles continuously get smaller because of environmental changes.

4,200,000 BC – Crocodylus thorbjarnarsoni

This is a very close relative of the modern day crocodile. Large skull and small raised rim in front of the eyes. Likely prayed on early humans. Lived in the Turkana basin in Kenya. Could be the largest known true crocodile.

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