Crocodiles, in their modern form, have been lounging on sand banks and splashing about in rivers for at least 80 million years. With such legendary survivability to boast of, you'd expect these ancient animals need not worry about rival predators. But you'd be wrong. Crocodiles are occasionally targeted by big cats and, although croc babies have higher hatch rates and fare better against threats when compared to other reptiles, many youngsters still wind up as food for hungry predators.

Earlier this year, Colin Pretorius witnessed the very real challenges of croc parenthood play out on the banks of the aptly named Crocodile River on the southern edge of South Africa's Kruger National Park.

Pretorius watched from a restaurant deck overlooking the river as a female croc meticulously dug a burrow in a sandbank before filling the hole with a clutch of eggs. After depositing her brood-to-be, the crocodile "moved off a short distance to bask in the sun, but close enough to keep an eye on her babies,” Pretorius explained to Latest Sightings. Before long a pair of Nile monitor lizards emerged looking for an easy meal. 

"The crocodile tried to chase the lizards away for some time, but the monitors prevailed and got what they came for," he explained. Croc eggs are common fare for these unfussy eaters that are known to scoff down everything from fish and crustaceans to small mammals and carrion. According to the South African National Biodiversity Institute (SANBI), "Hunting strategies vary, but it is rare for the Nile monitor to shy away from a challenge." Some records even suggest that the typically solitary animals will work together when raiding nests, with one individual responsible for distracting the mama croc while the other lizard darts in to snatch an egg or two.

These hefty reptiles – second in size only to Nile crocodiles – are found almost anywhere in sub-Saharan Africa where permanent water exists. Nile monitors are highly adaptable and have even colonised the Florida Everglades courtesy of lizards brought into the United States for the pet trade.

Commandeering an egg from a crocodile is no small feat and the wily lizards will usually stay within a safe distance of the water's edge in case they need to flee from attack. A laterally flatten tail allows Nile monitors to glide easily through the water and they often opt for an aquatic escape when under threat. If cornered and forced to fight, they will lash with their tails to inflict significant wounds. Sharp teeth and claws add to the arsenal, and if under serious threat the lizards will eject a foul-smelling musk to deter attackers.

In this case, the duo's multi-pronged onslaught eventually resulted in success as they made off with at least one egg. The challenge of stealing croc eggs is made significantly more difficult due to the fact that the hefty reptiles are known to defend their nests from marauding predators. Crocodilians (and birds) are the only living representatives of archosaurs, a group that also includes the extinct dinosaurs and pterosaurs. All but a few archosaur species take care of their eggs by incubating them and in some cases they also stick around to guard the hatchlings. Nile crocodiles are particularly attentive parents and will not only guard the eggs, but will respond to calls emitted by the baby crocs to aid in the hatching process. Newborns are watched over by mom (and dad in some cases), and when under threat vocalisations trigger a rapid response from the protective parents.

Sadly for at least one unborn croc hatchling, this reptilian showdown ended in success for the monitor lizard.

Top header image: Peter Nijenhuis/Flickr