Baby crocs are born ferocious, says study

By Amy Middleton with AAP 2 August 2013
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Week-old saltwater crocs are just as aggressive as their adult counterparts, says new research.

MOST KIDS ARE TAUGHT to play nice, but this doesn’t appear to be the case for saltwater crocodiles. A new study suggests that salties are born with their killer instincts fully programmed.

The finding reveals that crocodile hatchlings display the same aggressiveness toward each other as their fully grown counterparts, all before they are one week old.

“The saltwater crocodile has a reputation for being one of the most aggressive species in the world as an adult,” says Matthew Brien, a biologist at Charles Darwin University in the Northern Territory and leader of the research. Matthew adds that the baby crocs he has been observing have proven just as voracious.

Surprising saltwater croc behaviour

Matthew has been studying saltwater crocodiles (Crocodylus porosus) in captivity in Darwin, Northern Territory. Because juvenile crocs are notoriously difficult to observe due to their size and effective camouflage, Matthew established a series of infrared CCTV cameras to keep an eye on the crocs at night.


“During the day these animals rest, but once the lights go out it is a whole different story,” says Matthew. “This is the first time we have really been able to observe the behaviour of baby crocodiles without them sensing we are watching.”

The findings, published recently in the journal Behaviour, suggest that baby crocs are born with an innate set of behaviours, including an instinctive aggression.

“I was just shocked to see them lining each other up and striking each other with their heads, just like the adults do,” he says. “Biting each other, twitching their tails and puffing themselves up.”

Purpose of aggression in crocodiles

As with other social animals, the fight instinct is key to establishing and maintaining dominance hierarchies among crocodiles. Early markers of aggression are also important because saltwater crocodiles prefer to assert their supremacy without having to actually fight.


“They smash each other in the beginning, but then they learn not to do that as much later on because it’ll lead to injury,” says Matthew.

Matthew says there have been no prior reports of this behaviour on record. “In fact, most people have reported this aggressive behaviour in saltwater crocs happening after a few months, when they get a bit bigger.”

Dr Hamish Campbell, a crocodile biologist at the University of Queensland, welcomes the research. “What is most interesting is that the agonistic behaviours and strategies used by the hatchlings are the same as in the adult animal, suggesting that being aggressive is all part of a crocodile’s survival strategy,” he says.


Hamish also told Australian Geographic that while studying crocodiles in the lab, “Hatchling crocodiles that are kept together exhibit very different growth rates. This research explains why.”

Recently, Hamish conducted research into the social hierarchy of saltwater crocodiles, supporting the theory that alpha or ‘boss’ crocs dominate over their territory, while other males become nomadic.

“I wonder if those aggressive hatchlings end up being the territory-holding male adults, whilst the subordinate ones end up undertaking a lifetime of wandering,” Hamish ponders.