How did the massive 'salty' crocodile captured in Australia get so big?

Australian parks and wildlife rangers captured a monster of a crocodile Monday (July 9), according to The Sydney Morning Herald. The beast was 15 feet 5 inches long (4.7 meters) and weighed a whopping 1,300 lbs. (600 kilograms).

If a reptile long enough to block two lanes of traffic sounds big to you, you've got good instincts. Experts told Live Science that this Australian saltwater crocodile (a "salty" in Aussie parlance) was unusually large, even for its hefty species — though it wasn't the biggest size crocodiles like this can reach.

"This animal was very large, but saltwater crocodiles can actually get much bigger," said Stephanie Drumheller-Horton, a paleontologist at the University of Tennessee, Knoxville, and a reptile expert. "Lolong, a saltwater crocodile from the Philippines, was 6.17 m [20 feet 3 inches] long and holds the Guinness World Record for the largest crocodile ever captured. Other than Lolong, there are records of a saltwater crocodile skin from Papua New Guinea which was 6.2 m [20 feet 4 inches] in length. And, of course, there are always rumors of even bigger animals in the wild." [Photos Comparing Alligators and Crocodiles]

It's not surprising that this news comes out of Australia, said Selina Groh, a Ph.D. student at the UCL-Birkbeck Department of Earth and Planetary Sciences in London and expert in crocodylians (a group that includes crocodiles, alligators and the Indian gharial).

"Around the world, there are about 23 species … of crocodylians," Groh told Live Science. "Of these, the salties in Australia are the largest that exist in the world — only the Nile crocodile in Africa and the American alligator come close."

Still, the scientists said, a typical salty doesn't get this big.

To reach this size, Groh said, this crocodile likely had the benefit of warm weather, plenty of room to roam and large prey to hunt.

"Optimal climate conditions (such as in some places in Australia) with few cold periods make it easier for the crocs to grow larger," Groh said.

Salty males tend to be much larger than females, Drumheller-Horton said, though age is a big factor in how big these beasts can grow.

"We used to think that crocodylians … had what we call indeterminate growth, which means that they kept growing throughout their lives," Drumheller-Horton said. "There has been research on American alligators that suggest that this might not be the case and that growth does taper off in very old animals. But it is absolutely true that these animals keep growing long after they reach sexual maturity. So, basically, a bigger crocodile is an older crocodile."

The Australian rangers who trapped the crocodile told the Herald that this crocodile "might be" over 60 years old.

Groh said that the animal's large size certainly made it an even more formidable predator.

"Crocodiles and alligators have some of the strongest bite force amongst all living animals, and the strength of bite force is directly correlated with body size," Groh said. "This increase in bite force also makes them potentially more dangerous."

Saltwater crocs are particularly powerful biters, even among crocodylians, Drumheller-Horton said, pointing to records of bites topping 3,600 pounds-force (16,000 newtons).

That made removing this crocodile from an inhabited area a particularly good idea, Groh said, pointing to evidence that saltwater crocodiles are especially likely to attack humans and that bigger crocs are more dangerous to human life.

Still, if we lived in an earlier point in the last 200 million years, when dozens more crocodylian species roamed the Earth, a 4.7-m capture likely wouldn't have made news, Drumheller-Horton said.

"As a paleontologist," Drumheller-Horton said, "I feel obligated to point out that while a 4.71-m-long croc is large by modern standards, fossil crocs and their close relatives got to be much bigger. Several extinct species topped 10 m [33 feet] in length, including DeinosuchusPurussaurus and Sarcosuchus."

Originally published on Live Science.