The boys were swimming in a watering hole in World Heritage-listed Kakadu National Park, a popular Outback tourist destination that lies southeast of Darwin, capital of the Northern Territory.
Thirteen people, six of them children, have reportedly been killed by saltwater crocodiles—salties, as they're locally known—in the area over the past dozen years. Wildlife officials have long struggled to manage the crocs in the park; the big reptiles have been a draw for tourists, but they can be dangerous.
"One boy fought off the crocodile, and then the crocodile turned and took the other boy," police Sergeant Stephen Constable told Australian Broadcasting Corp. radio about this weekend's incident.
The boy who was bitten first by the croc fought it off, but he suffered deep wounds to both his arms in the process. The body of the other boy, who reportedly lived in the small Aboriginal settlement of Mudginberri, is still missing.
Search crews have been combing the area with boats and a helicopter.
Constable told the media that the saltie croc was likely around 3 meters (10 feet) long. Were it much larger, it is unlikely that a child would have been able to escape its jaws, he said.
On Monday, rangers shot two crocs in the same area, although neither displayed any evidence of having been involved in the attack. One was 15 feet, 5 inches (4.7 meters) long and the other was 14 foot, 1 inch (4.3 meters).
The watering hole, or billabong as it is locally known, is partially wet during the dry season but has a higher water level during the (current) wet season.
In 2002 a 23-year-old German tourist was killed in Kakadu National Park by a 15-foot, 1,100-pound (4.6-meter, 500-kilogram) saltwater crocodile when she disregarded warning signs and went for a late-night swim.
Crocodiles have killed about 700 people worldwide over the past five years, compared with an annual average of 5 people killed by sharks, almost 3,000 by hippos, 500 by elephants, and 50 to 100 by bees.
Saltie crocs (Crocodylus porosus) are "living fossils" that have remained largely unchanged for 100 million years (see video). They have extremely powerful jaws and are the largest crocodilians currently living on the planet. The crocodilian group includes crocodiles, alligators, and caiman.
Average-size males reach 17 feet (5 meters) and 1,000 pounds (450 kilograms), but specimens 23 feet (7 meters) long and weighing 2,200 pounds (1,000 kilograms) are not uncommon.
Salties are considered "opportunistic predators"; they lurk patiently beneath the surface near the water's edge, waiting for potential prey to come by.
They are thought to feed on anything they can get their jaws on, including water buffalo, monkeys, wild boar, and even sharks. Without warning, they explode from the water with a thrash of their powerful tails, grasp their victim, and drag it back in, holding it under until the animal drowns.
Salties are excellent swimmers that have been seen far out to sea, though they also inhabit brackish and freshwater regions of eastern India, Southeast Asia, and northern Australia.
The crocs are thought to have an average life span in the wild of 70 years. Population estimates range from 200,000 to 300,000 worldwide.
Saltwater crocs are not currently endangered, but they face threats from illegal hunting and habitat loss, as well as from people who are afraid of them.
"World's Most Aggressive Crocodiles"
Saltwater crocs have a reputation for being dangerous to people. In one well-known case in April 2007, a partially sedated saltwater crocodile at a Taiwanese zoo bit a veterinarian's forearm off. After seven hours of surgery, the appendage was successfully reattached.
In December 2013, a study conducted by researchers at Charles Darwin University in the Northern Territory found that the saltie was much more aggressive than six other species of crocodiles from around the world.
The research was conducted in Australia and India and followed juvenile salties for two years, monitoring their behavior with infrared cameras.
The saltwater crocs were the only species to show agitated tail twitching followed by lunging head strikes at their opponents.
"They get in an agitated state, then wind themselves up and swing their heads into other crocodiles," Matthew Brien, a wildlife biologist at Charles Darwin University involved in the research, told the Guardian.
"When you see larger salties, especially males during mating season, it's quite fearsome," he said. "It's like a sledgehammer that would certainly shatter your head."
Other crocodilians that the scientists studied showed more social and less aggressive behaviors.
The researchers speculated that the salties may be hardwired for aggression to decrease competition and to take advantage of their large size.
Croc Safety Tips
In December, the government of Queensland, Australia, released new guidelines on staying safe from crocs, under a campaign called "Be croc wise."
People should heed warning signs, avoid leaving food or bait in croc-prone areas, and stand back from the water while fishing, the guidelines advise. Also, don't clean fish at the water's edge.
People are advised to "never swim in water where crocodiles may live even if there is no warning sign present," the guidelines say, and should avoid dangling their arms or legs over the side of a boat.
In Australia, it is also illegal to approach a saltie closer than ten meters unless part of a "commercial crocodile viewing tour" or if the waterway is too narrow to allow a wider berth.