JWM: Is Australia’s croc success killing humans across sea?

Saltwater crocodiles (Crocodylus porosus) have rebounded in northern Australia, but the swelling populations may be creating problems across the Timor Sea to the north, where the young nation of Timor-Leste is seeing a dramatic increase in crocodile attacks on humans.

Local crocodile populations in Timor-Leste are also on the rise, researchers say, thanks in large part to the end of a protracted fight for independence. But Timor-Leste’s limited crocodile habitat probably can’t explain the increase in crocodile attacks, they say. They believe the crocodiles are swimming from crowded areas in northern Australia in search of new territory 450 kilometers across the sea.

“If you want, it’s a conservation success story,” said Sebastian Brackhane, lead author on a study on the phenomenon in the Journal of Wildlife Management. “But it comes at a cost of many human lives, which is the dilemma of the whole situation.”

Brackhane began studying the crocodiles of Timor-Leste in his master’s work at Germany’s University of Freiburg. For many residents of Timor-Leste, he found, the crocodile is revered, tied to creation stories of a “Grandfather Crocodile.” Crocodiles attacks against humans, he said, are often seen against this background as punishments for “acts against nature.”

Although numbers are lacking, Brackhane said, local knowledge and national experts suggest crocodile populations suffered under Portuguese and Indonesian colonization and during the occupation of United Nations peacekeeping forces from 1999 to 2004. Since independence in 2002, laws protecting the crocodile, as well as local reverence for it, allowed its numbers to rise.

In the same period, attacks against humans multiplied. Between 1996 and 2006, an average of .55 attacks per year were reported. Between 2007 and 2014, that number soared to 13 attacks a year — a 23-fold increase — with traditional subsistence fishermen most often the victims.

It’s unlikely all those attacks can be attributed to the Timor-Leste’s resident crocodile population, Brackhane said. “There’s very limited habitat,” he said. “The core habitat is limited to a narrow strip along the coastline. There’s not actually enough habitat where crocodiles could nest and breed.”

He believes the crocodiles are swimming from Australia’s Northern Territories, where conservation measures in the 1970s allowed the population there to rebound and, in many places, reach carrying capacity.

The species is known for its ability to swim long distances — sometimes 1,000 kilometers or more, Brackhane said. Oil rig workers in the Timor Sea have reported seeing crocodiles in the waters between Australia and Timor-Leste, and Australian crocodiles are known to have dispersed from their territories.

Brackhane and his Australian colleagues would like to compare DNA samples of Timorese and Australian saltwater crocodiles to see if some are indeed coming from Australia. If they are, he said, management efforts in Australia could help limit crocodile attacks in Timor-Leste, where local customs often discourage even relocating individual crocodiles.

“This spiritual and cultural dimension is really something that’s quite unique in the crocodile world,” Brackhane said. “The whole country has a creation myth based on the crocodile and that still affects current management regimes.”

In some areas, village elders have placed taboos against fishing in areas known as crocodile conflict hotspots, he said. That can help reduce attacks, but families rely on the fish for food, he said, and increasingly, Timor-Leste is likely to rely on tourism, but snorkeling and crocodiles are a bad combination.

“That’s the challenge of management now,” Brackhane said. “How can we manage a recovered crocodile population, which is still highly protected not only by law but also by local cultural attitudes, and is increasingly affecting the economic development of the island?”

Header Image: Crocodiles are revered in Timor-Leste, but they’re also responsible for a growing number of attacks against fishermen. ©Grahame Webb