Despite being poor swimmers, researchers have discovered that the saltwater crocodile (also known as estuarine) commonly travels long distances over open oceans by riding ocean currents. The discovery, published in Journal of Animal Ecology, solves an unknown mystery of why saltwater crocodiles (Crocodylus porosus) are found across vast distance in the Pacific, yet have not diverged into different species.
Researchers tracked 27 adult saltwater crocodiles for one year using tags and sonar transmitters. The tagging showed that crocodile individuals, both male and female, regularly traveled more than 50 kilometers from their local rivers into the open sea. One crocodile traveled 590 kilometers in 25 days; another traveled 411 kilometers in 20 days.
 A 4.8 m male estuarine crocodile ready for release with satellite transmitter. This crocodile traveled over 590 km by sea. Photo courtesy of: the Australia Zoo. |
The study found that the crocodiles begin their long-distance travel within an hour of the tide changing, allowing them to ride the current. When the tide turned the crocodiles would haul themselves up on to a river bank to wait for a favorable tide, sometimes they even waited days for the right tide.
“[The crocodiles] can survive for long periods in salt-water without eating or drinking, so by only travelling when surface currents are favorable, they would be able to move long distances by sea. This not only helps to explains how estuarine crocodiles move between oceanic islands, but also contributes to the theory that crocodilians have crossed major marine barriers during their evolutionary past,” lead author Dr Hamish Campbell from University of Queensland said.
The saltwater crocodile’s range extends from India to Fiji and from southern China to northern Australia. They are the world’s largest crocodile species.
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