Crocs go surfing, according to articles in Nature News and ScienceNOW 7 June 2010 and ScienceDaily 8 June 2010. A team of researchers which originally included the late Steve Irwin (also known as the “Crocodile Hunter”) have studied the way estuarine, or saltwater, crocodiles move around the waterways and coasts of northern Australia. The team tagged and tracked 27 adult crocodiles and also analysed data from previous tracking studies. They then compared the crocodiles’ journeys with records of currents and tides. They found the crocodiles regularly travelled distances of around 50km along rivers and out into the open ocean. When travelling in rivers and estuaries the crocodiles began long journeys within an hour of the tide changing and when the current was against them they moved onto the riverbank or dived to the river bottom. By comparing the crocodiles’ movements at sea with surface ocean currents the researchers concluded crocodiles were also able to make use of the currents that were flowing in the right direction. One male crocodile made a 590km journey from the Kennedy River down the west coast of Cape York Peninsula. This took 25 days and coincided with a seasonal current system that develops in the Gulf of Carpentaria. Another crocodile travelled more than 400 km from the east coast of Cape York Peninsula through the Torres Straits to the Wenlock River on the west coast of Cape York. During the 20 day trip it waited in a sheltered bay for four days and only passed through the Straits when the currents were flowing in the right direction.
Scientists have long wondered how the one species of the estuarine crocodile, Crocodylus porosus could have spread over many islands and coasts across an area extending from India and China to northern Australia to the Fiji islands in the Pacific even though they are not strong swimmers. This tracking study indicates the crocodiles “surf” the ocean currents. Hamish Campbell from University of Queensland, one of the researchers, explained: “The estuarine crocodile occurs as island populations throughout the Indian and Pacific Ocean, and because they are the only species of salt-water living crocodile to exist across this vast area, regular mixing between the island populations probably occurs. Because these crocodiles are poor swimmers, it is unlikely that they swim across vast tracts of ocean. But they can survive for long periods in salt-water without eating or drinking, so by only travelling when surface currents are favourable, they would be able to move long distances by sea. This not only helps to explain how estuarine crocodiles move between oceanic islands, but also contributes to the theory that crocodilians have crossed major marine barriers during their evolutionary past.”
Editorial Comment: This study does confirm previous anecdotal evidence of such river crocodiles being seen in the open ocean, and is a clue to how such animals survived Noah’s flood and spread out to colonise the newly formed continents and islands following the flood. It also confirms that since the crocodiles are all the same species, this study contributes nothing to the theory of evolution. (Ref. reptiles, crocodilians, migration)
Evidence News, 23 June 2010