Crocs Swim Hundreds of Miles to Return Home

Sept. 26, 2007 — Saltwater crocodiles are homebodies who will travel more than 250 miles back to their stomping ground, according to a team of Australian researchers, including the late naturalist Steve Irwin.

The discovery, revealed in the journal PLOS ONE , has implications for managing problem crocodiles as it may rule out relocation as an option.

The Australian Research Council-funded study used satellite tracking technology to follow three crocodiles that were relocated from their homes in Far North Queensland.

The crocodiles were captured in the wild, anaesthetised and a battery-run tracking device attached behind their neck. They were then relocated and released.

All three crocodiles found their way back to their capture sites. In the most extreme case, one of the crocodiles swam more than 250 miles around the tip of eastern Australia in 20 days.

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University of Queensland Professor Craig Franklin said the crocodile in question was airlifted from the Wenlock River on the west of Cape York Peninsula and flown 80 miles due east and released into the ocean.

The crocodile stayed on the east coast for a few months, making small journeys. But then "it decided to go home" and arrived back at the Wenlock River "in time for Christma," said Franklin.

Franklin said he is "staggered" by the crocodile's journey, but the team is yet to understand how the crocodile navigated its way home.

"Crocodiles are more closely related to birds, so maybe they are using similar navigational tools such as magnetic fields and smell," he said.

Franklin, from the School of Integrative Biology, says the key goal of the project is to understand more about the movement patterns of larger crocodiles to see if relocation would be an effective management strategy for problem crocodiles.

Problem crocs

In Queensland, Australia, problem crocodiles are "taken out of the system" and put in zoos and croc farms.

"It's sad because we are losing their genetic input in the wild and croc numbers in Queensland are still recovering from the killings the 1970s," he said.

The homing ability of the crocodiles would appear to rule out relocation.And relocation may even add to the problem as crocodiles become upset, and possibly more aggressive, when displaced.

"They seem to have a strong home fidelity," Franklin said.

The research is a collaboration between the university, the Queensland Parks and Wildlife Service and Irwin's Australia Zoo. Franklin said besides Irwin's "huge intellectual input," he also provided funding and logistical support to help catch the crocodiles.

The publication of the study was delayed by Irwin's death in September last year.