Australian-Geographic-Magazine-September-Octobe..

86 Australian Geographic

understand the method and purpose of the research

first. “It’s the largest and longest telemetry study on

crocodiles ever to be conducted,” Craig says. “And,

using acoustic telemetry, we’ll be tracking more than

100 crocodiles here for the next 7–10 years.”

The work is significant for the management of

crocodiles that live close to human populations and

therefore pose major safety risks. “In Queensland,

problem crocodiles were translocated up until about

2008. Our research demonstrated that crocodiles
      will home and return to the same area once removed.
      Now translocation is no longer employed as a
      management strategy and crocodiles are removed
      permanently to farms,” Hamish says.
      How crocs navigate, how far they travel, whether
      they maintain permanent territories, and how social
      hierarchies operate are among the questions the
      researchers seek to answer. The team has mapped a
      detailed picture of the Wenlock R iver group.
      “Correlating acoustic and satellite tracking results
      with environmental variables such as currents and
      tidal systems, we’ve shown that...not only do they
      home, but they’ve got quite a detailed understanding
      of how currents work and will only travel when they
      are favourable,” says Ross. “They’ll climb up on a
      riverbank and wait till the current turns in the
      direction they want to go and then they just swim
      out and hitch a ride.”
      The researchers have also observed that in
      pristine rivers such as the Wenlock, populations
      remain stable and balanced. Large, dominant males
      (longer than 4m) control movements in the river, and
      smaller males are forced to migrate, which accounts
      for some of the epic oceanic journeys recorded.
      This has important implications for the practice
      of removing the biggest crocs from waters close to
      human populations.
      “We don’t know the effect that removing these
      large males might have on the dynamics of a
      river,” Hamish says. “If, from an area near people,

you remove a large male that was controlling the

movement of smaller 2–3m males, it could cause

more of these smaller animals to move into that

area.” Larger numbers of highly mobile young males

pose a greater risk to humans, and so it’s vital to solve

these puzzles quickly.

 I

T ’ S W H Y, the next morning, our big, beautiful

saltie has been dragged from the river and is

now lying under the weight of eight of us: Terri

at the head and seven of us along the body. Craig

works fast, assisted by Bindi, clearly relishing her role

as technical assistant. First he scans for a tag. It’s a

recapture. Juergen has been trapped twice before.

This is great news, because it helps to build a detailed

picture year on year. He’s measured, has blood taken

and the acoustic tag that’s been surgically implanted

is checked and replaced under a local anaesthetic.

Meanwhile, I’m awestruck to be touching a wild

crocodile. I’d imagined the scaly skin to be hard

like armour so I’m surprised by the soft texture of

the scutes on his back. Juergen doesn’t move at all

during the encounter, and, all along his massive 4.7m

body, the jump team remains silent and respectful,

trying hard not to disturb the creature more than

necessary. Soon it’s time to release him; it’s by far

the riskiest part of the process and those not directly

involved, including me, are moved to a safe distance.

The blindfold and jaw tape are removed and the

jump team gets ready to f lee. Juergen, once free,

will be at his most dangerous and could move like

lightning in any direction. Hearts are once again

pumping as everyone prepares for the call to release.

The order comes and the team scatters, the jaw

ropes come away, and, after a brief hesitation, Juergen

heads down the bank, disappearing with barely a

splash beneath the coffee-coloured water. It’s a

textbook operation. Steve Irwin taught his people

well. They have perfected a capture and release

method that eliminates the need to tranquillise the

animals, and it’s a technique that has been adopted

by other crocodile researchers around the world.

FIND footage of crocodile captures online at:

http://www.australiangeographic.com.au/issue122

Touching time. Young Robert Irwin has to wait a few

more years before he’ll be allowed to join the jump

team, but, in the meantime, he enjoys close encounters.

AG

Larger numbers of highly

mobile young males pose a

greater risk to humans, and

so it’s vital to solve these

puzzles quickly.

ALL IMAGES RS

ag0914_cape_york_crocsP86 - 80 2014-08-08T16:11:14+10:00