Capture/Attachment

 

Capture

Ethics approval was obtained from the Animal Ethics Committee at Charles Darwin University.

Experienced crocodile catchers from Parks and Wildlife Service, Northern Territory were used to capture the chosen crocodile using the harpoon method.  It is generally agreed that this is a quick and efficient method of capturing many different sized crocodiles, potentially reducing the amount of stress experienced by the animal.  It consists of a 3m long pole with a 2 or 3 pronged, barbed harpoon head, joined by a piece of rope.  The preferred target area was the neck, which is highly muscular and relatively free of skin bones.  Once harpooned, the crocodile was initially allowed to pull away, then was pulled in slowly.  Upon capture the crocodile was sedated with valium.

Once captured, a snout rope was placed over the top jaw to secure the animal, then once closed, a cord or tape was tied around both jaws.  The eyes were covered with a burlap sack and duct tape to minimize visual stimulation.  The crocodile was then secured to the side of the boat and taken to the boat ramp area, where attachment was to take place.  The rear legs were bound alongside the body with nylon webbing. 

This took place in the evening as the darkness makes it easier to spot crocodiles.  This is done by sweeping a flashlight over the water, making the eyes of the crocodile bright red.

Securing the jaws of Sputnik

Transporting Sputnik back to the shore to attach the transmitter

Back on the boat ramp awaiting attachment

Attachment

We were fortunate enough to have Dr Mark Read from the Queensland Parks and Wildlife Service available to attach the transmitter for us.  The method used has been tried and tested on a number of currently tracked crocodiles in Northern Queensland, and is a variation from the Winston Kay method.

After capturing and restraining the crocodile, the nuchal shield area was cleaned using chlorhexidine scrub and rinsed using 70% ethanol.  A local anaesthetic (such as lignocaine) was used to anaesthetise the nuchal shield area.  This was administered using multiple intra-muscular injections of 1.5 to 3mls which were placed around the base of the nuchal shield . After approximately 20 minutes the anaesthetised area was stimulated to check for a reaction from the crocodile.  When no response was observed a portable drill fitted with a sterilised 3mm drill-bit was used to drill eight holes in the four largest scales of the nuchal shield area to feed plastic-coated braided stainless steel wire (100kg breaking strain) through. 

The transmitter was then placed between the nuchal shield area and two pre-cut lengths of plastic coated stainless steel wire were used to secure the transmitter to the nuchal shield by threading the wire through the holes drilled in the scales and then through the attachment loops fixed to the lateral faces of the transmitter using a cross-over design.  The wire was then secured by using standard lead crimps that degrade over time to release the transmitter and wire.

Cleaning the nuchal shield area

Securing the transmitter with wire

Attaching the crimps

The finished product at 3am in the morning...