Sweetheart

Sweetheart Replica at ANSTO

Sweetheart is a giant crocodile which holds celebrity status in Australia and is famous for its boat attacking antics in the Northern Territory.

It's also famous at ANSTO because there is a replica on display at the ANSTO Visitor's Centre which is a hit with the kids on school visits.

Until 1979 the real Sweetheart prowled the Sweet's Lookout Billabong; a deep billabong in the Finniss River, downstream from the Rum Jungle uranium and copper mine site. Despite the name, Sweetheart was in fact a 'he' and was a big beast weighing in at 750kg and 5.1 metres from snout to tail tip.

But what was ANSTO's involvement with Sweetheart? The answer is that when Sweetheart was finally caught, ANSTO provided the nuclear techniques to analyse how his environment had affected him.

The Science

Annual periods of growth for crocodiles are recorded in free-floating bones called osteoderms. Typically these are composed of laminations that mark off the yearly aging of the animal. Sweetheart, a saltwater crocodile, (crocodylus porosus), was 50 years old.

In a wider study of lead contamination in crocodiles from the Kakadu National Park, in Australia's Northern Territory, samples of osteoderms showed very high levels in crocodiles known to eat magpie geese and other fauna shot with lead ammunition.

As a result of this work, and following experimental studies, the use of such ammunition was banned in Kakadu by the park's Board.

Laminated structures are also found in other long-lived organisms, such as mollusc shells and dugong tusks, and of course, tree rings. The deposition of radionuclides and other elements in these laminated structures can provide an archival history of exposure to environmental contaminants.

Once baseline elemental levels have been recorded, the impact of future environmental events can also be predicted.

Several nuclear techniques such as the use of Secondary Ion Mass Spectometry (SIMS) and Accelerator Ion Beam Analysis have been established at ANSTO for measuring trace nuclide and metal concentrations in these laminated structures.

The same technique has also been applied to mussel shells from the Finniss river. Their laminations have charted reduced yearly loads of uranium and other metals that were received from the Rum Jungle mine site, following a remediation project starting in the early 1980s.

The Sweetheart Story

Fact and fiction have become somewhat intertwined with this animal, because the billabong in which it resided contained more than one large crocodile. An even larger saltwater crocodile was caught alive in 1984 in a billabong a few kilometres from the site of Sweetheart's attacks.

Sweetheart gained notoriety in the 1970s when he started to attack boats, and didn't stop.

The first attack consistent with Sweetheart occurred in 1974. Three people were fishing from a boat at night when the crocodile surfaced, grabbed the cowling of the outboard motor and shook the boat violently. One person was thrown out but clambered back in; when another started the engine, the crocodile attacked the propeller.

In 1976, a similar attacked occurred; this time the crocodile damaged the cowling and punctured the aluminium hull. That same year, he slammed into a fishing boat from underneath, turning it around before surfacing beside it. In 1978 he attacked a moored boat, damaging the outboard engine and that same year he sank a fishing boat and continued to attack. He was beginning to be a nuisance so something had to be done.

Sweetheart was finally caught in July 1979 by a team from the Territory Parks and Wildlife Commission. He was then mounted and a full articulated skeleton prepared.

The original Sweetheart is now a permanent exhibition at the Museum and Art Gallery of the Northern Territory.