Scientists in Australia are now on a quest to work out the true age of Cassius, the recently deceased saltwater crocodile. 

The 18-ft croc was captured in the 1980s and lived in Marineland Melanesia Crocodile Habitat on Green Island, off the coast of Cairns, Queensland. 

At the time, experts estimated his age to be 80, which means by the time he died last weekend he was assumed to be 120 or maybe even more. 

However, this was only an estimate, so following his passing scientists have performed a necropsy in an effort to reveal his true age. 

Tragically, Cassius died only weeks after his ‘best mate’ George Craig, his experienced crocodile handler, left the island. 

In a post on Facebook, his caretakers at the wildlife centre said: ‘He was very old and believed to be living beyond the years of a wild croc.

‘Cassius will be deeply missed, but our love and memories of him will remain in our hearts forever.’

Sally Isberg, founder of the Centre for Crocodile Research in Australia’s Northern Territory, thinks Cassius’ true age can be revealed by studying the bones. 

Before his life a captivity Cassius was known to prowl the waterways of Australia before being taken to Marineland Marineland Melanesia Crocodile Habitat. Tragically, the croc died only weeks after his ‘best mate’ George Craig (pictured) left the island

The world’s largest captive crocodile, Cassius is pictured at the Marineland Melanesia on Green Island, Great Barrier Reef, Cairns, Australia

As an animal ages, its bones gradually acquire layers or ‘rings’ that can be counted, much like tree rings, to uncover its true age. 

Samples of the bone are now being sent away for analysis, although Dr Isberg said she’s concerned that growth rings may not be ‘easily discernible’. 

‘My plan is to send it to a lab that can cross-section it and look for growth rings, just like in trees,’ Isberg told ABC News. 

Of course, bone analysis couldn’t be done while the animal was alive, so only in death can Cassius be aged properly. 

Dr Isberg said a routine necropsy – a surgical examination of a dead body – has indicated there was not a ‘causal cause of death’. 

In other words, the 1,300 kg Cassius – who was frequently billed as the world’s biggest pet crocodile – simply died of old age, it’s thought. 

While the next step is analysis of the bones, it could take months for the results to come back and they may be inconclusive. 

Samples have also been taken from his major organs, while the skin and head are also being preserved. 

Green Island Marineland Melanesia’s George Craig (pictured) feeding Cassius who has died at the age of 110

Sadly, a health assessment conducted last year on Cassius found ‘no reason to believe Cassius will not live for years to come’. 

Saltwater crocodiles are very dangerous to humans and are responsible for at least several dozen attacks on people each year. 

Wildlife experts generally say saltwater crocs live for more than 70 years, but a more exact figure is not known for this species. 

Professor Adam Rosenblatt, a biologist at the University of North Florida, previously told Live Science that those in captivity tend to live longer. 

‘My own educated guess is that the maximum lifespan for crocodilians as a group is in the range of 100 to 120, but they would only attain those ages in captivity,’ he said.

‘In the wild most crocodilians probably don’t live past 60.’ 

The oldest known crocodile, Freshie, lived to be an estimated 140 years old after being captured by Steve Irwin in 1970. 

As the name suggests Freshie was a freshwater crocodile, a species not thought to live as long as saltwaters.  

Saltwater crocodiles are very dangerous to humans and are responsible for at least several dozen attacks on people each year

Cassius is the largest crocodile to ever be caught alive in Australia. He measured 18 ft 0 in (5.48 metres) in length and weighed around 1,300 kg (2,870 lb)

Cassius lived at the Marineland Melanesia Crocodile Habitat since 1987 after being captured in the Finniss River, near Darwin, in 1984. 

At the time, Cassius was said to be between 30 and 80 years old, an estimate based on a size comparison with crocs held in captivity since birth. 

In 2011, Cassius set the Guinness World Record as the largest living crocodile in captivity. 

The croc had an especially close bond with his caretaker Craig and the pair would sit quietly together for ‘hours on end’, said Toody Scott, a former keeper and Craig’s grandson. 

‘In the last couple of years, George has been getting around on a mobility scooter and every time he came near the enclosure, Cassius would come over to him,’ Scott added. 

Cassius was touted as a ‘living dinosaur’ because he looked so ancient – making him a particular draw for tourists. 

Marineland Melanesia is a small habitat that takes in ‘problematic’ crocodiles that have been deemed a threat to humans. 

Craig established the centre in 1971 after spending 18 years safely capturing and relocating rogue crocodiles to help prevent attacks on villages.