A north Queensland wildlife sanctuary is calling for community donations of old boiler hens to assist with the return to health of one of their saltwater crocodiles.

Jupiter is a 4.3-metre crocodile who was rehomed at Billabong Sanctuary south of Townsville after being removed from the city's Strand beach area in March 2016.

At the time of his capture, Jupiter had only one eye, was missing most of his teeth, was very thin and quite badly scarred.

Due to his condition, rangers estimated his age to be about 70 or 80 years old.

'Can't keep the food up to him' says ranger

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After 10 months in captivity the crocodile's teeth are starting to grow back but he is still 150 kilograms underweight so the park is calling for donations of unwanted or elderly chickens to include in Jupiter's diet.

The park feeds Jupiter commercially available chicken frames and pet food but whole birds provide additional nutrients, said park curator Brad Cooper.

"Those whole chickens are really important because they have got all the feathers and entrails and all the good stuff which have all the vitamins and minerals that we think he needs," Mr Cooper said.

He said the killing of any animals for food was very closely regulated by the park's governing body and veterinarians.

"It is absolutely against the law to be feeding anything live, so they are put to sleep in the most humane way," Mr Cooper said.

Since summer started, Jupiter's appetite has increased hugely and park staff are having trouble keeping up with his demand.

"We just can't keep the food up to him; he is a very hungry crocodile at the moment," Mr Cooper said.

Mysteries of crocodile's wild life surface

After nearly a year in captivity, rangers think they have uncovered some of the mysteries of Jupiter's life in the wild.

They now think Jupiter is closer to 50 years in age and was likely injured in territorial altercations.

"We thought that he was an old crocodile failing to establish and maintain a territory [and] most likely being denied hunting opportunities," Mr Cooper said.

"But he may have just had one serious encounter with a bigger crocodile [and] that's how he lost the eye and got so many scars."

Rangers suspect the injured Jupiter would have retreated to a creek to heal for a year and may not have eaten in that time, which was why he was so underweight.

"See, crocodiles can go without food, we think, for about that long [so] he would have been drawing on those fat reserves," Mr Cooper said.

He said Jupiter was becoming more active as he recovered and his teeth grew back.

"If the Townsville community can help out with [chicken] donations, we have got pretty high hopes that by this time in 2018 he will be 150kgs heavier," Mr Cooper said.

"That's going to make him our second biggest crocodile in the park."