Authorities are working to solve a mystery involving cattle thought to have been washed onto a small island in the Tweed River by floodwater.

Fisherman Nathan Hall said he spotted a brown cow on the 5.67-hectare Chinderah Island about two weeks after catastrophic flooding in northern New South Wales in February 2022.

He has been keeping an eye on her ever since.

"Looking at the island she's living on, there's only a very small amount of grass area, and the rest is all mangroves and mud," Mr Hall said.

"It's not really the sort of grass that I'm used to seeing cows live in."

The island is close to the mouth of the Tweed River, and the water surrounding it is usually salty.

Mr Hall said he had been making regular deliveries of fresh water "for the last six months, at least".

"I've got three 20-litre drums, and every time I go down that way in the boat, I stop and pour 60 litres of water into a half-drum tin we've got down there," he said.

Recently, Mr Hall discovered a new resident - The black bull !

"I have stopped in and visited [the cow] over the time until now, but then seeing the black bull a few days ago was a bit of a shock to me," he said.

How the bull arrived on the island is a mystery and no-one has claimed ownership of either animal.

Hunt for owner:

Speaking on condition of anonymity, a farmer with cattle agisted on nearby Dodds Island said he had 30 cows wash away in the 2022 floods.

He said 20 of those animals were still unaccounted for and that the cow could be his.

He suggested the bull may have washed onto the island during last week's floods or that the cow may have calved him on the island.

Mr Hall said that both seemed in good condition.

"When I saw them the other day, the floodwater was still very fresh and they were drinking straight from the river," he said.

 "They came within six feet of the boat like they wanted to hop in with me."

Mr Hall said he would like to see the cattle brought back to the mainland.

"The best way to do it would be when the run-out tide is, and the animals could swim with the water rather than against it," he said.

"There's been plenty of interest, and give us another week and we'll get them off the island and get them back to living where they should be."

Retrieval delayed

Returning the animals to the mainland is proving easier said than done amid debate about who is responsible for them.

Tweed Shire Council said Chinderah Island and Dodds Island were privately owned and that the animals were the responsibility of the relevant property owners.

Council rangers visited Chinderah Island this week.

"A visual inspection indicated that the cattle currently on the island are in good condition," team leader Kristian Pakula said.

"The availability of suitable water and sufficient feed was also confirmed.

"Correspondence has been issued to the owner of the island advising them as to the presence of the cattle, and the matter has now been referred to the RSPCA."

Council said the rangers did not observe any tags that could help to identify the animals

RSPCA NSW has confirmed that its inspectors have also checked on the welfare of the cattle.

"There are no immediate animal welfare concerns and investigations into the ownership of the animals are still continuing," the organisation said.

Original Story By | Kim Honan