A new study provides the strongest evidence to date that cancer is extremely rare in turtles, a finding that could offer valuable clues for preventing or fighting cancer in humans.

Experts at the University of Nottingham analysed medical records and necropsies (autopsies) from hundreds of zoo turtles, including from Chester Zoo.

While previous research had hinted that cancer might be uncommon in turtles, the new analysis, published in BioScience, shows that only about 1% of individuals are affected - far less than in mammals or birds.

The study was led by Dr Ylenia Chiari from the School of Life Sciences at the University of Nottingham, alongside Dr Scott Glaberman from the University of Birmingham, in collaboration with a team of researchers from zoos across the US, UK, and Europe.

The work was only possible thanks to a global network of zoos that have spent decades keeping detailed records and collaborating to support science, highlighting the vital role zoos can play in discovery research.

The findings were striking not only for the low number of cancer cases, but also because, when tumours did appear, they almost never spread.

Some turtle species grow to tremendous size. Galapagos and Aldabra giant tortoises, for example, can weigh hundreds of kilograms.

Turtles are also known for their long lifespans, and many are centenarians.

One radiated tortoise at Chester Zoo named Burt was born in 1945 and may live to over 100, while some Galapagos and Aldabra giant tortoises have lived beyond 150 years.

Species that are both large and long-lived are expected to face higher cancer risk, since more cells mean more opportunities for something to go wrong.

But turtles seem to defy this pattern.

"This research underscores the immense value of zoo-based science," said Dr Helena Turner, research officer at Chester Zoo.

"At Chester Zoo, we've long been committed to detailed health monitoring and the long-term care of our animals.

"It's fantastic to see these efforts not only contribute to advancing scientific knowledge around cancer resistance but also support vital conservation work to protect these remarkable species, that may hold keys to medical breakthroughs benefiting both wildlife and humans."

The turtle's secret may lie in strong defences against cell damage, a slow metabolism that reduces cellular stress, and unique genes that protect against cancer.

Turtles could offer valuable clues for preventing or treating cancer in humans and are a promising model for studying healthy aging and cancer resistance.

Dr Ylenia Chiari said: "Turtles, especially iconic species like Galapagos and Aldabra giant tortoises, are famous for living long lives and growing to tremendous sizes.

"You'd expect that to mean more cancer, but our study, which combines decades of zoo records with previous research, shows how incredibly rare cancer is in these animals.

"It highlights turtles as an untapped model for understanding cancer resistance and healthy aging, and it shows the vital role zoos play in advancing science through collaboration."

Dr Scott Glaberman added: "Biodiversity has so much to teach us about how the world works.

"While fascinating in their own right, extreme species like giant tortoises may have already solved many of the problems humans face, including those related to aging and cancer.

"That makes biodiversity doubly worthy of protection."

Several species of turtles are classified as Endangered or Critically Endangered according to the IUCN Red List, due to different threats including pressure from climate change, habitat loss, and illegal pet trade.

Many of the zoos that contributed data to the study, including Chester Zoo, are involved in conservation breeding programmes that aim to pull species like these back from extinction.