15 Feb 2023

“Chester Zoo is a leader in wildlife reproduction research and we’re always looking for new, innovative ways to support the animals in our care and help protect those in the wild.”

One of our latest, most exciting advances is ‘Cryoconservation’.

Using state-of-the-art technologies, we use liquid nitrogen to cryogenically freeze tissue samples to the incredibly low temperature of -196°C! The tissues are collected from animals that have passed away at the zoo and include animals’ ovaries, testicles, sperm, and ears.

Dr Sue Walker, Head of Science at Chester Zoo shares everything you need to know about Cryopreservation at the zoo.

Dr Sue Walker
Dr Sue Walker

This seemingly sci-fi new method presents a unique opportunity to ensure that genetic variation in animal populations is not lost. This is important because low genetic variation leads to all sorts of problems, including making animals less adaptable to changes in the environment and more vulnerable to extinction. With many species facing huge threats in the wild, protecting their genetic diversity is now more important than ever.

As reproductive technologies advance in the future, these frozen tissue samples could be used to further conserve species globally by generating sperm and eggs: imagine transforming an ear tissue into a sperm cell!

The frozen biobank has successfully cryo-preserved multiple cell types from animal species including the Eastern black rhino, black jaguar, Javan green magpie and mountain chicken frog.

Cryoconservation involves using a type of cell called induced pluripotent stem cells. Amazingly, these cells can be turned into any type of cell under the right conditions. Consequently, our conservationists can use these wonder cells to restore the genetic diversity that’s been lost in animal populations.

Our scientists here at the zoo have teamed up with some of the UK’s leading animal reproduction experts and conservation biologists and founded Nature’s SAFE, which stands for Saving Animals From Extinction.

Nature’s SAFE is one of Europe’s only charitable living ‘cryobanks’ that is focused on preserving and regenerating the cells of the planet’s most precious animals. We’ve made dozens of contributions to Nature’s SAFE, which has successfully cryopreserved many different cell types from over 150 different animal species, including highly threatened species such as ring-tailed lemur, eastern bongo, mountain chicken frog, grevy’s zebra, and Javan green magpie.


Using this cutting-edge scientific method to create a frozen bank of animal DNA will help to preserve genetic variation for the future and could help to protect some of the world’s most endangered species from extinction.


Become a scientist for the day! Grab your science journal and discover our five WONDERLABS to learn loads about the incredible science we do to prevent extinction!

18 February – 5 March