Targeted breeding of giant tortoises in European zoos

Many of you who regularly visit Zurich Zoo are familiar with the Galápagos giant tortoises Jumbo and Nigrita. The former is known for his impressive size and Nigrita is the oldest animal in the zoo. The two are also the parents of over 116 babies that have hatched at the zoo since 1989. This made Zurich Zoo the first European institution capable of breeding Galápagos giant tortoises. 

One of the questions visitors ask most often is: “Why aren't the baby tortoises released on the Galápagos Islands?”

The answer is simple.

Jumbo comes from Isabela Island and belongs to the species (Chelonoidis becki), while Nigrita comes from Santa Cruz Island and belongs to the species (Chelonoidis porteri). The two would therefore never have encountered each other in the wild. Their offspring are therefore hybrids, i.e., mixed breeds that do not occur in nature. 

In 2004, the European Association of Zoos and Aquaria (EAZA) initiated a conservation breeding program for Galápagos giant tortoises. This program is coordinated by Zurich Zoo. For several years now, more and more baby giant tortoises have been hatching in other institutions as well. The aim of the breeding program is to preserve species in the long term. Therefore, breeding hybrids should be avoided in the future.

To this end, it is necessary to determine the exact species of the adult giant tortoises in the breeding program in order to provide long-term breeding recommendations for animals of the same origin. Although there are written proofs of origin for all animals in the breeding program, the species of the animals is not reliably documented in these documents.

In order to verify the exact origin of each animal, blood samples are taken from all adult tortoises in the breeding program and analyzed in the laboratory using the latest genetic methods. According to the current state of genetic research on Galápagos giant tortoises, there are 15 species, 3 of which are considered extinct. The discovery of giant tortoise hybrids, most of which carry genes from two of the extinct species, has made it possible to breed back Pinta tortoises (Chelonoidis abingdoni) and Floreana tortoises (C. elephantopus) at the Charles Darwin Research Station.

We are curious to see which tortoise species are present in European zoos. If there are enough animals of a particular species, that species can be bred specifically. These young animals could then be returned to the corresponding Galápagos island if necessary to contribute to the preservation of their species. In this way, European zoos are actively contributing to the long-term conservation of Galápagos giant tortoises.

We are delighted that Zurich Zoo, as the studbook keeper, is committed to the conservation of Galápagos giant tortoises. For this reason, we support this sustainable program. 

Help us to make it possible that one day there will be as many tortoises on all the Galápagos Islands as there were in Darwin's time.