PREVIEW

Zookeepers at London Zoo are celebrating a milestone achievement in the rearing of Critically Endangered Rüppell’s griffon vultures (Gyps rueppelli): for the first time in the zoo’s history, keepers have successfully returned a hand-reared vulture chick to its parents to continue the rearing process.

This success story, which combines diligent hand-rearing by keepers with the natural bonding between vulture parent and chick, holds promise for London Zoo to expand its contribution to the global vulture population, through the conservation breeding programme.

Using a “dummy egg” technique – where a false egg is placed in the nest while the real egg is cared for in an incubator – the Zoo’s keepers were able to carefully monitor the newborn chick for its first five days post-hatch, maximising its chances of survival before it was returned to its parents. A wooden dummy egg was speedily placed in the vulture nest for expectant vulture mother Phil and father Cuthbert to tend to, during the 8-week wait for baby Rupert’s hatch. The vulture egg was kept at 36.6°C and monitored closely by keepers for an incubation period of 55 days. The process involved diligent care from the team, turning the egg three times a day to mimic the natural incubation of an egg in the nest. Keepers weighed the egg every day, tracking its progress on a graph, and adjusting the temperature and humidity of the incubator accordingly to allow for a successful hatch.

Details of this successful approach will be shared with conservation zoos worldwide, helping to build skills that can bolster the population of these critically endangered birds. This method of egg management was closely advised by colleagues from Rotterdam Zoo and the EAZA Ex situ Programmes.

Zookeepers hope this success can be repeated with the practice of 'double-clutching' - an incubation technique involving the strategic removal of newly-laid eggs to encourage the laying of more eggs. This method can be used to greatly increase the vulture population, while allowing parents to take an active role in rearing and older vultures to foster eggs.

When newly hatched, the fluffy vulture chick named Rupert weighed just 123g – the same as a small bar of soap. After being fed by zookeepers for 5 days, Rupert is now back in its nest, doted on by parents Phil and Cuthbert.

Zookeepers were excited when Rupert’s mother Phil laid her egg in mid-January, moving it to a special vulture egg incubator to give it the best possible chance of survival during the cold weather.

The whole bird team was on hand over several days to ensure the tiny vulture chick would hatch and survive. The team was supported by colleagues from The Horstman Trust – vulture specialists who offered instructional guidance over video call – to lead baby Rupert out of the egg and to safety.

“As soon as the shell breaks and the chick begins to hatch, the egg’s membrane starts to dry out and this can restrict the vulture chick’s movement”, said London Zoo keeper and bird specialist, Jessica Fryer. “Sometimes a chick won’t survive a hatch if that is left to happen, so it was essential that we were overseeing the entire hatch, intervening as necessary under the guidance of Holly Cale, curator of The Horstmann Trust.”

Following Rupert’s hatch on Wednesday 8 March, zookeepers spent 5 days hand-rearing the tiny chick before the moment came for it to be returned to parents Phil and Cuthbert. Rupert was placed inside the remnants of its eggshell and returned to the nest, ready for its parents to find on their return. For Phil and Cuthbert, Rupert is their second offspring, having welcomed their first chick Egbert into the world in 2023. The arrival of baby Rupert is the first time the two have ever reared a chick from infancy – a co-parenting challenge they have risen to remarkably.

Rupert is now the size of a small chicken, with early-stage feather growth. In June, zookeepers expect the chick to have fledged the nest at approximately 3.5 months old, at which point London Zoo’s veterinarian team can send a feather off for DNA testing to determine the bird’s sex.

Jessica added: “The threats to these vultures are huge, as successive and frequent mass poisonings in Africa are driving several species of African vultures to extinction. The Rüppell’s griffon vultures are also subject to similar threats to those facing other African vultures: loss of wild prey, habitat conversion into agro-pastoral systems, and collisions with powerlines.”

This milestone for vulture rearing at London Zoo marks a key step forward to boost population numbers. Rupert marks an important development for the European Breeding Programme for the Critically Endangered species, which forms a collaborative international network of conservation zoos to support the development of a healthy, genetically-diverse population.

“The lessons from this brilliant conservation success will benefit the global community of conservation zoos and help to continue the vital work needed to protect this species.”